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Interpretation Response #PI-81-0101


Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 02-25-1981

Country: US

View the Interpretation Document


Response text:

DATE:            25 Feb 1981

SUBJECT:       ACTION:           Interpretation – Section 192.311

FROM:           Robert L. Paullin
Associate. Director for Operations & Enforcement, DMT-10

TO:                Melvin A. Judah
Acting Associate Director for Pipeline Safety
Regulation, DMT-30
Section 192.311, a general construction requirement for transmission lines and mains, limits
plastic pipe repair to the use of a patching saddle or removal. Also, Paragraph 192.13(b) requires
that when a segment of pipeline is replaced, relocated, or otherwise changed, then that
replacement, relocation, or change must be made in accordance with this part. With these
requirements in mind, would the existing Part 192 permit the addition of a band clamp (compression
fitting) on an operating pipeline to permanently repair damage or a leak (1) on
a plastic transmission line or main? (2) on a plastic service line?
February 27, 1981
Mr. Keith A. Chen, P.E. Director - Research Wisconsin Gas Company
£26 Last Wisconsin Avenue
Milwaukee, Wisconsin 53202

Dear Mr. Chen:
Your letter to this office of February 6, 1981, concerns the use of full encirclement stainless
steel band clamps for permanent repair of damaged plastic pipe. We agree with your interpretation
that Subpart G of
49 CFR Part 192 (and, thus, §192.311) is only applicable during the construction of a transmission
line or main. However, as further discussed below, even if the band clamp were considered a
“patching saddle,” as intended by §192.311 (which it is not), its use to permanently repair plastic
pipe either during construction or after operation nay be prohibited under §192.703(b).

In regard to the term “patching saddle” as used in §192.311, these words were added to the final
rule as a result of comments to the proposed rule stating that defective plastic pipe should be
permitted to be repaired. These comments clearly had in mind the use of a saddle made of material
similar to that of the pipe being repaired that would be joined to the pipe by fusion, solvent
cement, adhesion, or similar methods. Typical comments that prompted the Office of Pipeline Safety
to permit use of a “patching saddle” were

"We feel that patching of a plastic vain should be allowed. Should be no difference between a patch
over a gouge or the installation of a service tee." (Iowa Public Service Company)

"The use of solvent weld half-soles on polyvinyl chloride pipe has proven to be a safe, economical
method of repair for scratches, gouges, and grooves on mains in service. (Central Telephone and
Utilities Corporation)Thus, a band clamp is inconsistent with the meaning intended by "patching
saddle.

Another reason why "patching saddle" does not mean a band clamp is that when §192.311 was issued,
§192.281(e)(2) was also issued, requiring a rigid internal tubular stiffener to be used in
conjunction with each
compression type mechanical coupling. This requirement recognizes the compressive forces of the
sealing
gasket used in a compression coupling and the fact that plastic materials under constant stress
will tend to
cold flow. A full encirclement stainless steel hand clamp, like a compression coupling, subjects
the plastic pipe
to compressive stress but does not provide internal support for the pipe that may be needed to
prevent cold
flow of the plastic.

Because of the question of cold flow of plastic pipe, we believe that the safety of a permanent
repair by use of a band clamp is questionable under some conditions, depending on the stiffness of
the elastic pipe involved. Where unsafe conditions would result, §192.703(b) would forbid use of
the band clamp as a repair method.

In your letter, you state that “Wisconsin Gas conducted tests on tile, stainless steel clamp, used
as a patching saddle which determined that the performance met the required safety and
serviceability tests of the code." We would appreciate your sending us these data and any other
data available on the problem
of cold flow of plastic pipe under continuous gasket pressure as discussed above.
Sincerely, SIGNED
MELVIN A. JUDAH Melvin A. Judah
Acting Associate Director for
Pipeline Safety Regulation
Pipeline Safety Regulation
Materials Transportation Bureau


Regulation Sections

Section Subject
§ 192.13 What general requirements apply to pipelines regulated under this part?