Surge control tanks and Surge anticipating valve

[sowhatso]

I am working in water project to rehabilitate water pumping stations , the stations were built before 6 years , the discharge operating pressure is around 35 bar , the original design for the stations included surge anticipating valve (SAV) to absorb the surge waves during the power failure and the pump shutdown . After two years of operation, several failures for the booster pumps and the valves at the discharge side of the pumps were occurred, part of the failures causes were expected to be due to the inefficient method of absorbing the surge waves by using the surge anticipating valves (SAV) , the consultant is proposing to install surge tanks (ST) to fix this problem , However they will keep the surge anticipating valves installed .
My question is, in case we will have the surge tanks operating with the surge anticipating valves:

1 - Is it recommended to have both systems (surge tank and surge anticipating valve) operating at the same time, and what is the disadvantages???

2- Incase, both systems will work, is it better to set the surge anticipating valve to OPEN at the same time the surge tank is working so as to quicken the absorbing of the surge waves, OR to set the surge anticipating valves to open at higher pressure setting after the pressure setting of the surge tank to make the surge anticipating valves work as BACKUP system in case the surge tank doesn’t work??

Thanks in advance for all your inputs ...

 

[BigInch]

Are you using pressure set valves relieving to the surge tank at a certain pressure setting, or a closed surge tank (no valves) with a minimum surcharge pressure held in the tank (kind of like an accumulator works)?



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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[MortenA]

Have they done any simulations to support their remediating actions - or is it just gut feeling?

Best regards

Morten

 

[sowhatso]

Biginch ,

the surge tank that we will use is a bladder tank , that will be charged for a certain value of pressure.

 

[BigInch]

That's what I thought. In that case, the surge tank will be active all the time and the valves can be set to open at a given pressure, so the tank can't actually function as a "backup" to the valves, although the valves could function as a backup to the tank (in the classical sense). I just don't know why you would want to have a valve (other than a relief valve on the tank) as a backup for a tank. Anyway, the net effect is that both will be active at the beginning of the surge, assuming that the pressure rises very fast and immediately passes valve set pressure, you will have pressures over tank preset pressure (active tank) and valve set pressure (active valves). Once pressure drops below valve set pressure, only the tank will be active again. That IMO means the tank is functioning as the backup device.

Its not apparent why you would need both systems. Either one should work, if designed and operated correctly. What's more interesting is to find out exactly why the failures occured. It sounds like nobody knows that yet. Was it a design error, such as insufficient valve flow capacity, a valve malfunction due to incorrect setting, no maintenance, unexpected operating condition out of range, operator error, etc. and find a solution that addresses the problem as directly as possible.

If you are going to build the tank, I'd make it big enough to handle all surge flows without the help of any valves to handle the highest pressure ranges.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[sowhatso]

BigInch,

Thanks alot.

 

[stanier]

In my experience surge anticpating valves only work in the mind of the salesman. They are designed for one set of conditons and then another comes along and they fail.

I support BigInch here in that you should size the surge tanks for all scenarios where surge will occur and forget about the surge anticipation valves.

Make sure the consultant looks at al the scenarios for the "worst" cannot be determined until this is carried out.