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 (b) Field Air Pressure Test for Casing Watertightness. Proceed as
follows:
(1) Make sure that the system is dry.
( 2 ) With the lines in operation, apply air pressure to the space
b e t w e e n the conduit and pipe until obtaining 20 psig. If the system is
r e a s o n a b l y watertight, this pressure should hold for at least 2 hours without
r e q u i r i n g any additional air supply.
( 3 ) During the. test, examine all accessible joints for leaks by
applying a solution of soap and water. Apply the soapy lather after wire
b r u s h i n g the joints.
( 4 ) Mark leaks, if any. Make repairs after rel e a s i n g the air
pressure, and test again.
For a complete
(5) Leaks can be detected using SF6 tracer gas
discussion of methodology, see NEESA 32-015, Location of Leaks in Pressure
Testable Direct Burial Conduits - Operator's Manual.
2.4.5 Class B Systems. When conduit leaks are suspected, perform the
f o l l o w i n g procedure before putting the line back in service.
(a) Permit all drainable water to drain back to manholes by loosening
the manhole glands as required.
( b ) If appreciable moisture is observed, put the line in service by
turning on the steam. T h i s will raise the temperature of the piping,
evaporating the moisture which is then released through the pipe ends in the
manholes.
(c) Emergency conditions may require digging down to the conduit, or to
o n e of the sealing strips, t o install a temporary vent until permanent repairs
can be carried out. This releases steam, preventing the buildup of excessive
p r e s s u r e s which may result in the failure of the conduit or the sealing strips.
( d ) Drying of Insulation. Use same procedure as described in paragraph
2 . 4 . 2 ( a ) for metallic casings. The rate of forced ventilation should be
limited to 2 cubic feet per minute during a 48-hour period. Allow a maximum
air pressure of 12 inches water gauge anywhere in the conduit airspace.
( e ) Odorization Test. One method often used to detect leaks is known as
t h e odorization test. T h i s test consists of introducing properly odorized air
under pressure into the airspace cavity of the conduit through a conveniently
located vent. With all other vents and drains closed, leaks can be located by
the odor of the escaping air.
Refer to paragraph 2.4.2.b(5).
(f) SF6.
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