American Petroleum Institute

Specification for Lease Automatic Custody Transfer (LACT) Equipment
 N SPEC 11N

Annotation

1. Scope

1.1 COVERAGE

This specification describes optimum requirements for assemblies designed for the unattended automatic custody transfer (ACT) of liquid hydrocarbons, such as crude oil and condensate, at rates below 11,000 U.S. barrels (1750m3) per 24-hour day, in field applications at less than 500 psig (3447 kPa) operating pressure.

1.2 One flow diagram illustrating acceptable locations for the charging pump, custody transfer liquid meter, monitor probe, sampling system, piping, valves and controls is presented in Fig. 1.

1.3 Although this specification depicts only one flow diagram, it is recognized that other component arrangements are possible. Any design that meets the requirements of this specification is acceptable by agreement between user and fabricator.

1.4 Appendix A contains specification data sheets for 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 specification include the surge tank, electrical power and instrument gas supply, signals to start and stop the pump, connecting piping and valves.

1.6 Compliance with the provisions of this specification may result in an approach to accuracy or may establish safeguards not necessary under all conditions. By agreement between the user and fabricator, non mandatory portions of this specification may be waived.

1.7 The compulsory verb form shall has been used where a deviation from the requirements may adversely affect the satisfactory operation of a system designed for optimum operation under typical producing conditions.