IMO Conventions

3. What classes of fires are the below sentences correspond to?

a) Class “A”                  b) Class “B”                   c) Class “D”

 

1. Flammable gas fires can be extinguished with dry chemicals that interrupt the chain reaction of the combustion (oxidation) process. 
2. Metals are carried in most forms as cargo. 
3. Lounges and recreation rooms may contain couches, chairs, tables, bars, television sets, books and other items that may be constructed of this class of materials.
4. Sand, graphite, various other powder extinguishing agents and salts of different types have been applied to metallic fires with varying success.
5. Water and other types of extinguishing mediums, such as foam and certain types of dry chemicals are also effective on this class combustibles.  
6. The advantage of aluminum lies in the reduction of weight.  A disadvantage, from the fire-fighting viewpoint, is the comparatively low melting point of aluminum as compared to that of steel.
7. Acetylene is typically found stored in cylinders for use on board.
8. The furnishings found in passenger, crew and officer accommodations are usually made of this class  materials. 

 

4. Retell all you knew about classes of fire. Use the following plan while retelling.

1. Classification of fires.

2. Materials corresponding to each class of fires.
3. Their location on board the ships.
4. Extinguishing mediums. Their advantages and disadvantages.
5. Means of extinguishing of different classes of fires.

 

Lesson 3.

 

1. Translate the following words and word combinations.

Generator, panel boards, switches, short circuits, overloading of conductors, arcing, overcurrent, in the vicinity of, internal combustion engines, combustible material, electrical shock, fuses, circuit breakers, overheating of bearings, excessive amount of current.

 

2. Write as many words as you can with the same roots as in such words:

Electricity, insulate, light, danger, heat.

 

3. Read and translate the text.

 

Class “C” Fires

Electrical equipment involved in fire, or in the vicinity of a fire, may cause electric shock or burns to firefighters.  This Subsection discusses some electrical installations found aboard a vessel, their hazards and the extinguishment of fires involving electrical equipment.

 

Types of Equipment

•  Generators.  Generators are machines that produce electrical power.  These machines are usually driven by internal combustion engines, or in older vessels, steam produced in an oil-fired boiler.  The electrical wiring in the generator may be insulated with a combustible material.  Any fire involving the generator or its prime mover will involve a high risk of electrical shock to personnel.

•  Panel boards.  A panel board has fuses and automatic devices for the control and protection of

lighting and power circuits.  The switches, fuses, circuit breakers and terminals within a panel

board all have electrical contacts.  These contacts may develop considerable heat, causing

dangerously high temperatures and unnecessary operation of overcurrent devices, unless they are

maintained in good condition.  Overcurrent devices are provided for the protection of conductors

and electrical equipment and open the circuit if the current in that circuit produces an excessively

high temperature.

•  Switches.  Switches are required for the control of lights and appliances and for disconnecting

motors and their controllers.  They are also used to isolate high voltage circuit breakers for

maintenance operations.  Switches may be of either the air-break or the oil-break type.  In the

oil-break type, the device that interrupts the circuit is immersed in oil.  

The chief hazard is the arcing produced when the switch is opened.  In this regard, oil-break

switches are the more hazardous of the two types.  The hazard increases when a switch is operated much beyond its rated capacity, when its oil is in poor condition or when the oil level is low.  Then the arc may vaporize the remaining oil, rupture the case and cause a fire.  However, if properly used and maintained, these switches present no hazard.

•  Electric Motors.  Many fires are caused by electric motors.   Sparks or arc, from short circuiting motor windings or improperly operating brushes, may ignite the motor insulation or nearby combustible material.  Other causes of fires in motors include overheating of bearings due to poor lubrication and grimy insulation on conductors preventing the normal dissipation of heat.

Electrical Faults that Cause Fires

•  Short Circuits.  If the insulation separating two electrical conductors breaks down, a short circuit occurs.  Instead of following its normal path, the current flows from one conductor to the other.  Because the electrical resistance is low, a heavy current flows and causes intense local heating.  The conductors become overloaded electrically, and they may become dangerously overheated unless the circuit is broken.  If the fuse or circuit breaker fails to operate, or is unduly delayed, fire can result and spread to nearby combustible material.

