STCW & SHIP FIRE PREVENTION

STCW & SHIP FIRE PREVENTION

FIRE TRIANGLE: IF ANY ONE SIDE OF “FIRE TRIANGLE” IS REMOVED, FIRE WILL BE EXTINGUISHED.
METHODS OF FIRE FIGHTING: THERE ARE FOUR METHODS OF FIGHTING FIRE
  • SMOTHERING – REMOVING THE AIR.
  • STARVING - REMOVING THE BURNING MATERIAL FROM THE SURROUNDING.
  • COOLING – REMOVING THE HEAT.
  • INHIBITING – RETARDATION OF THE COMBUSTION REACTION.
FIRE TRIANGLE

Types of fire

In the European Standard "Classification of fires" (EN 2:1992, incorporatiing amendment A1:2004), the fires are classified as:
Class A fire: Ordinary combustibles such as wood, paper, carton, textile, and PVC;
Class B fire: Flammable liquids and solids which can take a liquid form, such as benzene, gasoline, oil;
Class C fire: Flammable gases, such as butane, propane, and natural gas;
Class D fire: Combustible metals, such as iron, aluminum, sodium, and magnesium;
Class F fire: Cooking media, such as oils and fats, in cooking appliances;
A fire involving energized electrical equipment is not classified by its electrical property.

SHIP FIRE PREVENTION

SMOTHERING

IF THE OXYGEN CONTENT OF THE ATMOSPHERE IN THE IMMEDIATE NEIGHBORHOOD OF BURNING MATERIAL CAN BE SUFFICIENTLY REDUCED COMBUSTION WILL CEASE. THIS PRINCIPLE IS INEFFECTIVE IN THE CASE OF CELLULOID AND SIMILAR SUBSTANCES, WHERE BURNING OF THE MATERIAL CONTAINS WITHIN ITSELF, IN A CHEMICALLY COMBINED FORM.

PRACTICAL ASPECT: ON A SMALL SCALE IT IS EMPLOYED IN A SNUFFING  CANDLE. PERSONS CLOTHING CAN BE SMOTHERED WITH A RUG / BLANKET
ON A LARGE SCALE, IN CAPPING A BURNING WELL. BATTERING DOWN OF A SHIP’S HOLD WHEN A FIRE BREAKS OUT BELOW DECKS WILL OFTEN HOLD THE FLAMES IN CHECK UNTIL PORT IS REACHED.

PRACTICAL APPLICATION OF SMOTHERING METHOD
  • USE OF FOAM: THIS FORMS A VISCOUS COATING OVER THE BURNING MATERIAL AND LIMITS THE SUPPLY OF AIR.
  • USE OF DRY POWDER: SODIUM BICARBONATE FROM A PRESSURIZED EXTINGUISHER. CARBONATE WHEN FINELY DIVIDED ABSORB HEAT AND THUS HAS COOLING AND FLAME INHIBITING EFFECT.
  • USE OF INERT GAS: THE VIGOROUS DISCHARGE OF INERT GAS, SUCH AS CARBON DIOXIDE & NITROGEN IN THE IMMEDIATE VICINITY OF THE FIRE REDUCES THE OXYGEN CONTENT OF ATMOSPHERE BY PROVIDING A TEMPORARY BLANKET EFFECT.

STARVATION

THE EXTINCTION OF FIRE BY STARVATION IS APPLIED IN THREE WAYS. BY REMOVING COMBUSTIBLE MATERIAL FROM THE NEIGHBORHOOD OF THE FIRE. 
Ex: DRAINING OF FUEL FROM BURNING OIL TANKS, DISCHARGING OF CARGO AT A SHIP FIRE.
BY REMOVING THE FIRE FROM THE NEIGHBOURHOOD OF COMBUSTIBLE MATERIAL.
Ex: PULLING APART A BURNING HAYSTACK.
BY SUB-DEVIDING THE BURNING MATERIAL. 
Ex: SMALLER FIRES PRODUCED MAY BE EXTINGUISHED MORE EASILY, SUCH AS EMULSIFICATION OF THE SURFACE OF BURNING OIL.

COOLING

THE PROCESS OF REMOVING THE HAET FROM FIRE IS CALLED COOLING. THIS IS NORMALLY DONE BY WATER, AS WATER HAS MORE COOLING EFFECT AND VERY HIGH LATENT HEAT. APPLICATION OF JET OR SPRAY OF WATER TO A FIRE, EMULSIFICATION OF THE SURFACE OF OIL BY MEANS OF THE EMULSIFYING TYPE OF SPRINKLER HEAD.

INHIBITING

IN THIS HEAT PRODUCING CHEMICAL REACTION OF SUBSTANCES IS CHECKED OR STOPPED. THIS APPLIES TO ONLY FLAMING MODE AND NOT TO THE GLOWING MODE. IN THIS FLAME INHIBITING EXTINGUISHING MEDIUM INTERFERES WITH THE ACTIVE SPECIES IN FLAME CHAIN REACTION WHICH WOULD OTHERWISE FUNCTION AS “CHAIN CARRIERS”. THIS METHOD EXTINGUISHES THE FLAME VERY RAPIDLY.
    Ex: DCP OR HALON GAS – THESE ACT BY CHEMICAL INTERFERENCE WITH THE CHAIN REACTION OF FLAME PROPAGATION.

PROPERTIES OF FLAMMABLE MATERIAL

FLAMMABILITY: THIS IS THE ABILITY OF SUBSTANCE TO BURN. IN THIS VAPOR GIVEN OFF BY FLAMMABLE MATERIAL CAN BURN WHEN MIXED WITH AIR IN THE RIGHT PROPORTION IN THE PRESENCE OF AN  IGNITION SOURCE.

IGNITION POINT: IT IS THE LOWEST TEMP., TO WHICH A FLAMMABLE SUBSTANCE MUST BE HEATED TO IGNITE.

FLASH POINT: IT IS THE LOWEST TEMP., AT WHICH THE VAPOUR OF THE SUBSTANCE ARE AVAILABLE IN SUFFICIENT QUANTITY TO PRODUCE A MOMENTARY FLASH WHEN A FLAME IS APPLIED.

FIRE POINT: IT IS THE TEMP., AT WHICH THE HEAT FROM THE COMBUSTION OF BURNING VAPOR IS CAPABLE OF PRODUCING SUFFICIENT VAPOUR TO ENABLE COMBUSTION TO CONTINUE.

SPONTANEOUS / AUTO / SELF IGNITION TEMP: IT IS THE LOWEST TEMP., AT WHICH THE SUBSTANCE WILL IGNITE SPONTANEOUSLY i.e., THE SUBSTANCE WILL BURN WITHOUT THE INTRODUCTION OF A FLAME OR OTHER IGNITION SOURCE.

