[Mechanical Equipment Technology Edition] Daily Question 201802028: Common Faults in Refrigeration Systems (9.9)
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This post was last edited by YORK Industrial Refrigeration on 2018-3-2 at 13:18. Starting from now, in order to enhance communication among members, a \"Question of the Day\" activity has been launched on the Mechanical Equipment Technology forum. We hope everyone will participate actively to progress and improve together! ! ! Rewards: 3 points for active participation, 10-15 points for correct answers. This question is valid for two days; no score will be assigned after that period. After a major repair of a screw compressor, is it necessary to conduct a leak test? How to do it? Seal the air intake and exhaust ports with flanges, connect the pressure testing pipeline, pressurize to the operating pressure, and conduct a leak test using soapy water. ============================== High-quality promotions: Mechanical equipment---Maintenance procedures for York screw compressors https://bbs.hcbbs.com/thread-1806833-1-1.html Mechanical equipment---Upgrading of York Quinton control centers https://bbs.hcbbs.com/thread-1804837-1-1.html Mechanical equipment---Major repairs for GEA Grasox screw compressors https://bbs.hcbbs.com/thread-1800467-1-1.html Mechanical equipment---Disassembly and maintenance of British HOWDEN screw compressors https://bbs.hcbbs.com/thread-1832529-1-1.html Mechanical equipment---Disassembly and maintenance of Japanese Maekawa MYCOM screw compressors https://bbs.hcbbs.com/forum.php?mod=viewthread&tid=
It’s needed, but I don’t know how to do it
It’s needed; it seems to be for measuring the pressure before and after, but I’m not sure exactly
It is necessary to conduct a single-unit pressure test after the maintenance is completed, and to maintain the pressure in the system once the unit has been reset (by closing the compressor inlet valve and the oil exhaust valve)
It needs to be done. First, perform a gas-tightness test using N2 or dry, oil-free air; once this is successful, carry out a vacuum test to determine whether the vacuum level can be maintained over time.
The answer is； Open all valves that connect the tube closure unit to the atmosphere and external systems, open the valves between the various devices within the unit, fill the system with ammonia or plant air, and conduct a leak test using soapy water. If there are no abnormalities, continue to increase the pressure to 1,4 MPa. Hold under pressure for 24 hours.
After maintenance, the screw compressor must undergo a gas-tightness test before it is reinstalled and put back into operation. Close tightly all valves of the screw compressor that are connected to the outside environment; where necessary, use blind flanges for isolation. According to relevant regulations: during vacuum testing, the pressure within the system should be reduced to below 5.33 KPa (meaning the vacuum level should be above 96 kPa), and the pressure rise within 8 hours should not exceed 1.33 kPa. The requirements for vacuum level should also vary depending on the local atmospheric pressure. Generally, the required vacuum level is obtained by multiplying the local atmospheric pressure on that day by a coefficient of 0.96. When performing a vacuum leak test, a vacuum pump should be used to create a vacuum. For small refrigeration systems or in cases where there is no vacuum pump, the refrigeration compressor itself can also be used to create a vacuum.
It is necessary to conduct a single-unit pressure test after the maintenance is completed, and to maintain the pressure in the system once the unit has been reset (by closing the compressor inlet valve and the oil exhaust valve)
It is necessary to close all valves that connect the unit to the atmosphere and external systems, open the valves between the various devices within the unit, fill the system with ammonia or plant air, and then use soapy water to detect leaks. If there are no abnormalities, continue to increase the pressure to 1.4 MPa. Hold under pressure for 24 hours.