API Spec 11N:1994 pdf download.Specification for Lease Automatic Custody Transfer (LACT) Equipment
1 Scope
1.1 COVERAGE This specifcation describes optimum requirements fr assemblies designed fr the unattended automatic custody transfr (ACT) of liquid hydrocarbons, such as crude oil and condensate, at rates below 11,000 U.S. barrels (1750m 3 ) per 24-hour day, in field applications at less than 500 psig (3447 kPa) operating pressure. 1.2 One flow diagram illustating acceptable locations fr the charging pump, custody transfr liquid meter, monitor probe, sampling system, piping, valves and contols is pre­ sented in Fig. L 1.3 Although this specifcation depicts only one flow dia­ gram, it is recognized that other component arrangements are possible. Any design that meets the requirements of this specifcation is acceptable by agreement between user and fbricator. 1.4 Appendix A contains specifcation data sheets fr a standard API LACT Unit. Two identical data sheets are shown, one with U.S. Customary units and the other with metric units. 1.5 Required ACT system elements not described in this specifcation include the surge tank, electrical power and in­ strument gas supply, signals to start and stop the pump, con­ necting piping and valves. 1.6 Compliance with the provisions of this specifcation may result in an approach to accuracy or may establish saf­ guards not necessary under all conditions. By agreement be­ tween the user and fbricator, non mandatory portions of this specifcation may be waived. 1. 7 The compulsory verb frm shall has been used where a deviation fom the requirements may adversely afect the satisfctory operation of a system designed fr optimum op­ eration under typical producing conditions. 1.8 This specifcation presents the concurrence of the in­ dustry on current system requirements for ACT. There is equipment now in the design or feld-proving stage that may further improve the art of ACT. Such developments are en­ couraged and every efort should be made to expedit their reduction to practice and standardization.
7 Strainer and/or (Optional) Air/Gas Eliminator
7 .1 The strainer and air/ gas eliminator, as sepaate or inte­ gral units, shall be located upsteam fom the meter, in a hor­ izontal pipe with the air release head located at a piping elevation higher than the meter case. 7 .2 The strainer basket should be made of non-corrosive material with 1 /4 inch (6.35mm) mesh size. Smaller mesh may be specified by agreement between the user and the fbricator. 7 .3 A bottom drain connection and valve plus a quick opening top cover should be provided on the stainer. 7.4 Pressure gauges with soft seat, isolation needle valves should be provided on both sides of the strainer. 7 .5 When the air elimination feature is specifed, the vapor relief shall be piped through a soft-seat check valve to a skid edge.

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