Ansi requirement to protect gas pipes from corrosion

1. GPTC GUIDE FOR GAS TRANSMISSION AND §192.465
DISTRIBUTION PIPING SYSTEMS: 2009 Edition SUBPART I
(6) Cracks in gouges.
(7) Coating defects.
(b) No individual in-line inspection tool is universally applicable for the identification, measurement,
and assessment of every type of anomaly. Tool selection and performance may be dependent
upon the following parameters.
(1) Type and size of anomalies to be detected.
(2) Desired data resolution and sizing accuracy of anomalies.
(3) Length of pipe to be inspected.
(4) Ability to couple tool to pipe wall.
(5) Desired tool speed.
(6) Physical condition of the pipeline.
(i) Internal cleanliness.
(ii) Pipe wall deformations.
(iii) Change in pipe wall or grade.
10.4 Reference.
See guide material under §192.150.
§192.467
External corrosion control: Electrical isolation.
[Effective Date: 09/05/78]
(a) Each buried or submerged pipeline must be electrically isolated from other underground
metallic structures, unless the pipeline and the other structures are electrically interconnected and
cathodically protected as a single unit.
(b) One or more insulating devices must be installed where electrical isolation of a portion of a
pipeline is necessary to facilitate the application of corrosion control.
(c) Except for unprotected copper inserted in ferrous pipe, each pipeline must be electrically
isolated from metallic casings that are a part of the underground system. However, if isolation is not
achieved because it is impractical, other measures must be taken to minimize corrosion of the
pipeline inside the casing.
(d) Inspection and electrical tests must be made to assure that electrical isolation is adequate.
(e) An insulating device may not be installed in an area where a combustible atmosphere is
anticipated unless precautions are taken to prevent arcing.
(f) Where a pipeline is located in close proximity to electrical transmission tower footings,
ground cables or counterpoise, or in other areas where fault currents or unusual risk of lightning
may be anticipated, it must be provided with protection against damage due to fault currents or
lightning, and protective measures must also be taken at insulating devices.
[Issued by Amdt. 192-4, 36 FR 12297, June 30, 1971; Amdt. 192-33, 43 FR 39389, Sept. 5, 1978]
GUIDE MATERIAL
1 ELECTRICAL ISOLATION (§192.467(a), (b), and (c))
1.1 Insulating devices. (§192.467(a) and (b))
Insulating devices may consist of insulating flange assemblies (see guide material under §192.147),
unions or couplings, or fabricated insulating joints. These devices should be properly rated for
temperature, pressure, and dielectric strength. Typical locations where electrical insulating devices
should be considered include the following.
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2. GPTC GUIDE FOR GAS TRANSMISSION AND §192.467
DISTRIBUTION PIPING SYSTEMS: 2009 Edition SUBPART I
(a) At supporting pipe stanchions, bridge structures, tunnel enclosures, piling, and reinforced concrete
foundations where electrical contact would preclude effective cathodic protection (CP). It may be
necessary to electrically isolate the piping from such a structure, or the piping and structure from
adjacent underground piping.
(b) At metallic curb boxes and valve enclosures. These should be designed, fabricated and installed in
such a manner that electrical isolation from the piping system will be maintained.
(c) Where a pipe enters a building through a metallic wall sleeve and where it is intended to maintain
electrical isolation between the sleeve and the pipe. To accomplish this, insulating spacers should
be used.
(d) At river weights, pipeline anchors, and metallic reinforcement in weight coatings. These should be
electrically isolated from the carrier pipe and installed so that coating damage will not occur.
(e) Points at which facilities change ownership, such as meter stations and well heads.
(f) Connections to main line piping systems such as gathering or distribution system laterals.
(g) Inlet and outlet piping of inline measuring or pressure regulating stations or both.
(h) Compressor or pumping stations, either in the suction and discharge piping or in the main line
immediately upstream and downstream of the station.
(i) In stray current areas.
(j) At the termination of service line connections and entrance piping to prevent electrical continuity with
other metallic systems.
1.2 Casings. (§192.467(c))
(a) New installations.
(1) Spacers and sealing. All new construction of cased metallic pipelines should provide for the
installation of insulating type casing spacers or other suitable means to prevent physical contact
between the carrier pipe and casing. The ends of the casing may be sealed with a
non-conductive sealing method to prevent mud, silt, and water from entering the annular space
between the casing and the carrier pipe. It may be necessary to fill this annular space with a
non-conductive type casing filler to ensure continued isolation in those installations where end
seals alone may not be sufficient to resist the entrance of water.
