S3OP - Antisurge Training Manual

U

PID A/D

RAM F

GLOBAL SUPPLIERS OF TURBINE

ID

AND COMPRESSOR CONTROL SYSTEMS

Title Page

Series 3 Plus Antisurge Controller Training Reference Manual Operations Module 1 Publication S3OP_AS (3.1) November 2000

4725 121st STREET DES MOINES, IOWA 50323-2316, U.S.A. Tel: (1) 515-270-0857 Fax: (1) 515-270-1331 Web: www.cccglobal.com

© 2001, Compressor Controls Corporation. All rights reserved. This manual is for the use of Compressor Controls Corporation and is not to be reproduced without written permission. The impeller and TTC logos, Total Train Control, TTC, Recycle Trip, Safety On, Air Miser, TrainView, and WOIS are registered trademarks; and the Series 5 logo, Reliant, Vanguard, TrainTools, TrainWare, SureLink, Guardian, and COMMAND are trademarks of Compressor Controls Corporation. Other product and company names used herein are trademarks or registered trademarks of their respective holders. The control methods and products discussed in this manual may be covered by one or more of the following patents, which have been granted to Compressor Controls Corporation by the United States Patent and Trademark Office: 4,486,142 5,347,467 5,622,042 5,879,133 6,116,258

4,494,006 5,508,943 5,699,267 5,908,462

4,640,665 5,599,161 5,743,715 5,951,240

4,949,276 5,609,465 5,752,378 5,967,742

Many of these methods have also been patented in other countries, and additional patent applications are pending. The purpose of this manual is only to describe the configuration and use of the described products. It is not sufficiently detailed to enable outside parties to duplicate or simulate their operation. The completeness and accuracy of this document is not guaranteed, and nothing herein should be construed as a warranty or guarantee, express or implied, regarding the use or applicability of the described products. CCC reserves the right to alter the designs or specifications of its products at any time and without notice. The protection provided by this product may be impaired if it is used in a manner not specified by Compressor Controls Corporation.

Contents -1

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1.1 Compressors . . . . . . . . . . . . 1.1.1 Reciprocating Compressors . . 1.1.2 Rotating Compressors. . . . . 1.2 Operating Map . . . . . . . . . . . 1.2.1 Operating Point . . . . . . . . 1.2.2 Speed Curves . . . . . . . . . 1.2.3 Performance Limits . . . . . . 1.2.4 Axes . . . . . . . . . . . . . . 1.3 Surge . . . . . . . . . . . . . . . . 1.3.1 Phenomenon . . . . . . . . . . . 1.3.2 Protection Method . . . . . . .

. . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. 1-1 . 1-2 . 1-2 . 1-4 . 1-4 . 1-5 . 1-6 . 1-7 . 1-8 . 1-9 . 1-11

Antisurge Control . . . . . . . . . . . . . . . . . . . . . . 2-1 2.1 Surge Limit Line . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2.1.1 Axis Selection . . . . . . . . . . . . . . . . . . . . . . . 2-2 2.1.2 Description of "Surge Limit Line" . . . . . . . . . . . . . 2-5 2.1.3 Formulas for Hp and Qs . . . . . . . . . . . . . . . . . . 2-6 2.1.4 S-value "Ss" . . . . . . . . . . . . . . . . . . . . . . . . 2-6 2.1.5 Speed Characterizer. . . . . . . . . . . . . . . . . . . . 2-7 2.2 Surge Control Line . . . . . . . . . . . . . . . . . . . . . . . 2-9 2.2.1 Safety Margin . . . . . . . . . . . . . . . . . . . . . . . 2-9 2.2.2 S-value . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11 2.2.3 Flow Characterizer . . . . . . . . . . . . . . . . . . . . 2-12 2.3 "Recycle Trip" Algorithm . . . . . . . . . . . . . . . . . . . . 2-13 2.4 "Safety On" Algorithm . . . . . . . . . . . . . . . . . . . . . . 2-16 2.4.1 Surge Detection using the "Safety On Line" . . . . . . . . 2-16 2.4.2 Surge Detection using a "Surge Signature" . . . . . . . . 2-17 2.4.3 "Safety On" Response. . . . . . . . . . . . . . . . . . . 2-18 2.5 Summary (Example) . . . . . . . . . . . . . . . . . . . . . . 2-19

S3OP_AS (3.1) - Series 3 Plus Operations Antisurge Training Manual

Contents -2

Antisurge Application Additional Control Functions . . . 3-1 3.1 Pressure Limiting . . . . . . . . . . . . . . . . . 3.2 Actuator Output Conditioning . . . . . . . . . . . 3.2.1 Valve Flow Characterization. . . . . . . . . 3.2.2 Valve Dead Band Compensation . . . . . . 3.2.3 Output Clamps. . . . . . . . . . . . . . . . 3.2.4 Tight Shut-Off . . . . . . . . . . . . . . . . 3.2.5 Output Reverse . . . . . . . . . . . . . . . 3.2.6 Output Tracking . . . . . . . . . . . . . . . 3.3 Operating States . . . . . . . . . . . . . . . . . 3.3.1 Operating State Transitions . . . . . . . . . 3.3.2 Manual Operation . . . . . . . . . . . . . . 3.3.3 Manual Override . . . . . . . . . . . . . . . 3.3.4 Loop Checks With the Compressor On-Line

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. 3-1 . 3-2 . 3-3 . 3-4 . 3-5 . 3-6 . 3-6 . 3-6 . 3-7 . 3-7 . 3-8 . 3-8 . 3-10

Series 3 Plus Gains and Biases . . . . . . . . . . . . . . 4-1 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 Gains and Biases Chart . . . . . . . . . . . . . . . . . . . . . 4-3

Series 3 Plus Antisurge Controller Fallback Strategies . 5-1 Constant Output (Mode fD 31) . . . . . . . . . . . . . Minimum Flow Control (Mode fD 32) . . . . . . . . . . Default Compression Ratio (Mode fD 33) . . . . . . . . Assumed Sigma (Mode fD 34) . . . . . . . . . . . . . Fallback Speed (Mode fD 35) . . . . . . . . . . . . . . Assumed Vane Angle (Mode fD 36) . . . . . . . . . . . Assumed Adjacent Stage Flow Rate (Mode fD 37) . . . Alternate K for Valve-Sharing Controllers (Mode fD 38). Temperature-Based Polytropic Head (Mode fD 39) . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

5-1 5-1 5-2 5-2 5-2 5-2 5-3 5-3 5-3

Antisurge Application Typical Surge Test Procedure . . 6-1 Background Summary . . . . . . . . . . . . . Surge Testing in AUTOmatic . . . . . . . . . . Surge Testing in MANUAL . . . . . . . . . . . Surge Testing On-Line . . . . . . . . . . . . . Determining Surge Line without Surge Testing .

February 26, 2001

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

6-1 6-2 6-5 6-6 6-6

Contents -3

Series 3 Plus Antisurge Controller Operating Principles. 7-1 Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1 Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 Auxiliary Window . . . . . . . . . . . . . . . . . . . . . . . . 7-3

Series 3 Plus Antisurge Controller Configuration Planner. . . . . . . . . . . . . . . . . FM301/L

S3OP_AS (3.1) - Series 3 Plus Operations Antisurge Training Manual

Contents -4

February 26, 2001

Introduction

1-1

Chapter 1: Introduction In almost all Petrochemical processes, Compressors are used to transport or compress gasses. Most processes depend on these compressors, so it is important that they are operated in a reliable fashion. To accomplish this one needs to know as much as possible of the state in which the machine is running, so measures can be taken to prevent shutdowns and keep the downtime of not only the compressor but the whole process to a minimum. This Training Manual describes the main features of the

COMPRESSOR

CONTROLS

CORPORATION

Control System. In chapter 2 the Antisurge algorithms are discussed.

Major control system objectives (user benefits) 1.

Increase reliability of machinery and process •

Prevent unnecessary process trips and

•

Minimize process disturbances

•

Prevent surge and surge damage

•

Simplify and automate startup and shutdown

downtime

2.

Increase efficiency of machinery and process •

Operate at lowest possible energy levels

•

Minimize antisurge recycle or blow-off

•

Minimize setpoint deviation

•

Maximize throughput using all available horsepower

•

Optimize loadsharing of multiple units

© Copyright 1997 Compressor Controls Corporation. All rights reserved. Reproduction by permission only.

1.1 Compressors

In the field two basic types of compressors are used: Rotating and Reciprocating.

S3OP_AS_Intro1 Antisurge Application Training Manual

1-2

Introduction

1.1.1 Reciprocating Compressors

The Reciprocating Compressors are Compressors of the Piston type. They work like a reversed combustion engine and are used in applications where a very high compression ratio is required.

1.1.2 Rotating Compressors

There are two distinct types of Rotating Compressors: the Axial and the Centrifugal Compressors. Axial Compressors are used in applications that need high flow rates, while Centrifugal Compressors are used in applications that require a high compression ratio in combination with lower flow rates. Compressors that combine these two types are also seen. In those cases the first few stages of the Compressor are Axial (to create high flow rates) and the last few stages are Centrifugal (to build up more pressure).

Centrifugal compressors • Widespread use, many applications • Gas is accelerated outwards by rotating impeller • Can be built for operation as low as 5 psi, or operation as high as 8,000 psi (35 kPa or 55,000 kPa) • Sizes range from 300 hp to 50,000 hp DIFFUSERS

IMPELLERS

Single Case Compressor © Copyright 1997 Compressor Controls Corporation. All rights reserved. Reproduction by permission

February 26, 2001

Centrifugal Impeller

Introduction

1-3

Axial compressors •

Gas flows in direction of rotating shaft

•

Can be built for lower pressures only

10 to 100 psi (0.7 to 6.8 Bar) •

High flow rate

•

Efficient

•

Not as common as centrifugals

Stator Blades

Shaft

Rotor Blades

Casing Rotor Blades

Stator Blades Casing


Compressor system classifications Single-Section, Three-Stage

Parallel Network

Single-Case, Two-Section, Six-Stage

Two-Case, Two-Section, Six-Stage

Series Network



Introduction

1.2 Operating Map

From paragraph 1.1 you can extract that the two quantities flow and compression are very important when selecting a compressor for a certain application. The range of operation depends on your process and should be covered by the selected compressor. While describing the operating range of a Compressor one often uses the so-called Compressor Map or Performance Map. Measured on the axes are pressure and flow (alternative axes are discussed in 1.2.4.).

1.2.1 Operating Point

When monitoring a Compressor one can look at mechanical quantities like vibrations and displacements or bearing and oil temperatures, but one can also look at process quantities like gas flow and pressures. The first will give you information about mechanical wear and/or problems, the latter will give you process/operating information. Using this information in the Operating Map will result in an up-to-date point of operation of the Compressor, the so-called Operating Point. All process variations will normally result in a movement of the Operating Point in the Compressor Map.

erusserP

1-4

P1

Operating Point

Q1 February 26, 2001

Flow

Introduction

If a Compressor operates with a fixed speed, the movement of the Operating Point in the Compressor Map will be restricted to a single line. This line is called the Speed Curve or Performance Curve belonging to this specific speed. When operating a Variable Speed Compressor (also a compressor with inlet guide vanes, or suction throttling), the Compressor Map contains a number of Performance Curves. When changing the speed or valve position, the Operating Point will move from one Performance Curve to the other, creating one more degree of freedom in the Compressor Map. The movement of the Operating Point from one Performance Curve to another is based on the resistance felt by the compressor and follows a Resistance Curve.

erusserP

1.2.2 Speed / Performance and Resistance Curves

1-5

Resistance curve

N

max

Operating Point

P1

Performance curve for a specific speed N1 N

min

Q1

Flow


1-6

Introduction

1.2.3 Performance Limits

Of course the movement of the Operating Point in the Compressor Map is restricted by a number of limits. The most obvious limits in the Operating Map are the following:

Developing the compressor curve process limit

Rc

maximumspeed

surge limit

power limit

stonewall or choke limit Actual available operatingzone

minimum speed

Qs, vol Figure 2:Limits

February 26, 2001

1:

Minimum Speed Limit, Throttle or Guide Vane Opening

2:

Maximum Speed Limit, Throttle or Guide Vane Opening

3:

Maximum Process Limiet or Discharge Pressure (Piping)

4:

Maximum Load Limit (Motor Power/Current, PSteam);

5:

Choke Limit (Stone Wall);

6:

Surge Limit.

