PD Pumps to Meter Flow?
PD Pumps to Meter Flow?
(OP)
I was wondering if anyone has any experience with using screw pump (speed to meter flow rate. In theory it should work (i.e. volume per rotation x RPM = volumetric flow), but there has to be something that I am missing otherwise EVERYONE would be doing it. Can this be done? If so, what kind of accuracy/repeatable am I looking at?





RE: PD Pumps to Meter Flow?
RE: PD Pumps to Meter Flow?
respectfully
RE: PD Pumps to Meter Flow?
RE: PD Pumps to Meter Flow?
There are many PD metering pumps (additive injection comes to mind) that are used to meter the dosages without a flow meter. Hence, in practice in addition to theory, it also works.
You didn't give much information, such as size of pump, flow range, process fluid, accuracy required, etc. More information would help the fora to give a better informed answer.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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RE: PD Pumps to Meter Flow?
RE: PD Pumps to Meter Flow?
Flowrate = 150 m3/hr
Suction P = tank head
Discharge P = 700 kPa
Temp. = 15 C
SG = 0.93
Viscosity = 350 cSt
Thanks to everyone for their answers.
RE: PD Pumps to Meter Flow?
Your application is not what I was thinking - 150 m3/hr is substantially more than additive injection.
What accuracy are you looking for? Is it a "at least" case, or "within x% case"? Depending on the accuracy you need, looks like you will need a flow meter.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: PD Pumps to Meter Flow?
You can determine the pump's volume versus speed factor from the manufacturer's data and periodically determine a correction factor by pumping at a constant speed and taking tank guage readings (assuming you can stop flow into the tank while doing this and that you have a tank gauge table). This deals with changes in pump performance as it wears or as product characteristics change and also enables you to determine correction factors at various speeds, pump pressures and tank heads for additional accuracy.
Alternatively, if you have access to a mobile meter prover and provide typical meter proving connections downstream of the pump, you should be able to determine the above-noted correction factors (more quickly, accurately and with less operational disruption) by feeding a frequency signal from a variable speed drive into the prover counter (or a constant frequency signal if you don't have a variable speed drive).
I think it will be difficult to predict with confidence the accuracy you will achieve; you'd better treat this as an experiment and leave a spool in the piping for a meter in case you need to add it later.
RE: PD Pumps to Meter Flow?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: PD Pumps to Meter Flow?
Designs that have met these challenges more easily are the diaphragm type, plunger type (both recips) and gear type. These designs can be manufactured to tighter tolerances and with lower clearances which is must for this application.
Screw pump designs probably fall short here.
By virtue of being positive displacement pumps some degree of accuracy would definitely be realised. It is difficult to quantify that with these designs.
It is advised that u get hold of the vendor. They can provide you with performance curves for the pump. The performance curves of these pumps would not only give you flow rate with respect to speed but also flow rate at different viscosities and differential pressures. You can also inquire from their design staff about the test tolerances on capacities. You may like to visit the IMO site:
http://www.imo-pump.com/tech.htm
for some of the models the performance curves given are quite detailed. You may not need all the experimentation to calibrate the pump.
good luck
RE: PD Pumps to Meter Flow?
DB
RE: PD Pumps to Meter Flow?