2350 Industrial Road, Sapulpa, OK 74066 • Main: 918-445-1141 • sales@weamco.com Bulletin MPD-112 Toll Free: 800-331-3790 • Fax: 918-445-4617 • www.weamco.com 5-19 Page 3 of 8 Conventional Liquid Meter Provers Design and Construction B. Sizing and Volume Requirements 1.  Prover sizing (pipe diameter) is first determined by maximum and minimum sphere velocities per API Chapter 4, Paragraph a. Maximum:  Bidirectional - 5 ft/sec. or higher Unidirectional - 10ft/sec. b. Minimum:  Depends on lubricating properties of the product—low velocities May cause sphere to jerk or surge Weamco recommends 1.0 ft/sec. minimum (API accepts 0.5 ft./sec. minimum) 2. Prover volume (pipe length) is determined by: a.  API specifies “the accumulation of 10,000 unaltered meter pulses between detector switches.” b. Meter “K” factor (or pulses per unit volume). c. Repeatability of the detector switches and system d.  Use of double chronometry to allow design of reduced volume or small volume provers  A prover must be capable of repeating the volume between detector switches by 0.02 percent. (By water-draw calibration)  Prover sizing and volume must be considered with other factors to have a “Realistic prover design”, e.g.: space available, costs, meter selection or number of meters and pulses transmitted, product service, and etc. C. Pre-Run Length  A prover must have a sufficient pre-run length from the launch chamber reducer to the first detector switch to allow the 4-way diverter valve to cycle completely and seal properly before the displacer triggers the first detector switch. This also allows the displacer to reach stable, uniform velocity.