UPPER FLAMMABLE LIMIT: IT IS THE CONCENTRATION OF FLAMMABLE VAPOUR IN AIR ABOVE WHICH THE MIXTURE BECOMES TOO RICH TO IGNITE AND PROPEGATE COMBUSTION.

LOWER FLAMMABLE LIMIT: IT IS THE CONCENTRATION OF FLAMMABLE VAPOUR IN AIR BELOW WHICH THERE IS INSUFFICIENT FLAMMABLE VAPOUR TO SUPPORT AND PROPAGATE COMBUSTION.

STATIC ELECTRICITY: IT IS THE ELECTRICITY PRODUCED IN DISSIMILAR MATERIALS THROUGH PHYSICAL CONTACT AND SEPARATION i.e., A SAMPLING APPARATUS LOWERED IN TO A TANK CONTAINING CHARGED PETROLEUM LIQUID.

FLAMMABLE RANGE: IT IS THE RANGE OF CONCENTRATION OF A FLAMABLE VAPOUR IN AIR WITH WHICH THE VAPOUR AND AIR MIUXTURE IS FLAMABLE.

FLAMMABILITY: IT IS THE ABILITY OF SUBSTANCE TO BURN VAPOUR GIVEN OFF BY A FLAMMABLE MATERIAL, WHEN MIXED WITH AIR IN RIGHT PROPORTION IN THE PRESENCE OF THE IGNITION SOURCE. NORMAL AIR CONTAIN -  21%  OF O2  AND 78% OF N2 AND SMALL TRACES OF CO2 , WATER VAPOUR etc. IN CARGO TANKS AS THE PERCENTAGE OF HYDROCARBON INCREASES, OXYGEN CONTENT DECREASES.

LOWER FLAMABLE LIMIT (LFL): FOR A MIXTURE OF AIR AND THE FUEL TO BE COMBUSTIBLE, MINIMUM QUANTITY OF THE FUEL VAPOUR SHOULD BE PRESENT IN THE MIXTURE. THIS IS EXPRESSED AS PERCENTAGE OF FUEL VAPOUR IN THE MIXTURE OF AIR AND VAPOUR. THIS IS CALLED LOWER FLAMABLE LIMIT. THE MIXTURE WILL NOT BURN UNLESS FUEL VAPOUR CONTENT IN THE COMBUSTIBLE MIXTURE IS ABOVE LFL.

EVERY TYPE OF FUEL HAS DIFFERENT LFL.
POINT “F” – MINIMUM OF O2 REQUIRED FOR COMBUSTION  ( 11% BY VOLUME).
    LFL – LOWER FLAMABLE LIMIT
          – 1% OF C2H2 AT POINT “A”

Flamablity Diagram

UPPER FLAMABLE LIMIT (UFL):
WHEN THE PERCENTAGE OF FUEL VAPOUR IS INCREASED IN THE MIXTURE, THE PERCENTAGE OF AIR AND HENCE THE PERCENTAGE OF OXYGEN REDUCES.
SINCE THE OXYGENN CONTENT BELOW 11% IN THE MIXTURE DOES NOT SUPORT COMBUSTION, A STAGE MAY BE REACHED WHEN THE PERCENTAGHE OF VAPOUR IN THE MIXTURE IS SO HIGH THAT RESULTING PERCENTAGE OF OXYGEN IS TOO LOW TO SUPORT THE COMBUSTION AND MIXTURE WOULD NOT BURN EVEN WHEN IGNITED. THIS IS CALLED UPPER FLAMABLE LIMIT.
MIXTURE WILL NOT BURN IF THE FUEL VAPOUR CONTENT MORE THAN THE UFL.
UFL – UPPER FLAMABLE LIMIT
              - 11% OF C2H2 AT POINT “B”

EVERY FUEL HAS A LFL and UFL AND THE PERCENTAGE OF FUEL VAPOUR RANGE BETWEEN BETWWEN THESE TWO LIMITS IS CALLED “FLAMABLE RANGE”
POINT “A” – AT THE END OF BURNING IF THE PRODUCT OF COMBUSTION ARE ANALYSED, IT IS FOUND THAT ALL OF C2H2 VAPOURS ARE CONSUMED, WHILE SOME “O2” IS UNUSED AND STILL AVAILABLE.
POINT “B” – AT THE END OF BURNING, ON ANALYSIS, IT IS FOUND THAT ALL OF “O2” IS CONSUMED AND SOME UNBURNT C2H2 IS STILL AVAILABLE.

SOURCE OF IGNITION  (HEAT ENERGY)

  1. CHEMICAL HEAT ENERGY
  2. ELECTRICAL HEAT ENERGY
  3. MECHANICAL HEAT ENERGY
  4. NUCLEAR HEAT ENERGY
CHEMICAL:
  • HEAT OF COMBUSTION
  • HEAT OF PARTIAL OXIDATION
  • SPONTANEOUS HEATING
  • HEAT OF DECOMPOSITION (ONION, POTATO etc., IN CARGO HOLD)
  • HEAT OF SOLUTION (MIXTURE OF TWO CHEMICALS)
  • ELECTRICAL:
  • RESISTANCE HEATING
  • DI-ELECTRIC HEATING
  • INDUCTION HEATING
  • MECHANICAL:
  • FRICTIONAL HEATING
  • FRICTIONAL SPARKS
  • HEAT OF COMPRESSION

CLASSIFICATION OF FIRE

FIRES ARE CLASSIFIED ACCORDING TO THE TYPES OF MATERIAL WHICH ARE ACTING AS FUEL. FIRES BURNING WOOD, GLASSFIBRE, UPHOLSTERY AND FURNISHINGS. FIRES BURNING LIQUID SUCH AS LUBRICATING OIL AND FUELS. FIRES BURNING GAS FUELS SUCH AS LIQUIFIED PETROLEUM GAS. FIRES BURNING COMBUSTIBLE METALS SUCH AS MAGNESIUM AND ALUMINIUM. FIRES BURNING ANY OF THE ABOVE MATERIALS TOGETHER WITH HIGH VOLTAGE ELECTRICITY.

