PA PE
Civil/Environmental
- Oct 11, 2019
- 14
A client performs "churn tests" on two fire pumps on a weekly basis. The pumps are essentially run at shutoff head for a short time to verify that they are operable and are developing the proper head. A small amount of water is discharged through relief valves to prevent overheating. The local water Authority wants an estimate of the consumption through the unmetered fire service connection.
I attempted to estimate the flow using the pump curves and the inlet/outlet pressures but this was inconclusive. The pressure gauges indicated a differential that is 10 psi higher than the pump curve at shutoff head. Old gauges.
One of the pumps discharges through a turned down 1" pipe to the ground outside. The flow comes out at a pretty good velocity. The other pump discharges through a 4 inch pipe. This pipe is not flowing full and the water just rolls out of the pipe. In both cases the method of measuring the distance between the discharge and the point of contact on the ground will not work. I don't see a good way to attach flow meters to these pipes. It would take a pipe fitter a day to rig something up at both locations. Just by eyeballing the flows, I'm guessing that the flows are 10-20 gpm.
The detector check valve on the main supply has a bypass meter. We did some calculations showing that the losses through this bypass at 10-20 gpm would cause the main check valve to also open. This would void the readings from the bypass meter.
The only other thing I can think of is a bucket/stopwatch method using a common 5-gallon plastic pail. It's decidedly low tech and is like something that you'd do in your back yard. But it should be effective. I'm wondering if some source would have documentation for this test method. For instance, the Bureau of Reclamation has methods of measuring flow that are practical and low tech, but they don't have anything on a bucket test. It is covered on the sites of some residential well companies to determine the production of residential well pumps. Having some documentation would lend some authority to what we are proposing.
In any case, can anyone think of any other suggestions for measuring these flows?
I attempted to estimate the flow using the pump curves and the inlet/outlet pressures but this was inconclusive. The pressure gauges indicated a differential that is 10 psi higher than the pump curve at shutoff head. Old gauges.
One of the pumps discharges through a turned down 1" pipe to the ground outside. The flow comes out at a pretty good velocity. The other pump discharges through a 4 inch pipe. This pipe is not flowing full and the water just rolls out of the pipe. In both cases the method of measuring the distance between the discharge and the point of contact on the ground will not work. I don't see a good way to attach flow meters to these pipes. It would take a pipe fitter a day to rig something up at both locations. Just by eyeballing the flows, I'm guessing that the flows are 10-20 gpm.
The detector check valve on the main supply has a bypass meter. We did some calculations showing that the losses through this bypass at 10-20 gpm would cause the main check valve to also open. This would void the readings from the bypass meter.
The only other thing I can think of is a bucket/stopwatch method using a common 5-gallon plastic pail. It's decidedly low tech and is like something that you'd do in your back yard. But it should be effective. I'm wondering if some source would have documentation for this test method. For instance, the Bureau of Reclamation has methods of measuring flow that are practical and low tech, but they don't have anything on a bucket test. It is covered on the sites of some residential well companies to determine the production of residential well pumps. Having some documentation would lend some authority to what we are proposing.
In any case, can anyone think of any other suggestions for measuring these flows?