•  Overloading of Conductors.  When too large an electrical load is placed on a circuit, an excessive amount of current flows and the wiring overheats.  The temperature may become high enough to ignite the insulation.  The fuses and circuit breakers that are installed in electric circuits will prevent this condition.  However, if these safety devices are not maintained properly, their failure may result in a fire. 

•  Arcing.  An arc is pure electricity jumping across a gap in a circuit.  The gap may be caused intentionally (as by opening a switch) or accidentally (as when a contact at a terminal becomes loose).  In either case, there is intense heating at the arc.  The electrical strength of the arc and amount of heat produced depend on the current and voltage carried by the circuit.  The temperature may easily be high enough to ignite any combustible material near the arc, including insulation.  The arc may also fuse the metal of the conductor.  Then, hot sparks and hot metal may be thrown about and set fire to other combustibles.

Vocabulary.

The burns – ожоги

Oil-fired - использующий нефтепродукты в качестве горючего

Air-break type switch – воздушный тип (выключателя) (с разрывом дуги в воздухе)

Oil-break type switch – масляный выключатель

To interrupt - обрывать, прерывать, внезапно прекращать

To immerse - опускать, погружать, окунать

The arcing - электрическая дуга

Beyond – за пределами

To vaporize – испарять (ся)

To rupture – рвать, разрывать, прорывать

To ignite - воспламенять, зажигать; раскалять

Grimy insulation – грязная изоляция

Unduly - чрезмерно; неуместно; неоправданно

Intentionally - нарочно,  умышленно, намеренно

 

4. Choose the right sentences to the terms of left column.

Generators Panel boards Switches Electric Motors

1. They are used to isolate high voltage circuit breakers for maintenance operations. 2. Sparks or arc, from short circuiting motor windings or improperly operating brushes, may ignite the motor insulation or nearby combustible material.  3. The electrical wiring in it may be insulated with a combustible material.  Any fire involving it or its prime mover will involve a high risk of electrical shock to personnel. 4. Its electrical contacts may develop considerable heat, causing dangerously high temperatures and unnecessary operation of overcurrent devices, unless they are maintained in good condition.

 

5. Find the right answers to the questions.

What traumatism may electrical equipment on fire cause? What machines produce electric power? What material may the electrical wiring in the generator be insulated with? What is the purpose of panel boards? What are overcurrent devices provided for? What do switches isolate for maintenance operations? What is the main hazard when the switch is open? Why oil-break type of switches is more dangerous than air-break type? What causes may ignite the motor insulation?

High voltage circuit breakers. A combustible material. The arcing. The control and protection of lighting and power circuits. Sparks or arc, from short circuiting motor windings or improperly operating brushes, overheating of bearings, grimy insulation on conductors. Electric shock or burns. The protection of conductors and electrical equipment and open the circuit                                       if the current in that circuit produces an excessively high temperature. Oil may be in poor condition or of low level. Then the arc may vaporize the remaining oil, rupture the case and cause a fire. Generators.

 

6. Match the problem with its cause.

Causes	Problems
1.  The insulation separating two electrical conductors breaks down. 2.  Electrical resistance is low. 3.  Too large electrical load in a circuit causes an excessive amount of current flows. 4. The temperature of conductor becomes high. 5. The fuses and circuit breakers are not maintained properly. 6. The gap 7. Hot sparks and hot metals fused by the arc.	Setting fire to other combustibles. Intense heating in the arc. The temperature of a conductor rises and this may result in a fire. The ignition of the insulation. The wiring overheating. Short circuit. A heavy current causes intense local heating.

