Current through August, 2024
(a) Unless the requirements of this section
have been met, no person may subject:
(1) A
segment of steel pipeline to an operating pressure that will produce a hoop
stress less than thirty percent of SMYS and that is above the previously
established maximum allowable operating pressure; or
(2) A plastic, cast iron, or ductile iron
pipeline segment to an operating pressure that is above the previously
established maximum allowable operating pressure.
(b) Before increasing operating pressure
above the previously established maximum allowable operating pressure, the
operator shall:
(1) Review the design,
operating, and maintenance history of the segment of pipeline;
(2) Make a leakage survey (if it has been
more than one year since the last survey) and repair any leaks that are found,
except that a leak determined not be potentially hazardous need not be
repaired, if it is monitored during the pressure increase and it does not
become potentially hazardous;
(3)
Make any repairs, replacements, or alterations in the segment of pipeline that
are necessary for safe operation at the increased pressure;
(4) Reinforce or anchor offsets, bends and
dent ends in pipe joined by compression couplings or bell and spigot joints to
prevent failure of the pipe joint, if the offset, bend, or dead end is exposed
in an excavation;
(5) Isolate the
segment of pipeline in which the pressure is to be increased from any adjacent
segment that will continue to be operated at a lower pressure; and
(6) If the pressure in mains or service
lines, or both, is to be higher than the pressure delivered to the customer,
install a service regulator on each service line and test each regulator to
determine that it is functioning. Pressure may be increased as necessary to
test each regulator, after a regulator has been installed on each pipeline
subject to the increased pressure.
(c) After complying with subsection (b), the
increase in maximum allowable operating pressure must be made in increments
that are equal to 10 p.s.i.g. or 25 percent of the total pressure increase,
whichever produces the fewer number of increments. Whenever the requirements of
subsection (b)(6) apply, there must be at least two approximately equal
incremental increases.
(d) If
records for cast iron or ductile iron pipeline facilities are not complete
enough to determine stresses produced by internal pressure, trench loading,
rolling loads, beam stresses, and other bending loads, in evaluating the level
of safety of the pipeline when operating at the proposed increased pressure,
the following procedures must be followed:
(1) In estimating the stresses, if the
original laying conditions cannot be ascertained, the operator shall assume
that cast iron pipe was supported on blocks with tamped backfill and that
ductile iron pipe was laid without blocks with tamped backfill;
(2) Unless the actual maximum cover depth is
known, the operator shall measure the actual cover in at least three places
where the cover is most likely to be greatest and shall use the greatest cover
measured;
(3) Unless the actual
nominal wall thickness is known, the operator shall determine the wall
thickness by cutting and measuring coupons from at least three separate pipe
lengths. The coupons must be cut from pipe lengths in areas where the cover
depth is most likely to be the greatest. The average of all measurements taken
must be increased by the allowance indicated in the following table:
|
|
Allowance (inches) Cast Iron Pipe |
| Pipe size (inches) | |
Pit cast pipe | |
Centrifugally cast pipe | |
Ductile iron pipe |
| | |
| |
| |
|
| 3 to 8 ..........................| |
0.075 | |
0.065 | |
0.065 |
| 10 to 12..........................| |
0.08 | |
0.07 | |
0.07 |
| 14 to 24..................... | |
0.08 | |
0.08 | |
0.075 |
| 30 to 42.....................| |
0.09 | |
0.09 | |
0.075 |
| 48 ........................ | |
0.09 | |
0.09 | |
0.08 |
| 54 to 60..................... | |
0.09 | |
...............I |
................... |
(4) For cast iron pipe, unless the pipe
manufacturing process is known, the operator shall assume that the pipe is pit
case pipe with a bursting tensile strength of 11,000 p.s.i. and a modulus of
rupture of 31,000 p.s.i.
