API MPMS 4.2:2003 pdf download
API MPMS 4.2:2003 pdf download.Manual of Petroleum Measurement Standards Chapter 4-Proving Systems Section 2—Displacement Provers.
2.7 PRESSURE DROP ACROSS THE PROVER
In determining the size of the piping and openings to be used in the manifold and the prover, the pressure loss through the displacement prover system should be compatible with the acceptable pressure loss in the metering installation. Excessive pressure drop may prevent the meter from being proved at its normal flow rate(s) and/or minimum backpressure required for the meter.
2.8 METER PULSE TRAIN
The electrical pulse output from the meter can exhibit variations even though the flow rate through the meter is con- stain. These variations may be caused by mechanical and electrical imperfections of the meter, pulse generator, and in signal processing technique. Ideally, under stable flow conditions, the meter pulse train should be uniform. However, mechanical gears, bearing wear, blade imperfections, couplings, adjusting devices, counters, mechanical temperature correction devices, and other accessories reduce the uniformity of the meter pulses. For meters installed with a gear- stack, the further the pulse generator is from the meter, the more erratic the pulse train becomes.
Variations in the meter pulse output may result in unacceptable proving performance. Appendix E discusses the evaluation of pulse variations of meters.
2.9 DETECTORS
Detectors must indicate the position of the displacer within ± 0.005% of the linear distance between switches (a range of
0.0 1%). The repeatability with which a prover’s detector can signal the position of the displacer (which is one of the governing factors in determining the length of the calibrated prover section) must be ascertained as accurately as possible. Appendix A discusses this in more detail. For prover with external detectors, care must be taken to correct detector positions that are subject to temperature changes throughout the proving operation.
A detector switch is an externally mounted device on a prover, which has the ability to precisely detect, the displacer entering and exiting the prover calibrated section. The amount of fluid that is displaced between two detector switches is the calibrated volume of the prover. Provers typically have two detector switches. Additional switches may be used if more than one calibrated volume is required on the same prover, or they can also be used to signal the entrance of a displacer into the sphere receiving chamber.
3 General Equipment Considerations
3.1 MATERIALS AND FABRICATION
The materials selected for a prover shall conform to applicable codes, pressure and temperature ratings, corrosion resistance, and area classifications. Pipe, fillings, and bends should be selected for roundness and smoothness to ensure consistent sealing of the displacer during a prover pass. Detailed inspection should be performed on pipe and fittings used in the calibrated section to insure the roundness of the pipe and the fittings are free of mandrel marks from shaping or forming.
3.2 INTERNAL AND EXTERNAL COATINGS
Internally coating the prover with a material that provides a hard, smooth, long-lasting finish will reduce corrosion, prolong the life of the displacer and the prover. This will improve the meter repeatability when proving at low flow rates. Experience has shown that internal coatings are particularly useful when the prover is used with liquids that have poor lubricating properties, such as gasoline or liquefied petroleum gas:
however, in certain cases, satisfactory results and displacer longevity may be achieved when uncoated pipe is used. The materials selected for the internal coating application should be compatible with the liquid types expected. The coatings should be applied according to the manufacturer’s recommendations. Extreme caution should be exercised in the surface preparation so that the coating is applied over a clean white—blasted metal with a minimum anchor pattern as specified by the manufacturer.
Externally coating the prover section arid associated piping will reduce corrosion and will prolong the life of the prover, especially for installations where the prover is buried.
