23 CAR § 464-704. Accuracy requirements and testing schedules for diaphragm, orifice, rotary, and turbine meters

(a) Diaphragm meters under five hundred cubic feet per hour (500 CFH). (1)(A) Meters shall be tested for accuracy and adjusted, if necessary, to acceptable limits at least once every ten (10) years. (B) Accuracy limits shall be one hundred percent (100%) plus or minus five-tenths of a percent (±0.5%). (C) New meters accompanied by a certified test certificate are not required to be tested if the test results on the certificate are within accuracy limits. (2)(A) Meters shall be tested at both low and high flow rates. (B) Low flow rate shall be at twenty to forty percent (20% – 40%) of capacity. (C) High flow rate shall be at eighty to one hundred twenty percent (80% – 120%) of capacity. (D) Numerical accuracy difference between the two (2) rates shall not exceed one percent (1%). (3) Meters shall be tested by a slow-motion type or pilot-burner type of test after any repairs. (b) Diaphragm meters over five hundred cubic feet per hour (500 CFH). (1) New and shop-repaired meters. (A)(i) Shop-repaired meters and new meters not accompanied by a certified test certificate shall be tested for accuracy and, if necessary, adjusted to acceptable limits. (ii) Accuracy limits shall be one hundred percent (100%) plus or minus one percent (±1%). (iii) New meters accompanied by a certified test certificate are not required to be tested if the test results on the certificate are within accuracy limits. (B)(i) Meters shall be tested at both low and high flow rates. (ii) Low flow rate shall be at twenty to forty percent (20% – 40%) of capacity. (iii) High flow rate shall be at eighty to one hundred twenty (80% – 120%) percent of capacity. (iv) The numerical accuracy difference between the values for the two (2) rates shall not exceed one percentage point (1%). (2) In-service meters. (A)(i) Meters shall be tested for accuracy and, if necessary, adjusted to acceptable limits at least once every five (5) years. (ii) Accuracy limits shall be one hundred percent (100%) plus or minus two percent (±2%). (B)(i) Meters shall be tested at both low and high flow rates. (ii) Low flow rate shall be at twenty to forty percent (20% – 40%) of capacity. (iii) High flow rate shall be at eighty to one hundred twenty percent (80% – 120%) of capacity. (iv) The numerical accuracy difference between the values for the two (2) rates shall not exceed two percentage points (2%). (c) Orifice meters. (1) Periodic inspections. Meters must be inspected by qualified personnel at periodic intervals to ensure all elements and associated facilities function accurately. (2) Visual inspection. To verify the operation of the meter device, a visual inspection of the metering station shall be performed each time the chart is changed. (3) Inspection and calibration. (A) An inspection and calibration shall be performed semi-annually on the orifice meters, orifice plates, and installed auxiliary elements of the metering station. (B) Meters shall be maintained to an accuracy of one hundred percent (100%) plus or minus two percent (±2%). (C) Any components not functioning properly shall be repaired or replaced. (d) Rotary meters. (1) Meters shall be tested for accuracy and, if necessary, adjusted to acceptable limits at least once every five (5) years. (2) Accuracy limits shall be one hundred percent (100%) plus or minus one percent (±1%) at approximately twenty to one hundred percent (20% – 100%) of the meter's rated capacity. (3) New meters accompanied by a certified test certificate are not required to be tested if the test results on the certificate are within the accuracy limits. (e) Turbine meters. (1) Meters shall be tested for accuracy and, if necessary, adjusted to acceptable limits at least once every five (5) years. (2) Meters shall be maintained to an accuracy of one hundred percent (100%) plus or minus one percent (±1%). (3) New meters accompanied by a certified test certificate are not required to be tested if the test results on the certificate are within the accuracy limits. (f) Meter correcting instruments. (1)(A) Pressure correcting instruments or devices may be used where the pressure exceeds the normal delivered pressure. (B) However, calculated pressure factors may be used if delivered pressure is relatively constant. (2)(A) Each base pressure and base volume correcting device shall be tested for accuracy each time the associated meter is tested. (B) This requirement does not apply to constant pressure compensating indexes.