prEN ISO 16440

SLOVENSKI STANDARD
01-marec-2026
Naftna in plinska industrija, vključno z nizkoogljično energijo - Transportni
cevovodni sistemi - Načrtovanje, izvedba in vzdrževanje cevovodov z jekleno
oblogo (ISO/DIS 16440:2025)
Oil and gas industries including lower carbon energy - Pipeline transportation systems -
Design, construction and maintenance of steel cased pipelines (ISO/DIS 16440:2025)
Erdöl- und Erdgasindustrie - Rohrleitungs-Transportsysteme - Planung, Bau und
Instandhaltung von Rohrleitungen in Mantelrohren (ISO/DIS 16440:2025)
Industries du pétrole et du gaz naturel - Systèmes de transport par conduites -
Conception, construction et maintenance de conduites en acier moulé (ISO/DIS
16440:2025)
Ta slovenski standard je istoveten z: prEN ISO 16440
ICS:
75.200 Oprema za skladiščenje Petroleum products and
nafte, naftnih proizvodov in natural gas handling
zemeljskega plina equipment
77.140.75 Jeklene cevi in cevni profili Steel pipes and tubes for
za posebne namene specific use
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 16440
ISO/TC 67/SC 2
Oil and gas industries including
Secretariat: UNI
lower carbon energy — Pipeline
Voting begins on:
transportation systems — Design,
2026-01-01
construction and maintenance of
Voting terminates on:
steel cased pipelines
2026-03-26
ICS: 77.140.75; 75.200
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
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POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 16440:2026(en)
DRAFT
ISO/DIS 16440:2026(en)
International
Standard
ISO/DIS 16440
ISO/TC 67/SC 2
Oil and gas industries including
Secretariat: UNI
lower carbon energy — Pipeline
Voting begins on:
transportation systems — Design,
construction and maintenance of
Voting terminates on:
steel cased pipelines
ICS: 77.140.75; 75.200
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
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or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
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Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 16440:2025(en)
ii
ISO/DIS 16440:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Design . 2
4.1 General .2
4.2 Carrier pipe design .3
4.3 Casing design .3
4.4 Electrical isolation .3
4.5 Corrosion protection .4
5 Installation . 4
5.1 General .4
5.2 Handling and storage .4
5.3 New casing .4
5.3.1 General .4
5.3.2 Carrier pipe installation .5
5.3.3 Casing end seals .6
5.3.4 Test leads .6
5.3.5 Backfilling .7
5.4 Split-sleeve type casing extensions and installations .7
6 Inspection and monitoring . 8
6.1 General .8
6.2 Integrity inspection of carrier pipe .8
6.3 Monitoring of carrier pipe and casing .8
6.4 Leakage survey .9
6.5 Corrosiveness of the annular space .9
7 Maintenance and repair . 9
7.1 General .9
7.2 Maintenance of vents and test leads .10
7.3 Clearing of shorted casings .10
7.4 Filling of casings .11
Annex A (informative) Casing filling procedures for Dielectric Filler Materials .12
Annex B (informative) Examples of cathodic protection testing and monitoring techniques for
carrier pipes and casings . .15
Annex C (informative) Inspection tools for cased carrier pipe .30
Annex D (informative) Clearing a shorted casing .35
Annex E (informative) Removing and cutting a casing .37
Bibliography .39

iii
ISO/DIS 16440:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. The different approval criteria needed for the different types of ISO
documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/
IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 67, Oil and gas industries including lower carbon
energy, Subcommittee SC 2, Pipeline transportation systems.

iv
ISO/DIS 16440:2025(en)
Introduction
Users of this document are advised that further or differing requirements might be needed for individual
applications. This document is not intended to inhibit a vendor from offering, or the purchaser from
accepting, alternative equipment, or engineering solutions for the individual application. This might be
particularly applicable where there is innovative or developing technology. Where an alternative is offered,
it is advisable that the vendor identify any variations from this document and provide details.

v
DRAFT International Standard ISO/DIS 16440:2025(en)
Oil and gas industries including lower carbon energy —
Pipeline transportation systems — Design, construction and
maintenance of steel cased pipelines
1 Scope
This document specifies requirements, including corrosion protection, for the design, fabrication,
installation and maintenance of steel-cased pipelines for pipeline transportation systems in the petroleum
and natural gas industries in accordance with ISO 13623.
NOTE 1 Steel casings can be used for mechanical protection of pipelines at crossings, such as at roads and railways
and the installation of a casing at a highway, railway, or other crossing can be required by the permitting agency or
pipeline operator.
NOTE 2 This document does not imply that utilization of casings is mandatory or necessary.
NOTE 3 This document does not imply that cased crossings, whether electrically isolated or electrically shorted,
contribute to corrosion of a carrier pipe within a cased crossing. However, cased crossings can adversely affect the
integrity of the carrier pipe by shielding cathodic protection (CP) current to the carrier pipe or reducing the CP
effectiveness on the carrier pipe in the vicinity of the casing. Their use is not recommended unless required by load
considerations, unstable soil conditions, or when their use is dictated by sound engineering practices.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 15589-1, Petroleum, petrochemical and natural gas industries — Cathodic protection of pipeline systems —
Part 1: On-land pipelines
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
3.1
carrier pipe
pipe that conveys the fluid
Note 1 to entry: This applies to both transmission and distribution piping.
3.2
casing
steel pipe installed around a carrier pipe for mechanical protection
3.3
electrolyte
medium in which electric current is transported by ions