Introduction

1.2.4 Axes

1-7

Compressor manufacturers use several different kinds of Compressor Maps that differ mainly in the selection of the Axes. For the X-Axis (flow-axis) the following quantities are often used: 1:

∆Po,s: Differential Pressure [inches H2O, mbar] across the Flow Measuring Device in Suction;

2:

∆Po,d

Differential Pressure [inches H2O, mbar] across the Flow Measuring Device in Discharge;

3:

Qs

Volumetric flow [ft3/hr, m3/hr] in Suction;

4:

Qd

Volumetric flow [ft3/hr, m3/hr] in Discharge;

5:

W

Mass or Net flow [lb/hr, kg/hr];

For the Y-Axis (pressure-axis) the following quantities are often used: 1:

Pd

Pressure [psi, bar, kg/cm2] in Discharge;

2:

Ps

Pressure [psi, bar, kg/cm2] in Suction;

3:

∆Pc

Differential Pressure [psi, bar, kg/cm2] across the Compressor (∆Pc = Pd - Ps);

4:

Rc

Compression Ratio (Rc = Pd / Ps);

5:

Hp

Polytropic Head [ft lbf/lbm, kJ/kg];

6:

Had

Adiabatic Head [ft lbf/lbm, kJ/kg];

7:

His

Isentropic Head [ft lbf/lbm, kJ/kg].

The Axes that are selected by C.C.C. are discussed in paragraph 2.1.1.


1-8

Introduction

1.3 SURGE

Surge is defined as "self-oscillations of pressure and flow, often including a flow reversal".

Surge description •

Flow reverses in 20 to 50 milliseconds

•

Surge cycles at a rate of 0.3 s to 3 s per cycle

•

Compressor vibrates

•

Temperature rises

•

“Whooshing” noise or “Clanking” noise

•

Trips may occur

•

Conventional instruments and human operators may fail to recognize surge


Major process parameters during surge FLOW

1

2 TIME (sec.)

•

Rapid flow oscillations

•

Thrust reversals

•

Potential damage

•

Rapid pressure oscillations

3

PRESSURE with process instability

1

2 TIME (sec.)

3

TEMPERATURE

•

Rising temperatures inside compressor

1

2 TIME (sec.)

3


February 26, 2001

Introduction

1-9

1.3.1 Phenomenon

Figure 3:Typical Surge Cycle

A more thorough understanding of the Surge phenomenon can be attained by observing the movement of the Compressor Operating Point on its characteristic curve during Surge.

Consider a Compressor operating in steady state at point D. If the load is reduced, the Operating Point will move toward point A, the Surge Point. If the load continues to be reduced, the Operating Point will move to the left and cross point A. At point A, the Compressor is producing more flow than the load can absorb. This fluid is temporarily stored in the discharge volume, but the discharge pressure cannot rise above point A. The only relief for these conditions is for the Operating Point to jump to point B. This is the flow reversal often observed during Surge. With negative flow the discharge pressure drops (traject points B-C). At point C we find, that the compressor is now able to overcome the discharge pressure and forward flow can be re-established, so the Operating Point jumps to point D. Now the flow is in excess of the load and the Operating Point will move up the curve to reach point A again. This completes one Surge Cycle. The typical duration of one Surge Cycle is 0.33 to 3.0 seconds.


1-10

Introduction

Developing the surge cycle on the compressor curve (1) • • • •

Pd

Compressor reaches surge point A Compressor looses its ability to make pressure Suddenly Pd drops and thus Pv > Pd Plane goes to stall - Compressor surges B

Pd

A

C • Because Pv > Pd the flow reverses • Compressor operating point goes to point B

Rlosses

Pv

Pd = Compressor discharge pressure Pv = Vessel pressure Rlosses = Resistance losses over pipe

• D • • •

Pressure builds Resistance goes up Compressor “rides” the curve Pd = Pv + Rlosses • Electro motor is started • Machine accelerates to nominal speed • Compressor reaches performance curve •

Machine shutdown no flow, no pressure

Note: Flow goes up faster because pressure is the integral of flow

Q s, vol


• • •

Developing the surge cycle on the compressor curve (2)

From A to B From C to D A-B-C-D-A

• • • • B

20 - 50 ms Drop into surge 20 - 120 ms Jump out of surge 0.3 - 3 seconds Surge cycle

Pd

D

Result of flow reversal is that pressure goes down Pressure goes down => less negative flow Operating point goes to point C Machine shutdown no flow, no pressure

• • • •

Pv

Pd = Compressor discharge pressure Pv = Vessel pressure Rlosses = Resistance losses over pipe

System pressure is going down Compressor is again able to overcome Pv Compressor “jumps” back to performance curve and goes to point D Forward flow is re-established

Q s, vol


February 26, 2001

Rlosses

A

C • • •

Pd

Compressor starts to build pressure Compressor “rides” curve towards surge Point A is reached The surge cycle is complete

Introduction

1.3.2 Protection Method

1-11

The consequences of Surge are severe. Besides process disturbance and the eventual process trips and disruption, surge can damage the Compressor. Damage to seals and bearings is common. Internal clearances are altered, leading to internal recycle and thus lowering the Compressor's efficiency. Ongoing Surge can result in complete destruction of the rotor.

Some surge consequences •

Unstable flow and pressure

•

Damage in sequence with increasing severity to seals, bearings, impellers, shaft

•

I ncreased seal clearances and leakage

•

Lower energy efficiency

•

Reduced compressor life

Factors leading to onset of surge •

Start-up

•

Shutdown

•

Operation at reduced throughput

•

Operation at heavy throughput with:

•

-

Trips

-

Power loss

-

Operator errors

-

Process upsets

-

Load changes

-

Gas composition changes

-

Cooler problems

-

Filter or strainer problems

-

Driver problems

Surge is not limited to times of reduced throughput.

Surge

can occur at full operation


1-12

Introduction

This demands a reliable method of protection. As discussed in 1.3.1. a combination of high discharge pressure and low flow can result in Surge. Avoiding one or both of these situations prevents a Compressor from going into Surge. A working solution can be found in a Recycle or Blow-off line. Operating a valve, positioned in this line, reduces the discharge pressure and increases the load thus preventing Surge.

Basic antisurge control system •

The antisurge controller UIC-1 protects the compressor against surge by opening the recycle valve

•

Opening of the recycle valve lowers the resistance felt by the compressor

•

This takes the compressor away from surge

Rc

VSDS

Rprocess Rprocess+valve

Compressor

Suction

FT 1

PsT 1

UIC 1

Pd T 1

Discharge

2 r

q

• Surge parameter based on invariant coordinates Rc and qr – Flow measured in suction (∆Po) – Ps and P d transmitters used to calculate Rc

Major Challenges of Compressor Control

February 26, 2001

•

Location of the operating point

•

Location of the surge limit

•

High speed of approaching surge

•

Control loop interactions

•

Loadsharing for multiple compressor systems

•

Coordinating control of compressor and driver

Antisurge Control

2-1

Chapter 2: Antisurge Control 2.1 SURGE LIMIT LINE

To be able to prevent a Compressor from experiencing Surge, one needs to know exactly where the "Surge Limit Line" is situated. This information needs to be downloaded to the Controller that controls the Recycle Valve. If this Controller knows where to find the Surge Limit Line and knows the location of the Operating Point with respect to that line, then the Recycle Valve can be opened when necessary.

Calculating the distance between the Surge Limit Line and the compressor operating point The Ground Rule

–

The better we can measure the distance to surge, the closer we can operate from it without taking risk

The Challenge

–

The Surge L imit Line (SLL ) is not a fixed line in the most commonly used (SLL) coordinates. The SLL changes depending on the compressor inlet conditions: Ts, Ps, MW,

ks

Conclusion

–

The antisurge controller must provide a distance to surge calculation that

–

This will lead to safer control yet reducing the surge control margin which

is independent of any change in inlet conditions

means:

• •

Bigger turndown ratio on the compressor Reduced energy consumption during low load conditions on the compressor


2-2

Antisurge Control

2.1.1 Axis Selection

The Surge Limit Line is determined by a (number of) surge test(s) during the commissioning phase of a project. Information determined from this test is programmed in the Antisurge Controller. When running the Compressor, the location of the Surge Limit Line should not change when the process conditions change. This means that the selection of the Axes of the Compressor Map in which the Surge Limit Line is situated, is very significant. If for the Y-Axis discharge pressure is used, the Operating Point will not directly react to (only) suction pressure changes. This means that the Surge Limit Line is capable of movement and that is just what we do not want. Using ∆Pc or Rc on the Y-Axis will result in a direct movement of the Operating Point when suction pressure changes. If now the temperature of the gas changes, the internal energy of the gas changes. This again not directly resulting in the movement of the Operating Point, but a moving Surge Limit Line. It becomes clear that the selection of the Axes must result in a fixed Surge Limit Line and allow only Operating Point movement during as many process changes as possible.

Commonly used (OEM provided) coordinate systems of the compressor map •

s

p

s

c

s

d

Typical compressor maps include: (Q , H ), (Q , R ), or (Q , p ) coordinates, where:

Q s = Suction flow and can be expressed as actual or standard volumetric flow H p = Polytropic Head Rc = Compressor Ratio (p d / p s) pd = Discharge pressure of the compressor ps = Suction pressure of the compressor k s = Exponent for isentropic compression

•

These maps are defined for (1) specific set of inlet conditions:

p , T , MW and k s

February 26, 2001

s

s

Antisurge Control

2-3

The problem with commonly used (OEM provided) coordinate systems of the compressor map These coordinates are NOT invariant to suction conditions as shown

•

For control purposes we want the SLL to be presented by a single curve for a fixed geometry compressor

•

Developing invariant coordinates The following variables are used to design and to characterize compressors Through dimensional analysis (or similitude) we can derive two sets of invariant coordinates

•

•

Fundamental variables characterizing compressor operation H p= f0(Q,

ω, µ , ρ, a,

d,

α)

J = f1(Q,

ω, µ, ρ, a,

d,

α)

Invariant coordinates Dimensional analysis or Similitude

Set 1

Set 2

hr

Rc

qr

qr

Ne

Ne

α

where: • Hp • J • Q • • • • •

•

ω µ ρ

a d

α

= Polytropic head = Power = Volumetric flow rate = Rotational speed = Viscosity = Density = Local acoustic velocity = Characteristic length = Inlet guide vane angle

where: • hr • qr • Ne • • • •

α

jr Re Rc

α

jr

jr

Re

Re

= Reduced head = Reduced flow = Equivalent speed = Guide vane angle = Reduced power = Reynolds number = Pressure Ratio


2-4

Antisurge Control

Coordinates (H , Q ) and (h , q ) p

(Hp, Qs) NOT invariant coordinates

where: Hp Qs hr qr2 •

•

•

•

s

r

2

r

(hr, qr2) Invariant coordinates

= Polytropic head = Volumetric suction flow = Reduced head = Reduced flow squared

C.C.C. generally uses Polytropic Head (Hp) versus Suction 2 Flow squared (Qs ). Hp is measured in [kJ/kg], [m], [ft lbf/lbm] etc. and Qs is measured in [ft3/hr], [m3/hr], [tonnes/day] etc.

February 26, 2001

Antisurge Control

2.1.2 Description of "Surge Limit Line"

2-5

Most limits in a process are of the "one variable" type. This means that you only need to know the value of one specific transmitter, compare it with its maximum or minimum (limit) value, and control an actuator accordingly. The Surge Limit Line is slightly different. First of all the limit cannot be crossed without potential damage to your compressor, and secondly the limit is not the maximum or minimum value of only one physical transmitter signal. In case of the Surge Limit, the limit is line in the Compressor Map, with Hp on the vertical 2 Axis and Qs on the horizontal Axis. The challenge now is to find a way of describing the Surge Limit Line in such a way that we can see this limit as any other "one variable" type limit.

SLL

H

p

H

O.P.

p

α=

tan

Q2 H s

p

SLL

α

Q

2 s

Q2 s

If the Surge Limit Line is a straight line through the origin, this line can be described by determining the angle (α) the line makes with the vertical axis. If the angle is known, the tangent of the angle is also known. In other words, you can describe the Surge Limit Line by determining the quotient of 2 Qs and Hp for a single point on that line. If a similar calculation is made for a the Operating Point, the distance to the Surge Limit can be determined. Taking a closer look at 2 the formulas for Hp and Qs will lead to a surprising result.


