Section 336.2005. Reference test methods for staterequested tests of delivery vessels.

The following reference test  method  shall  be  used  to detect gasoline vapor leaks by a combustible gas detector:

(a)     Principle.   A  combustible  gas   detector  is  used   to    indicate any incidence of leakage from gasoline delivery vessel tanks and vapor control systems. This qualitative monitoring procedure is an enforcement tool to confirm the continuing existence of leak-tight conditions.

(b)         Applicability.   This   method   is   applicable   to    determining leak-tightness of gasoline delivery vessel tanks during  loading  without taking the  delivery vessel tank out of service. The method is  applicable only  if  the   vapor control system does not create back pressure in excess of the pressure limits of the delivery vessel tank compliance leak test. For vapor control systems, this method is applicable to determining leak-tightness at any time.

(c)     Apparatus and specifications. The following apparatus shall be used:

(i)       Manometer. Liquid manometer, or equivalent, capable of measuring up to 0.9 pounds per square inch (24.9 inches of water) gauge pressure within 0.003 pounds per square inch (0.1 inches of water) precision.

(ii)         Combustible gas detector. A portable hydrocarbon gas analyzer with associated sampling line and probe which complies with all of the following provisions:

(A)      Safety. The device is certified as safe for operation in explosive atmospheres.

(B)     Range. The device shall have a minimum range of 0 to 100% of the lower explosive limit (LEL) as propane.

(C)     Probe diameter. The sampling probe shall have an internal diameter of 0.625 centimeters (1/4 inch).

(D)      Probe length.  The probe sampling  line   shall  be  of   sufficient length for easy maneuverability during testing.

(E)     Response time.  The response time for full-scale    deflection    shall be less than 8 seconds for a detector with a sampling line and probe attached.

(d)    Test procedure. The following test procedure shall be complied with:

(i)       Pressure. Place a pressure  tap  in   the  terminal,   plant,  or service station vapor control system as close as possible to the connection with the delivery vessel tank.  Record the pressure periodically during testing.

(ii)         Calibration.   Calibrate  the   combustible   gas   detector    with 2.2% propane, by volume, in air for 100% lower explosive limit response.

(iii)             Monitoring  procedure.  During   loading  or  unloading,  check the periphery of all potential sources of leakage of the delivery vessel tank and of the terminal, plant, or service station vapor collection system with a combustible gas detector.   The check shall comply  with   the following procedure:

(A)     Probe distance. The probe inlet shall  be  2.5  centimeters   from the potential leak source.

(B)     Probe movement. Move the probe slowly (2.0 centimeters per  second).If there is any meter deflection at a potential leak source, move the probe to locate the point of highest meter response.

(C)     Probe position.   As  much  as  possible,   the  probe   inlet   shall be positioned in the path of (parallel to) the vapor flow from a leak.

(D)     Wind. Attempt, as much as possible, to block the  wind from the area being monitored.

(iv)         Recording. Record the highest detector reading and location for each incidence of leakage.

History: 1981 AACS; 1989 AACS; 2002 AACS; 2006 AACS.