Marine Engineering Study Materials

Precautions while Pressure Testing Refrigeration Plant

Before charging the plant with refrigerant, it must be pressure tested and pumped down. This article explains precautions and procedure to be carried out by a marine engineer for the pressure testing of refrigeration plant on ships.

Pressure test the plant with one of the following means:

• Dry air – pressurized cylinders containing dry atmospheric air may be used, but never use oxygen cylinders.
• Air compressor for high pressure.
• Nitrogen.

1. The plant compressors must not be used to pressurize the plant. Water or other fluids must not be used for pressure testing refrigeration plant.
2. If nitrogen is used, it is important to place a reducing valve with a pressure gauge between the nitrogen cylinder and the plant.
3. During pressure testing of the refrigeration plant, it is important to ensure that pressure transducers and other control equipment are not exposed to the testing pressure. The compressor stop valves must also be closed during pressure testing.
4. Plant safety valves must normally be blanked-off during pressure testing, as their opening pressure is lower than the testing pressure.
5. During this pressure testing, no person should be allowed to be present in rooms housing plant parts or in the vicinity of the plant outside the rooms.
6. The entire unit must be pressure tested in accordance with the local regulations for pressure testing refrigeration plant.
7. The test pressure must never exceed the design pressure of the refrigeration plant.
8. If it is required that the compressor should be pressure tested together with the unit or with the plant, the testing pressure must not exceed the value prescribed in the instruction manual of the refrigeration plant.
9. Please observe that manometers, pressure controls, pressure transmitters and other control equipment are not exposed to testing pressure.
10. After doing pressure testing of refrigeration plant, reduce the pressure to say 10 bar for a period of 24 hours, for an initial leak test – as a tightly sealed plant will maintain this pressure throughout the period.
11. During the leak test, it is permitted to enter the room and approach the plant.
12. By way of a second leak test, examine all welds, flange joints etc. for leakage by applying soapy water, while maintaining the 10 bar pressure.
13. When pressure testing, compile a pressure test report containing the following:

• Date of pressure testing,
• Person carrying out the test,
• Comments.

REFERENCE: Instruction Manual for SABROE Reciprocating Compressors SBO 21, 22, 41, 42, 43

Related Links:

Pressure Testing Refrigeration Plant on Ships

Pumping Down of the Refrigeration Plant on Ships

Maintenance of Reciprocating Refrigeration Compressors on Ships

Troubleshooting of the Reciprocating Refrigeration Compressor Plant on Ships

Capacity Control or Regulation for Refrigeration Compressor on Ships