THESE CLASSIFICATIONS ARE ALSO USED FOR EXTINGUISHERS AND IT IS ESSENTIAL TO USE THE CORRECT CLASSIFICATION OF EXTINGUISHER FOR A FIRE, TO AVOID SPREADING THE FIRE OR CREATING ADDITIONAL HAZARDS. MANY FIRE EXTINGUISHER WILL HAVE MULTIPLE CLASSIFICATIONS SUCH AS A, B and D

FIRE EXTINGUISHING AGENTS

FIRE EXTINGUISHING AGENTS

CARBON DIOXIDE: AT NORMAL TEMP., CO2 IS 1.5 TIMES HEAVIER THAN AIR. IT IS EASILY LIQUEFIED AND BOTTLED. IT IS STORED UNDER PRESSURE OF 50bar IN STEEL CYLINDERS. WHEN CO2 IS APPLIED TO FIRE, THE LIQUID CO2 BOILS OFF RAPIDLY AS A GAS, EXTRACTING HEAT FROM THE SURROUNDING ATMOSPHERE. IT EXTINGUISHES FIRE BY SMOTHERING i.e., BY DISPLACING OXYGEN. ABOUT 20-30 % OF THE ATMOSPHERE SHOULD CONTAIN CO2 TO EXTINGUISH THE FIRE. CO2 IS QUICK AND CLEAN, NON-TOXIC, DOES NOT HARM MOST FAFRIC AND DOES NOT CONDUCT ELECTRICITY. SO IT CAN BE USED ON ELECTRICAL IT DOES NOT DAMAGE EXPENSIVE CARGO OR MACHINERY. IT LEAVES NO UNDESIRABLE RESIDUE TO BE CLEARED OFF AFTER USE. SO IT CAN BE USED TO EXTINGUISH FIRE IN CARGO AND MACHINERY SPACES BY PROVIDING FIXED CO2 INSTALLATIONS.

ADVANTAGES OF CARBON DIOXIDE:
  1. NON-CORROSIVE.
  2. DOES NOT CONDUCT ELECTRICITY.
  3. LEAVES NO RESIDUE.
  4. EASILY AVAILABLE.
  5. NOT SUBJECTED TO DETERIORATION IN QUALITY WITH AGE.
DISADVANTAGES OF CARBON DIOXIDE:
  1. TOXIC AND HAZARDOUS TO HUMAN BEING.
  2. LITTLE COOLING EFFECT & DANGER OF RE-IGNITION IF AIR IS READMITTED IN ROOM.
  3. SOLID CO2 PARTICLES GENERATE SPARK DUE TO STATIC ELECTRICITY, SO UNSUITABLE IN OIL TANKERS
WATER: IT IS MOST EFFICIENT , CHEAPEST AND READILY AVAILABLE MEDIUM. IT HAS A COOLING EFFECT AND NO-TOXIC. IT ABSORBS HEAT AND EXPANDS TO 1700 TIMES OF IT’S VOLUME TO PRODUCE STEAM WHICH HAS SMOTHERING EFFECT.
IT IS SAFE TO USE ON MOST OF THE FIRES, IT CAN BE EASILY DIRECTED OVER A CONSIDERABLE DISTANCES.

DISADVANTAGES:
  1. IT CONDUCTS ELECTRICITY.
  2. IT CAN CAUSE DAMAGE TO CARGO & MACHINERY.
  3. LOSS IN STABILITY OF SHIP WHEN USED IN LARGE QUANTITY.
FOAM:
IT IS MOST SUITABLE FOR EXTINGUISHING FIRES INVOLVING FLAMMABLE LIQUIDS. IT EXTINGUISHES BY FORMING A LAYER OF SMALL BUBBLES ON THE SURFACE OF THE LIQUID PREVENTING FUEL FROM VAPOURISING AND RESTRICTING THE OXYGEN SUPPLY TO IT.
IT IS INSOLUBLE IN MOST OF THE LIQUIDS AND LIGHT IN WEIGHT, SO IT FORMS A BLANKET TO COVER THE SURFACE OF BURNING LIQUID AND THUS EXTINGUISHES THE FIRE.

FOAM CAN BE GERATED BY MECHANICAL OR  CHEMICAL MEANS.
MECHANICAL FOAM IS GENERATED BY AGITATION OF A DILUTED FOAM COMPOUND SOLUTION IN PRESENCE OF AIR. THESE COMPOUND INCLUDE SOAPS, GLUE AND WETTING AGENT MIXTURES. CHEMICAL FOAM IS GENERATED BY MIXING AN ALKALI (SODIUM BI-CARBONATE) WITH A SOLUTION OF ALUMINIUM SULPHATE, IN PRESENCE OF A STABILIZER (i.e., SOAP) THIS PRODUCES SKIMMED BUBBLES CONTAINING CO2 “HIGH EXPANSION FOAM” HAS A VERY HIGH EXPANSION RATION OF AROUND 1000 TO 1 INSTEAD OF 8 TO 1 FOR STANDARD FOAM. THIS TYPE FOAM IS USED FOR DEALING WITH CARBONACEOUS FIRES IN COMPARTMENTS WHICH ARE INACCESSIBLE AND WHICH LEND THEMSELVES TO COMPLETE FLOODING  OF THE COMPARTMENT.

DRY CHEMICAL POWDER:
WATER CANNOT BE USED ON MOST FIRES AS IT CAN BE EXPLOSIVELY DISASTROUS. IN VIEW OF THIS OTHER MEDIUMS ARE USED. CHIEF AMONG THEM IS DRY CHEMICAL POWDER. IN THIS SODIUM BICARBONATE IS USED AS BASIS ALONG WITH ADDITION OF METALLIC STEARATE AS WATER PROOFING AGENT. DRY CHEMICAL POWDER IS EXPELLED FROM CONTAINER BY GAS PRESSURE.

IT IS ESPECIALLY EFFECTIVE ON BURNING LIQUIDS SUCH AS LIQUIFIED GAS, OIL ESCAPING FROM LEAKING LINES AND JOINTS. ON ACCONT OF IT’S UNIQUE ABILITY TO QUICKLY STOP COMBUSTION OF GASES, CHEMICAL PRODUCTS etc., IT HAS BECOME MOST POPULAR MEDIUM IN GAS CACCIERS AND TANKERS. DRY CHEMICAL POWDER IS ELECTRICAL NON-CONDUCTOR , THUS IT CAN BE UTILISED ON FIRES INVOLVING LIVE ELECTRICAL EQUIPMENTS. IT INHIBITS THE COMBUSTION REACTION.

Solas convention

The International Convention for the Safety of Life at Sea (SOLAS) is an international maritime safety treaty. It ensures that ships flagged by signatory States comply with minimum safety standards in construction, equipment and operation.

1974 version
The intention had been to keep the Convention up to date by periodic amendments, but the procedure to incorporate the amendments proved to be very slow,As a result, a complete new convention was adopted in 1974 which includes all the agreements and acceptable procedures. Even though the Convention was updated and amended numerous times, the Convention in force today is sometimes referred to as SOLAS, 1974.

The latest Convention in 1974 included the "tacit acceptance" procedure whereby amendments enter into force by default unless nations file objections that meet a certain number or tonnage.

Types of Bulkheads.

'A' Class Divisions
Class differences "A" are the bulkheads and decks of steel or any other equivalent material which is capable of preventing the passage of smoke and flames to the end of the test standard of the hour of fire. They are well reinforced. They are insulated with unauthorized combustible materials so that the average temperature of the un-exposed side does not rise above the initial temperature or temperature at any point above 140 ° C, including any junction, rise above 180 ° C above the original temperature, Within the time, specified below:

"A-60" 60 minutes

"A-30" 30 minutes

"A-15" 15 minutes

"A-0" 0 minutes.