2-6

Antisurge Control

2.1.3 Formulas for Hp and Qs

Polytropic Head:

H p = Z avg ×

 Rσ − 1 R0  × Ts ×  c MW  σ 

(1)

Volumetric Flow:

Q

R0 × T × ∆P MW P

(2)

Ts ) Ps )

(3)

s

=

Z

s

×

o

s

s

with:

and:

2.1.4 S-value "Ss"

σ=

(T (P

log log

d d

Rc = Pd Ps

(4)

2

As shown the quotient (called "K-value") of Hp and Qs determines the Surge Limit Line. In the field every Surge Limit Line has a different quotient or K-value. To create a universal way of control, C.C.C. created a patented new variable, the S-value. In C.C.C. Controllers this variable is defined as:

S-value:

where:

S SLL = Ss = K ×

Qs2 K= Hp

Hp Qs2

(5) O. P .

(6) SLL

This S-value is proportional to the angular distance between the Operating Point and the Surge Limit Line. This S-value will always be 1 (one) when the Operating Point is on the Surge Limit Line! Including Formulas 1, 2, 3 and 4 in 5, gives us the following result:

 Rcσ − 1     σ  Ss = K × × Ps ∆Po

February 26, 2001

(7)

2-7

Antisurge Control

In C.C.C. documentation the following reduced formula is often used:

Ss = K ×

H p ,red Qs2,red

Rcσ − 1 = σ

where:

H p,red

and:

Qs2,red =

∆Po

Ps

(8)

(9)

(10)

Formulas 9 and 10 are called "Polytropic Head Reduced" and "Suction Flow Reduced". After manipulating the formulas for Polytropic Head (1) and Volumetric Suction Flow (2), it shows that you only need to know the values of five transmitters to be able to calculate the formula for the S-value (7). These five are:

2.1.5 Speed Characterizer

1:

Differential Pressure across a Flow Measuring Device

∆Po

2:

Discharge Pressure

Pd

3:

Suction Pressure

Ps

4:

Discharge Temperature

Td

5:

Suction Temperature

Ts

In case of a Variable-Speed Compressor, the Surge Points for different Speed Curves will hardly ever be located on a single straight line through the origin of the Operating Map. If calculated, the results of the surge tests for various speeds of the compressor, will give you different K-values (taking into account, that the S-value for an Operating Point moving across the Surge Limit Line has a value of 1 (one)). In other words, the K-value is not constant but is a function of the actual speed of the compressor: K N = f ( N ) . This function of compressor speed is called a "Speed Characterizer" and contains the information gathered from the surge tests. The next example will illustrate this.


2-8

Antisurge Control

Surge test

Speed N

Calculated KN

Constant K

1

70%

0.50

0.5

f(0.7) = 1.0

2

80%

0.75

0.5

f(0.8) = 1.5

3

90%

1.00

0.5

f(0.9) = 2.0

Formula 8 now changes in: Ss

Characterizer

= K × f (N) ×

H p ,red Qs2,red

f(N )

(11)

The K-value and ten points for the Characterizer f(N) are entered in the Antisurge Controller. The K-value in formula 11 now mainly functions as a gain on the Speed Characterizer. In addition to the five transmitters discussed in the last paragraph, this formula needs the value of a speed transmitter to be able to calculate the S-value.

Building the Surge Limit Line •

Any curvature of the Surge Limit Line can be characterized as a function of the ordinate h r

r

•

The The surge surge parameter parameter is is defined defined as: as:

•

The The function function f f

f (h ) Ss = K . 1 2 r qr ,SLL

2 returns the value of q on the SLL for input h 1 returns the value of qr on the SLL for input h r

h h

r

h h

r

2 r,SLL

q q

February 26, 2001

2 r

q q

Antisurge Control

2-9

2.2 SURGE CONTROL LINE

The Surge Control Line (SCL) defines the desired minimum distance between he operating point and the Surge Limit Line (SLL). The SCL is always to the right of the SLL, as shown in the Figure below.

2.2.1 Safety Margin

The Surge Limit Line is an unstable limit... when the Operating Point crosses this limit the compressor will experience (at least) one Surge Cycle. This might trip your machine or even lead to a total process shutdown. The only way to prevent this from happening is to keep the Operating Point a reasonable distance away from the Surge Limit Line. This means that the Recycle Valve as discussed in paragraph 1.3.2 needs to be opened when the Operating Point reaches a pre-selected minimum distance to surge. This minimum distance is called the "Safety Margin" and can be visualized in the Operating Map by drawing a line in front of the Surge Limit Line.

SLL

H

p

SCL

b1 O.P.

“Surge Control”Zone

Q2 s


2-10

Antisurge Control

The distance between the Surge Limit Line and the "Surge Control Line" (S.C.L.) is determined by the constant factor. The Recycle Valve will be closed as long as the Operating Point is on the right side of the Surge Control Line. When the Operating Point reaches or crosses the Surge Control Line, it enters the Surge Control Zone and the Recycle Valve will be opened. It is possible to have the S.C.L. location based upon a minimum margin (b1) plus an extra margin whenever needed.

Adding a Safety Margin (b1) b = b1 + (b2

•

n) + (b3

•

The area around the SLL is unstable

•

Controlling the Operating Point at

•

Td0

•

dS/dt)

SLL SCL

h r

r

the SLL can lead to surge

•

We need to add a safety margin to control the Operating Point in a stable area

b1 b1 = Initial Safety Margin b2 = Safety On Response n = num ber of surges b3 = Adaptive Gain Response Td0 • dS/ dS/dt = derivative of S SCL = Surge Control Line SLL = Surge Limit Line

February 26, 2001

2 rr

q

Antisurge Control

2-11

This extra margin is added whenever there has been a disturbance in the process which causes the Operating Point to move towards surge... the bigger the disturbance, the faster the Operating Point moves, the more margin is added and the sooner the valve is opened. This movement of the Operating Point is monitored automatically by the controller calculating a variable known as dS dt . This is known also as a derivative response or adaptive gain.

Adaptive Gain Rc

Td0

Td0

•

• dS/dt ~ 1

•

•

•

•

b = b1 + (b2

•

b1 is the Initial Safety Margin

•

b2 is the Safety On response

•

b3 is the Adaptive Gain response

•

When the operating point is moving

n) + ( b3

Td0

dS/dt)

quickly towards the SLL, the

dS/dt ~ 0

change in S with respect to time (dS/dt) is great

• 2 rr

q

When the operating point is moving slowly towards the SLL, the change in S with respect to time ( dS/dt) is small

2.2.2 S-value

The control action that opens the valve is of the Proportional Integral type (PI). Looking at the S-value of the Operating Point with respect to the Surge Control Line will change formula 8 to the next formula:

S=K×

H p red ,

Qs red 2

+ b × f ( ∆Po ) 1

(12)

,

Notice that the S in formula 12 has no subscript "s". The difference between this S and the Ss from formula 8 is that it equals 1 (one) when the Operating Point is situated on the Surge Control Line rather than on the Surge Limit Line.


2-12

Antisurge Control

The control action that opens the Recycle Valve uses the S-value as its Process Variable. As long as S is smaller than 1, the Output of the Antisurge Controller will be such that the Recycle valve will stay closed. When S grows bigger than 1, the Recycle Valve will be (PI) opened until S is again equal to, or less than 1. The operator interface of the Antisurge Controller does not show this S-value. Instead of that it shows, from the derived S value, DEViation.

DEV

Deviation:

= 1− S

(13)

Deviation is 0 (zero) when the Operating Point is situated on the Surge Control Line, positive on the right, and negative on the left side of the Surge Control Line.

Introducing the distance between the operating point and the Surge Control Line •

Because S > 1 (a positive) in the Surge region (a negative situation) We introduce parameter

•

DEV = 1 - S

The parameter DEV is independent of the size of the compressor and will be the same for each compressor in the plant

•

The parameter DEV is always the distance between the Surge Control Line and the Operating Point

SLL S= 1 SCL DEV =0

h h

r

•

S > 1

DEV < 0

• S S< < 1 1

DEV > 0

Surge margin (b1)

2.2.3 Flow Characterizer

: One standard surge parameter in the plant No operator confusion: • DEV > 0 Good • DEV = 0 Recycle line • DEV < 0 Bad

Benefits

2 rr

q

In formula 12, the function f ( ∆Po ) can be manipulated to create different shapes for the Surge Control Line. Most common is f ( ∆Po ) = 1 , the Control Line will then be shaped like the one in figure 8. If f ( ∆Po ) = 1 ∆Po , the Surge Control Line will be parallel to the Surge Limit Line. In C.C.C. documentation this function is called f ( ∆Po ) . 4

February 26, 2001

Antisurge Control

2.3 "RECYCLE TRIP" ALGORITHM

2-13

The Speed Curves in the Compressor Map are very flat in the region of surge. The effect will be that the flow will oscillate more when the Operating Point moves closer to surge. In other words, a small change in Polytropic Head will result in more change in Flow when the Operating Point moves closer to the Surge Limit Line. The control action that opens the Recycle Valve when the Operating Point is moving to the left of the Surge Control Line, is of the Proportional Integral type. This is a Closed Loop control action and is typically slow. Increasing the speed of control (smaller Proportional Band and/or higher Reset Rate) will have a negative outcome on the stability of the system. In the C.C.C. Antisurge Controller an extra line is added between the Surge Limit Line and the Surge Control Line.

SLL

H

RTL

SCL RT

p

O.P.

Q2 s


2-14

Antisurge Control

The extra line is called the "Recycle Trip Line" (R.T.L.). When the Operating Point crosses this line, an Open Loop response is initiated. This open loop control algorithm is added to the PI control to increase the speed of response of the control system. The objective is to prevent surge due to large or fast process disturbances. The distance between the Recycle Trip Line and the Surge Control Line is determined by the constant factor RT.

Rc

Output to Valve

SLL = Surge Limit Line RTL = Recycle Trip® Line SCL = Surge Control Line

qr2 Total Response PI Control Response

Recycle Trip® Response Time

February 26, 2001

Antisurge Control

2-15

The Recycle Trip algorithm opens the Recycle Valve with a step or series of steps with a magnitude defined by formula 14 and a time interval C2. Stepping up the opening of the Recycle Valve continues as long as the Operating Point stays on the left side of the Recycle Trip Line and the movement is in the direction of the Surge Limit Line (positive dS dt ). Eventually the Recycle Trip algorithm closes the Recycle valve exponentially. This closing begins when the Operating Point crosses the Recycle Trip Line again but this time going away from the Surge Limit Line. For Series 2, 3, or 3+ the valve will close approximately 2/3 (actually 63%) of the way during the first Tl (lag time) and the remainder during the next three Tl's for a total of four Tl‘s whether starting at 100% open or 10% open. Tl is in seconds so if Tl is set to 60, it would take about four minutes for the valve to close. In Series 4, the valve closes with an adjusted Ki (reset rate).

OUTPUT Quick Opening

Slow Closing

Step 3 Step 2 Step 1 C2

C2

Step magnitude:

TL

TIME

|RT| = C1(Td1•dS/dt - C0•dRT)

(14)

The magnitude of each step is further subject to the restriction that the term between brackets has a value between 0 and 1. The slow closing part of Recycle Trip provides a smooth transition from the sharp action of the open loop response back to the more precise PI response.


2-16

Antisurge Control

2.4 "SAFETY ON" ALGORITHM

Surge could still occur if parameters are incorrectly set (or have been changed), if transmitters are improperly spanned, if impulse lines are plugged (or contain moisture), or if a process valve (Check Valve or Recycle Valve) response has deteriorated (either is stuck or trim is plugged causing reduced flow). In this event, an adaptive surge detection algorithm in the Antisurge Controller will detect the Surge Cycle and take measures to prevent this from happening again. Surge can be detected in two ways: using the "Safety On Line" (S.O.L.) or using a "Surge Signature".

2.4.1 Surge Detection using the "Safety On Line"

In paragraph 1.3.1 it shows that when a compressor experiences surge, the Operating Point will jump form the Surge Limit Line to the left side of the vertical axis (negative flow). In the Antisurge Controller this surge is normally detected with a detection line situated on the left side of the Surge Limit Line. This line is called "Safety On Line" (S.O.L.) and initiates the "Safety On" Response.

