SCBA , SELF CONTAINED BREATHING APPARATUS ON CHEMICAL TANKERS - CAPT AJIT VADAKAYIL

SCBA consists of a portable supply of compressed air contained in a cylinder or cylinders attached to a carrying frame and harness worn by the user. 

Air is provided to the user through a face mask which can be adjusted to give an airtight fit. A pressure gauge indicates the air pressure in the cylinder and an audible alarm sounds when the supply is running low .

Only positive pressure type sets are recommended to be used in enclosed spaces.

Air is admitted to the face mask through a lung demand valve which opens when the user inhales. The lung demand valve can be by-passed giving an positive flow of air into the face mask. The use of this by-pass valve causes rapid depletion of the air cylinder.

If the equipment is of the positive pressure type, no by-pass valve is needed since the air supply system is designed to keep a positive pressure in the face mask at all times.

When using the equipment the following precautions are necessary:

The high pressure test, low pressure test and vacuum test must be conducted.

HP test: Open the bottle valve and check the pressure. Now shut the valve so that only the tubes to the face mask is now under pressure. Wait for 2 minutes and check for pressure drop , which will happen if the connectors are leaking.

LP test: Now slowly remove the air pressure. The audible low pressure alarm or whistle should now sound. Remember in some IBC sets, the alarm cannot be triggered by very less volume of air held in the tubes. It will indeed sound when the air bottle comes to the requisite pressure of 45 bars. Check this out before you condemn the set.

Vacuum test:   The face mask must be checked if it gives a tight fit on your face. Long beards are discouraged on Chemical tankers. Facial hair adversely affects the mask’s seal.

The number and types of outfits vary between vessels. However, in all cases , the BA sets must be kept well maintained. Read the manufacturers manuals and ensure that operating instructions are laminated and attached to the apparatus.

All bottles must be numbered and kept fully charged. Whenever a bottle is discharged, ensure recharging takes place as soon as possible.

 Do not allow bottles to become totally discharged. SCBA compressors must be kept in good order. The apparatus stowage positions shall be clearly marked .

It is essential that crews become thoroughly familiar with the type of apparatus found aboard their vessel. Drills should be frequently carried out using the apparatus which must be kept in perfect order and ready for instant use.

SOLAS requires tankers to have at least 4 sets.  3 nos additional IBC sets are required on chemical tankers. These must be stored in easily accessible ( from outside ) locations. If stored in lockers, the outside of the locker doors must be posted with IMO sign to indicate contents.

Breathing apparatus must always be used whenever emergency entry is made into a space which is known to contain toxic gas or smoke, or to be deficient in oxygen. It should also be used if there is a possibility that any of these conditions may exist or occur during the period of occupation.

Entry into an enclosed space under these conditions should, however, only be permitted in exceptional circumstances and when there is no practicable alternative.

Remember, the air supply of a 1800 litres free air  self contained unit will usually only be sufficient for 30 minutes entry time (allowing for 40 litres/minute usage). 

The consumption during rest is 10 litres a minute light work is around 30 litres per minute while the consumption during heavy strain like firemans lift of an unconscious person is greater than 100 litres/ minute.

The pressure guage must be monitored frequently to check on reserve air. The wearer must report this by walkie talkie.

Gas masks and canisters of the type which depend on chemical absorbents to protect the user from poisonous gases do not give protection against petroleum gas in high concentrations or against oxygen deficiency. Gas masks do not manufacture or provide oxygen. They can never substitute a breathing apparatus.

Ample time should be allowed for getting out of the hazardous atmosphere. In any event the user must leave immediately the low pressure alarm sounds .

If the user has reason to suspect the efficiency of the equipment he must leave the compartment immediately.

Air bottles must be refilled promptly, after use. The face mask adjucting straps must be kept slack. The official plan must be modified if the SCBA sets are not available in different parts of the ship and cannot be accessed  easily in case of smoke in the accommodation due to fire.

Air cylinders must be hydraulically tested every 5 years. Steel carbon composite cylinders must be hydraulically tested first after 3 years of construction, and then every 5 years.

At least 2 units must be in close proximity to each other, with internal and external access to them, considering these sets are used in pairs and never alone. All SCBA sets shall be tested and serviced annually by an approved service agency.

http://ajitvadakayil.blogspot.in/2011/01/airline-breathing-apparatus-on-chemical.html

CAPT AJIT VADAKAYIL

30 YEARS IN COMMAND