High pressure and low pressure air systems

Question 1

What are the advantages of compressed air?

Answer 1

1. Easily distributed
2. Can be easily stored
3. Flexibility and reliability of use
4. Low risk of fire

Question 2

What 2 categories can high pressure air be divided into?

Answer 2

1. HP air operating at 276 bar
2. Reduced HP air operating below 276 bar as required by specific equipment.

Question 3

How is high pressure air reduced so it can be used by specific equipment?

Answer 3

Via a reducing valve

Question 4

HP air can be divided into 2 areas, what are they?

Answer 4

IMS (Inside machinery space)
OMS (Outside machinery space)

Question 5

State the uses for HP air

Answer 5

1. Diesel engine starting
2. Gas turbine starting
3. Ship siren operation
4. Breathing apparatus charging
5. Weapon systems operation
6. Hydraulic system accumulator charging
7. Air driven machinery operation
8. Cross connection to low pressure air system

Question 6

What does HPAC stand for?

Answer 6

High pressure air compressor

Question 7

There are 4 stages to air compression leading to 276 bar. State the pressure of each stage.

Answer 7

Stage 1 - 4 bar
stage 2 - 17.5 bar
stage 3 - 68 bar
stage 4 - 276 bar

Question 8

How often do separator bottles drain?

Answer 8

Every 30 minutes

Question 9

State the 10% over pressure value for each stage of compression.
PRV - pressure relief valve

Answer 9

1st PRV - 4.4 bar
2nd PRV - 19.25 bar
3rd PRV - 74.9 bar
4th PRV - 303.6 bar

Question 10

What is the name of the air compressor used to create HP air

Answer 10

Hamworthy air compressor

Question 11

What alarms and warnings feature on the Hamworthy?

Answer 11

1. High water temperature
2. Low oil pressure

Question 12

What temperature does the high water temperature switch operate at?

Answer 12

54 degrees C

Question 13

What pressure does the low oil pressure switch operate at?

Answer 13

0.69 bar

Question 14

What pressure does the water jacket safety valve operate at?

Answer 14

3.5 bar

Question 15

What pressure does LP air operate at?

Answer 15

Up to 8 bar

Question 16

State the 3 ways LP air can be produced.

Answer 16

1. Hydrovane compressor
2. Rotary compressor
3. Supplied via a reducing station from the HP ring main

Question 17

What is LP air used for?

Answer 17

1. Pneumatic tools
2. Radar wave signals
3. Emergency stern seal inflation
4. Pneumatic surveillance panels

Question 18

State the hazards of working with HP/LP air

Answer 18

1. High pressure air directed towards the body can be lethal as air can enter the bloodstream
2. Explosion oil and grease can explode when brought in contact with pressurised air.

Question 19

What precautions are taken when working with HP/LP air?

Answer 19

1. Ear defenders are to be worn
2. Silicone grease is used to prevent dieseling
3. Hoses are secured (‘‘whipped’’) at both ends to prevent flailing
4. Hoses are dated with expiry dates

Question 20

State the safe working practices when filling air bottles

Answer 20

1. Bottle must be located on purpose built rack
2. Operators must be wearing PPE
3. Hoses must be in good condition and connected with the correct spanner
4. Good condition O seals must be used
5. Bottle should be filled slowly to avoid overheating

Question 21

What PPE is required when charging air bottles?

Answer 21

1. Goggles
2. Ear defenders