SOL

H

SLL RTL

SCL

SO p

O.P.

Q2 s

February 26, 2001

Antisurge Control

2.4.2 Surge Detection using a "Surge Signature"

2-17

In some cases the flow measurement system damps the flow signal in such a way that peaks of the internal compressor flow will not be visible. This can happen when the orifice or venturi tube is located at a considerable distance from the compressor, or if the characteristics of the impulse lines to the transmitter are not optimal (too long, too small, filled with fluid etc.). This could lead to a situation that the controller does not notice the Operating Point moving to the left side of the Safety On Line, which in turn means that the controller does not detect surge. If this is the case, the controller can use an additional method of detecting surge .

Surge Occurs

Flow

Rate of Change

Discharge Pressure

Rate of Change

At the moment of surge, the "Rate of Change" of the flow signal and the "Rate of Change" of the pressure signal will both be maximum (either negative or positive). The Safety On algorithm can monitor these signals and look for a Rate of Change greater than a pre-selected threshold. The following modes can be used to initiate the "Safety On" Response: 1:

Rapid Change in both Flow and Pressure signal.

2:

Rapid Change in either Flow or Pressure signal.

3:

Rapid Change in Flow signal only.

4:

Rapid Change in Pressure signal only.


2-18

Antisurge Control

2.4.3 "Safety On" Response

The "Safety On" Response will be triggered by one of the surge detection methods. This response will limit both the number of surge cycles which do occur and the likelihood of their recurrence. The Safety On algorithm increases the Safety Margin (initially determined by the b1 factor) each time a surge is detected. The additional safety is determined by the b2 factor. After the first surge cycle the Safety Margin is b1 + b2, after n surge cycles the Safety Margin has grown to b1 + (n x b2).

SOL SLL

H

(RTL)

(SCL)

RTL SCL

p

RT

b1 + b2

O.P.

Safety Margin = b1 + n × b 2

Q2 s

The Safety On Response allows Operations time to sit down with Maintenance, Engineering, Management and CCC if necessary in an attempt to find out why this response was triggered and to solve the associated problem. Once the determination has been made and the problem has indeed been corrected, then and only then is it safe to press the RESET key and extinguish the Safety On lamp thus resetting the actual Safety Margin to the initial Safety Margin b1.

February 26, 2001

Antisurge Control

2.5 SUMMARY (EXAMPLE)

2-19

This paragraph describes an example of an Operating Point moving through the Operating Map and initiating specific Antisurge Controller control actions.

SOL

H

SLL RTL

D C

p

B

SCL

E

A

O.P.

Q2 s

Step 2 Step 1

output

A

B

C

D

E

Time

When the Operating Point moves from point A to B, the Recycle Valve stays closed. At point B the valve is opened gradually on PI control. Crossing of the Recycle Trip Line (point C) will initiate the first Recycle Trip step. If the Operating Point still moves towards the Surge Limit Line after C2 seconds (point D), the second step is created. Assuming that this action turns the Operating Point around, The Valve would begin closing when the Operating Point crosses the R.T.L. again going the correct direction.


2-20

Antisurge Control

February 26, 2001

Additional Control Functions

3-1

Chapter 3: Additional Control Functions 3.1 Pressure Limiting

The Antisurge Controller can also limit a maximum discharge pressure or minimum suction pressure (plus a maximum compression ratio Pd/Ps in Series 4) by increasing the opening of the recycle valve. These limiting functions open the recycle valve and does not conflict with antisurge protection.

Limiting Ps or Pd using the antisurge controller VSDS Compressor

FT 1

Suction

•

Ps T 1

PdT 1

Discharge

UIC 1

The antisurge controller can be configured to limit: • Maximum discharge pressure (P ) • Minimum suction pressure (P ) • Both maximum P and minimum P This does NOT conflict with antisurge protection d

s

d

•

s


3-2


3.2 Actuator Output Conditioning

It is desirable to have the best control valve for antisurge control. Sometimes, especially during a retrofit, acquiring a new valve may be cost prohibitive. In this case, the Antisurge Controller has algorithms for actuator output conditioning that may help overcome any undesirable valve characteristics that may exists in the installed valve. The actuator output may be modified by the following algorithms: • Valve Flow Characterization adapts the controller to valves with non-liner characteristics. • Valve Dead Band Compensation adapts the controller to valves with worn actuator linkages. • The Output Clamps limit the control signal’s range. The Remote Low Output Clamp allows a companion device to increase the low clamp (and thus the minimum recycle rate). • The Tight Shut Off Response fully closes the control valve when it is at its low clamp position and the operating point is safely to the right of the surge control line. • Output Reverse adapts the controller to a signal to-close or signal-to-open valve. • Output Tracking keeps the control signal equal to a specified analog input whenever a discrete input is asserted.

February 26, 2001


3.2.1 Valve Flow Characterization

3-3

If your control valve exhibits inherently non-linear flow, you can render its actual flow linear with respect to the intended flow rate by selecting an appropriate Valve Flow Characterizer. The following figure illustrates the relationship between the intended recycle flow and intended valve position for each pre-defined characterizer:

Valve Flow Characterization Intended Valve Position

m r rit aeni ev l la V

m ge tri enta e lv rc Va l pe ua eq

g n i mi nep r o t ev kci laV uq

Used to improve controllers operation when non-linear valves are used

Control Response (Intended Flow)

• • • •

Often used on retrofits to avoid additional investment in a new valve Works well with equal percentage characteristics Works less satisfactory with quick opening characteristics Can be custom characterized by 10-pt linear interpolation in Series 4. For quick-opening valves, the flow is assumed to be proportional to the square root of the fractional valve opening. Thus the control signal is obtained by squaring the intended flow rate calculated by the control algorithms. If the intended flow is 50 percent (1/2), for example, the valve position would be 2 25 percent [(1/2) = 1/4]. For a signal-to-open valve with a 4-to-20 mA actuator, the output signal would be 8 mA. Conversely, the flow rate for an equal-percentage valve is assumed to be proportional to the square of the fractional valve opening. Thus the control signal is obtained by taking the square root of the intended flow rate. For example, if the intended flow is 25 percent (1/4), the valve position would be 50 percent (1/2). For a signal-to-open valve with a 4-to-20 mA actuator, the output signal would be 12 mA.


3-4


Due to wear or design imperfections, the positioning of a control valve might exhibit a dead band which must be overcome when the control action reverses direction. The Antisurge Controller can counter this effect by adding or subtracting a Valve Dead Band Bias to the intended valve position.

Signal

3.2.2 Valve Dead Band Compensation

OUT 1

to tua c A

Int

d en

r

o n tr o C

V ed

e alv

al ig n S l

s it Po

ion

Time This bias is added when the control response is rising and subtracted when it is falling. Thus, a change in the control response’s direction produces a step change in the control signal with a magnitude equal to twice this bias. It is better to set this bias slightly too high (as opposed to too low), so that a change in the direction of the control action will actually reverse the movement of the valve. A small antisurge PI loop dead zone should then be configured to prevent such movements from causing valve “chatter” when operating on the surge control line. Valve dead-band compensation can be disabled by assigning its bias a value of zero.

Note:

February 26, 2001

This feature will not move the actuator control signal beyond either of its output clamps.


3.2.3 Output Clamps

3-5

The range of the actuator control signal (ACS) is defined by the Output Low Clamp and Output High Clamp. These clamps are implemented by raising or lowering the accumulated integral response as needed to keep the ACS within the specified range. These clamps are entered as the minimum and maximum intended valve positions, which correspond to the highest and lowest values that would be displayed on the front-panel OUT readout. That is, the output will be constrained such that OUT never displays a number less than OUT LOW or higher than OUT HIGH. Any Valve Open relays will be triggered whenever the actuator control signal is greater than the low output clamp.

Note:

Because these clamps apply only when the controller is operating automatically, they do not restrict your ability to manually adjust the actuator control signal. When setting these clamps, keep in mind that they are applied after flow characterization and valve dead band compensation but before the tight shut-off response and output reverse. A 4-to-20 mA output is automatically generated with an offset zero, so you do not have to define that offset by setting the corresponding output clamp.

Remote Low Output Clamp

The Antisurge Controller can be configured to use the output of another controller as its Remote Low Output Clamp when that signal is less than the low output clamp. This prevents the Antisurge Controller from reducing its output below that of the remote device, without risking integral windup or restricting its ability to open the valve as needed to prevent surge. In contrast to Output Tracking, this feature holds the recycle valve open far enough to satisfy both controllers. If the Output Reverse feature is set up for a signal-to-close valve, the complement of the designated signal is used as the remote low output clamp. The remote device must then be set up to decrease its output when a higher low clamp is desired.


3-6


Note:

The remote low clamp is ignored when the controller is operating in its Stop or Purge state. It does apply to manual operation, in which event raising the remote clamp can increase the displayed output (and open the valve) but lowering it will have no effect. The remote low output clamp will be ignored if the specified signal variable is outside its transmitter testing limits.

3.2.4 Tight Shut-Off

The Tight Shut-Off response can be used to fully close the recycle valve when the operating point is to the right of the Tight Shut-Off line and the output is already at its minimum clamp. This line is always to the right of the SCL

The Tight Shut-Off Line (Pressure)

Hp

SLL

SCL The Tight Shut-Off Line

Tight shut-Off Line

defines the minimum SCL DEViation above which the Tight Shut-Off Response can reduce the recycle valve output

to

zero.

Qs2

(Flow)

3.2.5 Output Reverse

The output may be configured for a Fails-Open valve (reverse acting) or for a Fails-Closed valve (direct acting). Surge control normally uses a Fails-Open valve

3.2.6 Output Tracking

In a redundant Series 3 Plus system, the redundant controller will track the output of the primary controller when the tracking discrete is asserted. In Series 4 the Output is calculated and verified in the Backup controller independently.

February 26, 2001


3.3 Operating States

There are several Operating States of the Antisurge Controller that are part of the Automatic mode of control where the Antisurge controller modulates the recycle valve

Table 3-1 Operating states Name

Run

Stop

3.3.1 Operating State Transitions

3-7

Display

Description

RUN

The compressor is loaded and the control response is being varied to prevent surge.

OFF

This compressor section is unloaded but the valve is being modulated to protect another.

STOP

A normal shutdown was or is being used to idle or shut down the compressor.

ESD

An emergency shutdown was used to idle or shut down the compressor.

Purge

PURGE

The compressor is unloaded but the recycle valve is fully closed.

Track

TRACK

Actuator control signal is tracking the output of another device or controller.

Transitions between states occur as follows: • When its compressor is stopped or idling, an Antisurge Controller operates in a Stop state that fully opens the recycle valve. If the compressor is stopped, this minimizes any reverse flow or rotation that might occur if the discharge check valve leaked. If it is idling, this minimizes the drive power and risk of surge. • If the compressor is then purged, the Antisurge Controller can select a Purge state that fully closes the recycle valve so purge gas can be forced through the compressor. • When the compressor is loaded, the Antisurge Controller selects its Run state, which reduces the recycle rate as much as possible without risking surge. It will continue to modulate that valve as needed to prevent surge with a minimum of recycling as long as the compressor is running. • While the compressor is being unloaded, the Antisurge Controller will either ramp its recycle valve open (a normal shutdown) or open it as fast as possible (an emergency shutdown).


3-8


The controller startup and shutdown features initiate and stop the continuous recalculation of its output signals, thus providing transitions between its Run and Stop operating states. While these might be used to sequence a compressor startup or shutdown, they can alternately be set up to load and idle a running compressor.

3.3.2 Manual Operation

In Series 3 Plus, when manual operation is selected, momentarily pressing the Raise or Lower key will change the actuator control signal by 0.1 percent, holding either down changes it at a steadily increasing rate. The resulting value can be monitored via the OUT readout, an analog output assigned the Out function, or the Displayed OUT input register. Alternately, the control signal can be set directly by writing to the Actuator CS holding register. In Series 4, the Manual Target is normally used to select the desired output for the actuator. Alternately, the control signal can be set directly by writing to the MODBUS Manual Target holding register if configured or through an OIS. Although the Output Clamps do not apply in manual, the Remote Low Output Clamp does. Thus, you can raise the control signal above the high or reduce it below the low clamp parameter, but cannot reduce it below an analog low clamp. While in manual, the controller will continue to calculate and display the deviation between the operating point and the surge control limit, so you can tell if the compressor is moving too close to surge by watching the DEV readout. Pressure Limiting is suspended during manual operation.Initiating Manual

3.3.3 Manual Override

February 26, 2001

Manual Override is a parameter that is used to set the how the controller will react in the Manual Operation. When the controller is in Manual and the MOR is set “OFF” (or “Soft” manual), the controller will switch back to the AUTOmatic Mode if the Operating point crosses the RTL. If the MOR were set to “ON” (or “Hard” manual), the controller will continue to stay in manual even if the compressor is surging.


