EXPLAIN/EQUIPMENT/ARRANGEMENT/APPROXIMATE CONSUMPTION/ ALARM TEST/ FUNCTION CHECKS/ MAINTENANCE AND CHECKS ON SCABA IN SHIP'.

Explain about SCABA and how you will use in emergency? How you will pressure test for remaining air in bottle or how you will make alarm?

A breathing apparatus normally known as the BA set or the SCBA (Self contained Breathing apparatus)

or CABA (Compressed air breathing apparatus) is an equipment used to supply fresh air for human breathing when a person is entering any space where the atmosphere is a suspect and may not support human life

-When entering into an enclosed space

-When entering into a space to fight fire
The Self Contained Breathing Apparatus (SCBA) or Compressed Air Breathing Apparatus (CABA):

The equipment is designed on an open-circuit system. The exhaled air is discharged to the atmosphere and

the wearer of this apparatus gets his fresh air from the air cylinder attached to the equipment.

The equipment consists of:

-One or two cylinders containing air under pressure

-A harness to mount the cylinders on the back of the person.

-A respiratory system which incorporates a means of reducing the pressure of the air from the cylinder

and of supplying the wearer on demand with air according to his requirements, and

-A facemask attached to a demand valve, which maintains a positive pressure inside the mask at altimes.

The arrangement of a typical apparatus is as follows:

-The cylinders contain approximately 1240 litres of free air compressed to give approximately 31 minutes of full air usage time and 21 minutes of working duration under normal circumstances Please note that the usage time greatly varies from person to person and the workload the person is performing.

-A reducing valve is connected after the cylinders to reduce the pressure to approximately about 4 bars. This pressure is further reduced by the demand valve, which is attached to the mask of the wearer.

-The demand valve supplies air to the wearer when he inhales and closes when he exhales.

-An Exhalation valve releases the exhaled air from the facemask

-When approximately 10 minutes of air is left (air cylinder pressure about 50 bar), a warning whistle will sound continuously warning the user that his air supply would soon be over and he has to move out

-This warning signal will sound continuously till the air in the cylinder is over.

-The facemask is made of moulded rubber with a series of adjustable rubber straps to secure it to the

head of the wearer and fitted with quick release arrangements.

-The user should have a good field of vision so that the wearer does not need to turn his head

constantly

-A gauge is provided to indicate the pressure of the air in the cylinder.

-Spare cylinders should be provided for each set of breathing apparatus and a small air compressor to

charge these cylinders is provided.

If the facemask is dislodged whilst the wearer is in a smoky or toxic atmosphere, it is vital that the wearer

should hold his breath and immediately replace the dislodged mask. If for any reason, there is likelihood of delay in doing so, the wearer should be evacuated to fresh air at the earliest, even though he may not feel any ill effects from the few breaths of contaminated air, which he has been forced to inhale.

An approximate Consumption and duration table:

Here we have taken an average consumption of 40 litres of air per minute being required by human

being when doing heavy work.

.

Hence if we have a cylinder of 1200 litres capacity fully charged then

Nominal working duration = 1200/40 = 30 minutes

10 minutes (period for which the alarm whistle

will blow and time required for the wearer to get back to safe atmosphere) = 20 minutes.

ALARM TESTING:

-Open cylinder valve.

-Line will pressurized with 200 bar pressure.

-Pressure gauge indicate 200 bar pressure.

-Close cylinder valve.

-Check pressure should not drop 10 bar in a minute.

-Now to make alarm test, operate demand valve and pressure will start to reduce from high pressure line.

-When on pressure gauge the pressure will reach around 55/60 bar the alarm will sound.

-It will indicate that now you have only 8-10 min for escape.

-As soon as you heard sound, escape from that compartment.

Function Checks:

-Close cylinder valve.

-Breathe normally to vent system.

-During venting observe gauge - whistle alarm should sound at preset pressure of 55bar +/-5bar.

-When gauge indicates zero, hold breath. Face piece should hold onto face indicating positive seal.

-Open cylinder valve slowly, but fully to pressurize system

-Inhale and hold breath. Unit must balance, i.e. no audible leak

-Continue breathing. Expired air should easily flow out of exhalation valve

-Press center of rubber cover on demand valve checking supplementary supply.

Note: If leak detected, open cylinder valve, readjust head harness and retest

During Use

-Cylinder pressure must not be less than 80% full

-Check gauge reading regularly. Whistle will sound at 55 bar +/- 5 bar.

-When whistle sounds, exit and go to safe area, by shortest and safest route.

-Do Not remove equipment until in safe area, clear of hazard.
  
After use

-Press and hold down the button and remove the demand valve.

-Removing mask: Insert index finger behind the tabs on the neck straps and press the buckles forwards

with thumb, pulling the mask forward off your face and then up and back over your head.

-Close cylinder valve and remove face piece.

-Unbuckle waist belt, lift shoulder strap buckles to loosen, remove equipment

Maintenance on facemask

-Cleaning: The mask must be cleaned after every use. Do not use any organic solvents such as acetone

alcohol etc.

Clean the mask with a cloth and lukewarm water mixed with all-purpose detergent. Rinse thoroughly under

running water

-Disinfecting: Disinfect mask after every use. Place mask in disinfectant bath. Only use approved

disinfectants. Excessive disinfectant concentrations and over-long disinfecting times can damage the mask.

Rinse thoroughly under running water.

-Drying: Leave to dry in air. Maximum temperature 60°C. Keep out of direct sunlight.

-Testing: The mask must be tested every time it has been used, repaired or serviced as per manufacturers

instructions.

-Visual inspection of the speech diaphragm: The speech diaphragm and O-ring must be clean and

undamaged. If not, clean or replace.

-Visual inspection of inhalation valve: The inhalation valve is visible in the mask connector. Check by blowing

into it that both wings of the valve disc move freely. Replace if seized.

-Visual inspection of exhalation valve: Remove the protective cap from the connector. Press one arm of the

spring clamp inwards and remove the clamp. Hold valve disc by the nipple and lift out of guide. The valve

disc and seat must be clean and undamaged. Clean or replace if necessary. Moisten valve disc with water and refit. When the seat is

horizontal, the valve disc must slide into the guide under its own weight. 

Additionally requires following checks to be carried out:

-Every month the air bottles, bottle valves, reduction valve, intermediate hose, manometer, carrying

back plate, the lung demand regulator, the warning alarm for withdrawal, and the breathing mask

shall be examined and checked in accordance with the manufacturer's manual.

-Every year all valves, sealing and speech membranes shall be checked.

-Every second year the exhalation disc must be replaced. This should be done even if the mask has not

been used

-Every five years the complete breathing apparatus shall be submitted to a major service check, which should include a major overhaul of the reduction valves in an authorized workshop and a pressure

test of the air bottles shall be carried out by an approved service company.

If an air bottle shows any sign of corrosion or if it has been exposed to damage or overheating it shall
be replaced instantly.


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