A prototype or platform partition should be tested according to the FireCode test procedure to ensure that it meets the above requirements for integrity and temperature rise.

Class A fire protection doors

The construction of the doors in the class A walls and the fastening means in the closed position provides a fire resistance, such as the passage of smoke and flames, as far as possible, similar to the bulkheads in which they are located.

Class A fire-resistant doors, made of steel or an equivalent material.

In These doors should be capable of being opened and closed from each side of the bulkheadby one person only.
Fire doors in main vertical zone bulkheads, galley boundaries etc., other than power operated water tight doors should be (1) self closing and and be capable of safe operation with an angle of inclination of upto 3.5 degrees opposing closure, and in no more than 40 sec. and no less than 10 sec. with the ship in upright position. (3) the doors except for those for emergemcy escape trunks Shall be capable of of remote release from the central control stations and should also be capable of release individually from a position at both sides of the door.  Release switches shall have an on-off function to prevent automatic resetting of the system.  (4) hold back hooks not subject central control station release are prohibited, (5) a door closed remotely shall be capable of being reopened locally from both sides of the door and after such opening, the door shall automatically close again.(6) there should be fire door position indicator on the indicator .

Indicator panel in the central control room and the release mechanism shall be so designed that the door will automatically close in the event of power supply failure. (7)  local power supply accumulators for power operated doors shall be provided in the immediate vicinity of the doors to enable the doors to be operated at least 10 times (open and close)  after  disruption of the control system or the central power supply using local controls. (8) the components of the local control system shall be accessible for maintenance and adjusting.

(9) In the event of a fire, the control system shall operate the door at the temp. of at least 200 deg. For at least 60 min. served by the power supply and the power supply for all other doors not subject to fire shall not be impaired, and (10) at temperatures  exceeding 200 deg. C the control system shall automatically be isolated from the power supply and shall be capable of keeping the door closed upto at least 945 deg.C.

'B' Class Divisions
Class differences "B" are the bulkheads, decks, blankets and coatings

Approved non-combustible materials to prevent sufficient flame to pass through the end of the first half hour of the standard fire test. They have an insulation value so that the average temperature of the un-exposed side does not exceed 140 ° C above the initial temperature or the temperature at any point, including any junction, rises more than 225oC to the initial temperature, the following phases:

Class "B-15" 15 minutes

Class "B-0" 0 minutes.

A prototype or platform partition should be tested according to the FireCode test procedure to ensure that it meets the above requirements for integrity and temperature rise.
 
Class B fire protection doors

The construction of all doors in the partition type "B" and the means in the closed position represents the equivalent of fire as far as possible bulkheads in which the doors of the exception that can lie vent openings in the lower part of the doors, with a total area of ​​the lower opening Or equal to 0.05 m2. (1) These doors must be closed. Retaining hooks are not permitted. The doors of class B fire must be built with non-flammable materials approved. Class B fire protection doors built with approved non-combustible materials in accordance with the test method Code for fire.

Class differences, C '

Class differences "C" are the non-flammable materials, the bulkheads, decks, ceilings and linings, which limit requirements for the passage of smoke and flames or temperature rise. Door Class "C" is the type of doors installed in the class partitions "C". The approved noncombustible materials must be constructed.

Fire dampers

Valves are penetrating into the ventilation ducts installed bulkheads and bridging the class "A" to maintain the division of fire resistance capability and prevent the spread of smoke and flames in adjacent compartments through the ventilation system.

fire integrity

Resistance to fire is to keep the grounding element's resistance with a bulkhead or deck intact for a period of time, 60 minutes for class "A" and 30 minutes for class "B".

Fire Detection Systems

The PURPOSE of this regulation is to detect a fire in the space of origin and to provide for alarm for safe escape and fire fighting activity.  For this purpose :
(1) Fixed Fire Detection  and fire alarm system installations shall be suitable for the nature of the space,fire growth potential  and potential generation of smoke and gases, (2)  manually operated call points shall be placed effectively to ensure a readily accessible means of notification and (3) fire petrols shall provide an effective means of detecting and locating fires and alerting the navigation bridge and fire teams.  Fire Detection Systems. – General Requirements.

A fixed fire detection and alarms system shall be provided as per this regulation.
 A fixed fire detection and alarm system and a sample extraction smoke detection system required as per regulations mentioned in Chapter II-2, Part C, of SOLAS shall be of an approved type and comply with Fire  Safety Systems Code.
The function of such systems shall be tested under varying conditions of ventilation after installation.
Such installed systems shall be periodically tested for proper functioning under simulated fire conditions to the approval of Administration.

Detection in Machinery Spaces:
A fixed fire detection and fire alarm system shall be installed in (i) periodically unattended machinery spaces and (ii)m/c spaces containing all automatic and remote control systems and equipment approved in lieu of continuous manning of the space and also  in continuously manned spaces having a central control room.
This system shall be so designed and installed that all the fire detectors  of  suitable type will be capable of detecting the smoke or fire rapidly in any part of the spaces under working varying condition of temperature and ventilation.

Detection in Accommodation and Service Spaces and Control Stations:
(1)  Smoke detectors shall be fitted in all stairways, corridors, and escape routes and if found necessary, special purpose smoke detectors shall be fitted within ventilation ducting.

Fire Extinction Systems. – General Requirements
This system is brodadly divided in three parts:
Regulation 8 of Part C of Chapter II-2 of SOLAS.  Control of Smoke spread :  For this purpose, means of controlling smoke in atriums, control  m/c spaces and concealed spaces shall be provided.
For example, in most cargo ships of any type of all the supply air fans (usually 4) for machinery spaces, at least one fan is reversible and can be used as an exhaust fan in the event of fire and generation of smoke in the m/c spaces.
In accommodation, gallies, Navigation Bridge, Steering Flat  a provision for exhaust fans is made to expel smoke from the concerned spaces.

(2) Regulation 9 of Part C of Chapter II-2 of SOLAS.
Containment of Fire:  For this purpose (i) the ship shall be subdivided by thermal and structural boundaries,
 (ii) thermal insulation of boundaries shall have due regard to the fire risk of the space and adjacent spaces,
(iii)  The fire integrity of the divisions shall be maintained at openings and penetrations by using approved materials and methods by adhering to the relevant regulations of the SOLAS.

(3) Regulation 10 of Part C of Chapter II-2 of SOLAS.
Fire fighting:  For this purpose, following functional requirements will be met : (A) fixed fire extinguishing systems shall be installed, having due regard to the fire growth potential of the protected spaces, and (B) adequate number of approved type of fire extinguishing appliances shall be readily available.
 (C) Water supply systems  with approved type and sufficient number of fire pumps, fire mains, hydrants, hoses and nozzles complying with the regulations of the SOLAS requirements shall be provided.

