[email protected] Oral Preparation Notes INSTRUMENTS INSTRUMENTS ON BOA RD A SHIP:
HYDROMETER: Hydrometer is used to measure density of dock water (DW) Units of density of water – T/M3 Hydrometer is used: For a draft survey – Loading/unloading a ship To calculate dock water allowance (DWA) – DWA is calculated to find out how much loadline will submerge in port Formula for - DWA = FWA X (1025 – DW density) 25 STEPS TO BE FOL LOW ED WHEN USING USING A HYDROMETER:
Hydrometer should have a certificate for marine use Check the physical condition of hydrometer, scale, floating bulb and weighted bulb should not be cracked or damaged Check errors of hydrometer using distilled water Take a clean bucket and take samples from 6 points around the ship from at least half draft depth Make sure sample is taken away from overboard discharges and floating debris Make sure bucket is filled enough so that hydrometer doesn’t touches the bottom and floats freely Let water settle down Put hydrometer in bucket and give it a slight spin to break surface tension Make sure hydrometer doesn’t touches the sides of the bucket Take the reading from the lower meniscus HYGROMETER:
Hydrometer is used: To calculate humidity in air and predict fog To decide whether to ventilate or not Why is dry and wet bulb kept in Stevenson screen?
Dry and wet bulb are kept in Stevenson screen to prevent it from sudden gust of wind and variable evaporation rate. It is placed at least 1.5m above deck. How to predict fog?
Take the dry bulb and wet bulb temperatures from windward side - for any given time Calculate their difference known as depression of wet bulb Get the dew point temperature from dew point temperature table using dry bulb temperature and depression of wet bulb Get sea temperature for that time from engine room (E/R) Plot these temperatures against time axis for successive hours Extend these lines, wherever dew point temperature and sea temperature meet each other that is the predicted time of fog
1
[email protected] Oral Preparation Notes DEFITNITIONS:
Humidity – Quantity of water vapor present in the atmosphere Relative humidity (RH) – It is the percentage ratio of present water vapour a sample can hold to the maximum quantity of water vapour that sample can hold at that temperature Dew point – When RH is 100% saturated H o w t o d e c i d e v e n t i la la t e o r n o t ?
Cold to Hot – Ventilate NOT Hot to Cold – Ventilate HOLD PRECISION ANEROID BAROMETER (PAB): It is used to get the pressure at any position How to use a PAB?
Put the damper (to prevent sudden change in pressure by sudden gust of wind, rolling and pitching Press push button and turn the dial Stop when green light breaks Take the reading, if a reading is between two readings then take the odd one Apply calibration calibration correctio correction n (issued (issued by met office) office) Apply temperature temperature and and height height correction, correction, using a table in the the box or mariners handbook. handbook. Pressure taken on the ship is above sea level and we know that pressure decreases as altitude increases, therefore this correction is always added. W h a t i s d i u r n a l v a ri ri a t io io n o f p r e s s u r e ?
Atmospheric Atmospheric pressure pressure for any region changes from maximum to minimum everyday. everyday. There are 2 maximum and 2 minimum pressures for any region at very nearly the same times each day. Maximum is about 2200hrs and minimum at about 0400 and 1600hrs The variation in pressure is called diurnal variation of pressure W h y d o y o u m o n i t o r p r es es s u r e o n b o a r d ?
Pressure is monitored on board in order to know the diurnal variation of pressure in the position of the ship. If diurnal variation of pressure drops more than 3mb than average it means ship is in the vicinity of a storm and if it drops more than 5mb it means TRS is within 200nm
MAGNETIC COMPASS:
There are 2 types of compass cards: Dry card: Made up of rice paper Consists of 7 needle magnets suspended underneath the card via silk threads due to which compass points to North Wet card: Made of mica or plastic Consists of one ring magnet due to which compass points to North
2
[email protected] Oral Preparation Notes
Liquid inside the bowl is ethyl alcohol and water in the ratio 2:1 Why do you have that liquid? It provides damping effect Acts as antifreez antifreeze e till -30 degree degree celcius celcius Prevents liquid from evaporating What to do if you get a bubble?
Turn the bowl upside down and bring filling cap up and top it up with pure alcohol If there is no filling cap then inject it with a syringe What is the trouble with the bubble?
Restricts card movement Loss of flotation Optical error while taking a reading What is binnacle made of?
