API MPMS 3.1A:2005 pdf download

API MPMS 3.1A:2005 pdf download.Manual of Petroleum Measurement Standards Chapter 3—Tank Gauging Section 1A—Standard Practice for the Manual Gauging of Petroleum and Petroleum Products.
3.IA.7.3.3 Portable Electronic Gauging Equipment
3.IA.7.3.3.1 General
Portable electronic gauging devices (PEGDs) usually consist of an electronic sensing device suspended on a measuring tape, and a housing with readouts. if used for custody transfer gauging, these devices shall be capable of demonstrating the same measurement accuracy as the non-electronic gauging tape and bob, and shall be calibrated or verified against a reference measurement (Refer to Appendix A).
The device may be designed for open, restricted, or closed gauging applications. Closed and restrictive gauging operations will generally require the portable electronic gauging tape to be used in conjunction with a compatible vapor lock valve.
3.IA.7.3.3.2 Construction and Graduation
The tape cross-sectional area shall be designed for the increase of tension due to the weight of the sensor probe assembly when the tape is vertically suspended in air. The material of construction and graduation of the main measuring tape should comply with the specification for gauge tapes given in 7.1.
3.IA.7.3.3.3 Marking
The graduated tape, the sensor probe and the body of the winding frame of each PEGD shall be marked with unique serial number(s) that can be annotated on the calibration certificate for the purpose of audit trail.
3.IA.7.3.3.4 Zero Point
The zero point of the level measured by a portable electronic gauging tape shall be the reaction point at which the sensor detects a liquid surface when operating in the outage mode. Because the electronic sensor(s) usually need to be protected from mechanical damage, the zero point of the tape/ probe combination is generally not the bottom surface of the sensor probe. Thus the zero point will not he directly verifiable without vertical suspension into a liquid surface. In these circumstances, the zero point is at a fixed distance from the bottom surface of the probe. The zero offset distance shall be verified and stated on the certificate of the said unit.
If the portable electronic gauging tape can be used to measure the reference height of a tank, then it will be necessary to add this distance (the zero point offset distance) to the observed tape reading to calculate the actual reference height value.
3.IA.7.3.3.5 Reading Index Mark with Use of a Vapor Lock Valve
Portable electronic gauging tapes that are designed for use via a vapor lock valve should be provided with a reading index mark. The offset distance of the center of the reading index mark from the point of the portable electronic gauging tape which corresponds to the gauging reference point (or datum point of the vapor lock valve) should be pre-set. The offset distance should be specified by the manufacturer.
3.IA.7.3.4 Water Indicating Paste
Water gauging pastes are used with gauge bars and bobs and tapes to indicate the petroleum and free water interface. The paste should not react with the petroleum, but should change color upon contact with free water.
3.IA.7.3.5 Gasoline Indicating Paste
In very light petroleum, the level of the liquid cannot be read on the tape because the petroleum evaporates while the tape is being raised from the liquid. To overcome this problem, gasoline paste is applied to the tape. When the paste comes in contact with the petroleum, it changes color or dissolves away thus giving a reading (cut).
3.IA.7.3.6 Oil Thief
A trap type core thief is a sampling device that may be used to approximately measure free water or emulsified oil, sediment, and water levels in tank bottoms. The oil thief may also be used to take spot samples of petroleum. Reference API MPMS Chapter 8 for construction.
3.IA.8 Gauging Accuracy
3.IA.8.1 EQUIPMENT ACCURACY
3.IA.8.1.1 Accuracy Requirements of Non-electronic Steel Tape and Bob
a. Accuracy
New tapes shall be inspected throughout their entire length to determine that the numerals and increments between the numerals have been placed on the tape correctly. The accuracy of the working tape and bob attached shall be verified by comparison with a reference measurement device (e.g., master tape) that has been certified by or is traceable to the National Institute of Standards and Technology (NIST), or other national weights and measures standards authorities, using the procedure in Appendix A.