(i)  Fire mains and hydrants materials readily rendered ineffective by heat shall not be used.
(ii) Their arrangement shall be such as to avoid the possibility of freezing, with adequate provisions for the drainage of the mains.
The number and position of hydrants should be such that at least two jets of water from two different hydrants may reach any part of the ship.
There will be an  isolating valve and a relief valve on the fire main line as approved by the regulations.
Pressure at the hydrants: For cargo ships above 6000 grt   it should be 0.27N/mm2.

(vi) Fire pumps : For cargo ships of 1000 grt  and above, there will be at least two independently driven fire pumps, which will  have the provision for being started and stopped by local and remote  switches (normally situated on the Bridge).
Emergency fire pump :  The space containing the emergency fire pump shall not be contiguous to the boundaries of the m/c spaces  or those spaces containing main fire pumps.  There will be no direct access between the m/c space and the emergency fire pump spaces.
The emergency fire pump shall have two sources of electrical power supply, one from the power mains and the other from the emergency generator bus bars.
Ventilation arrangements to the emergency fire pump spaces shall be such as to preclude the possibility of smoke from m/c space fire entering or being drawn into the space.
(viii) Fire hoses shall be of non perishable material  approved by the Administration and should have a length of at least 10 mtrs, but not more than 15 mtrs in m/c spaces and not more than 25 mtrs for open  decks on ships with breadth in excess of 30 mtrs.
(ix) Standard nozzle sizes shall be 12mm, 16mm and 19 mm.  For accom. Spaces a nozzle size greater than 12 mm and for cargo spaces a nozzle size greater than 19 mm need not be used.  The size should be adequate to obtain the max. discharge possible from two jets at the approved pressure.  Nozzles shall be of approved dual purpose type( i.e. spray/jet) incorporating a shut off.
(x) Portable fire extinguishers:  Their type and design shall comply with the requirements of the Fire Safety systems Code.
Ships of 1000 grt annd above will have at least 5 portable fire extinguishers in accom. Spaces, service spaces and control stations.  CO2  fire extinguishers shall not be placed in accom. Spaces.  In control stations and other spaces containing electrical or  Or electronic equipment, only those fire extinguishers whose extinguishing media are not electrically conductive or harmful  shall be used.
Spare charges shall provided for 100% of the first ten extinguishers and 50% for the remaining fire extinguishers capable of being recharged on board. Instructions for recharging shall be carried on board.
(xi) Fixed fire extinguishing systems: These systems for m/c spaces may be any of the following types: Fixed gas fire extinguishing system, a fixed high expasion foam fire extinguishing system or a fixed pressure water spraying fire extinguishing systems, all complying with the provisions of the Fire Safety Systems Code.

Here fire extinguishing systems using Halon 1211, 1301, and  2402 and perfluorocarbons shall be  prohiibited.
(xii) There shall be at least one portable foam applicator unit complying with the provisions of the Fire Safety Systems Code.  In addition, in each space, approved foam type fire extinguishers each of at least 45 ltr capacity shall be provided.  Additionally, there shall be provided a sufficient number of portable foam extinguishers so located that no point in the space more than 10 m walking distance from an extinguisher and that there are at least two such extinguishers in each space.
(xiii) Paint Lockers shall be protected by  (i) Co2 system designed to give a minimum volume of free gas equal to 40% of the gross volume of the paint locker, (ii) a dry powder system giving at least 0.5 kg powder/m3 of the space, (iii)  a water spraying or sprinkler system connected to ship’s fire mains designed for 5 ltr/m2 /min.  All above systems shall be operable from outside the protected space.
(ivx)  Fire Extinguishing systems for cargo spaces:  Fixed Co2 or inert gas system complying with the provisions of the Fire Safety System Code.  For cargo tank protection on Tankers a fixed deck foam fire extinguishing systems complying with provisions of the Fire Safety System Code shall be used.
(xv) Approved Fire Fighter’s Outfits (atleast two in  nos.) shall be carried by all ships.  Additionally, on tankers two extra sets will be carried.

 # The article was written by two author and then merged before publishing. Various books are used as reference before writing this article but no part is being reproduced but stated in a different easy way.

# Cover image credit: Pintrest  (If you have any problem regarding the post contact us!)
 


Author Arpit Singh & Amit                        


Rudder angle indicator | Definition, Working and Circuit Diagram


Rudder angle indicator | Definition, Working and Circuit Diagram
A device to display the current position of the rudder installed in the control house of the bridge. In the angle indicator system Rudder is independent of the steering system and is only for the display. There is an IMO requirement which states regardless of the steering control system there must be installed steering indicator system installed on board. The specification of the rudder angle is required for each cockpit and steering position in the rudder emergency room.

The various regulatory authorities vary the requirements of the Rudder Level Indicator (RAI). DNV needs a second angle indicator independent bar on deck. Regulation of the Panama canal requires large instruments (min 192x192mm) Bridge, visible wing operator and IMO pull to train / MED (ISO 20673) requires that the accuracy of the system is over a degree.

Rudder angle indicator consists of a control unit, a transmitter and receiver. This includes indicators with different dimensions, different scales and rudder angle display.

Basic Steering gear system

A rudder angle indicator consists of a transmitter and a receiver direction of the rudder rudder. The emitter is connected to the steering head by means of a lever, etc. in the wheel housing. Communicates rudder direction and rotation angle for self-synchronization of the machine in the sender and causes the self-synchronization of the machine, in the receiver that I have in the wheelhouse or another that is for with their directions of synchronicity. Self-synchronous transmitters and display units used in the control angle display systems are manufactured by various companies refer to names such as Selsyns, Synchro, and Automatic Syns Telmotors.
Non Follow-up Steering System
Non Follow-up Steering System

Control equipment – conveys a signal of the desired rudder angle from the bridge to the steering flat where it is received to activate the power unit and transmission system until the desired rudder angle is reached. This equipment can be of 2 types (1)hydraulic telemotor systems (tele- means far away in Greek & motor means motion or movement) & (2) electrical electronic control equipment.

Hydraulic telemotor systems:  The telemotor employs master and slave principle. The transmitter is situated on bridge and the receiver at the steering gear unit. Mechanical movement is transduced hydraulically or electrically for distance telemetering and is then transduced back again.