(2) Joining. Lengths of casing should be joined by a full weld, or other type of joint that will provide
an adequate seal against water entrance. Any holes in the casing should be closed by welding,
or otherwise sealed.
(3) Insertion. Care should be taken during installation to reduce the possibility of electrical shorts.
The carrier pipe should be as straight as practical. The internal diameter of the casing should be
adequate to ensure physical clearance from the carrier pipe. The carrier pipe should be carefully
inspected and all coating damage repaired. Care should be taken during insertion of the carrier
pipe. To prevent damage to the coating and spacer, the casing should be clear of any mud,
water, or debris prior to insertion of the carrier pipe. When existing buried pipe is being used as
the casing, steps should be taken to ensure that the casing pipe is free of weld protrusions and
other obstructions that might cause jamming of the carrier pipe during insertion.
Where insulating type casing spacers are used, one should be installed as close as practical to
each end of the casing. Vent connections, when required, should be installed prior to the
insertion of the carrier pipe to preclude the possibility of damage to the carrier pipe.
(b) Existing installations.
Where there is an indication on existing installations that corrosion is occurring on the carrier pipe or
where a CP installation is rendered inadequate as a result of low resistance between the casing and
carrier pipe, practical measures to help ensure adequate corrosion protection on the pipeline may
consist of one or more of the following.
(1) Filling the annular space between the carrier pipe and casing with a non-conductive filler.
(2) Applying additional CP to the pipe.
(3) In some cases where the carrier pipe is electrically shorted to the casing, it may be practical to
expose the ends of the casing and physically realign the carrier pipe to give enough clearance
for inserting electric insulating material in sheet form between the casing and carrier pipe. The
feasibility of safely moving the carrier pipe to clear a short should be determined prior to
performing the work. See 4 of the guide material under §192.703.
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3. GPTC GUIDE FOR GAS TRANSMISSION AND §192.467
DISTRIBUTION PIPING SYSTEMS: 2009 Edition SUBPART I
2 INSPECTION AND TESTING (§192.467(d))
The required monitoring of CP systems and the evaluation of such test data is generally sufficient to
ensure that electrical isolation is adequate on cathodically protected piping. However, specific electrical
tests on insulating devices should be made where deemed necessary to ensure the adequacy of
electrical isolation and to pinpoint operational problems on CP systems.
3 COMBUSTIBLE ATMOSPHERE (§192.467(e))
(a) Precautions to prevent arcing may be taken by installing galvanic anode type grounding cells or
commercial lightning or fault arrestors across the insulating devices.
(b) Where lightning arrestors are installed across insulating devices within a building or other confined
space anticipated to have a combustible atmosphere, the physical installation of the lightning
arrestors should be made outside the confined space. Electrical conductors of adequate size
should be installed from the insulating point to the lightning arrestors.
4 PROTECTION OF INSULATING DEVICES (§192.467(f))
It is recommended that the operator make a study in collaboration with the electric company on the
common problems of corrosion and electrolysis, taking into consideration the following factors.
(a) The possibility of the pipeline carrying either unbalanced line currents or fault currents.
(b) The possibility of lightning or fault currents inducing voltages sufficient to puncture pipe coatings or
pipe.
(c) CP of the pipeline, including the location of ground beds. (This is particularly important if the electric
line is carried on steel towers.)
(d) Bonding connections that exist between the pipeline and the overhead electric system at the
following.
(1) The steel tower footing;
(2) The buried grounding facility; or
(3) The ground wire.
(e) Protection of insulating joints in the pipeline against induced voltages or currents resulting from
lightning strikes. This can be obtained by:
(1) Connecting buried sacrificial anodes to the pipe near the insulating joints;
(2) Bridging the pipeline insulator with a spark-gap; or
(3) Other effective means.
(f) Cable connections from insulating devices to lightning and fault current arrestors should be short,
direct, and of a size suitable for short-term, high current loading.
(g) The electrical properties of nonwelded joints. (Where the objective is to ensure electrical continuity,
it may be achieved by using fittings manufactured for this purpose or by bonding the mechanical
joints in an approved manner. Conversely, if an insulating joint is required, a device manufactured
to perform this function should be used. In either case, these fittings should be installed in
accordance with the manufacturer's instructions.)
5 REFERENCES
(a) NACE RP0177, "Mitigation of Alternating Current and Lightning Effects on Metallic Structures and
Corrosion Control Systems."
(b) NACE RP0200, "Steel-Cased Pipeline Practices."
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