Pressure safety
Refrigeration systems containing a liquid under pressure and safety standards that must be adhered to, and that there are certain legal requirements. Under European Pressure equipment Directive (PED) and the UK Pressure Equipment Regulations main responsibilities are placed on the user/owner of the system. They are clear and practical means of legislating for safe use in refrigeration. Responsibility of contractors and users already use such a safer procedure, well before the introduction of these rules. In addition to the regulations themselves HSE published a " Safety of pressure systems - Approved code of practice", which is clear and useful. Rules apply to the vapour compression refrigeration systems, including the drive of compressor engines, including standby compressor engines, with a total installed capacity of more than 25 kW.
Equipment plant will be built with appropriate standards and will be pressure-tested for safety and leaks prior to shipment. In case of doubt, the test certificate must be requested in all subjects. According to the PED, the court, including the compressors are subdivided depending on the refrigerant and volume.
Those falling into certain categories will be CE marked and for the smaller size, not categories, application of sound engineering practice can be obtained from the manufacturer.
Should I keep the Safe Handling of Refrigerants Certificate for working with refrigerants. This can be obtained through short-term courses. Maintenance engineers must keep yourself updated on safety and training requirements.
Now mount the pipeline is completed, should be pressure tested for safety and integrity. Institute of Refrigeration set of rules indicates that the system will be tested in 1.3 times the maximum working pressure. For example, R404A
- 24.8 X 1.3 = 32.2 bar gauge (467 psig) on the high side
- 14.1 in X 1.3 = 18.3 bar gauge (265 pounds per square inch) at the bottom
It is assumed that the maximum condensing temperature 55C and a maximum ambient temperature of 32C, as specified in the standard security EN378. Ready-made components and pressure vessels that have already passed the test should not be reused if they are not part of the schema that can't be isolated, when the test pressure must not exceed the original figure. Now hydraulic testing is considered unnecessary, due to the extreme complexity of the destruction of the test fluid then. However, it should always be borne in mind that testing with gases is a potentially dangerous process, and should be guided by considerations of safety. In particular, the personnel should be evacuated from the area and personnel testing themselves be protected from the blast which would appear if the pressure is exploded.
The system should be pressure tested with a " dry " (oxygen-free) nitrogen (ofn) or high purity nitrogen. Nitrogen is used from standard cylinders, put about 200 bar and the correct pressure reducing valve must always be used to obtain the test pressure required. Separate sensor is used to verify the test pressure, because of the pressure reducing valve will be affected by the gas flow.
If the high side is tested, low-side has to be thrown into the atmosphere, in case of leakage between them, which can lead to excessive pressure on the low side. It may be necessary to remove the safety valves. Other valves inside the path should be open or closed, it must obtain the test pressure. Servo valve is not open to " dead " chain, and must be opened mechanically.
The test pressure shall be maintained for at least 15 minutes, If the pressure is not significantly reduced in this period nitrogen slowly ventilated until the pressure in the system is reduced to the pressure test (leakproofness) pressure. Reference should be made to the code of practice or guidelines issued by the Institute of refrigeration (See section " Bibliography").....
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Installation and Construction