Auto & Follow up Steering System
Auto & Follow up Steering System
                            
Hydraulic Transmitter: As the bridge steering wheel is moved to starboard the rotating pinion causes the RH ram to move down, pushing oil out to the receiver unit along the RH pipe. The LH ram moves up, so allowing a space for oil to come from the receiver unit. The fluid being virtually incompressible, any down movement of the RH produces an identical movement at the receiver unit. This in turn displaces the same quantity of fluid which is taken up in the extra space created by the LH ram moving up. The fluid in the replenishing tank acts as reservoir. The casing is usually gunmetal with bronze rams, and copper pipes are led in by drilled leads in the casting. A device (called bypass valve) is required in the system to allow for variation in oil volume due to temperature changes and also to allow for equilibrium between both sides of the system. This bypass valve also has function of topping up the system in the case of leakages and acts as relief valve in case of pressure rise.

Bypass valve: Operation can only be carried out when the wheel is in the mid position. This is achieved by having the operating rod butting against a circular disc, in mid position of the wheel the slot in the driven revolving disc allows the operating rod to be depressed through it. With some types the operating rod is depressed by hand, whilst with some types the rod is automatically depressed by a cam each time the wheel passes mid position. In case of hand operated types the rod is operated at regular intervals and must be operated when either pressure gauge registers above 4.5 bar with wheel in mid position. When the rod is depressed both sides of system are connected thus giving pressure balance. The connection to the replenishing tank is also joined to both sides of the system, so that any expansion or contraction of the oil can be compensated.


Hydraulic Receiver: Consider the starboard (clockwise) movement of the bridge wheel. The depressed RH ram pressurizes the right hand side of the system. The pressure force acts on the central web of the moving cylinder until the movement caused corresponds to the movement of the ram in the steering telemotor. Oil is pushed back on the left hand side of the moving cylinder central web to the steering unit. After a small initial movement the LH sleeve butts against the nut and further movement by the moving cylinder to the left compresses the springs. When the steering wheel is returned to mid-ship the springs, which are under initial compression, return the moving cylinder to mid position. For port wheel rotation the LH ram of the steering unit moves down and the receiver moving cylinder goes in the opposite direction i.e. in this case left to right.
The moving cylinder is connected by a linkage to the control unit of the steering engine. Thus any movement of the bridge telemotor unit by wheel rotation is almost directly operating the control device which causes rotation of the steering engine and rudder movement.


electrical electronic control equipment: This system is based on the electrical and electronic circuits, the monitoring and control of the valves, which control the movement of the rudder. The system also includes a logic circuit that prevents the side rudder from reaching its physical limits. In the steering system can only work, under preset electronic limits. When the bar has reached a limit, the power of the solenoid valve closes automatically.

Electronic Steering Control
Electronic Steering Control

The system consists of the following parts: The control unit transmits to the angle of the desired direction from the bridge in the direction of the plane,Hand Steering without follow-up, Hand Steering with follow-up and Auto Steering using Gyro Compass.

The power supply provides the energy to move the rudder at the desired angle and the transfer unit to move the motions of the rudder.

The central steering of the movement of the rudder affect the ship's engines control. And rudder actuators single unit servo steering is the torque means is applied to the i-th rudder shaft. Lance or Quadrant

Control system of the device by means of which the commands from the computer to the power units of the steering mechanism and other necessary parts are transmitted to operate the steering. Including transmitters, receivers, hydraulic control pumps and motors associated hoses and cables.

The rudder actuator, the element that directly moves to a hydraulic pressure on the mechanical effect moves the rudder. Wheel drive means that the parts that transfer the force from the actuator to the aileron of the flow including the rudder. Power unit means:
  • in the case of electrical steering gear ; an electric motor and its associated electrical equipment
  • in case of electro-hydraulic steering gear ; an electric motor and its associated equipment and connected pump
  • in case of other hydraulic steering gear ; a driving engine and connected pump

Steering Gear Regulations

1.Every ship is to be provided with two power unit (main and auxiliary) steering gear, each independent of the other. This is because if one fail another can take over the power. If however two identical power unit is available, the presence of stand-by(Auxiliary) is not required.  

2.The capacity of the unit must be such that, it may swing the rudder from 35º on one side to 35º to the other side of the ship with the maximum speed and at deepest draft.The time required to do so must not exceed 28 Seconds.

3.Steering gear must be power operated if rudder stock diameter is greater than 120mm. Mostly we use hydraulic power for operating the rudder post.

Power of the auxiliary steering shall be such that rudder can be swung from 15º on one side to 15º to the other in 60 seconds at deepest draft and of 7 knots.

5.Steering gear should be prevented from any abnormalities, such as overloading, short circuit, overload, and visual and audible indicator should be available on bridge, ECR and steering gear room, alarms and trips is also present to minimize the damage.

6.For Hydraulic Oil tank, Low level alarm is present.

7.A Tanker of 10000 GRT and more must be provided with two steering gear systems, So in case of failure the steering gear change automatically to the stand-by Steering gear system within 45 seconds, along-with alarm for indication. It is provided for a reason, that if in case failure occur the ship keep moving in the same direction.

#Cover image credit: http://marine-data.co.uk


Author Arpit Singh & Amit                                                                Article Requested by: kesavan s


Welding (Marine Engineering)

 

Welding ( Marine Engineering )

History:
Method of joining metals have been known for thousand of years, but for most of this period the only form of welding was forge welding by a blacksmith.

Number of new welding principles emerged at the end of 19th Century, sufficient electrical current could then be generated for Electric Arc Welding and Resistance Welding. Arc welding was initially carried out using Carbon Electrode, shortly followed by use of steel rods, important advancement was made by development of Coated Electrode.

Another method of welding was also developed at that time, which was Gas Welding. The use of Oxygen and Acetylene made it possible to produce a comparatively high flame temperature 3100℃, that is higher than other hydrocarbon based gas. The intensity of all these heat sources enable heat to be generated in, or applied to the work piece quicker than it is conducted away into the surrounding metal.

Thus it is possible to generate a molten pool, which solidifies to form the unifying bond between the parts being joined.

Welding process maybe divided into two main group, pressure welding and non pressure welding, any welding process that require pressure is generally referred as Forge Welding, and these method usually does not require filler metal or flux, the part to be welded however, should be clean and free from grease, dirt, oil, etc. This welding method is the oldest, and require metal to be welded to rise in temperature and hammering the surfaces to form a union.

Resistance Welding is another form of Forge Welding, current and pressure is applied to the metal to be welded without any filler metal or flux.

The Welding process which does not require any pressure to be welded but only the current and filler metal and flux are .The most popular form of Fusion Welding is Electric Arc Welding or Metal Arc Welding Process.

Welding Terminology

  1. Pressure Welding: Welding in which sufficient outer force is applied to cause more or less plastic deformation of both the facing surface generally without the addition of filler metal. The facing surface are heated in order to permit or facilitate bonding
  2. Fusion Welding: Welding without the use of outer force in which the facing surfaces must be melted. Molten filler metal is added.
  3. Surfacing: Producing a layer of different metal by welding, example: with higher corrosion, abrasion or heat resistance than the parent metal.
  4. Deposition Rate: Amount of metal supplied to the joint per unit time during welding.
  5. Heat Affected Zone (HAZ): Area of base metal which is not melted during welding but whose physical properties are altered by heat induced from weld joint.


