API MPMS 4.9.1:2005 pdf download
API MPMS 4.9.1:2005 pdf download.Manual of Petroleum Measurement Standards Chapter 4-Proving Systems Section 9—Methods of Calibration for
Displacement and Volumetric Tank Provers Part 1—Introduction to the Determination of the Volume of Displacement and Tank Provers.
4.3 APPLICATIONS
A prover calibration is initially performed at the manufacturing plant where the prover is built, and often again after it has been installed at the operating facility. From this time forward, regular calibrations shall he perfbrmed according to a predetermined schedule.
There are many reasons to account for the necessity of frequent and regular recalibration of a prover, some of these, but not all, are as follows:
• Frequency of use and general wear
• Detector maintenance, wear, adjustment or replacement
• Deposit build-up on the prover walls (e.g. wax, paraffin, etc.)
• Loss of or damage to, the internal coating of the prover walls
• Physical damage to the prover
• Maintenance on the calibrated section of the prover
• Over-pressurization of the prover
• Constructional changes to the prover
Prover calibrations are often witnessed by the interested parties. See Appendix A for information on calibration witnesses.
All provers shall bc re-calibrated at regular intervals. Some provers arc re-calibrated more frequently than others to minimize the risk of measurement ciors or to limit the level of measurement loss by lowering the overall uncertainty of the prover volume. The frequency of use of the prover and the volume throughput measured at the facility should be considered when determining the appropriate frequency for recalibration. See API MPMS Chapter 4.8 “Guide to the Operation of Provers,” for additional information.
Consideration of the following items will help to establish the possible loss exposure and measurement risk, and will help to determine a required frequency of calibration for all provers:
• Volume through the metering system associated with the prover between prover calibrations
• Number of meters regularly proved by the prover and their frequency of proving
• The total yearly value of each product metered
• Service conditions and properties of products being metered and proved
• Whether the prover is portable or stationary
• The different types products being metered
• The range of properties of liquids being metered
• The required yearly maintenance and repair
• The total overall condition, including detectors and sphere displacer
Portable provers can be subject to more severe conditions of operation. Even the total yearly road usage should he looked at when considering a recalibration frequency. Careful observation and evaluation should establish whether more frequent recalibration is required of a portable prover when compared to a stationary prover.
Present day industry practice has established recalibration frequencies for provers that range from one year up to five-year cycles. This is based on the determination of normal wear, measurement risk management, volume of loss exposure, and any other relevant measurement factors. In some extreme cases prover recalibrations on three month or six month cycles have been judged to be necessary. See Appendix B, and API MPMS Chapter 4.8, for addItional information on the calibration frequency of provers.
5.0 Types Of Provers
The following describes the most common types of provers. See other sections of API MPMS Chapter 4 for additional detail on prover design.
These types of unidirectional provers may he subdivided into the following two categories depending on the manner in which the displacer is handled:
a. The manual-return unidirectional prover, sometimes referred to as the measured distance, is an elementary form of an in-line prover that uses a section of pipeline as the prover section. Prover detector switches that define the calibrated volume of the prover section are placed at selected points along the pipeline. A displacer-launching device is placed upstream from the prover section, and receiving facilities are installed at some point downstream from the prover section. Conventional launching and receiving scraper traps are usually used for this purpose. To make a proving run, a displacer (a sphere or specially designed piston) is launched and allowed to displace the reference volume before being received downstream and manually transported back to the launching site. This type of prover is no longer in common use.
h. The circulating-return unidirectional prover, often referred to as the endless loop, has evolved from the prover described above. In the endless ioop, the piping is arranged so that the downstream end of the loop crosses over and above the upstream end of the looped section. The interchange is the means by which the displacer is transferred from the downstream to the upstream end of the loop without being removed from the prover. The displacer detectors are located inside the looped portion at a suitable distance from the inter-change. Continuous or endless prover loops may he automated or manually operated.
