(a) All meters shall be adjusted to register accurately with a tolerance of not more than two percent.

1. (1) Steam flow meters of the area and velocity types shall be tested using air or steam as the testing medium except as provided in section 400.4(b) of this Part.
2. (2) In tests employing steam as the testing medium, the steam used shall in no case contain more than one percent moisture and may be slightly superheated.
3. (3) In tests employing either air or steam as the testing medium and flow tubes with orifices as the reference standards, the test equipment and test procedure shall conform with the applicable provisions set forth in the American Society of Mechanical Engineers Standards, covering flow measurement (presently designated PTC 19.5; 4-1959), in effect at the time of test.

4. (4) In tests conducted in accordance with paragraph (3) of this subdivision, meters shall be tested at the load points specified below:

   1. (i) Area type meters. One test shall be made at each of six load points starting at approximately one-sixth load and continuing in equal steps to 100 percent of meter rating.
   2. (ii) Velocity type meters. Two tests shall be made at each of three load points approximately equal to 50 percent, 60 percent and 70 percent of meter rating.

5. (5) In tests employing steam as the testing medium and a condensate weighing scale as the reference standard, meters shall be tested at the load points specified below:

   1. (i) Area type meters. Two tests shall be made at each of six load points starting at approximately one-sixth load and continuing in equal steps to 100 percent of meter rating.
   2. (ii) Velocity type meters. Two tests shall be made at each of three load points approximately equal to 50 percent, 75 percent and 100 percent of meter rating.
6. (6) Each main line metering orifice plate used in conjunction with a steam flow meter of the velocity type shall be inspected and its diameter measured for conformity with the original installation at least once every five years.

7. (7) The diameter of each main line metering orifice plate removed from service shall be measured and entered on a record which shall be retained for a period of at least one year.

   (c) Steam flow meters—head type.

8. (1) The test made in accordance with section 400.6(a) of this Part of steam flow meters of the head type shall consist of the following:

   1. (i) Certification of the primary element, including the orifice plate, for conformance with the applicable provisions set forth in the American Society of Mechanical Engineers Standards, covering flow measurement (presently designated PTC 19.5; 4-1959), in effect at the time of the test.
   2. (ii) Verification of the correctness of the meter constant.
   3. (iii) The test of the secondary element (flow mechanism) shall be made in place on the customer's premises at each of five load points approximately equal to 20 percent, 40 percent, 60 percent, 80 percent and 100 percent of meter rating.
9. (2) On subsequent tests, the procedure in subparagraph (1)(iii) of this subdivision shall be followed.
10. (3) Each metering orifice plate shall be inspected and its diameter measured for conformity with the original installation at least once every five years.

11. (4) The diameter of each metering orifice plate removed from service shall be measured and entered on a record which shall be retained for a period of at least one year.

    (d) Steam condensate meters.

12. (1) Steam condensate meters shall be tested using water as the testing medium.
13. (2) Two tests shall be made at each of two load points with the meter passing a known quantity of water at rates of flow approximately equal to first, 100 percent and second, 50 percent of meter rating.

(b) Steam flow meters—area and velocity types.