Electric Arc Welding

In this, a electric spark is struck between electrode and the metal to be welded. The heat which is generated cause the electrode to melt and the molten metal is transferred from the electrode to the metal.
If the electrode is bare, that is without flux(Coated electrode), the arc that is generated tend to wander and is difficult to control. Also it is open to the atmosphere contamination , that result in porous brittle weld. To avoid these defect, flux coated electrodes are generally used.
The flux coating melt at high temperature than the electrode core, thus coating protrudes beyond the core during welding, thus avoiding wandering of arc, that is it provide stability, and concentration of the arc. The coating also shield the arc and the molten metal pool from atmospheric contamination, by forming a shield of inert gas around it as coating vaporize.
Silicate that is formed from coating, form slag upon the surface of the hot metal and this and this protect the hot metal from the atmosphere as it cools down, slag can be removed easily when metal cools down.

Electric arc welding maybe done by using A.C or D.C supply. A.C supply is usually used for following reason:

Advantages

1 less planet maintenance
2 Higher efficiency than D.C plant
3 More compact plant

Disadvantage of A.C plant:

1 More difficult to weld Cast Iron and Non-Ferrous metal
2 High voltage is used so higher the shock risk.

Defects in Weldings:

  1. Overlap: it is caused when weld metal overflow without fusion on parent metal. This can be detected by Magnetic crack detector
  2. Undercut: This occur due to higher current or low speed of welding, it cause the wastage of parent metal and groove and channel is formed at the toe of the weld.
  3. Spatter: This is the globules or particle of metal scattered on  or around the weld, this occur due to high voltage or current making metal to splash.
  4. Blowhole: cause due to entrapment of Gas in large cavity.
  5. Inclusion:  Any slag or other entrapped matter, surface of metal to be welded should be cleaned and should be freed from grease, oil, dirt, etc. During the welding process slag must not be allowed to be get infront of the molten metal or it may get entrapped. So, during the changing of electrode, the metal should be allowed to be cooled and slag must be removed to avoid Inclusion.
  6. Lack of Fusion: this occur between weld metal and parent metal, between different layer of weld metal or between contact surface of parent metal, it is caused by incorrect voltage , curren, dirt or grease.

For Full Article Goto ShipDiggers.

Author : Arpit Singh

Watch Keeping at sea for Marine Engineers | Step-by-step


Watch keeping is an integral part of marine engineer’s duties on board ship. The technicians perform tasks and routines for monitoring the ship's engine room. The clocks are divided into three periods of four hours and the following work must be carried out and checks carried out at sea.

  • Check the colour of  exhaust emission from funnel.
  • Check the Economizer temperatures, pressure drop and the system for any leakage.
  • Check the oil fired boiler water level, blow through gauge glass and check pressure.
  • Check the boiler circulating pump for operating pressure, vibration, noise, gland leakage and bearing oil level.
  • Check and confirm normal operation of incinerator if running.
  • Check the waste oil tank level and temperature, drain off water.
  • Check Main & Aux. engine header tank levels, if they require filling record the quantity of water added.
  • Check the temperatures and pressure of the fuel valve cooling system. Examine the level of the F. V. C  header tank, check for contamination and confirm through flow.
  • Check stern tube header tank level, return flow, sump, pump and oil condition.Examine M. E cylinder tops for leakage, movement, overheating and any temperature or pressure outside the normal parameters.
  • Check for exhaust gas leaks.Examine turbo charger oil levels, pump operation, temperatures, pressures and differentials, whilst checking also for any unusual noise or vibration.
  • Monitor air cooler pressure drop, and ensure Makers operating parameters are adhered to with regard to dew point temperature.
  • Check cylinder oil day tank level and individual lubricators for level, flow and function.
  • Check all bunker fuel tanks for level, temperature and drain for water.
  • Check fuel fine filter differential.Examine fuel pumps for leakage or unusual noises.Ensure oil mist detector is functioning correctly and test alarm.
  • Check ME governor oil level and fuel pump racks.
  • Examine auxiliary blower if running and scavenge belt to ensure that scavenge and air cooler drains are clear.
  • Feel over scavenge belt.Test air line drains for water.
  • Check all standby pumps are on auto mode and ready to start.
  • Check air compressor  oil level, and the temperatures and pressures whilst  running.
  • Check fresh water generator for normal operation & also chemical dosing to feed line.
  • Check sewage treatment plant for normal operation.
  • Examine A/E and check all running parameters are within limits. Fuel leakage, non fitting of double skin pipes and removed  protection or insulation from exhaust manifolds to be rectified immediately .
  • Check A/E bilge’s for leakage.
  • Confirm that an alternator engine is on standby in the control room and that the L. O priming pumps are on Auto.
  • Checking drinking and domestic water hydrophore systems for levels, and leakage. Ensure that the Calorifier, circulating pump and UV Sterilizer are operating satisfactorily.
  • Examine boiler feed water system for normal pump operation and check the cascade tank for temperature and level. Also check that there is no hot well contamination with fuel oil due fuel oil heating coil leaks.
  • Examine air reservoirs and check the drains for water, ensure that control and service air reducing valves are functioning correctly and that the control air dehydrator is operating normally.
  • Examine the purifier room for leakage, ensure that running purifiers and operating normally with regard to oil levels, flow rates, temperatures and pressures. 
  • Ensure lowest throughput for L O purifiers.Check Calorifier.
  • Examine Booster pumps, flow-meter and heaters for normal operation without leakage.
  • Ensure that all main engine pumps are running normally and that standby pumps are ready for Auto operation.
  • Check HFO Serv & Sett tanks levels and temp. Drain off water.
  • Check all running purifiers for normal operation. Check gear case oil level, Separated Oil temperature and feed rate, motor load etc.
  • Skim off sludge from recycle tank.
  • Check F. O booster p/p, check F. O temperature.
  • Check JCW pump and motor for normal operation.
  • Check M/E Lubricating Oil Pressure (Bearing), X-Head Oil Pressure and Piston Cooling.Check piston cooler and L. O cooler in/out temp.
  • Check sounding of all sludge tanks, bilge storage tanks, compare with previous sounding.
  • Check M/E L O pump discharge filter Pressure drop.
  • Check M/E L O pump/motor for normal operation.
  • Check thrust bearing L. O temperature Fwd/Aft.
  • Check E/R bilge level with special attention under the flywheel.
  • Check L. O levels and temps of intermediate shaft bearings.
  • Check stern tube L. O sump level, oil pressure, temp and return flow.
  • Check M/E L. O sump sounding. compare with earlier soundings recorded.
  • Check and confirm L. O purifier is operating normally note L. O temperature.
  • Check piston cool leak off tank, open skimming v/v to skim off oil from top.
  • Check piston cooling water tank level top up if required.
  • Check and confirm main S. W p/p, motor and auxiliary  S. W pump/motor working normally.
  • Check piston cooling p/p pressure and in/out temp of all units check flow.
  • Check A/E load and winding temp. Do a function test on alarm panel. Reconfirm all running parameters of M/E and A/E.
  • See the Chief Engineer’s standing instruction book and also notice board for daily instruction and guidance. Discuss with outgoing watch keeping engineer if there have been any special operations problems during his watch or any change in status of running machinery Function and lamp test of Alarm panel.
  • Check no alarms are inhibited.Ensure no alarms indicating abnormal condition are active.
  • Ensure air and water on deck shut if not required.
  • Log down all parameters in log book
  • Check for following hazards and rectify :-
  • No Fuel, L. O or water  leaks.
  • No loosely stowed equipment.
  • Gas bottles shut and welding plant shut down.
  • Fuel high pressure pipes for M/E & A /E’s secure and no leaks.
  • No abnormal vibrations of any type.
  • No water tight openings open unnecessary.
  • Ensure that the welding equipment is off.Double check additional A/E on standby, and Emergency Generator on Auto.
  • Double check M. E controls on Bridge and max speed limit set as per Chief Engineer’s instructions
  • Check no alarms have been isolated, unless authorized by C/E and E/O. Note there are no existing alarm condition, unless a valid reason and C/E and E/O aware of.
WHEN IN DOUBT DO NOT HESITATE TO CALL CHIEF ENGINEER


