THE USE OF STRAIN GAUGE STRESS MONITORING SYSTEMS ON AMMONIA REFRIGERATION PIPEWORK AFFECTED BY UNDERGROUND MINING SURFACE SUBSIDENCE

摘要

In 2008, an underground long wall coal mine was drilled approximately 200meters deep under part of an exiting turkey processing facility which uses ammonia refrigeration piping systems for process cooling and cold storage. To minimize the risk of pipe work failure due to stress induced by ground subsidence, the pipe work at this site was replaced before the mining commenced. The replacement piping design was modelled using the Whesso Pipe Stress Analysis software PSA 5 and for selected sections of piping additional pipe support displacements (to simulate ground subsidence) were added to the model. This was necessary to demonstrate compliance with The Australian Standard AS4041 -Pressure Piping.Strain gauges were installed on 64 sections of pipe work identified as likely to experience high stress. A web based monitoring and alarm system was installed to provide early warning if predetermined trigger levels were exceeded.The paper discusses why flexibility analysis should be carried out on ammonia refrigeration piping systems, compares the predicted stresses with actual measured stress at a number of piping locations, shows how remedial action reduced actual stresses and provides lessons learnt from strain gauge installation and monitoring at an industrial food processing facility.