POSITION OF THE ORIFICE AND THE CONTROL VALVE
POSITION OF THE ORIFICE AND THE CONTROL VALVE
(OP)
THE ORIFICE SHOULD BE LOCATED UPSTREAM OR DOWNSTREAM OF THE CONTROL VALVE??? WHY ?? WHICH POSITION IS MORE ACCURATE?? THE POSITION AFFECTS MORE IF IT IS A LIQUID OR IF IT IS A GAS??? WHERE CAN I FIND SOME INFORMATION??
REGARDS
REGARDS





RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
the API MPM (AGA has information on the industry standards for measurement.
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
I've seen a lot of PID's and the flow measurement it's always upstream the control valve (Liquid and gas cases). I wonder the reason and I think it's because we calculate the orifice of measurement with a pressure among other qualities of the fluid (Viscosity, spgr, temperature). The pressure will vary downstream the control valve, but upstream the control valve the pressure will remain constant. I was thinking that maybe we need a constant pressure for the measurement device, the orifice in this case.
Anyway I'll look up in the API MPM that dcasto said.
Regards
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
The API MPMS is a complete manual of standards. I don't have the complete set of the standards. Addressing chapters, the head type flow measurement standards are mostly chapter 14.3. Other standards include chapter 21, chapter 5 for Coriolis, etc.
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
I meant that the orifice should be upstream the control valve. In order to don't short the straight run of the meter you have to assure that there is enough straight pipe (I guess is 5 pipe diameters downstream the orifice and 20 pipes diameters upstream the orifice)
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
The instrumentation engineer wants, as mentioned, a fully developed flow profile into the meter. The straight piping requirements will vary depending on the upstream piping configuration and what type of error you can accept. A process control application is less critical obviously than a custody transfer service.
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
Qh = C’√hwPf
Qh = Volumetric flow rate, cfh
C’ = Modified orifice constant
hw = Differential pressure, inches of water
Pf = Metering pressure, psia
Assume Pf is measured with a transducer that has an error of 1 psi. A 1 psi error relative to Pf = 52 psia will introduce much more total error than a 1 psi transducer error relative to, say, Pf = 520 psia.
There are requirements for upstream and downstream lengths unobstructed pipe or flow conditioning. You should get a copy of AGA Report 3 for specifics. By the way, control valves and regulators also have requirements for lengths of unobstructed pipe up and down stream. Check the manufacturer’s specs.
The attached paper is pretty informative.
ht
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
Oh and because pressure is under the radical, the error is is cut in half (approximately).
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
You must be a technician. Obviously my illustration was not intended for someone of your level of sophistication. If you look at the illustration for what it is, an illustration, you will begin to understand why the natural gas industry installs orifice meters up stream of the pressure regulation. It's not about winning.
RE: POSITION OF THE ORIFICE AND THE CONTROL VALVE
Doug