Surge Vessel Precharge Pressure

<...GCC...>

Wha'?

<...Is there any limitation for precharge pressure and why?...>

The structural design of the vessels?

<...How to reduce this pressure?...>

Bleed some of the precharge from them?

Are each station working at a different pressure?. What are the required pressure of each station including pump start/stop(cut in/cut off) pressure?. Are the rubber bladders and tanks rated for those pressures?.

What did the vendor recommend when you contacted them ?

I've only done a handful of surge tank designs, but a 30 bar preload surprised me. I'm curious, what type of water supply application is this?

Precharge pressure depends on the working pressure of the system. Normally precharge to ~ 1/2 the absolute working pressure. Then when the surge vessel sees system pressure the air compresses to 1/2 the vessel volume and you have 1/2 water, 1/2 air in the vessel, usually about right to handle higher and lower pressure fluctuations.

Does it(air pressure) have any relationship to the cut-in pressure?. We charge with nitrogen instead of air as air in contact with moisture will corrode the interior of the vessel.

Yes, you want the cut-in pressure to be above the pre-charge pressure. Then as the system pressure slowly falls, the pump restarts before all the water has left the vessel. If the cut-in pressure is lower, when all the water has left the vessel the pressure falls rapidly to cut-in point, and when the pump starts there is no surge protection till pre-charge pressure is reached, potentially causing water hammer.

Hi Ali

1. The initial pressure would depends on the final volume of air that you want it to be in the surge vessel. You can use following equation

Po = P x (V/Vo)

where, Po is the initial pressure, P is the normal operating pressure V stands for volume of air and V/Vo is the ratio of final volume to that initial volume of air inside the surge vessel. Vo = volume of surge vessel.

2. Let say if you want the air final volume to be 1/2 of initial volume (V/Vo = 0.5) than Po = 0.5P. If the final volume is 1/4 (V/Vo = 0.25, water 3/4 full) then Po = 0.25P

3. The above equation is derived from the universal gas law PV=nRT. Since nRT are all constants, pressure is a function of volume only.

Project water supply to top of mountain including 5 nos pump station with 2+1 high pressure pumps with FLOW 52 LPS as below Head. DI pipe line by length of almost 21 km

1- no.1 pump station Head 174 mtr

2- 351 mtr

3- 348

4- 411

5- 356

ali