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Siemens: How do you reduce water hammer by utilizing your valve positioner?

27 July 2016

water-hammer-pic2.storyWater hammer is a very common term in the world of water. Not only can this phenomenon happen in water treatment plants but it can also happen in just about any pumping system and even in steam systems. The effects of water hammer vary from loud banging noise to pipe vibration, pipe breakage, equipment damage and, sometimes, total system failure.

What is water hammer and what causes it?

In valve applications, water hammer is the result of a valve suddenly closing in a system. The water (fluid or gas) is forced to stop and change direction suddenly. This creates a pressure surge and causes massive “wave like” forces to move back and forth through the pipeline. The quicker the valve closes, the more severe the effects will be to the pipe, valve, and system.

There are more than a few ways that today’s marketplace deals with water hammer. Some of these include re-sizing the piping to decrease velocity, utilizing water towers and/or air vessels, installing water hammer arrestors, shortening pipe lengths, and rearranging larger piping with shorter small- run pipes to reduce velocity. Additionally, some plants will utilize a controller to ramp the valve in a slower manner. In these situations, a controller is an additional piece of equipment required to control the valve. This works in conjunction with a traditional pneumatic valve positioner since they cannot ramp on their own.

How do you manage water hammer?

A much more savvy way of dealing with water hammer is to address this phenomenon at its source with your valve positioner. A smart, digital valve positioner will typically give you configurability and some will be able to ramp your valve open and closed as slow or fast as you require. This means you can eliminate the controller and potentially many of the solutions that the industry uses today to deal with water hammer. You can also rely on your positioner to monitor the stroking speeds. If the positioner says the valve is stroking open in five seconds and you’re experiencing pressure surges, simply adjust the ramping parameter to the desired stroke time in seconds to slow it down. The same can be done on the down stroke when you are closing the valve.

In conclusion, water hammer is a common occurrence throughout many plants and the effects of it can be very expensive and time consuming. Invest your resources into a solution that will address the source of the issue. The configurability of today’s digital valve positioners is what makes them a great fit for water hammer applications. It allows plants to control the source of the issue with a device they may already be using.

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