inlet shall be not less than 75 mm 3 inches in diameter.
(4) The meter shall be of the orifice type, of proper size, and
installed in accordance with the recommendation of AGA GMC.
Before tube tests are started, the calibration of the orifice
meter shall be checked with a standard displacement type gas meter
of not less than 39.33 L/s 5,000 cubic feet per hour (cfh)
capacity which has been accurately calibrated volumetrically in a
manner satisfactory to the [Contracting Officer] [Contractor
Quality Control representative]. When checking the orifice meter,
the inlet of the standard gas meter shall be connected to an
opening in a steel plate clamped in the test box and the outlet of
the gas meter shall be to the atmosphere. The checking of the
orifice meter shall be done in the presence of the [Contracting
Officer] [Contractor Quality Control representative]. The
calibration of the orifice meter may be checked with an orifice
plate, calibrated as described above, suitably arranged for
clamping into the test box.
(5) The test air supply shall be such as to give a continuous
nonpulsating flow of air with a relative humidity between 10 and
25 percent. A suitable equalizing tank and moisture control
equipment, with recording hygrometer, shall be provided for the
purpose.
(6) Each diffuser tube shall be tested dry for its permeability
rating. All tubes shall be kept dry from the time they leave the
kiln until tested.
(7) Each diffuser tube shall have practically uniform
permeability throughout its face area, free from dead areas or
areas with large bubbles, as determined visually by the method of
testing hereinafter specified.
(8) The uniformity testing apparatus shall be similar to the
permeability rating apparatus, and shall provide for submerging
the tube under 25 mm one inch of water after it is clamped into
position.
(9) Diffuser tubes to be tested for uniformity shall be saturated
with tap water, clamped in position in the apparatus, and
submerged to a depth of 25 mm one inch with tap water. Air shall
then be diffused through the tube at a rate of 61 L/s per square
meter 12 cfm per square foot for one minute. The rate of air flow
shall be reduced to 5 L/s per square meter 1.0 cfm per square foot,
the uniformity of diffusion observed and recorded as satisfactory
or rejected.
(10) Uniformity tests will be required on not less than one tube
selected at random from each 100 accepted for permeability. If
these tests do not show substantial uniformity, such additional
tests shall be made as may be necessary to assure the [Contracting
Officer] [Contractor Quality Control representative] that tubes
with uniform permeability are being obtained. If the additional
tests indicate that 10 percent or more of the tubes are
non-uniform, the entire 100-tube batch shall be tested
individually for uniformity, and the additional cost of such
inspection shall be borne by the Contractor.
SECTION 11375N
Page 88
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