API MPMS 4.3 1988 pdf download

API MPMS 4.3 1988 pdf download.Manual of Petroleum Measurement Standards Chapter 4 Proving Systems Section 3-Small Volume Provers.
4.3.1 Introduction The use of small volume provers has been made possible by the availability of high-precision displacer­ position detectors used in con junction with pulse­ interpolation techniques (see Chapter 4.6). The small volume prover normally has a smaller base volume than that of conventional pipe provers (see Chapter 4.2) and is usually capable of fast proving passes over a wide range of flow rates. Small volume provers have a volume between detec­ tors that does not permit a minimum accumulation of 10,00 direct (unaltered) pulses fom the meter. Small volume provers require meter pulse discrimination us­ ing a pulse-interpolation counter or another technique that increases the resolution (see Chapter 4.6). This may include using provers with both large and small base volumes, depending on the pulse rates of the me­ ters to be proved. The small volume prover may be used in many applications in which pipe provers or tank provers are commonly used. Small volume provers may be sta­ ionary or portable. The volume required of a small volume prover can be less than that of a conventional pipe prover when high­ precision detectors are used in conjunction with pulse­ interpolation techniques. Pulse-interpolation methods of counting a series of pulses to fractional parts of a pulse are used to achieve high resolution without count­ ing 10,000 whole meter pulses fr a single pass of the displacer between detectors (see Chapter 4.6.) To achieve the required proving accuracy and repeat­ ability, the minimum volume between detector switches depends on the discrimination of a combination of pulse-interpolation electronics, detectors, and uniform meter pulses, as well as flow rate, pressure, tempera­ ture, and meter characteristics. 4.3.1.1 SCOPE This chapter outlines the essential elements of a small volume prover and provides descriptions of and oper­ ating details for the various types of small volume pro­ vers that meet acceptable standards of repeatability and accuracy.
4.3.1.2.1 Interule spacing refers to variations in the meter pulse width or space, normally expressed in per­ cent. 4.3.1.2.2 Meter proof refers to the multiple passes or round trips of the displacer in a prover for purposes of determining a meter factor. 4.3.1.2.3 A meter prover is an open or closed vessel of known volume utilized as a volumetric reference stan­ dard for the calibration of meters in liquid petroleum service. Such provers are designed, fabricated, and operated within the recommendations of Chapter 4. 4.3.1.2.4 A prover pass is one movement of the dis­ placer betweeq the detectors in a prover. 4.3.1.2.5 A prover round tip is the result of the for­ ward and reverse passes in a bidirectional prover. 4.3.1.2.6 A proving timer/counter is a high-speed counter used in double chronometry to measure time with a pulsed signal of known fequency.
4.3.2 Small Volume Prover Systems The small volume prover is available in several difer­ ent confgurations tat allow a continuous and uniform rate of flow. Al types operate on the common principle of the repeatable displacement of a known volume of lquid in the calibrated setion of a pipe or tube. A displacer travels through a calibrated section wth its limits defned by one or more highly repeatable de­ tectors. The corresponding metered volue simulta­ neously passes through the meter, and the whole num­ ber of pulses is counted. Precise calculations are made using a pulse-interolaton technique (see Chapter 4.6). The two types of continuous-fow small volume pro­ vers are unidirectional and bidirectional. Te uni­ directional prover allows the displacer to travel and measure in only one direction through the proving sec­ ton and has a means of returing the displacer to its starting position. The bidirecional prover alows the displacer to travel and measure frst in one direction and then in the other and is capable of reversing the fow through the prover secton. Both unidirectional and bidirectional small volume provers must be constucted so that the full fow of the stream passing though the meter being proved will pass through the prover. 4.3.3 Equipment The small volume prover must be suitable fr the intended fuids, pressures, temperatures, and type of installation. The materials used must be compatible with the fluid stream and the location where the prover will be installed. A small volume prover will normally consist of the fllowing elements: a. A precision cylinder. b. A displacer piston, spheroid, or other fluid­ separation device. c. A means of positioning and launching the displacer upstrea of the calibrated section. d. A displacer detector or detectors. e. A valve arrangement that allows fuid flow while the displacer is traveling fom one positon to the opposite position.