water hammer relief valve

[amazing azza]

Friends, can a pressure-relief valve across the discharge and suction piping of a centrifugal pump set be used for water hammer relief? If so, what is the proper way of sizing it?

Illustration:

 

[bimr]

The water hammer pressure wave travels too quickly for a conventional relief valve to open and release it. In addition, you have not posted enough information on the water hammer problem to fully understand the problem.

One option that may lessen the water hammer effects is the installation of a pump control if the water hammer transients are occurring during pump start up or shut down.

Link to Pump Control Valve

Another pump control valve is the Pressure Relief Valve. This is a fast opening, slow closing relief valve that provides system protection against high pressure surges on pump start up and pump shut down by dissipating the excess pressure to a safe location and dissipating the excess pressure to a safe location.

Pressure Relief

Another option that may help is with the installation of a silent check valves. Certain valves, such as swing check valves, tilting disc checks and double door check valves also can contribute to water hammer problems. These check valves are prone to slamming because they rely on reversing flow and backpressure to push the disc back onto the seat so that the valve closes. Silent check valves can be effective in reducing and sometimes eliminating water hammer.

Quick Closing Check Valve

The first thing you should do is to study causes, consequences and solutions before spending money on the problem.

Water hammer Article

There are also Pressure Relief Valves designed to maintain constant upstream pressure within close limits. In operation, the valve is actuated by line pressure through a pilot control system, opening fast to maintain steady line pressure but closing gradually to prevent surges

 

[LittleInch]

Can it?

Maybe but depends as bimr says on the speed of pressure rise and quantity of liquid.

You can analyse these scenarios in a number of transient pipeline simulations, but usually need to pay for both the software and the person to input the data to get any meaningful results. This would give you the data required to size the valve or valves a sit may need more than one.
This is but one way of many to solve a surge problem caused presumably by pump shutdown.

The impact on the upstream system would also need to be considered and you may just be moving the problem somewhere else.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[hydtools]

If a relief valve were to work, you need to connect its input between the valve and pump. Dowmstream of the valve as shown will not work.

Ted

 

[mk3223]

Depending on the loads, may consider the discharge to the point of the suction origin such as vessel or tank, and away from the pump suction.
In some cases, the surge arrestor may be considered for the water hammer protection of the system.

 

[georgeverghese]

Generally, one does not design for water hammer relief - the preferred approach is to design to avoid liquid hammer. Tell us what you think is causing this hammer and we can suggest ways to avoid it. For example, if the hammer occurs when a distant discharge side automated valve is suddenly closed, one approach would be to install a tamper proof closing speed controller on this automated valve.

 

[Valvecrazy]

I agree pressure relief valves can't work fast enough to stop hammer and it is best to design to prevent hammer in the first place. Need more info.

 

[amazing azza]

Thank you for all the responses. Sorry, it took me a second to work through all of them.

As correctly guessed by georgeverghese it is indeed a distant solenoid valve. (The pump keeps running). To make matters worse, it is at 7m up in the air. The pump is at 0m, and the bulk of the distribution loop is at 3m high.

Based on your responses I gather that the pressure reducing valve as originally supposed would not be effective.

Could one install a spring loaded disk check (does that qualify as a silent check?) immediately at the base of the upward branch?

 

[Valvecrazy]

If you can slow the closing speed of the distant solenoid valve enough the hammer will go away.

 

[amazing azza]

I've actually procured one of SMC's "anti-hammer" solenoids, but have not yet commissioned it. Interested to see how it performs. To explain the origin of the question a little bit: I was doing some work on the pump inlet/outlet piping and the idea of the relief valve came to mind.

 

[LittleInch]

What actually happens?

A distinct "bang" or a less sharp increase in pressure?

Fast shock eave type events are difficult to control by check valves and mechanical means like relief valves. Some accumulators can handle this but slowing down the closure is key.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

If you are using a solenoid valve, that would mean that your piping is small diameter.

A slow closing solenoid would work:

slow closing solenoid valve

A water hammer arrestor would probably work as well:

water hammer arrestor

 

[Valvecrazy]

A water hammer arrestor before the slow closing solenoid would be best.

 

[georgeverghese]

Obviously, as the slow closing solenoid valve approaches full close position, given that this pump is still running, you'd have to enable min flow recycle to prevent dead heading the pump also. Presume you've already got this - the crudest form of a min flow recycle would be an excess pressure relief valve or PCV as you've shown in your first sketch , but the PRV / PCV discharge should ideally lead back to the source vessel and not to pump suction.

 

[amazing azza]

Hi guys, it is a very distinct bang with a concomitant spike in line pressure. I'll see if I can find one of those water hammer arrestors, they look worth adding to the stockroom. The dead head is handled in a clever way (thanks itsmoked!), if interested, details can be found in my water distribution thread.

 

[bimr]

In the future, look into buying an automatically controlled pump set for a small plant water distribution system.

Grundfos makes a pump system like this with pump and controller that will automatically control the pressure.

Link to Grunfos