Caution:

3-9

CCC always recommends setting the MOR parameter to “OFF” since it disables all surge protection while the controller is in the Manual Operation

Manual Override (MOR) Normally, the Antisurge Controller will transfer from MANUAL to AUTOMATIC operation when the operating point of the compressor crosses the Recycle Trip

Line.

The MOR function allows MANUAL to

SLL

RTL

override this feature. dPc

• •

SCL

Manual Manual override override is is normally normally set set to to OFF. OFF. Manual Manual override override must must be be ON ON for for “Hard “Hard Manual” Manual” operation operation

The Manual Override function is typically turned on during maintenance and troubleshooting of control inputs such as transmitters. Once the controller is placed in the Manual Operation by the operator, the maintenance technician can manipulate the input signal for loop verification and calibration without the controller accidentally switching to the Automatic Mode and opening the recycle valve. The operations personnel must monitor the DEViation during this period since there will be no surge protection by the controller. The operator can open the recycle valve to protect the compressor during a disturbance at this time.


3-10


3.3.4 Loop Checks With the Compressor On-Line

This section details the procedure for performing loop checks on-line. Step 1: Unlock engineering keyboard on the Antisurge Controller so that parameter changes can be made. This is accomplished as: Step 2:

Step 3: Step 4:

Step 5: Step 6: Step 7:

Step 8:

Note:

February 26, 2001

Set MOR to 'On'. This is accomplished as: MODE:A MOR 1 Using the front operations panel, put Antisurge Controller in Manual. Using the 'Up' arrow on the front operations panel, open the antisurge valve to a level that will protect the machine under all circumstances. Perform loop check or transmitter calibration. Using the front operations panel, put Antisurge Controller in Automatic. Set MOR to 'Off'. This is accomplished as: MODE:A MOR 0 Lock engineering keyboard on the Antisurge Controller so that parameter changes can not be made. This is accomplished as:

It is possible to perform this work without using step 4, opening the antisurge valve, if so desired. This is not advised by CCC but can be done if process conditions warrant. Be advised that there will be no surge control of any kind during this time and the machine will be completely unprotected.

Series 3 Plus Gains and Biases

Chapter 4:

4-1

EXAMPLES Transmitter Pd Ps

Range 0-200 psig 0-100 psig

If the Signal on Both Transmitters are 50% and: Pd = 100 psig SV2 = 0.50 Ps = 50 psig SV3 = 0.50 Then the Ratio of the Compressor is: + 14.7 Rc = =100 50 + 14.7

1.77

If the Controller Has No Gains and Biases, it will calculate RC as: Rc = =0.50 0.50

1.00

WHICH IS NOT CORRECT !

S3OP_AS_GB Antisurge Application Training Manual

4-2

Series 3 Plus Gains and Biases • How

to calculate Gains and Biases for this example: Pd

Gain 2

Pd

Bias 2

Ps

Gain 3

Ps

Bias 3

200 200 +14.7 14.7 200 +14.7 100 200 +14.7 14.7 200 +14.7

= 0.932 = 0.068 = 0.466 = 0.068

Pd = Gain 2• SV2 + Bias 2 Ps = Gain 3• SV3 + Bias 3 Pd1 = 0.932• 0.50 + 0.068 = 0.534 Ps1 = 0.466• 0.50 + 0.068 = 0.301 ∴ Rc1 = = 0.177 = Rc

February 26, 2001


4-3

Gains and Biases Chart Input ∆ Po

(Flow)

Channel ∆Po ∆Po, span

CH1 =

Transmitter

Gain

Bias

∆ Po,span

0.999

00.0

Pd

Pd - PdL CH2 = Pd, span

Pd,span

Pd, span Pd, span + PdL

PdL Pd, span + PdL • 100

Pd

CH2 =

Pd - PdL Pd, span

Pd,span

Pd, span Pd, span + Patm + PdL

Patm + PdL • 100 Pd, span + Patm + PdL

Ps

Ps − PSL CH3 = Ps, span

Ps,span

Ps, span Pd, span + PdL

PsL Pd, span + PdL • 100

Ps

CH3 =

Ps,span

Ps, span Pd, span + Patm + PdL

PsL • 100 Pd, span +Patm + PdL

Ps

Ps − PSL CH3 = Ps, span

Ps,span

Ps, span Pd, span + PdL

Patm + PsL • 100 Pd, span + PdL

Ps

CH3 =

Ps,span

Ps, span Pd, span + Patm + PdL

Patm + PsL • 100 Pd, span + Patm + PdL

(abs)

(gauge)

(abs)

(abs)

(gauge)

(gauge)

Ps − PSL Ps, span

Ps − PSL Ps, span

(abs)

(gauge)

(abs) {with Pd,span = (abs)}

(abs) {with Pd,span = (gauge)}

(gauge) {with Pd,span = (abs)}

(gauge) {with Pd,span = (gauge)}

N

CH4 =

N − NL Nspan

Nspan

0.999

00.0

Td

CH5 =

td − tdL td, span

td,span

td, span td, span + 460 + TdL

460 + TdL td, span + 460 + TdL • 100

Ts

CH6 =

ts − tsL ts, span

t s,span

ts, span td, span + 460 + TdL

460 + TsL • 100 td, span + 460 + TdL

0.999

00.0

(Speed)

(deg F)

(deg F)

α

(Angle)

CH7

S3OP_AS_GB Antisurge Application Training Manual

4-4


February 26, 2001

Series 3 Plus Antisurge Contoller Fallback Strategies

5-1

This procedure details all the Fallback Strategies available for Series 3 Plus Antisurge Controllers Increase compressor system reliability and availability with fall-back strategies • •

• •

•

Over 75% of the problems are in the field and not in the controller The CCC control system has fall-back strategies to handle these field problems The controller continuously monitors the validity of its inputs If an input problem is detected the controller ignores this input and automatically switches to a fall-back mode Benefits – Avoids nuisance trips – Alarms operator of latent failures – Increases machine and process availability

Constant If the suction flow-measurement input should fail, the only Output (Mode recourse is to open the antisurge valve far enough to prevent fD31) surge under the worst possible process conditions.

The corresponding fallback mode is enabled by setting Mode fD 31 to "ON". Then, when the signal to analog input CH1 is outside its acceptable range, the controller will revert to manual control and ramp its output to the level set by COND CONST 1. Assuming that you would want to open the recycle valve 99.9%, enter: MODE:A fD 31 1 COND:A CONST 1 999

S3OP_AS_FB Antisurge Application Training Manual

5-2


Minimum Flow Presuming that the flow input (CH1) is judged reliable but other Control (Mode input(s) are not, surge can often be prevented by maintaining the fD32) value of the flow signal above some minimum level. The corresponding fallback mode is enabled by setting Mode fD 32 to "ON". The controller can then resort to maintaining PV1 (the internal process variable corresponding to flow input, CH1) above the local setpoint, the initial value of which is set by COND CONST 2. That value is usually calculated as S = 1 = (CONST 2 / ∆Po',min) + b, where ∆Po',min is the value of PV1 at the desired minimum flow, which is CH1 (at that point) after a gain and bias has been applied. So, if ∆Po,min = 50" H2O and the flow transmitter span = 0 to 125" H2O, SV1 would equal 50/125 or 0.4 and since the gain and bias on CH1 is usually equal to 1 and 0 respectively, ∆Po',min = PV1 = SV1 = 0.4. So, solving for CONST 2 yields CONST 2 = (1 - b1) * (∆Po',min) or, if b1 = 20%, CONST 2 = (1 - 0.2) * (∆Po',min) = (0.8) * (0.4) = 0.32. Enable this strategy (with this example value) as:

MODE:A fD COND:A CONST

Default Compression Ratio (Mode fD 33)

32 2

1 320

The controller can substitute a default compression ratio if the discharge pressure input (CH2) fails. The corresponding fallback mode is enabled by setting Mode fD 33 to "ON". The default compression ratio is set by COND CONST 3. Enable this strategy as: MODE:A fD 33 1 COND:A CONST 3 ###

Assumed If either of the temperature inputs fail (CH5 or CH6), adequate Sigma surge protection can often be achieved by substituting a (Mode fD 34) constant value for sigma.

The corresponding fallback mode is enabled by setting Mode fD 34 to "ON". The default value of sigma is set by COND CONST 4. Because the calculated value for sigma can prove unreliable during compressor start-up, CONST 4 will also be used as the start-up value for sigma. Enable this strategy as: MODE:A fD 34 1 COND:A CONST 4 ###

February 26, 2001


5-3

Fallback The controller can substitute an assumed rotational speed when Speed (Mode the speed input (CH4) fails. fD 35) The corresponding fallback mode is enabled by setting Mode fD 35 to "ON". The default speed value is set by COND CONST 5. Enable this strategy as: MODE:A fD 35 1 COND:A CONST 5 ###

Assumed When the chosen fa mode requires a Guide Vane Angle signal, Vane Angle the controller can substitute an assumed vane angle whenever (Mode fD 36) that signal goes outside its acceptable range.

The corresponding fallback mode is enabled by setting Mode fD 36 to "ON". The default vane angle is set byCOND CONST 6. Enable this fallback strategy as: MODE:A fD 36 1 COND: A CONST 6 ###

Assumed The controller can substitute an assumed adjacent stage flow Adjacent rate if the controller fails to receive that variable via serial Port 1. Stage Flow The corresponding fallback mode is enabled by setting Mode fD Rate 37 to "ON". The default flow rate (∆Po ) is set by COND CONST (Mode fD 37) 7. Enable this strategy as: MODE:A fD COND:A CONST

Alternate K for Valve-Sharing Controllers (Mode fD 38)

37 7

1 ###

When several Antisurge Controllers are used to protect a multi-section compressor with only one antisurge valve, the primary controller (the controller with MODE:A SS 1 enabled) can be setup to use a different Surge Limit Line Slope Coefficient (K) when it loses communication with one or more secondary controllers (those with MODE:A SS 2 enabled). This fallback strategy is enabled by setting Mode fD 38 to "ON". The default K value is set by COND CONST 8. Enable this strategy as: MODE:A fD 38 1 COND:A CONST 8 ####

S3OP_AS_FB Antisurge Application Training Manual

5-4


TemperatureBased Polytropic Head (Mode fD 39)

February 26, 2001

If the discharge pressure input fails (CH2), it is also possible to prevent surge by using the temperature ratio method of calculating reduced polytropic head (instead of the compression ratio method in Mode fD 33). Since it will still be necessary to use the default value for sigma (CONST 4), Mode fD 34 must also be enabled in order for Mode fD 39 to function. Mode fD 39 will be used in preference to Mode fD 33 (if both are enabled). The corresponding fallback mode is enabled by setting Mode fD 39 to "ON". Enable this strategy as: MODE fD 39 1

Series 3 Plus Surge Testing (Typical Procedures)

Chapter 6: Background Summary

6-1

The reason for performance testing or surge testing a compressor is to insure that the actual location of the so-called Surge Limit Line at any given point in time is known by or can be determined by the antisurge controller. The primary difficulty with this task is that the location of the Surge Limit Line (SLL) varies with changes in inlet conditions ... suction pressure, temperature, molecular weight, etc. This method for determining the distance from the compressors' so-called operating point to its associated surge point on the Surge Limit Line is discussed in detail in other CCC texts. In order to prevent a surge event it is necessary to know the relative distance between the operating point and the surge point for that specific performance level. Performance or surge testing and the use of the patented Compressor Controls Corporation algorithms based on reduced head versus reduced flow help insure that the relative distance from surge can be continually calculated from the required analog inputs. For a variable speed machine that can generate an appreciable compression ratio with variable molecular weight the following analog inputs to the antisurge controller would be required: Analog input 1 ∆ Po,sDifferential Pressure across flow measuring device in the suction of the compressor (discharge flow can be used with appropriate change in algorithm) Analog input 2 Pd Discharge Pressure, with tap as close as possible to discharge of compressor Analog input 3 Ps Suction Pressure, with tap as close as possible to suction of compressor Analog input 4 N Rotational Speed of compressor Analog input 5 Td Discharge Temperature, with tap as close as possible to discharge of compressor

