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The
vacuum tester consists of a 16 cfm (at no load) vapor-oiled
rotary vacuum pump powered by a 5 HP 4 cycle Briggs & Stratton
gasoline engine with drive belt guard, twenty feet of vacuum
hose with brass quick disconnect coupling on each end, a
welded steel testhead of the proper size to fit inside the
opening of the manhole cone. The test head is equipped
with an inflatable rubber bladder to seal to the manhole and
is equipped with a pressure gauge and relief valve for
inflating the bladder, a 0-30 "Hg liquid-filled vacuum gauge,
a double air fill and exhaust manifold with quarter turn ball
valves, two bolt on steel feet, and a bridge assembly with
height rod adjustement.
Vacuum tests
are performed on precast manholes do determine their
resistance to infiltration of water. The amount of
vacuum lost over a predetermined time is used as the pass/ no
pass test.
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