Avoiding water hammer and other hydraulic transients

Water hammer may occur upon rapidly closing a water pipe valve. Oscillating pressure waves generated in the system may cause significant equipment damage, including joint leaks and even pipe rupture. Similar phenomena can occur when starting and stopping pumps. As various situations can cause potentially damaging pressure waves, water hammer and related phenomena are grouped as "hydraulic transients." The phenomena are not limited to water pipes and may occur in any liquid, including condensed gases such as chlorine, ammonia, and liquefied natural gas (LNG). Hydraulic transients deserve more coverage in college courses and textbooks on process safety, while at an industrial level, the topic should be considered in design and hazard reviews. This article provides a brief introduction to the topic with a focus on mitigation methods. Available options should be evaluated during the design process rather than applied retroactively after a problem becomes evident.