May 19, 2022


Water hammer


What is water hammer?

Water hammer is an unintended pressure wave that occurs briefly in a pipe system. This is caused by sudden changes in the flow rate within a pipe. This phenomenon is called "water hammer" because pressure waves are often accompanied by a sound that sounds like a hammer hitting something hard. This occurs when a pump fails, or when shutting down too quickly.

Excessive pressure can lead to leaks or pipe ruptures, valves can bend and fasteners crack. Situations that no manufacturing company wants to end up in. Water hammer can therefore have many adverse effects and it is therefore important to limit the risks to a minimum.

Pipe breakage or damage to the pumps, valves and other equipment/equipment

Water hammer is therefore a phenomenon that occurs when in turbulently moving liquid the local pressure becomes lower than the vapor pressure of the liquid. If the pressure subsequently increases again, it can rise to well above the current strength class of the pipes used, resulting in pipe breakage and/or damage to the pumps. To prevent this, a water hammer facility, a smart pump control, a flywheel on a pump, a damper on the pipeline or a bypass is required. It is of course best to completely prevent water hammer by optimally shaping and matching all components involved and the expected working conditions. For example, by moving a valve to a part of the pipe where the pressure is higher. Or by reducing the pressure drop per valve by placing several valves in series. Or by increasing the pressure in the relevant part of the system (for example with pumps).

Water hammer occurs when

Water hammer occurs when a partial vacuum is created in the down pipe. When the pump is started afterwards, water fills the vacuum at a high flow rate and presses against the closed check valve and the stationary water column in the line. This creates a pressure wave or water hammer. This pressure wave can cause pipes to rupture and couplings, and damage the pump and/or motor. When a pressure wave occurs, the system should be turned off immediately and the problem solved.

Industrial processes

So quickly closing a valve downstream of a running pump can cause water hammer. But there are more reasons:

  1. Stopping a Pump: When water moves through a pump, the sudden stop of the pump will cause water hammer. The pump basically acts like a downstream valve that closes suddenly.
  2. Closing of a non-return valve: When a non-return valve closes, water hammer occurs. Check valves close almost immediately if the differential pressure is less than the check valve specifications.
  3. At steam start-up: High condensation at steam start-up can lead to liquid condensate moving at high speed. As soon as the liquid hits a sharp bend, the phenomenon of water hammer occurs.
  4. Upstream of a running pump: The reverse effect when a valve upstream of a running pump is suddenly closed. Shortly afterwards, a vacuum is created after the valve, possibly resulting in the imploding of the pipe.
  5. Filling an empty pipe: the variation of water hammer that occurs when filling an empty pipe with liquid at a high flow rate. The air escapes through a small opening. When the air has completely escaped from the pipe, the flow suddenly stops causing water hammer.

Water hammer: the causes

The most important questions are of course: 'How did it come about, where did it come from? Where is the fault?” The valve is found to be leaking, warped, or of poor quality. However, the latter is not always the cause, and in most cases the problem can be solved from insightful engineering. Water hammer can be solved by, for example, throttling the valve or turning the closing direction so that the valves turn against the flow.

Flowcomm and water hammer analysis

Flowcomm recommends water hammer analysis and control calculations with a focus on the production line. We regularly see at our customers that water hammer is caused by sudden pressure differences, caused by the valves in the pipework. This leads to wear and can also cause damage in the production line. Precisely because of the adverse effects of water hammer, it is important to keep water hammer risks to a minimum. This can be done by checking the pipe system and performing a so-called water hammer analysis. That is the basis for choosing designs and facilities that reduce the pressure that occurs to acceptable proportions. Every production company needs a professional partner for this.

Flowcomm delivers solutions

Flowcomm provides solutions for the product industry. Provides process components. Works with a team consisting of application-oriented specialists. And, in all cases, provides the most suitable technical solutions with targeted support in the engineering process.

As far as we are concerned, the problem of thermal expansion of valves is a thing of the past. Our valve bodies are produced from solid bar stock, resulting in a solid body with close tolerances. Any deformation of our valves, under the influence of expansion due to temperature differences in the piping, is therefore kept to a minimum.

The expertise of Flowcomm

Flowcomm has the in-house expertise to immediately identify the problem for a customer. Has the components to fix it. Quickly see where the problem is. With many years of experience, Flowcomm technically provides the most suitable, ready-made solution for the problem. We also provide a guarantee with our advice. This is the promise we keep. As an individual employee and as a team. This requires optimal effort and a strong empathy for the customer's situation. Also in the problems of the customer. No matter how difficult and complex. But we are happy to take on that challenge, because we focus fully on the possibilities. What seems out of the question for a customer is the way to what is possible for us. We see opportunities where others face a wall. And the latter in particular makes us what we are; a strong partner for co-engineering.

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Water hammer