Air

Question 1

Describe the two main dangers associated with high pressure air systems ?

Answer 1

1. Dieseling ( combustion of hydrocarbons )
2. Embolisms ( Air bubble in blood stream )

Question 2

List the routine to be carried out to safely isolate HP air systems.

Answer 2

1. A minimum of two valves in each supply must be closed ( legal requirement )
2. The system downstream of isolations is to be thoroughly drained ( drain valves to be left open )
3. Isolation valves must be checked for leaks
4. where ever possible valve covers are to be used.
5. Tag out / rip out labels are to be filled in correctly, counter signed and securely attached

Question 3

List and briefly describe the advantages of air systems.

Answer 3

1. Readily available supply- reliability of source

2.Flexibility of use- wide variety of applications

3. Ease of storage - compressible medium allowing storage of large quantities
4. Easily transferred - through small bore pipes, no complicated systems required
5. Low fire risk- non combustible medium

Question 4

Give a description of the main and dedicated storage bottles fitted to a typical HP air system.

Answer 4

Main storage bottle : increase the capacity of the system and fluctuate with system pressure. They provide a a reserve of stored energy allowing the ship to recover from total electrical failure. They also help to maintain system pressure when compresor in shut down.

Dedicated storage bottles: directly connected to an individual item of the ships equipment. They are connected to the ring main but a non return valve is fitted on the supply like. This means that they do not fluctuate with system pressure and when filled will remain full.

Question 5

Give a description of the pressure vessel register

Answer 5

Is used to record the identification , test details and test periodicities of all non transportable compressed air and nitrogen cylinders , hydraulic accumulators , dryers , separators

Question 6

Give a description of how HP air cylinders are maintained in the RN ships

Answer 6

1. Bottles , cylinders and receivers are stamped with a unique serial number , start life date and the last test date
2. Identification numbers and the next test date are recorded in the pressure vessel register
3. Drain valves and springs must be correctly positioned at the bottom of the bottle so that all free water (condensation) can be drained out
4. Bottles must be drained using the drain valve in accordance with instruction in relevant Brs
5. Start life date triggers all subsequent timings for inspection and maintenance is not negotiable.

Question 7

Give a description of relief valves fitted on HP air equipment.

Answer 7

Relief valves are valves which are spring loaded to the shut position. When the force acting on the valve overcomes the tension of the spring the valve will lift releasing pressure to the atmosphere.

Question 8

Describe a BA charging panel

Answer 8

The BA charging panel is a two stage filter panel which consist of

1. Water separator within manual drain valve
2. Filter pack containing sponge filter for removal of oil ( coalescer )
3. Further water removal by two stage dessicant
4. Charcoal filter to remove chemicals and odour
5. Sintered bronze filter to remove particulates and dust