Issue link: https://onenorgren.uberflip.com/i/850945
What is "water hammer" and why does it matter? We've all heard it – that bang in the pipes when we turn off the shower or faucet suddenly. Sometimes multiple bangs shudder through the pipe as the water bounces back and forth. The same phenomenon can happen in large commercial or industrial fluid systems. Water hammer, also called fluid hammer or hydraulic shock, is a wave or surge caused when a fluid in motion is forced to stop suddenly. In process applications this happens when a fast-acting valve closes a pipe while the water upstream is still moving. The water hits the closed valve and bounces back, creating a pressure spike in the system upstream. How bad is it? Pressure spikes have been measured as high as 15 times higher than the normal water pressure in the pipeline. This exceeds typical UL rating safety factors and can damage equipment not designed to withstand pressures that high. Water hammer is a problem for applications using water from public utilities that usually comes in with a pressure rating between 70 and100 psi. Applications range anywhere from small dental offices to large manufacturing facilities. Water hammer is also a problem in mobile equipment that carries water, like concrete mixers or street sweepers. Industrial processes that use pressurized water can also be seriously impacted by water hammer. Repeated over-pressurization and vibration can cause damage ranging from premature wear to catastrophic failure of pipes, tubing, fittings, regulators, pumps, floats, gauges and anything else upstream from the closure point, as well as the unpleasant noise it creates. Effect of a pressure surge on a float gauge Typical solutions and their shortcomings Engineers, designers and maintenance professionals have come up with various ways to reduce the problems caused by water hammer. One obvious solution is to use a regulator upstream of the valve to lower the pressure rating and reduce the maximum pressure of the surge. However, the addition of a regulator will drop the flow rate, possibly reducing performance and productivity in the system. There are several mechanical methods to reduce the impact of water hammer. One is to install check valves upstream to control the distance the pressure spike travels. Another is to use accumulators; pressurized vessels that divert the excess fluid until the pressure spike abates. Large systems sometimes incorporate water towers to accommodate the surge. Alternatively, a shock absorber, also called a water hammer arrestor, can be installed upstream to absorb the shock of the pressure spike. Adding components like these increases cost and complexity as well as introducing additional potential failure points into a system. Another tactic is to modify the whole system design. Inserting elbows and loops into piping may slow the velocity of the water hammer surge. Unfortunately, this also increases the space required for the piping and, again, increases complexity and the chance for error. 04 A white paper