S3OP_AS_ST Antisurge Application Training Manual

6-2


Analog input 6 Ts Suction Temperature, with tap as close as possible to suction of compressor The choice of performance testing or surge testing a compressor is based upon your confidence in the accuracy of the manufacturers' compressor map. This map be have been generated by bench testing the compressor or by computer simulation. Bench testing is usually done with nitrogen or air, which may not be the gas you are compressing, which can lead to discrepancies between actual and predicted surge points. Maps are also created holding suction conditions constant. Another reason for surge testing may be that the geometry of the compressor has changed due to damage of the compressor seals caused by repeated and numerous surge cycles during the compressors' history, corrosion of the wheels due to caustic fluids, or the deposit of waxes on the wheels. Since the severity of a compressor surge is determined by its performance level (the lower the performance, the smaller the surge event) and the speed of the compressors' operating point when it crosses the Surge Limit Line (the lower the velocity, the smaller the surge event), the first step in conducting a performance or surge test would be to initially test a machine at low performance level. The second step is going to be to insure that you bring the operating point across the Surge Limit Line at the lowest possible velocity. The tests would then be repeated for progressively higher performance levels. So for a given test, you have two goals ... first, find the surge point for that performance level (the parameter SPEC RESP:A K, the inverse slope of the Surge Limit Line) and second, to not damage the machine in the process. Therefor you would need to somehow bring the operating point just to the right of an unknown location (the SLL), bring it to a complete stop and then just barely allow it to move into the SLL, at the lowest possible velocity (to insure no damage to the machine) and then to, of course, immediately stop the surge event ... to limit the surge event to one small cycle of surge. So the primary task is how to do just that, to somehow bring the operating point just to the left of an unknown location (the SLL), bring it to a complete stop and then just barely allow it to move into the SLL. Let's examine the following techniques.

February 26, 2001


Surge Testing in AUTOmatic

n n n n n n n n

n

n n

n

6-3

Hold Rotational Speed Constant Put Antisurge Controller in Manual Open Antisurge Valve 100% Block Compressor in Using Discharge Block Valve Throttle Inlet Valve to Reduce Flow Set Antisurge Controller Parameters for Test Put Antisurge Controller in Automatic Operating Point Will Sit on Control Line Keeping Valve Open Slowly Reduce “K” Value, thus “artificially” Closing Valve Repeat Until Compressor Surges Recycle Trip and Safety On Responses will Bring Controller Out of Surge After One Surge Cycle “K” Value on Engineering Display Represents Location of Surge Limit Line

Step 1: First, reduce the flow somewhat through the compressor (possibly with an inlet throttling valve), with the antisurge valve closed. Step 2: Next, hold compressor at a minimum performance level with the CCC Performance Controller in MANUAL. Step 3: Put the Antisurge Controller in MANUAL and open recycle valve 100%. Step 4: If possible (and / or desirable), isolate compressor from the process (probably with a discharge block valve), so that the upcoming surge event and its associated disturbance do not upset the process. Step 5: Disable all derivative responses (Set MODE:A fC 3 and MODE:A fC 4 to OFF). This is so that during the performance test, the location of the Surge Control Line (SCL) cannot move automatically (fC3) and that the opening of the antisurge valve on Recycle Trip (RT) is a fixed amount, not altered by the speed or velocity of the operating point (fC4). Step 6: Disable all Fallback Strategies (Set MODE:A fD31 through fD39 to OFF). Step 7: Set SPEC RESP:A b1 to 00.0 (this puts the SCL on top of the SLL). S3OP_AS_ST Antisurge Application Training Manual

6-4


Step 8: Set SPEC RESP:A b2 to 40.0 (this will create a large margin of safety at the moment of a Safety On Response). Step 9: Set SPEC RESP:A RT to 05.0 and SPEC RESP:A SO to 10.0 (this puts the RTL and SOL just to the left of the SCL and SLL). Step 10: Set SPEC RESP:A C1 to 30.0 and SPEC RESP:A C2 to 0.40 (this sets the recycle trip valve opening to exactly 30% for 0.4 second). Step 11: Set SPEC RESP:A TL to 200 (this closes the recycle valve 63.2% of its total in approximately 200 seconds and closes it completely in approximately 800 seconds once the operating point returns to the right of the RTL and SCL). Step 12: Set PID:A PB 1 to 200 and PID:A Kr 1 to 04.0 (this sets the PI tuning constants to average, conservative values). Step 13: Set SPEC RESP:A K to .999 (this moves the SLL and therefor the SCL out to the right as far as possible). Step 14: Put the Antisurge Controller in AUTOmatic. DEViation will be positive and therefore PI control will start to close the recycle valve until DEViation is zero. Step 15: Reduce SPEC RESP:A K by a small amount. This amount can vary based upon experience and confidence, but .010 per step should be safe. DEViation will again be positive and therefore PI control will start to close the recycle valve until DEViation is again zero. Monitor vibration levels to give yourself the option of aborting the test if excessive levels are reached. If vibration levels are reached that you want to avoid in the future, abort the test at this point and use the value of SPEC RESP:A K appearing on the engineering panel display. Step 16: Repeat step 15 pausing to let operating point stabilize when DEViation becomes zero. At some point, the entered K value will reach the value representing the actual inverse slope of the SLL. At this point, the drop in DEViation (thus crossing the RTL and SOL) will cause a recycle trip response lasting until the operating point, moving to the right, crosses the RTL

February 26, 2001


6-5

which is now 35% (SPEC RESP:A b1 minus SPEC RESP:A RT) to the right of the SLL. Step 17: Put the Antisurge Controller in MANUAL and open the recycle valve 100%. Step 18: Note the value of SPEC RESP:A K. Step 19: Repeat steps 3 through 18 at several higher performance levels. Perform a total of at least three (3) surge tests for a variable speed machine. Instead of starting with the value of SPEC RESP:A K as .999, multiply the value of SPEC RESP:A K from the previous test by 1.1 and begin with that value for SPEC RESP:A K. Step 20: Enter the largest SPEC RESP:A K value from all tests into the Antisurge Controller, or even better, enter SPEC RESP:A K as .500 and calculate the appropriate function characterizer(s) required by the fA mode of the controller (MODE:A fA). Sometimes closing the recycle valve fully may not bring the compressor to surge. In this case, open the recycle valve in MANUAL as noted in step 3, throttle the inlet valve more, reducing the flow, and then repeat the technique of closing of the recycle valve in AUTO. This will then bring the compressor into surge and the procedure can be repeated for various performance levels.

Surge Testing in MANUAL

Under some circumstances surge testing of a compressor by closing the recycle valve in AUTOmatic is not possible. This applies to compressors where the recycle valve cannot be opened continually due to the absence of a cooler in the recycle line. In this case, another element such as a control valve in discharge can be gradually closed until the compressor surges. The engineer adjusts the SPEC RESP:A K parameter so that DEViation is equal to .000 while the discharge valve is closing. This will require that the engineer and the manual operator of the discharge valve are in constant radio communication with each other. Once the compressor surges, the drop in deviation will trigger Recycle Trip and Safety On responses and the location of the actual Surge Limit Line at that performance level is known as the value SPEC RESP:A K as seen on the engineering panel display.

S3OP_AS_ST Antisurge Application Training Manual

6-6


Warning!

Warning and Disclaimer: Compressor Controls Corporation does not warranty these techniques nor accepts responsibility for their execution by any other than duly authorized employees of Compressor Controls Corporation. These techniques are for your information only and under no circumstances should the existence of this document and its contents be construed as a fool-proof blueprint of performance or surge testing. Do not use these techniques without consent and approval of your senior corporate management and without the complete knowledge and understanding of surge control theory and the consequences of its inappropriate application.

Surge Testing On-Line

If the discharge piping cannot be isolated, surge testing must be performed on-line. By some means the operating point must be moved to the left, either by increasing discharge pressure or decreasing volumetric flow rate. Typically this is done by throttling a valve located downstream of the compressor. By closing this valve, the discharge pressure rises and the flow rate decreases. Now, by artificially closing the recycle valve in AUTO as described in the previous section, the compressor can be brought to surge. Sometimes closing the recycle valve fully may not bring the compressor to surge. In this case, open the recycle valve in MANUAL as in the previous section, throttle the discharge valve more, and repeat the closing of the recycle valve in AUTO. This will then bring the compressor into surge and the procedure can be repeated for various performance levels.

Determining Surge Line without Surge Testing

February 26, 2001

If the estimated performance curve of the compressor is to be used for establishing the Surge Line, the following procedure is used: The Surge Control Line parameters are set from the estimated performance curves or as determined in the Engineering Manual for the job. It is important to determine that the Surge Line thus established is not under conservative. The actual surge line should not be to the right of the estimated surge line. The operating point needs to be pushed to the left right on top of the estimated surge line and the compressor should not surge. Again, it will be easier to test this while the compressor is isolated from the process.

Series 3 Plus Antisurge Controller Operating Principles

Chapter 7:

7-1

SWITCHES Auto / Manual Switch

- Press to select automatic or manual operation. Reset Safety On Switch - Press to reset the controller for normal operation after a surge occurs (red light, SAFETY ON) Display Surge Count Switch - Press to display the number of surges in the ALT display that has occurred since the last reset of the Safety On. Display Limit Switch - Press to display the limiting variable in the DEV display, the limiting setpoint in the ALT display and which variable (Discharge or Suction) is being displayed in the AUX display. Up-Arrow/Down-Arrow Switch - Press to move the Antisurge output when in manual operation. Menu Switch - Press to display controller status or variable information in the display window. Scroll Switch - Press to select the display variable to be viewed on the display window.

S3OP_AS_OP Antisurge Application Training Manual

7-2


INDICATORS Label

Color

Meaning

What Can I Do?

Auto

Green

When lit, the controller is in the Automatic mode of operation.

You can switch to the Manual mode of operation using the Auto/Manual switch.

Manual

Yellow

When lit, the controller is in the Manual mode of operation. When flashing, Manual Override (MOR) is on.

You can switch to the Automatic mode of operation using the Auto/Manual switch.

RT

Yellow

When lit, the Recycle trip is active or the Margin of Safety is less than the RT threshold.

Nothing. This is a warning that a disturbance has occurred which the PI response could not compensate for but the RT response could. It is part of the normal operation of the controller.

SO

Red

When lit, the controller has detected a surge condition and has enabled a SAFETY ON response. This also means the surge count is greater than zero.

You should first determine what caused the SAFETY ON response: i.e. blocked discharge piping, damaged recycle valve, process conditions, etc. You can determine the number of surge conditions detected by pressing the Display Surge Count switch. You can reset the SAFETY ON and set the surge count to zero by pressing the Reset Safety On switch.

Limit

Yellow

When lit, the controller is in a limiting condition because the Discharge or Suction limiting variable is beyond their defined limiting threshold.

You can determine the value of the limiting variables by pressing the Display Limit switch. The controller will minimize the limiting condition by opening the recycle valve as needed. If possible, the process should be adjusted to prevent the limiting condition.

Tracking

Green

When lit, the controller is in a redundant operating mode and is tracking the active controller.

You can switch to the active operating mode by selecting this controller on the Redundant Control Selector.

TranFail

Red

When lit, one or more analog inputs are outside AN IN limits. It is not unusual to also see the Fallback indicator lit as well.

You can determine which analog input(s) triggered the TranFail alarm by using the MODE:D AN IN - (minus) key sequence on the Engineering Keypad. Use the scroll button to step through the successive channels.

Fallback

Yellow

When lit, the controller has enabled a Fallback control strategy due to the failure of analog and/or serial input(s).

You can check to see if the TranFail or ComErr indicators are lit. Then follow the procedure to determine the failed input for that indicator.

ComErr

Red

When lit, it indicates a serial communication error. It is not unusual to also see the Fallback indicator lit as well.

You can determine which serial input(s) triggered the ComErr alarm by using the MODE:D COMM - 2 (Serial Port 2), or MODE:D COMM - 3 (Serial Port 1) key sequence on the Engineering Keypad.

