Chevk Valve Losses
Chevk Valve Losses
(OP)
I got handed what should have been a cut and dry duplex lift station (4 HP pumps), however it does not work. There is about 5' of head I can not account for in the 4" forcemain.
In my calculation I used a friction loss co-efficient of 2 or 3 (notes are at the office) for a 4" swing check valve (Americal Flow Control was installed). Is this enough? I have not been able to locate a flow vs. loss diagram yet.
The station is pumping from 56 to 75 gpm depending on WW water level. I was wondering if this was enough to even open a 4" CV all the way, which I would think would add more friction loss to the system?
If I can be satisfied there isnt more loss in the CV than I am accounting for, my next guess is a local high point with a bit of air causing the losses.
Thanks,
Mike
In my calculation I used a friction loss co-efficient of 2 or 3 (notes are at the office) for a 4" swing check valve (Americal Flow Control was installed). Is this enough? I have not been able to locate a flow vs. loss diagram yet.
The station is pumping from 56 to 75 gpm depending on WW water level. I was wondering if this was enough to even open a 4" CV all the way, which I would think would add more friction loss to the system?
If I can be satisfied there isnt more loss in the CV than I am accounting for, my next guess is a local high point with a bit of air causing the losses.
Thanks,
Mike





RE: Chevk Valve Losses
RE: Chevk Valve Losses
If your are having a problem, then you should investigate the static head as represented by the difference in elevation.
Note that force mains should have a minimum flow of 2 fps. That is approximately 90 gpm.
RE: Chevk Valve Losses
sjohns4,
apart from that I agree with previous comments, I was wondering about your 'duplex' pump station. Is it a possibillity that pipeline layout is forcing one pump to pump 'against' the other by connecting pipelines higher in the system? (If your loss is connected with two pumps running together?)
RE: Chevk Valve Losses
Using as-built data, I'm still comming up a few feet of head short on what the gauge reads vs. what it should read though. I'm still thinking a local high point and velocities not enough to move the bubble down stream.
Mike
RE: Chevk Valve Losses
I suggest you turn on the pumps and check the dead head pressure on the pumps by closing isolation valves and looking at pressure. Sometimes the impeller is not seated correctly at the factory, etc. I always check pumps now and lots of times they don't meet their dead head pressure, which is one reason why you oversize.
RE: Chevk Valve Losses
RE: Chevk Valve Losses
With an existing system, get some good, calibrated instruments. Measure your static head and your head at various flow rates, using a valve to throttle the pumps as necessary (being careful not to damage the pumps). What you then measure is the system curve. As pipes get used, there are too many variables for you to be able to calculate the system curve reliably. The calculation will only give you an estimation of what the pumps will see.