Apparatus and method for proving at low temperatures
Apparatus and methods for proving a flow meter at low temperatures. A flow meter measuring low temperature fluids (e.g., less than about −50° F., or less than about −220° F.) must still be proved. Low temperature fluids can be destructive to piston or compact provers, or may require indirect proving methods. The apparatus disclosed is a low temperature prover directly coupled into the pipeline carrying the low temperature fluids. In some embodiments, a magnetic pickup coil and a magnetic member communicate between the displacer and the flow tube. The magnetic target member may be carbon-free. In some embodiments, a pair of ultrasonic transceivers coupled to the flow tube communicate a signal across the flow tube and a displacer is moveable to interrupt the signal. In some embodiments, the flow tube includes an inner surface having a microfinish for lubrication. The displacer may be a piston rotatable while being moved axially.
1. A flow meter prover for low temperature fluids comprising:
an inlet configured to be directly coupled to a pipeline carrying the low temperature fluids;
an outlet configured to be directly coupled to the pipeline carrying the low temperature fluids;
a flow tube coupled between the inlet and the outlet;
a displacer moveable in a flow passage of the flow tube;
wherein the flow tube and the displacer are configured to receive the low temperature fluids; and
at least one of a magnetic pickup coil and a pair of transceivers coupled to the flow tube;
wherein the displacer is configured to communicate with the at least one of the magnetic pickup coil and the pair of transceivers;
wherein the displacer includes a vane disposed at an angle relative to the flow direction of the low temperature fluids.
2. The prover of claim 1 further comprising:
a magnetic member coupled to the displacer communicating with the magnetic pickup coil via magnetic reluctance.
3. The prover of claim 2 wherein the displacer is a piston and the magnetic member is a target ring wrapped around the piston.
4. The prover of claim 1 further comprising:
a carbon-free target member coupled to the displacer communicating with the magnetic pickup coil.
5. The prover of claim 4 wherein the carbon-free target member comprises at least one of high mu (μ) metal, HYMU metal, and HYMU 80 metal.
6. The prover of claim 4 wherein the carbon-free target member comprises a nickel alloy, an iron alloy, a molybdenum alloy, or any combination of nickel, iron or molybdenum.
7. The prover of claim 1 wherein:
the pair of transceivers communicate a signal across the flow passage in the flow tube; and
the displacer is moveable in the flow passage to interrupt the signal.
8. The prover of claim 1 wherein the flow passage includes an inner surface having a microfinish.
9. The prover of claim 8 wherein the microfinish maintains a microscopic film of the low temperature fluids between the flow passage inner surface and the displacer for lubrication.
10. The prover of claim 8 wherein the microfinish is in the range of 32 microinch to 16 microinch.
11. The prover of claim 1 wherein the displacer is a piston including a set of inner vanes extending along a longitudinal axis of the piston and set at an angle relative to the axis.
12. The prover of claim 1 wherein the vane rotates the displacer in response to the flow of the low temperature fluids.
13. The prover of claim 1 wherein the low temperature fluids include a temperature of less than about −50° F.
14. The prover of claim 1 wherein the pair of transceivers comprises a pair of ultrasonic transceivers.
15. The prover of claim 1 wherein the low temperature fluids include at least one of liquid natural gas (LNG), liquid nitrogen, liquid butane, liquid propane, and liquefied petroleum gas (LPG).
16. A flow meter prover for low temperature fluids comprising:
a flow tube having a flow passage therein and a magnetic pickup coil mounted thereon; and
a piston disposed in the flow passage and including a carbon-free magnetic member;
wherein the piston is moveable to move the magnetic member past the magnetic pickup coil and communicate with the magnetic pickup coil via magnetic reluctance;
wherein an inner surface of the flow passage includes a microfinish configured to maintain a lubricating microfilm of the low temperature fluids;
wherein the carbon-free magnetic member comprises at least one of high mu (μ) metal, HYMU metal, and HYMU 80 metal.
17. The prover of claim 16 wherein the piston includes a set of piston rotating vanes.
18. The prover of claim 16 further comprising:
a pair of ultrasonic transceivers disposed on the flow tube and communicating across the flow passage; and
wherein the piston movement interrupts the ultrasonic transceiver communication.
19. A system for proving low temperature fluids comprising:
a pipeline carrying the low temperature fluids;
a prover coupled into the pipeline and receiving the low temperature fluids, wherein the prover comprises:
a flow tube including a piston moveably disposed therein; and
at least one of a magnetic pickup coil and a pair of transceivers coupled to the flow tube;
wherein the piston is configured to communicate with the at least one of the magnetic pickup coil and the pair of transceivers;
wherein an inner surface of the flow tube includes a microfinish configured to maintain a lubricating microfilm of the low temperature fluids;
wherein the piston is configured to rotate while being moved axially.
20. The system of claim 19 wherein the pair of transceivers comprises a pair of ultrasonic transceivers.
21. The system of claim 19 wherein the low temperature fluids include a temperature of less than about −220° F.
22. The system of claim 19 wherein the piston includes a carbon-free magnetic target member.