 

7. Speak about:

1. Which equipment may be involved in a fire.

2. Why can they be involved in a fire.
3. What electrical faults can cause fires.

 

8. Translate into English.
1. Одной из распространенных причин пожара на борту судов является неисправности и нарушение правил эксплуатации электрооборудования.
2. В электроустановках некоторых производств существует опасность пожара или взрыва по причинам искрения или недопустимого перегрева токоведущих частей.
3. Причины пожаров в электроустановках следующие:

- короткие замыкания.  При коротких замыканиях по  проводникам протекают большие  токи, в следствие чего происходит  нагрев проводников, загорается  изоляция и окружающие предметы.

- перегрузки. Возникают при  протекании токов, больших номинальных.  Происходит при неправильном  выполнении монтажных работ и  при подключении к сети нагрузки, на которую она не рассчитана.

- большие переходные сопротивления.  Возникают из-за сужения путей  протекания тока, что вызывает  местный нагрев. Неразъемные соединения  необходимо выполнять не на  скрутках, а сварные или паяные, разъемные - большого сечения  и массы, или с отводными  радиаторами;

- электрические искры  и дуги.

 

Home task.

 

1. Read and translate the texts.

Hazards of Electrical Fires

•  Electric Shock.   Electric shock may result from contact with live electrical circuits.  It is not

necessary to touch one of the conductors of a circuit to receive a shock.  Any conducting material that is electrified through contact with a live circuit will suffice.  Thus, firefighters are endangered in two ways:  First, they may touch a live conductor or some other electrified object while groping about in the dark or in smoke.  Second, a stream of water or foam can conduct electricity to firefighters from live electrical equipment.  Moreover, when firefighters are standing in water, both the chances of electric shock and the severity of shocks are greatly increased.

•  Burns.  Many of the injuries suffered during electrical fires are due to burns alone.  Burns may

result from direct contact with hot conductors or equipment, or from sparks thrown off by these

devices.  Electric arcs can also cause burns.  Even persons at a distance from the arc may receive

eye burns.

 

Locations of Electrical Equipment Onboard

Electric power is essential to the operation of a vessel.  The equipment that generates, controls and delivers this power is found throughout the vessel.  Some of this equipment, such as lighting devices, switches and wiring, is common and easily recognized.  

•  Engine Room.  The source of the vessel’s electric power is its generators.  At least two generators are located in the engine room and often three or four generators are fitted.  While the others are operating, one is always held in reserve for backup duty.  The generators supply power to the main electrical switchboard, which is typically in the same area as the generators in the engine room.  The switchboard houses the generator control panels, as well as a distribution section.  If a fire breaks out in the vicinity of the generator switches or the main switchboard, the vessel’s engineer can stop the generator by mechanical means.  This will de-energize the panel board and switches.  Also nearby is the engine room console, which contains controls for the fire pumps, ventilating fans, engineer’s signal alarm panel, temperature detection system and other engine room equipment.

•  Emergency Generator Room.  An emergency generator and switchboard are available for use on most vessels in case the main generator fails.  It will provide power for emergency lighting and equipment only.  They are located in the emergency generator room, which is outside the main engine room.

•  Passageways.   Electrical distribution and lighting panel boards are located along passageway

bulkheads.  Much of the vessel’s electrical wiring is placed in the passageway overheads.  Access panels are provided in these overheads to allow work on the wiring, and these panels can be removed to check the area for fire extension.

•  Other Locations.  The bridge contains much electrical equipment, including the radar apparatus, bridge console, smoke detector  indicating panel and lighting panel boards.  Below decks, in the bow and stern, are electrical control panels for the capstan and winch motors.  A power panel board in the machine shop controls the electric-arc-welding machine, buffer and grinder, drill press and lathe.  There is still much more electrical equipment located throughout every vessel.  The important point is that the hazards of live electrical equipment must be considered whenever a shipboard fire is being fought. 

 

Extinguishment of Class “C” Fires

When any type of electrical equipment is involved  with fire, its circuit should be de-energized. 

However, recognizing that the circuit may not be de-energized, the fire must be extinguished using a non-conducting agent, such as CO2 or dry chemical.  In considering the application of a fire extinguishing agent, an electrical circuit or panel should always be considered energized.

Vocabulary.

To grope about –  искать, нащупывать