Any non magnetic material such such as wood, wood, fibre, fibre, brass, plastic What is bowl made of?
Brass or glass What maintenance will you carry out on a magnetic compass? Take compass error every watch No electrical installations around the compass within 1.5m Check for structural changes around the compass Check location of corrector magnets (back of deviation card) Check free movement of the card (deflection error) and gimble Report any problems to the master W h a t w i l l y o u d o i f c o m p a s s b o w l b r ea ea k s ?
Replace it with the spare bowl kept upside down in the navigation locker Do not calculate the deviation because deviation is in the ship What corrector m agnets are soft and w hat are hard?
Soft – Flender bar and Kelvin balls Hard – Fore and aft hard iron magnetic correctors, Athwartship hard iron magnetic correctors and Heeling error bucket How is expansion of liquid com pensated for?
By an expansion chamber at the bottom of the bowl
3
[email protected] Oral Preparation Notes AZIMUTH RING:
Parts of azimuth ring: Mirrored prism Magnifying lens H o w t o c h e c k e r r o r in i n a a zi zi m u t h r i n g ?
Select a terrestrial object Take a bearing of the object “arrow down” Take a bearing of the same object “arrow up” Compare the 2 readings – If same then there is no error in the azimuth ring if not then there is a error If bearings are different then it should not be used and sent ashore for repair H o w t o u s e an an a z im im u t h r i n g ?
Use “arrow down” for terrestrial objects View reflected image of compass card and actual terrestrial object in case of terrestrial objects Use “arrow up” for celestial objects View reflected image of celestial body and actual compass card in case of celestial objects HYDROSTATIC RELEA SE UNIT (HRU): (HRU):
Strong white rope is secured to the liferaft cradle and attached to the liferaft lashing via senhouse clip When ship sinks a water pressure within 1.5 - 4m activates HRU and a very sharp knife cuts this rope and liferaft floats in the water As ship sinks painter gets a jerk with which CO2 bottle gets activated, activated, liferaft gets inflated, weak link breaks and liferaft floats free HRU is replaced after 2 years EMERGENCY TOWING ARRANG EMENT (ETA): (ETA):
New and existing tankers of 20,000 DWT and above should be fitted with an ETA Aim of the equipment equipment is to facilitate facilitate salvage salvage and and therefore therefore reduce reduce the risk risk of pollution pollution Arrangement Arrangement should be capable capable of rapid deployment deployment at all times in the absence absence of main power Towing gear should have the following components: Pickup gear Chafing gear Towing pennant Fairlead Strong point Rolling pedestral Length of towing pennant should be atleast twice the lightest seagoing condition at the fairlead plus 50m and should have a hard eye at the end to allow connection of standard bow shaped shackle 4
[email protected] Oral Preparation Notes
Fairleads and strong points should have sufficient strength to withstand towing operation Chafing chain to extend atleast 3m beyond the fairlead and to be fitted with a pear shaped link at the end for connection of a bow shackle Aft gear should should be pre rigged rigged and capable capable of being being deployed deployed in 15 15 minutes Forward gear should be capable of deployed in 1 hour Gear should be clear marked, inspected regularly and maintained in good working order NAVIGATIONAL NAVIGATIONAL EQUIPMENT EQUIPMENTS S ON B OARD R A D A R ( Ra Ra d i o D e t e c t i o n A n d R a n g i n g ) : How will you test your RADAR prior departure?
Check if its safe to turn on RADAR – local regulations, terminal requirement, men working on mast Switch on power button and wait – warming up Increase brightness, gain, tuning and clutter (sea/rain) Check speed input – log not GPS Set up trails, vectors and parallel indexing Set up 2 RADAR’s, 1 for short range and 1 for long range VARIOUS SITUATIONS: Ice navigation – X band (3cm, 9GHz) Search and rescue – X band Coastal navigation – X band Heavy rain – S band (10cm, 3GHz) E r r o r s / l i m i t a t io io n s o f a R A D A R :
Side error: If there are 2 equi distant targets, RADAR strikes the targets bounces back and can show 2 or more targets Minimum range: Target may not be detected because of being outside VBW (vertical beam width) range Blind sector limitation: Targets cannot be detected in blind sectors usually behind the funnel Range discrimination: When 2 targets have same bearing, different ranges RADAR may show it as a single target Bearing discrimination: When 2 targets have same range, different bearing RADAR may show it as a single target Target swap: If 2 targets are nearby there information can swap Multipath error: It happens usually in ships with a crane. Echo bounces back from crane and shows another target Second trace echo: In this target seems to be near but actually its far 5
[email protected] Oral Preparation Notes
W h a t d o y o u m e a n b y s e a s t a b i li l i z ed ed a n d g r o u n d s t a b i l i ze ze d ?
