coupling is hinged on one side, clamped around the pipe, and then
pinned on the other side. The clamp is pulled tightly shut with the
assistance of the tightening handle.
Stab Lock Couplings - Stab lock couplings are the second type of
coupling being evaluated for use with aluminum pipe. The pipe
sections are stabbed into the coupling where a series of gaskets
inside the collar result in a seal being formed. Special pliers are
utilized to break apart these sections of pipe in the event that a
section needs to be replaced.
Cutting and Grooving Procedures for Steel Pipe.
Grooved pipe is used
for coupling pipe sections together with the split-ring, groove-type
coupling. Due to layout or damage, a section of pipeline must be cut to
a nonstandard length and regrooved to allow for proper assembly. A
portable cutting, grooving, and beveling machine is used to perform this
task. These machines are packaged in a kit and are included in the welded
pipeline construction tool set. The kit includes two large suitcases and
two pipe stands. The machine is powered by a 250 cubic-foot-per-minute
(CFM) air compressor or by a generator. It is used primarily during
mainline pump station construction. It takes about 30 minutes to cut and
groove each end of the pipe.
Welding of Pipeline.
Pipe to be welded will have a beveled edge on it
to facilitate making a good weld. Rebeveling, because of damage to the
edge, or cutting and beveling are accomplished with the machine described
above. The bevel is cleaned of slag with a bevel grinding machine.
PART B - VALVES
Gate Valves - Gate valves have a gate in the form of a disk or wedge,
which is raised to permit the flow of fuel and lowered to stop the
flow of fuel.
Rising-Stem Gate Valves - Rising-stem gate valves are threaded on the
upper end of the stem. The lower end is attached to a disk. When the
hand wheel is turned both the stem and disk are raised and lowered.
When the valve is fully opened it will allow pipeline scrapers, poly
pigs, etc., to pass through. By looking at the valve from a distance
you can tell whether or not the valve is open or closed. The stem of
the valve is easy to sabotage. The exposed surface of the upper stem
on the rising stem gate valve should be protected by placing a split,
one-inch hose or some similar device around the stem in the yoke area.
A fine film of motor oil can be used to lubricate the thread on the
stem. This valve is used in the pipeline at intervals at the bottom
of long slopes, on both sides of a stream crossing, and at storage
tanks.
Nonrising-Stem Gate Valves - The threaded lower end of the stem on a
nonrising-stem gate valve screws into the disk, thereby raising or
lowering the disk while the stem is retained in place by a thrust
collar. The packing gland must be monitored and replaced as
necessary.
12-89
QM 5099
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