Does anyone know when to use a surge relief valve?

I.e. what conditions call for one--> To clarify I am working on a pump station design retrofit. I'm trying to figure out whether or not I need to add a surge relief valve to the pump discharge header. It was suggested that I may need one on the discharge header b/c there has been a "significant increase" in the static head. What does an increase in static head have to do with wether or not a surge relief valve is needed?

The static head does not have much to do with the potential for surge except that the maximum water pressure is a combination of the surge pressure and the static pressure.

A surge relief valve is used to minimize the effects of water hammer. The potential for a water hammer is unique to the application and is a function of the number of pumps, pipe velocity, discharge piping layout, type of valves and valve closing times, variable speed drives, power failure, elevation, etc.

You need to do an analysis of the pump station and distribution system to see if you will have a surge. For example, suppose the power fails, what happens? Is the outgoing water going to reverse direction and slam the pump discharge check valves closed creating a water hammer?

Do you have a long pipeline with high velocity? If the pump stops quickly, what will happen?

You are somewhat fortunate that you are modeling an existing pump station. You can start your analysis by discussing the potential for water hammer with the current water department people. What happens with the current system? Is water hammer presently  a problem?

It is good practice to select equipment to minimize water hammer. Select valves that will close slowly rather than slam. Use lower pipe velcities. Plan for emergencies such as power failure. Use electrical equipment that has soft starts.

There are two sorts of damage from surge. The obvoius one is pipeline failure. The more onerous and costly is fatigue damage that results in component wear over the life of the asset. Many studies have concluded that the initial cost of an asset is only 12% of the whole of life costs. It doesnt need much increase in maintenance for costs and resources to mount up over the years. Because its incremental it isnt identified by the "beanies" so easily!

That is where VFD drives are a potential for savings cost. Not only can you run your plant more efficiently to cater for diurnal demand but they protect when there is a surge for frequent stopping and starting. They are of NO use when there is a power failure and so the surge analysis is still required for this event.

Building a plant and then testing it to see if there is surge is 18th Century mentality. Much the same as increasing pipe wall thickness and flange rating to cater for a high surge and ignoring the faitgue damage.

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