§ 3174.6 Oil measurement by tank gauging—procedures. ( a ) The procedures for oil measurement by tank gauging must comply with the requirements outlined in this section.
( b ) The operator must follow the procedures identified in API 18.1 or API 18.2 (both incorporated by reference, see § 3174.3) as further specified in this paragraph to determine the quality and quantity of oil measured under field conditions at an FMP. ( 1 ) *Isolate tank.* Isolate the tank for at least 30 minutes to allow contents to settle before proceeding with tank gauging operations. The tank isolating valves must be closed and sealed under § 3173.2 of this part.
( 2 ) *Determine opening oil temperature.* Determination of the temperature of oil contained in a sales tank must comply with paragraphs (b)(2)(i) through (iii) of this section, API 7, and API 7.3 (both incorporated by reference, see § 3174.3). Opening temperature may be determined before, during, or after sampling. ( i ) Glass thermometers must be clean, be free of fluid separation, have a minimum graduation of 1.0 °F, and have an accuracy of ±0.5 °F.
( ii ) Electronic thermometers must have a minimum graduation of 0.1 °F and have an accuracy of ±0.5 °F.
( iii ) Record the temperature to the nearest 1.0 °F for glass thermometers or 0.1 °F for portable electronic thermometers.
( 3 ) *Take oil samples.* Sampling operations must be conducted prior to taking the opening gauge unless automatic sampling methods are being used. Sampling of oil removed from an FMP tank must yield a representative sample of the oil and its physical properties and must comply with API 8.1 or API 8.2 (both incorporated by reference, see § 3174.3).
( 4 ) *Determine observed oil gravity.* Tests for oil gravity must comply with paragraphs (b)(4)(i) through (iii) of this section and API 9.1, API 9.2, or API 9.3 (all incorporated by reference, see § 3174.3). ( i ) The hydrometer or thermohydrometer (as applicable) must be calibrated for an oil gravity range that includes the observed gravity of the oil sample being tested and must be clean, with a clearly legible oil gravity scale and with no loose shot weights.
( ii ) Allow the temperature to stabilize for at least 5 minutes prior to reading the thermometer.
( iii ) Read and record the observed API oil gravity to the nearest 0.1 degree. Read and record the temperature reading to the nearest 1.0 °F.
( 5 ) *Measure the opening tank fluid level.* Take and record the opening gauge only after samples have been taken, unless automatic sampling methods are being used. Gauging must comply with either paragraph (b)(5)(i) of this section, API 3.1A, and API 18.1 (both incorporated by reference, see § 3174.3); or paragraph (b)(5)(ii) of this section, API 3.1B, API 3.6, and API 18.2 (all incorporated by reference, see § 3174.3); or paragraph (b)(5)(iii) of this section for dynamic volume determination. ( i ) For manual gauging, comply with the requirements of API 3.1A and API 18.1 (both incorporated by reference, see § 3174.3) and the following: ( A ) The proper bob must be used for the particular measurement method, *i.e.,* either innage gauging or outage gauging;
( B ) A gauging tape must be used. The gauging tape must be made of steel or corrosion-resistant material with graduation clearly legible, and must not be kinked or spliced;
( C ) Either obtain two consecutive identical gauging measurements for any tank regardless of size, or: ( 1 ) For tanks of 1,000 bbl or less in capacity, three consecutive measurements that are within 1/4-inch of each other and average these three measurements to the nearest 1 ⁄ 4 inch; or
( 2 ) For tanks greater than 1,000 bbl in capacity, three consecutive measurements within 1 ⁄ 8 inch of each other, averaging these three measurements to the nearest 1 ⁄ 8 inch.
( D ) A suitable product-indicating paste may be used on the tape to facilitate the reading. The use of chalk or talcum powder is prohibited; and
( E ) The same tape and bob must be used for both opening and closing gauges.
( ii ) For automatic tank gauging (ATG), comply with the requirements of API 3.1B, API 3.6, and API 18.2 (all incorporated by reference, see § 3174.3) and the following: ( A ) The specific makes and models of ATG that are identified and described at *www.blm.gov* are approved for use;
( B ) The ATG must be inspected and its accuracy verified to within ± 1 ⁄ 4 inch in accordance with API 3.1B, Subsection 9 (incorporated by reference, see § 3174.3) at least once a month or prior to sales, whichever is latest, or any time at the request of the AO. If the ATG is found to be out of tolerance, the ATG must be calibrated prior to sales; and
( C ) A log of field verifications must be maintained and available upon request. The log must include the following information: The date of verification; the as-found manual gauge readings; the as-found ATG readings; and whether the ATG was field calibrated. If the ATG was field calibrated, the as-left manual gauge readings and as-left ATG readings must be recorded.
( iii ) For dynamic volume determination under API 18.2, Subsection 10.1.1, (incorporated by reference, see § 3174.3), the specific makes and models of in-line meters that are identified and described at *www.blm.gov* are approved for use.
( 6 ) *Determine S&W content.* Using the oil samples obtained pursuant to paragraph (b)(3) of this section, determine the S&W content of the oil in the sales tanks, according to API 10.4 (incorporated by reference, see § 3174.3).
( 7 ) *Transfer oil.* Break the tank load line valve seal and transfer oil to the tanker truck. After transfer is complete, close the tank valve and seal the valve under §§ 3173.2 and 3173.5 of this part.
( 8 ) *Determine closing oil temperature.* Determine the closing oil temperature using the procedures in paragraph (b)(2) of this section.
( 9 ) *Take closing gauge.* Take the closing tank gauge using the procedures in paragraph (b)(5) of this section.
( 10 ) *Complete measurement ticket.* Following procedures in § 3174.12.