(a) Gauge lines connecting the pressure taps to the mechanical recorder must:

1. (1) Have a nominal diameter of not less than 3/8 inch, including ports and valves;
2. (2) Be sloped upwards from the pressure taps at a minimum pitch of 1 inch per foot of length with no visible sag;
3. (3) Be the same internal diameter along their entire length;
4. (4) Not include tees, except for the static-pressure line;
5. (5) Not be connected to more than one differential-pressure bellows and static-pressure element, or to any other device; and
6. (6) Be no longer than 6 feet.

(d) The following information must be maintained at the FMP in a legible condition, in compliance with § 3170.7(g) of this part, and accessible to the AO at all times:

1. (1) Differential-pressure-bellows range;
2. (2) Static-pressure-element range;
3. (3) Temperature-element range;
4. (4) Relative density (specific gravity) of the gas;
5. (5) Static-pressure units of measure (psia or psig);
6. (6) Meter elevation;
7. (7) Meter-tube inside diameter;
8. (8) Primary device type;
9. (9) Orifice-bore or other primary-device dimensions necessary for device verification, Beta- or area-ratio determination, and gas-volume calculation;
10. (10) Make, model, and location of approved isolating flow conditioners, if used;
11. (11) Location of the downstream end of 19-tube-bundle flow straighteners, if used;
12. (12) Date of last primary-device inspection; and
13. (13) Date of last meter verification.