Fault

Red

When lit, an electronic failure has been detected within the controller. Disconnect it from the process

The controller’s output signal is totally unpredictable when the Fault indicator is lit. Process disruptions or compressor damage can result if it is not immediately disconnected from your process. You can replace this controller with your spare controller. (See the section: “Controller Change-Out”)

February 26, 2001


7-3

AUXILIARY These are what can be viewed in the Auxiliary Window display. WINDOW (Note - some of the displays may not be needed for your application)

For Display Status

RUN/STOP/ OFF/PURGE /TRACK)

...Press Menu Button

...Press Menu Button

Differential Pressure

ÎPo)

Polytropic Head Exponent

Discharge Pressure

D Press)

Compression Ratio

Suction Pressure

S Press)

Temperature ratio

Speed)

Speed

Rotational Speed

Discharge Temp

Mass Flow Rate

(

...Press Scroll Button

(

Sigma)

(

Rc)

(


(

Rt)

(

...Press Scroll Button (


D Temp)

(


(

Speed)

(

Flow)

(

Suction Temp

S Temp)

(


User Defined


User Defined

Chan 7 Chan 8

S3OP_AS_OP Antisurge Application Training Manual

7-4


February 26, 2001

L COMPRESSOR CONTROLS CORPORATION

Series 3 Plus Antisurge Controller Configuration Planner CCC No.: ____________________________

Completed By: ___________________________

Customer: ____________________________

Date: ___________________________

Tag No.: ____________________________

Software Rev.: ___________________________

S/N: ____________________________

Checksum: ___________________________

®

Service: ______________________________________________________________________ ______________________________________________________________________ Controller ID Number (1 to 8): ________________

Computer ID Number (1 to 64): _____________

Proximity to Surge (Application Function) Application Function ________ 00, 01, 31, 33, 34, 35, 46-48, 50, 51, 61, 62, 64-69* Surge Limit Line Coefficient ________ normalization constant for S Initial Surge Control Bias ________ % DEV Filter Constant ________ seconds 00.0 to 99.9 Sigma Filter Constant ________ seconds 000 to 999 Constant Sigma Off / On fA modes 65 to 69 only

[MODE:A fA] [SPEC:A K] [SPEC:A b 1] [PID:A Tf 1] [PID:A Tf 2] [MODE:A fC 2]

*Available but not generally recommended application functions are 02, 32, 36 to 45, 52, 53

Input Signals ∆Pc Substitution Off / High / Low ∆Tc Substitution Off / High / Low Rotational Speed Source ________ Control Line Argument ________ Function 5 Argument ________

High for Pd, Low for Ps High for Td, Low for Ts Off for CH4 or Controller ID of source CH# of analog input, Off = ∆Po CH# of analog input, Off = σ

[MODE:A SS 6 1] [MODE:A SS 6 2] [MODE:A ANIN 4] [MODE:A fC 1] [MODE:A SS 9]

Off or CH# of analog input Off or A/S Controller ID for adjacent stage fA 34, 35, and 64 (0.00 to 9.99) fA 34, 35, and 64 (0.00 to 9.99) fA 34, 35, and 64 (–9.99 to 9.99) 00.0 to 99.9 CH# of analog input for mass flow Pc abs. pressure when input = 0 (00.0 to 99.9) CH# of analog input for mass flow Tc abs. temperature when input = 0 (000 to 999)

[MODE:A SS 8] [MODE:A SS 5] [SPEC:A C 3] [SPEC:A C 4] [SPEC:A C 5] [COND:A β 5] [MODE:D fD 2] [COND:D CONST 2] [MODE:D fD 3] [COND:D CONST 3]

Calculated Flows Flow Element Pressure Input ________ Adjacent Section Controller ________ Sidestream Flow Coefficient ________ Main Flow Coefficient ________ Combined Flow Coefficient ________ Mass Flow Coefficient ________ Comp. Pressure Input ________ Comp. Pressure Offset ________ Comp. Temperature Input ________ Comp. Temperature Offset ________

Calculated Variable Displays Polytropic Exponent Display Off / On Sigma Compression Ratio Display Off / On Rc Temperature Ratio Display Off / On Rt Rotational Speed Display Off / On Speed Rotational Speed Coefficient ________ rpm 0 to 99999 Mass Flow Display Off / On Flow Displayed Mass Flow Coef. ________ 0 to 99999 Flow Variables Decimal Position 0 / 1 / 2 / 3 / 4 for Flow and UsrQ Mass Flow Input ________ CH# of analog input for mass flow ∆Po, Off = UsrQ Net Mass Flow Display Off / On** Net Mass Flow Coef. ________ 0 to 99999

[COND:D DISPLAY 1 1] [COND:D DISPLAY 1 2] [COND:D DISPLAY 1 3] [COND:D DISPLAY 1 4] [COND:D DISPLAY 1 4 HIGH] [COND:D DISPLAY 1 5] [COND:D DISPLAY 1 5 HIGH] [COND:D DISPLAY 1 5 •] ∆Po,c [MODE:D fD 1] [COND:D DISPLAY 1 7] [COND:D DISPLAY 1 7 HIGH]

**If

enabled, you must configure the Mass Flow Display and define the Reported Flow [COND:A f(X) 2, see page 6] and Recycle Flow [COND:D f(X) 2, see page 8] characterizers.

Values above 999 display as A## and are entered as HIGH # # (102.4 displays as A2.4 and is entered as HIGH 2 4)

February, 2001

Page 5 of 12

FM301/L (5.0)

Series 3 Plus Antisurge Controller Configuration Planner CCC No.: __________________________

Tag No.: ___________________________

Date: ______________________________

Proximity to Surge (Continued) Characterizing Functions Y Coordinate Characterizer: Rc: 0.00 ______ f1 (Rc): ______ ______ 0

1

Reported Flow Characterizer: Rc: 0.00 ______ f2 (Rc): ______ ______ 0

1

______ ______

______ ______

______ ______

2

3

4

______ ______

______ ______

______ ______

2

3

4

Rotational Speed Characterizer: N: .000 ______ ______ f3 (N): ______ ______ ______ 0

1

Control Line Characterizer: X: .000 ______ f4 (X): ______ ______ 0

1

General Characterizer: X: .000 ______ f5 (X): ______ ______ 0

1

2

______ ______

______ ______

3

4

______ ______

______ ______

______ ______

2

3

4

______ ______

______ ______

______ ______

2

3

4

0.00 to 9.99 ______ ______ ______ ______ 5

6

0.00 to 9.99 ______ ______ ______ ______ 5

5

7

9

8

9

[COND:A X 3 and f(X) 3] ______ ______ 1.000 ______ ______ ______ 7

8

9

[COND:A X 4 and f(X) 4] ______ ______ 1.000 ______ ______ ______

6

0.00 to 9.99 ______ ______ ______ ______

8

[COND:A X 2 and f(X) 2] ______ ______ 10.00 ______ ______ ______

6

0.00 to 9.99 ______ ______ ______ ______ 5

7

6

0.00 to 9.99 ______ ______ ______ ______ 5

[COND:A X 1 and f(X) 1] ______ ______ 10.00 ______ ______ ______

7

8

9

[COND:A X 5 and f(X) 5] ______ ______ 1.000 ______ ______ ______

6

7

8

9

Fallback Strategies Default Output Fallback Fallback Minimum Output Minimum Flow Fallback Default Minimum Flow Compression Ratio Fallback Default Compression Ratio Sigma Fallback Default Sigma Speed Fallback Default Speed Function 5 Fallback Default f5 Argument Adj. Section Flow Fallback Default Adj. Section Flow Valve-Sharing Fallback Alternate K Polytropic Head Fallback

Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On

%

revert to manual control 00.0 for filtered value used when head cannot be calculated

% used if Pd input fails 0.00 to 9.99 also used as initial value during startup .000 to .999 % used if MODE:A SS 9 input fails % fA modes 34, 35, and 64 only % used if valve-sharing communication fails .000 to .999 will not work unless fD 3 4 is enabled

[MODE:A fD 3 1] [COND:A CONST 1] [MODE:A fD 3 2] [COND:A CONST 2] [MODE:A fD 3 3] [COND:A CONST 3] [MODE:A fD 3 4] [COND:A CONST 4] [MODE:A fD 3 5] [COND:A CONST 5] [MODE:A fD 3 6] [COND:A CONST 6] [MODE:A fD 3 7] [COND:A CONST 7] [MODE:A fD 3 8] [COND:A CONST 8] [MODE:A fD 3 9]

Operating State General Ramp Rate Stopping Ramp Rate Stop/Purge Companion Shutdown Request Purge State Safety On Auto-Reset Manual While Stopped Minimum Flow and Pressure Minimum Speed

________ ________ ________ Off / On Off / On Off / On Off / On ________ ________

repeats/min. for bumpless transfers repeats/min. 0.00 to 9.99 Off or Controller ID for S2 and S3 signals On to enable discrete shutdown requests if On, shutdown resets surge count % %

[PID:A G] [COND:A LVL 3] [MODE:A fB –] [MODE:A fB 1] [MODE:A fB 2] [MODE:A fB 3] [MODE:A fB 4] [COND:A LVL 1] [COND:A LVL 2]


FM301/L (5.0)

Page 6 of 12

Software Revision 754


Tag No.: ___________________________

Date: ______________________________

Surge Protection Responses Manual Override Manual Override Off / On

Off for surge protection in manual

[MODE:A MOR]

006 to 999 00.0 to 99.9 allowable deviation (±)

[PID:A PB 1] [PID:A Kr 1] [PID:A r 1]

PI Response DEV Proportional Band ________ DEV Reset Rate ________ repeats/min. DEV Dead Zone ________ % Recycle Trip® Recycle Trip Line Distance ________ Max. Recycle Trip Step Size ________ Recycle Trip Repeat Interval ________ Recycle Trip Time Lag ________ Derivative Recycle Trip Off / On Recycle Trip Gain ________ Recycle Trip Time Constant ________

% % seconds seconds

minimum time between Recycle Trips first-order-lag time constant

seconds

used only if fC 4 is On used only if fC 4 is On

[SPEC:A RT] [SPEC:A C 1] [SPEC:A C 2] [SPEC:A TL] [MODE:A fC 4] [SPEC:A C 0] [PID:A Td 1]

Derivative Response Derivative Response Off / On Maximum Derivative Response ________ % Derivative Resp. Time Constant ________ seconds Derivative Response Dead Zone _______ %/160 msec.

threshold above which response > 0

[MODE:A fC 3] [SPEC:A b 3] [PID:A Td 0] [PID:A r 3]

The rate of decay for the Derivative Response is set by the General Ramp Rate (listed under Operating State on page 2)

Safety On® Safety On Incremental Bias ________ % increase in surge control margin for each surge [SPEC:A b 2] Surge Relay Threshold ________ surge count to trip Surg discrete out [COND:D CONST 0] Safety On Line Distance ________ % used by all fD 2 modes [SPEC:A SO] Surge Detection Method Off / 1 / 2 / 3 / 4 Off for SOL only, 1 for Flow and Pressure, [MODE:A fD 2] 2 for Flow or Pressure, 3 for Flow only, 4 for Pressure only Flow Rate of Change Thresh. ________ %/160 msec not used if fD 2 = 4 [SPEC:A A 1] Flow after Pressure Time Lag ________ seconds used only if fD 2 = 1 [SPEC:A A 2] Pressure Rate of Change ________ %/160 msec not used if fD 2 = 3 [SPEC:A A 3] Pressure after Flow Time Lag ________ seconds used only if fD 2 = 1 [SPEC:A A 4] Safety On Repeat Interval ________ seconds minimum time between surges [SPEC:A A 5]

Limiting Control Discharge Pressure Discharge Pressure Limiting Off / On Max. Discharge Pressure ________ % Pd Proportional Band ________ Pd Reset Rate ________ repeats/min.

limiting control above this limit 006 to 999 00.0 to 99.9

[MODE:A MVAR 2] [COND:A SP 2] [PID:A PB 2] [PID:A Kr 2]

limiting control below this limit 006 to 999 00.0 to 99.9

[MODE:A MVAR 3] [COND:A SP 3] [PID:A PB 3] [PID:A Kr 3]

Suction Pressure Suction Pressure Limiting Off / On Min. Suction Pressure ________ % Ps Proportional Band ________ Ps Reset Rate ________ repeats/min.