Sea stabilized: This is where the RADAR is hooked t o the ship’s log and gives the ship’s speed through the water Ground stabilized: This is where the RADAR is hooked up with Doppler log and gives the ship’s speed over ground What is short pulse and long pu lse:
Short pulse: It is best for finding targets in heavy rain shower Long pulse: It is best for finding a target on the opposite side of heavy rain shower What set up you had on your last ship’s RADAR? On my last ship we used to have: Ship’s head up , sea stabilized, relative motion Scale used to vary depending in which area we are, traffic conditions, etc Sea and rain clutters were removed using anti-sea and anti-rain clutters knob We used to make use of EBL (Electronic bearing line) and VRB (Variable range marker) H o w t o c h e c k t h a t RA RA D A R i s w o r k i n g a t i t s b e s t ?
By doing a performance monitoring button which would test the performance of the magnetron How to ch eck the performance of the RADAR?
Press the performance monitor button Switch to 12 miles scale It then checks the performance of TR monitor (Transmission performance) and TX monitor (Receiving performance) If they are as per manufacture’s in structructions that means RADAr is working well
AIS:
Information provided by AIS: Static information: MMSI IMO number (where available) Call sign & name Length and beam Type of ship and Location of the position-fixing antenna on the ship (aft of bow/ port or starboard of centreline)
6
[email protected] Oral Preparation Notes
Dynamic information: Ship’s position with accuracy indication and integrity status Position time stamp (in UTC) Course over ground (COG) Speed over ground (SOG) Heading Navigational status (e.g. at anchor, underway, aground etc. - this is input manually ) and Rate of turn (where available) Voyage related information: Ship’s draught Hazardous cargo (type) Destination and ETA (at masters discretion) and Route plan (waypoints) Short safety-related messages: Free format text message - sent as required L i m i t a t i o n s o f A IS :
Gives outdated information Limited vessels carry AIS: 300GT and above on international voyages 500GT and above on domestic voyages All passenger passenger ships ships I n c o m p a t i b l e c o d i n g a n d d e c o d i n g b e t w e e n s h i p a n d s h o r e s t a t io io n s
CPA/TCPA based on COG/SOG Assigned mode problem problem Antenna location not set up up properly properly Legalities:
Mandatory – 100nm from UK coast International regulations – No need at port unless local regulations ask for. Master has over riding power.
ECHO SOUNDER:
Components of echo sounder: Transducer Amplifier Pulse generator Recorder C o n t r o l s i n a ec ec h o s o u n d e r :
Range switch Gain switch 7
[email protected] Oral Preparation Notes
Unit selector (m/feet) Paper speed control Zero draft adjust Transducer change over L i m i t at at i o n s o f e c h o s o u n d e r :
Shallow water Different layers Pythagoras error Electrical noise Mechanical noise Biological noise Wrong scale being used Salinity – speed of sound increase Cavitation – propeller bubble Draft mark – stylus position wrong ECDIS ECDIS (Electron (Electron ic Chart Display Info Info rmatio n System ):
Limitations of ECDIS: Software virus Hardware failure Sensor failure Datum errors Information overload ECDIS accuracy – 2 pixels, 20m No worldwide coverage of ENC charts Zooming in gives false sense of space, decreases accuracy Reported depth not triggering any alarms No dedicated menu to plot visual bearings Use of simplified symbols might mislead Route checking not reliable Full information not available at certain scales Any abnormalities abnormalities to be reported reported to MCA MCA Difference between ENC Navigation al charts ):
ENC Vector S57 Digitized Multiple layer No worldwide coverage yet Variable scale CATZOC Borderless No compass rose
(Electronic
navigational
i. ii. iii. iv.
vii. viii. ix.
charts)
and
RNC
(Raster
RNC Raster S61 Scanned copy Single layer v. Worldwide coverage vi. Fixed scale Source data box With borders Compass rose available 8
[email protected] Oral Preparation Notes
Display can be customized Always WGS84 Safety monitoring available Orientation of screen possible
x. xi. xiii.
