API MPMS 5.4:2005(R2015) pdf download.Manual of Petroleum Measurement Standards Chapter 5—Metering
5.4.1 Introduction
API Chapter 5.4 of the Manual of Petroleum Measurement Standards is intended to be a guide for the selection and application of accessory equipment that is used with liquid hydrocarbon meters to obtain accurate measurements and optimum service life. Accessory equipment is any device that enhances the utility of a measurement system. Selecting the kinds of accessory equipment that are described in this sec- tion depends on the function, design, purpose, and manner in which a specific measurement installation is to be used. This publication does not endorse or advocate the preferen- tial use of any specific type of equipment or metering system, nor does it intend to restrict the development of any particular meter, instrument, or accessory equipment.
5.4.2 Scope
This section of API MPMS Chapter 5 describes the charac- teristics of accessory equipment that may be used with meters in liquid hydrocarbon service. Having a knowledge of these characteristics helps designers and operators of meter instal- lations provide satisfactory quantity measurement results. Certain minimum requirements for devices that monitor tem- perature, density, and pressure are discussed in this section. Most system hardware, such as non-control valves, vents, and manifolding, is not discussed in this section.
5.4.7.2 READOUT
An electrically driven primary readout indicates quantities in the desired standard units of measurement, such as gallons, barrels, or cubic meters; it also indicates decimal fractions of these units, if required. The accuracy of the readout depends on system resolution, which is proportional to the number of pulses per unit quantity. Electromechanical registers are limited in speed. Their adequacy should therefore be considered before a decision is made about installation. Electronic readouts are not limited in speed, but they depend on electrical power for proper perfor- mance. During a power failure, standby power is needed to verify and retain meter registration if a mechanical means is not available.
5.4.7.3 PRINTER
Several types of electrical printers are available. The two common ones include electromechanical mechanisms in the final stages. The first type is designed so that each adjacent digit advances the next digit into position as it would in a mechanical readout. This type of printer is simple, inexpen- sive, and widely used, but it has limited speed and longevity. The second type of printer includes individual digit mod- ules that remain in a rest position until they are called on to print the throughput quantity that is stored in a memory. This type of printer has high resolution, high speed, and excep- tional longevity.