ISO/DIS 16440:2025(en)
3.4
electrolytic contact
ionic contact between the carrier pipe and the casing pipe through an electrolyte
3.5
end seal
device installed over or within the end of a casing to keep water, deleterious materials and debris out of the
casing or provide a watertight seal between the casing and the carrier pipe
3.6
holiday
unintentional discontinuity in a protective coating that exposes the bare steel surface to the environment
3.7
isolator
spacer
dielectric device designed to electrically isolate a carrier pipe from a casing and provide support for the
carrier pipe
3.8
metallic short
unintentional contact between two metallic structures
3.9
P/S potential
pipe-to-electrolyte potential
structure-to-electrolyte potential
potential difference between the surface of a buried or submerged metallic structure (pipe or casing) and
the electrolyte that is measured with respect to a reference electrode in contact with the electrolyte
3.10
split sleeve
casing installed in situ by welding two halves of the casing together around the carrier pipe
3.11
tunnel liner plate
steel plate used when micro tunnelling, used to shore horizontal excavations in soft ground
3.12
C/S potential
casing–to–electrolyte potential
potential difference between the surface of a buried or submerged metallic casing and the electrolyte that is
measured with respect to a reference electrode in contact with the electrolyte
4 Design
4.1 General
The purpose of a casing is to provide additional mechanical protection to the carrier pipe. A casing can also
be required by a permitting authority to allow replacement of a carrier pipe without excavations at the
location of a crossing.
A carrier pipe within a casing without a filler installed in the annulus is not designed to be cathodically
protected. It is designed to be electrically isolated from the casing with non-conducting spacers, or isolated if
the annulus of the casing is filled with a dielectric filler material. The carrier pipe is designed to be protected
with a protective coating.
ISO/DIS 16440:2025(en)
4.2 Carrier pipe design
The carrier pipe shall be coated for corrosion protection. The application of an abrasion resistant coating
over the corrosion coating should be considered.
NOTE 1 See NACE/SP 0169 for details of abrasion resistant coatings.
The carrier pipe shall be supported inside the casing with high dielectric isolating spacers and outside the
casing to prevent sagging. Sagging can lead to metallic contact between the casing and the carrier pipe and
to carrier pipe stresses.
NOTE 2 See NACE/SP 0286 for details of isolation techniques.
4.3 Casing design
Casing design shall be in accordance with the local, national, or industry requirements/standards.
The casing should be kept as short in length as possible to minimize the risk of electrical shorting over time
due to soil stress and pipe movement.
The casing internal diameter shall be selected based on the nominal diameter of the carrier pipe, the
thickness of any abrasion resistant coating, such as concrete, duroplastic material, or epoxy polymer and the
design of the isolators between carrier pipe and casing.
For individual carrier pipes with a nominal diameter of 200 mm (8.0 in) or greater, the outer diameter of the
casing should be a minimum of 100 mm (4.0 in) larger than that of the carrier pipe or if installing parallel
cable or conduits the casing should be a minimum of 300 mm (12.0 in) larger than that of the carrier pipe.
For individual carrier pipes with a nominal diameter less than 200 mm (8.0 in), the diameter of the casing
should be a minimum of 50 mm (2.0 in) larger than that of the carrier pipe.
Uncoated casing should be used. Coated or non-conductive casing may be used if the casing can be
harmonized with the carrier pipe cathodic protection.
NOTE 1 The use of coated or nonconductive casing pipe is not recommended due to potential shielding problems
when cathodic protection is applied. If coated casings (either internally coated or externally coated or both) are used,
external cathodic protection will not provide protection to the carrier pipe in the event that the annulus is filled with
a conductive electrolyte.
If vent pipes are required, then they should be installed on both ends of the casing. Vent pipes should be
positioned so that they are not directly over any isolation spacer or end seal. If concrete coated pipe is used
and no isolating spacers are used, then the vent pipes should only be installed on the top of the casing. Design
consideration of vent design for future filling of the casing should it become necessary.
The casing vent hole should be at least one-half the diameter of the vent pipe, with a minimum of 25 mm
(1,0 in). The vent pipe should be a minimum of 50 mm (2.0 in) in diameter.
Vent pipes shall be designed to prevent intrusion of water and debris.
Casing end seals shall be installed to prevent ingress of water, deleterious material and debris.
Vent pipes are used for venting, monitoring the casing for carrier pipe leaks, filling the casing and as line
markers.
NOTE 2 NACE/SP 0200 gives guidance for design of end seals.
4.4 Electrical isolation
Sufficient isolators shall be designed to prevent metallic contact between the carrier pipe and the casing, and
to provide adequate support. Isolators shall be designed to minimize coating damage. The use of metallic
components in isolation spacers should be avoided.