Display cant be customized Depends on paper chart xii. Safety monitoring not available Orientation of screen not poss.
H o w c a n y o u g o p a p e r l es es s :
There should be 2 ECDIS onboard with separate power supply for each Must be able to share sensor Logs:
EM (Electro magnetic) log: Works on principle of electromagnetic induction Gives speed over water Used for collision avoidance Doppler log:
Works on principle of Doppler shift of frequency Gives speed over ground
G P S ( Gl Gl o b a l P o s i t i o n i n g S y s t e m ) :
Errors of GPS: Multipath error: It occurs when a GPS signal bounces of a nearby object Eg. Measure length of your living room with a tape one end to other keeping a sofa in b/w and passing tape over it Ionosphere error: It occurs when signals from satellite get delayed in reaching the receiver on passing through an area of charged particles of Ionosphere and our atmosphere Orbital error: Caused by small change in orbital position. Position of satellites obtained from signal information is a prediction of where the satellite should be at any given time, the actual position may vary Clock error: Caused by change in time of satellite and receiver. A slightest difference can make a range difference of 10s, 100s and 1000s of metres. Eg. A difference of 10 nanoseconds can make a difference of 3 metres in the position Dilution of precision: It is the measure of GPS satellite/receiver geometry A l o w D O P v al al u e i n d i c a t e s b e t t er er r e l at at i v e g e o m e t r y a n d h i g h e r c o r r e s p o n d i n g accuracy:
Best DOP = 0 Worst DOP = Infinity
9
[email protected] Oral Preparation Notes
HDOP (Horizontal DOP), VDOP (Vertical DOP), PDOP (Positional 3D DOP) and TDOP (Time DOP) – They follow mathematically from the position of the usable satellites
GMDSS CHECKS: CHECKS: Daily:
DSC internal tests (VHF) Emergency battery Check printers have ink and paper Check clocks against time ticks Radio log book is signed by master Weekly:
MF external test on 2187.5 KHz (Call coast station on its MMSI # from ALRS VOL 5) VHF test with spare batteries for testing purpose (But not on CH 16 use CH 15 or CH 17) Monthly:
Antennas free from corrosion corrosion or loose connections connections EPIRB – Physical condition, expiry of battery, self test, HRU and bracket SART – Physical condition, expiry of battery, self test 24V batteries SEA AREAS: Sea Area A1 – within range of a shore-based VHF-FM coast station (typically 20-
50miles from shore) – – within range of a shore-based MF coast station (typically 100-400 miles Sea Area A2 from shore, excluding Sea Area A1) – – within INMARSAT satellite coverage, between 70N and 70S, excluding Sea Area A3 Sea Areas A1 and A2 Sea Area A4 – – the Polar Regions excluding Sea Areas A1, A2 and A3 GMDSS CRS for each sea area must maintain DSC distress and safety watch as follows Sea Area A1 VHF Channel 70 Sea Area A2 MF 2187.5 kHz Sea Area A3 HF Frequencies in the 4,6,8,12 and 16MHz bands E P IR IR B ( E m e r g e n c y p o s i t i o n i n d i c a t i n g r a d i o b e a c o n ) :
EPIRB transmits at 406MHz using a COSPAS SARSAT system It can be tested with a self test function EPIRB can be activated by both means - manually or automatically When a ship is submerged to a depth of 2-4 metres below water level, EPIRB gets released via HRU which cuts its lashing and gets activated sending details like: 10
[email protected] Oral Preparation Notes
Ship’s name Call sign MMSI number Port of registry Current position etc. to the company and nearest shore station
SART (Search (Search and Rescu e Radar Radar Transpo nd er): er):
SART works on a X-band (3cm, 9GHz) RADAR Activating Activating SART: Remove it from its casing Turn the knob half way across to ON position A red ight will start start blinking, blinking, this is an indication indication that SART is activated activated Once been detected by any RADAR this light will turn green Once SART signal is received on a RADAR, it will appear as: Over 5 miles 12 blips will appear on the RADAR in the direction of SART in which the last blip is the position of the SART Between 1-5miles, 12 arcs will appear on the RADAR in the direction of SART When SART is within 1 mile, 12 concentric circles will appear on the RADAR
11