Pressure Override Control (POC) Pressure Override Control Off / On

[MODE:A SS 3]


February, 2001

Page 7 of 12

FM301/L (5.0)


Tag No.: ___________________________

Date: ______________________________

Load Sharing Load-Sharing Controller ________ Load-Sharing Gain ________ Load-Sharing Threshold ________ Series Load Balancing Off / On* Balancing Control Variable ________ Balancing Variable Characterizer: CV: .000 ______ ______ f6 (CV): ______ ______ ______ 0

1

Recycle Flow Characterizer: CR: .000 ______ f2 (CR): ______ ______ 0

1

Port 2 Recycle Balancing Recycle Balancing Controller 1 Recycle Balancing Controller 2 Recycle Balancing Controller 3 Recycle Balancing Controller 4 Recycle Balancing Controller 5 Recycle Balancing Controller 6 Recycle Balancing Controller 7 Recycle Balancing Controller 8

2

Load-Sharing Controller ID (1 to 8) –9.99 to 9.99 0.00 to 1.99

______ ______ 3

[MODE:A SS 4] [COND:A M 0] [COND:A β 3] [MODE:A fC 9] Off for R c or CH# of analog input [MODE:A fD 9] 0.00 to 9.99 [COND:A X 6 and f(X) 6] ______ ______ ______ ______ ______ 1.000 ______ ______ ______ ______ ______ ______ 4

5

______ ______

______ ______

______ ______

2

3

4

Off / On Off / On Off / On Off / On Off / On Off / On Off / On Off / On Off / On

6

0.00 to 9.99 ______ ______ ______ ______ 5

6

if On, overrides SS 7

7

8

9

[COND:D X 2 and f(X) 2] ______ ______ 1.000 ______ ______ ______ 7

8

9

[MODE:A SS HIGH] [MODE:A SS 7 1] [MODE:A SS 7 2] [MODE:A SS 7 3] [MODE:A SS 7 4] [MODE:A SS 7 5] [MODE:A SS 7 6] [MODE:A SS 7 7] [MODE:A SS 7 8]

*If enabled, you must define the Reported Flow [COND:A f(X) 2, see page 6], Balancing Variable and Recycle Flow Characterizers. If enabled in fA Mode 61 through 69, you must also set the Mass Flow Coefficient [COND:A β 5, see page 5].

Loop Decoupling Decoupling Controller 1 Decoupling Gain 1 Decoupling Controller 2 Decoupling Gain 2 Decoupling Controller 3 Decoupling Gain 3 Decoupling Controller 4 Decoupling Gain 4 Decoupling Controller 5 Decoupling Gain 5 Decoupling Controller 6 Decoupling Gain 6 Decoupling Controller 7 Decoupling Gain 7 Decoupling Controller 8 Decoupling Gain 8

Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On ________ Off / On ________

–9.99 to 9.99 –9.99 to 9.99 –9.99 to 9.99 –9.99 to 9.99 –9.99 to 9.99 –9.99 to 9.99 –9.99 to 9.99 –9.99 to 9.99

[MODE:A SS 0 1] [COND:A M 1] [MODE:A SS 0 2] [COND:A M 2] [MODE:A SS 0 3] [COND:A M 3] [MODE:A SS 0 4] [COND:A M 4] [MODE:A SS 0 5] [COND:A M 5] [MODE:A SS 0 6] [COND:A M 6] [MODE:A SS 0 7] [COND:A M 7] [MODE:A SS 0 8] [COND:A M 8]


FM301/L (5.0)

Page 8 of 12



Tag No.: ___________________________

Date: ______________________________

Control Valve Recycle Valve Direction Off / On On for fails-open valve [MODE:A REV] Valve Flow Characterizer Off / High / Low Off = linear, High = quick-open, Low = equal % [MODE:A fC 8] Remote Low Output Clamp ________ Off or CH# of analog input [MODE:A fE 4] Output Tracking ________ Off or CH# of analog input [MODE:A fE 5] Output High Limit ________ % high limit for displayed output [COND:A OUT HIGH] Output Low Limit ________ % low limit for displayed output [COND:A OUT LOW] Tight Shut Off Line Distance ________ % Dev threshold for fully closing valve [SPEC:A d 1] Valve Dead Band Bias ________ % added to or subtracted from Control Signal [COND:A OUT 1] Position Failure Threshold ________ % 00.0 to 99.9 % [COND:D LVL 5] Position Failure Delay ________ seconds 0.00 to 9.99 sec [COND:D CONST 5]

Valve Sharing / Cold Recycle Control Primary Controller ID ________ Valve Sharing Controller 1 Off / On Valve Sharing Controller 2 Off / On Valve Sharing Controller 3 Off / On Valve Sharing Controller 4 Off / On Valve Sharing Controller 5 Off / On Valve Sharing Controller 6 Off / On Valve Sharing Controller 7 Off / On Valve Sharing Controller 8 Off / On

Off or Controller ID of primary controller

[MODE:A SS 2] [MODE:A SS 1 1] [MODE:A SS 1 2] [MODE:A SS 1 3] [MODE:A SS 1 4] [MODE:A SS 1 5] [MODE:A SS 1 6] [MODE:A SS 1 7] [MODE:A SS 1 8]

For MODE:A fA = 00, the SS 1 parameters identify the Antisurge Controllers that will be monitored to determine how far to open the Cold Recycle Valve.

Analog Output 2 OUT2 Assigned Variable Flow / Out / S / UsrQ OUT2 Mass Flow Coef. ________

0 to 99.9 %

[COND:D OUT 2] [COND:D β 0]


February, 2001

Page 9 of 12

FM301/L (5.0)


Tag No.: ___________________________

Date: ______________________________

Analog Inputs Transmitter #1 Variable Measured Var. Display Measured Var. Label Decimal Position Maximum Value Minimum Value Process Variable Bias Process Variable Gain Offset Zero High Alarm Limit Low Alarm Limit

________ Off / On ________ 0/1/2/3/4 ________ ________ ________ % ________ Off / On ________ % ________ %

(normally Flow) 8 characters 0 for none, 1 for 999., 4 for .999 –9999 to 9999 –9999 to 9999 00.0 to 99.9 .000 to 1.000 On for 4-to-20 mA or 1-to-5 Vdc 00.0 to 102.4 00.0 to 102.4

[COND:D DISPLAY 0 1] [COND:D DISPLAY 0 1 –] [COND:D DISPLAY 0 1 •] [COND:D DISPLAY 0 1 HIGH] [COND:D DISPLAY 0 1 LOW] [COND:D BIAS 1] [COND:D GAIN 1] [MODE:D AN IN 1] [MODE:D AN IN 1 HIGH] [MODE:D AN IN 1 LOW]

Transmitter #2 Variable Measured Var. Display Measured Var. Label Decimal Position Maximum Value Minimum Value Process Variable Bias Process Variable Gain Offset Zero High Alarm Limit Low Alarm Limit

________ Off / On ________ 0/1/2/3/4 ________ ________ ________ % ________ Off / On ________ % ________ %

(normally Discharge Pressure) 8 characters 0 for none, 1 for 999., 4 for .999 –9999 to 9999 –9999 to 9999 00.0 to 99.9 .000 to 1.000 On for 4-to-20 mA or 1-to-5 Vdc 00.0 to 102.4 00.0 to 102.4



________ Off / On ________ 0/1/2/3/4 ________ ________ ________ % ________ Off / On ________ % ________ %

(normally Suction Pressure) 8 characters 0 for none, 1 for 999., 4 for .999 –9999 to 9999 –9999 to 9999 00.0 to 99.9 .000 to 1.000 On for 4-to-20 mA or 1-to-5 Vdc 00.0 to 102.4 00.0 to 102.4



________ Off / On ________ 0/1/2/3/4 ________ ________ ________ % ________ Off / On ________ % ________ %

(normally Rotational Speed) 8 characters 0 for none, 1 for 999., 4 for .999 –9999 to 9999 –9999 to 9999 00.0 to 99.9 .000 to 1.000 On for 4-to-20 mA or 1-to-5 Vdc 00.0 to 102.4 00.0 to 102.4



FM301/L (5.0)

Page 10 of 12



Tag No.: ___________________________

Date: ______________________________

Analog Inputs (Continued) Transmitter #5 Variable ________ Measured Var. Display Off / On Measured Var. Label ________ Decimal Position 0 / 1 / 2 / 3 / 4 Maximum Value ________ Minimum Value ________ Process Variable Bias ________ % Process Variable Gain ________ Offset Zero Off / On High Alarm Limit ________ % Low Alarm Limit ________ %

(normally Discharge Temperature) 8 characters 0 for none, 1 for 999., 4 for .999 –9999 to 9999 –9999 to 9999 00.0 to 99.9 .000 to 1.000 On for 4-to-20 mA or 1-to-5 Vdc 00.0 to 102.4 00.0 to 102.4


Transmitter #6 Variable ________ Measured Var. Display Off / On Measured Var. Label ________ Decimal Position 0 / 1 / 2 / 3 / 4 Maximum Value ________ Minimum Value ________ Process Variable Bias ________ % Process Variable Gain ________ Offset Zero Off / On High Alarm Limit ________ % Low Alarm Limit ________ %

(normally Suction Temperature) 8 characters 0 for none, 1 for 999., 4 for .999 –9999 to 9999 –9999 to 9999 00.0 to 99.9 .000 to 1.000 On for 4-to-20 mA or 1-to-5 Vdc 00.0 to 102.4 00.0 to 102.4



(normally Guide Vane Angle) 8 characters 0 for none, 1 for 999., 4 for .999 –9999 to 9999 –9999 to 9999 00.0 to 99.9 .000 to 1.000 On for 4-to-20 mA or 1-to-5 Vdc 00.0 to 102.4 00.0 to 102.4



(normally OUT1 Loopback) 8 characters 0 for none, 1 for 999., 4 for .999 –9999 to 9999 –9999 to 9999 00.0 to 99.9 .000 to 1.000 On for 4-to-20 mA or 1-to-5 Vdc 00.0 to 102.4 00.0 to 102.4



February, 2001

Page 11 of 12

FM301/L (5.0)


Tag No.: ___________________________

Date: ______________________________

Redundant Controller Tracking Redundant Tracking Off / On Modbus While Tracking Off / On

On enables tracking Off to give controllers same ID

[MODE:D fE 1] [MODE:D LOCK 0]

Computer Communications Read and Write Inhibit Write Inhibit Only Modbus Register Scaling Port 2 Baud Rate Port 3 Format Port 4 Format

Off / On On inhibits reads and writes [MODE:D LOCK 1] Off / On On allows reads, inhibits writes [MODE:D LOCK 2] Off / On On to divide range by 1.024 (Port 3 only) [MODE:D LOCK 7] 2400 / 4800 / 9600 baud 9600 recommended[MODE:D COMM 2] 4800 / 9600 / 19.2k baud Odd / Even / No Parity[MODE:D COMM 3] 4800 / 9600 / 19.2k baud Odd / Even / No Parity[MODE:D COMM 4]

Discrete Outputs For each output, enter one of the following functions, select + for normally de-energized operation or – for normally energized operation, and select NO for normally-open or NC for normally-closed contacts: Auto (Automatic operation), Lim (Limiting condition), MOR (in Manual with Override enabled), Off (never tripped), On (always tripped), Open (valve Open), OutF (Output Fail), RT (Recycle Trip), PosF (valve Position Failure), Run (Run state selected), SerC (Serial Communication error), SO (Safety On), Surg (Surge alarm count exceeded), or Tran (Transmitter failure). Relay #1 Relay #2 Relay #3 Relay #4 Relay #5

________ always – ________ + / – ________ + / – ________ + / – ________ + / –

NO / NO / NO / NO / NO /

NC NC NC NC NC

Main Fault

[MODE:D RA 1] [MODE:D RA 2] [MODE:D RA 3] [MODE:D RA 4] [MODE:D RA 5]

Miscellaneous Remote Parameter Switching Off / On Input Lockout Off / On Auxiliary Display Reset Off / On

If On, D7 loads alternate parameter set Must be OFF On to revert to Status Display after 60 sec.

[MODE:D LOCK 3] [MODE:D LOCK 6] [MODE:D LOCK 9]


FM301/L (5.0)

Page 12 of 12


COMPRESSOR CONTROLS CORPORATION 4725 121st Street, Des Moines, IA 50323-2316, USA • Phone: (515) 270-0857 • Fax: (515) 270-1331 ®

Printed in U.S.A.

S3OP - Antisurge Training Manual

Recommend Documents