7. To fully minimize the effects of refraction, it is advisable to use a
blower after the pipe run exceeds 50 feet (15 m). Operate the
blower at a speed that minimizes the effects of refraction.
As the pipe length increases, increase the speed of the blower.
8. When using a blower, make sure it is taking in fresh air through
the intake. On the discharge end, the nozzle should be angled to
bounce the air off the side of the pipe thereby creating a spiral or
corkscrew effect.
9. If possible, mount the nozzle on the side of the pipe or in the invert. Avoid attaching the nozzle at
the top of the pipe unless there is no other choice, as this will push the warmer gas through the
pipe. If a strong wind is blowing down the pipe and fighting the blower, it may not be needed.
10. In large diameter pipe, 18 inches (45 cm) and larger, it is better to position the blower nozzle off
the invert below the laminar surface of the gas. If this is insufficient, three alternatives are
possible. Use two electric blowers, a Homelite Model III-B (or equivalent) gas driven blower or a
short blast of air from an air compressor, to clean out the line.
11. If the beam still can not be controlled, have your backhoe excavate five buckets full and then one
or two empty buckets as if it were bailing water. The blower is pushing heavy fumes in the pipe
that can not get out of the trench without someone’s help. Cast the empty bucket on the low side
of the surface or on the downwind side of the cut.
Nozzle
Summary of Contents for DG613
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Page 5: ...Illustration Set Up A 1230 B 1237 C 1248 1 2 3 4 5...
Page 32: ...Calibration Checking Calibration...
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