FED-STD-791D
e. Tube, outlet, copper, approximately 3/16-in O.D., sealed at one end with
approximately 1/8-in hole, 1/2 in from sealed end.
f. Tubing, glass and rubber, as required.
g. Clamp, screw (for rubber tubing). Bath heating, water, 66 to 69C (150 to
155F).
4.9 Compressed-air supply.
5. MATERIALS
5.1 CAUTION - SOME MATERIALS ARE TOXIC AND HAZARDOUS. The
chemical materials listed in this section must be handled carefully. Federal Test Method 10000,
Material Handling Safety Precautions, is a reference which lists all toxic and hazardous materials
cited in FTMS 791. The synonyms, life hazard, flammability, handling and storage precautions,
emergency treatment and measures, and spill practices of each chemical are explained.
5.2 Gas, hydrocarbon, with known lower limit of explosiveness (in volume percentage of
gas concentration).
6. PROCEDURE
6.1 Prepare the 2-hole rubber stopper (for the volumetric flask) by inserting a short
length of glass tubing in one hole and the sealed end of the copper outlet tube, used in figure l, in
the other hole. Position the outlet tube so that the stopper seals the side opening of the tube; seal
the outside end of the glass tube with a short length of rubber tubing and a screw clamp.
6.2 Prepare an air-gas mixture of 50% explosiveness (for use in calibrating the
combustible-gas indicator), as follows:
a. Compute the volume of hydrocarbon gas (see. 5.2) required to produce a 2-L air-gas
mixture of 50-percent explosiveness.
b. Place approximately 500 mL of water in the 2-L volumetric flask, and invert in the
water tank.
c. Measure the required amount of hydrocarbon gas, using an inverted water-filled
100-mL graduated cylinder supported in the water tank so it will contain the computed
volume of gas when the water levels in the graduate and the tank are the same.
d. Transfer the gas to the volumetric flask by carefully raising the lip of the graduate
beneath the neck of the submerged flask.
e. Add air to the volumetric flask until the water levels (inside and outside) are at the
graduation mark.
f. Insert the prepared 2-hole stopper (see 6.1) into the volumetric flask taking care to
maintain the water seal of the gas mixture. Remove the flask from the tank and invert
several times.
6.3 Calibrate the combustible-gas indicator by passing the air-gas mixture through the
indicator and noting the reading as follows:
69
For Parts Inquires call Parts Hangar, Inc (727) 493-0744
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business