Author Amit                                                                            


High Voltage System on board Ship | Basics

High voltage system
 
Every day the owners and designers will show for greater profitability to larger ships. As the vessel size increases, it is necessary to install more powerful engines and other machines.

This increase in the size of the machines and other equipment requires more power and therefore higher voltage power system on board a ship must be used.

What is the high voltage?
In the maritime practice, most merchant ships have a neutral 3-phase 440 V Supply. This energy system belongs to the category of low voltage, used where Engine power requires an average power of 200 kW. In Straight terms Voltages up to 1000 V are known as low voltage system and if Greater than 1000 V voltages it is designated as high voltage system.

Advantages / disadvantages of HVS (high voltage system):

Advantage:

  • Reduction of the size of generators, motors, cables etc.
  • Weight and space saving
  • easy construction
  • Reduced installation costs
  • The reduction of losses - a more efficient use of energy
  • The reduced amounts of short circuit in the system, which decides the design and the implementation of Electrical equipment used in the energy system.

Disadvantage:

1. higher insulation requirements for cables and equipment used in the system.
2. Increasing the risk factor and the need for strict compliance with the strict safety precautions.

A work permit for H.V SYSTEM:

1. Before a work permit is issued, the authorized person or electrician must identify the equipment you are working or test to be performed.
2. If the order includes or may involve access to equipment where the confusion could occur, the authorized person (HT) / electrical engineer must identify the elements to the appropriate person (HV) and apply the parking meter.
3. Before a work permit , the authorized person (HV) / electrical engineer must demonstrate the isolation of the knowledgeable diagram (HV) and ground and show areas of safety precautions, isolation and the working point or test.
4.Authorized person (HV) / electrical engineer must ensure that the appropriate person (HV) cover all procedures and safety precautions.
5. If the competent person (HV) then accepts the approval or sanction, this person is responsible for the work or final proof until the license becomes invalid or punishment.
6. Select the point of work.
7. Grant of work permit, the isolation of the diagram and grounding, and the key for the security key field of the expert person (HV).
8. Persons who perform (HV) / Electrical Engineer tasks requiring a work permit or sanctions for the test must issue the documents themselves.
9. Set the block diagram and fill the logbook of the site.
10. All these documents must be signed by an authorized person (HV) / electrical engineer before starting work or test.

A typical high voltage system line diagram
A typical high voltage system line diagram

High voltage safety measures

For additional safety, high-voltage systems incorporate the advanced circuit breaker system into the system, as part of the HV devices in general. Since ship uses high voltage generators, the network provides the high voltage motor (for the drive, the side rams and Air compressor) and the branches of the main transformers to the control unit 440 V. Additional power connections are used to interface with the emergency switchboard.

HV circuit breakers and contactors

Probably the main difference between HV and LV system system occurs in the main area of ​​the HV. For HV, types of switches can be air breakage, break oil, gas from SF6 (sulfur hexafluoride) or loss of vacuum. Among these types, the most popular and reliable are the vacuum circuit breakers, which can also be used as motor starters, HV contactors.

Each phase of a circuit breaker or vacuum contactor comprises a fixed and movable contact in a sealed glass sleeve borosilicate and evacuated. The movable contact is actuated by flexible metal bellows by a loading motor / spring or a magnetic drive mechanism. The high electrical resistance of a vacuum allows a very short contact switch separation and rapid arc without sealing is achieved.

When an alternating current is interrupted by the disconnection of the contacts, an arc is formed by a metal vapor from the material on the contact surfaces, and further circulates alternating current to a zero current approaches. Wave form at this time, the arc is replaced by a high voltage strength region, which can withstand high voltage recovery. Most metal vapor condenses again to contacts and is available for the following arc. A small amount is placed in the shield around the contacts protecting the insulation sheath. Since the arc time is very short (usually in the order of 15 ms), the arc energy is much lower than that of the circuit breaker, so that the vacuum contacts suffer much less wear.

HV circuit breakers and contactors

Probably the main difference between HV and LV system system occurs in the main area of ​​the HV. For HV, types of switches can be air breakage, break oil, gas from SF6 (sulfur hexafluoride) or loss of vacuum. Among these types, the most popular and reliable are the vacuum circuit breakers, which can also be used as motor starters, HV contactors.

Each phase of a circuit breaker or vacuum contactor comprises a fixed and movable contact in a sealed glass sleeve of borosilicate. The movable contact is actuated by flexible metal bellows by a loading motor / spring or a magnetic drive mechanism. The high electrical resistance of a vacuum allows a very short contact switch separation and no arc when connection is achieved.

When an alternating current is interrupted by the disconnection of the contacts, an arc is formed by a metal vapor from the material on the contact surfaces, and further circulates until alternating current to a zero current approaches. At this time, the arc is replaced by a high voltage strength region, which can withstand high voltage recovery. Most metal vapor condenses again to contacts and is available for the arc flow. A small amount is placed in the shield around the contacts protecting the insulation sheath. Since the arc time is very short (usually in the order of 15 ms), the arc energy is much lower than that of the circuit breaker, so that the vacuum contacts suffer much less wear.



Author Amit |                                                                                     Article Requested By: KV Gupta