ISO/DIS 16440:2025(en)
Isolators shall be selected to ensure they have the mechanical strength required to withstand the installation
loads, considering all conditions including pipe weight, length of casing, conditions of weld beads, deflections
in the casing and other field conditions. Selection should confirm the ability of the isolators to provide
electrical isolation after installation and to position the carrier pipe properly for end seal application/
installation.
Test leads should be located (connected to the carrier pipe) on the carrier pipe at each end of the casing
to permit verification of metallic isolation. One test lead shall be required as a minimum. Test leads to be
installed in accordance with 5.3.4. Test leads to be installed after the carrier pipe is inserted in the casing.
Metallic shorts between the vent pipe, test leads and carrier pipe shall be prevented.
4.5 Corrosion protection
Consideration may be given to applying cathodic protection to the casing as required by conditions or
regulations. Cathodic protection design shall be in accordance with approved industry standards, such as
ISO 15589-1.
Consideration may be given to placing a high dielectric filler in the annular space or injecting a vapour phase
inhibitor. Annex A gives guidance on filling and the filling procedure.
Cathodically protected casings using the pipeline’s dedicated CP system may have a detrimental effect on
the carrier pipe.
AC corrosion should be considered as a possible problem when the pipeline is located in an area of AC
influence.(See ISO 18086).
Steel casings shall not be cathodically protected by the pipeline’s dedicated CP system because it may have a
detrimental effect on the carrier pipe.
5 Installation
5.1 General
This Clause provides requirements for the installation of new cased pipeline crossings, casing extensions
and new casing installation on existing pipelines.
5.2 Handling and storage
The carrier pipe and casing or tunnel liner plate shall be handled and stored in a manner that minimizes
coating and pipe end damage. Lifting shall be accomplished utilizing slings, wide belts, or appropriate end
hooks. If skids are utilized to support the carrier pipe or casing, padding material shall be used to prevent
coating damage. Skids shall be removed upon completion of the installation.
5.3 New casing
5.3.1 General
Cased crossings are installed using various techniques including boring, directional drilling, tunnelling and
open cutting.
NOTE 1 Filling of the annular space between the casing and excavation is sometimes required by the permitting
agency when the borehole is unstable or fracked out.
Welding of steel casings should be performed in accordance with the pipeline operator's line pipe welding
specifications.
NOTE 2 ISO 13847 provides guidance on welding.

ISO/DIS 16440:2025(en)
NOTE 3 Radiographic inspection of casing welds is normally not required.
Butt-weld alignment during casing fabrication shall be maintained to prevent casing, isolator, or spacer
damage during push/pull operations.
Slag and any welding debris shall be removed from inside the casing to prevent damage to the carrier pipe,
coating, isolator, or spacer.
Internal weld beads should be removed by grinding (when practical and allowed) to allow pulling or sliding
of the carrier pipe without damage to the isolators and coating.
The casing vent pipes should be installed before the carrier pipe to avoid coating damage. If the carrier pipe
is already in place when the vent hole is cut, measures shall be taken to prevent coating damage.
NOTE 4 The use of non-flammable insulating material to protect the carrier pipe coating is often required by the
pipeline operator during installation of the vent pipes to prevent coating damage to the carrier pipe.
If two vent pipes are used, the one at the lower elevation should be installed on the bottom of the casing to
facilitate possible filling of the casing If the vent pipe is doglegged, adequate separation and non-metallic
support between the vent pipe and carrier pipe shall be provided to keep the vent pipe from resting on the
carrier pipe and possibly shorting between the casing and carrier pipe.
5.3.2 Carrier pipe installation
Before the installation of isolators, the carrier pipe coating shall be inspected for coating holidays using an
electrical holiday detector.
NOTE 1 NACE/SP 0274 or NACE/SP 0490 provides guidance for holiday testing of the carrier pipe coating.
Isolators shall be installed according to the manufacturer’s instructions and in a manner that does not
damage the carrier pipe coating. Isolator runners (skids) shall be oriented to avoid a shorted condition. Bolts,
if present, should not remain at the bottom (6 o’clock) position. Clearance between isolator extremities and
casing should be a minimum of 25 mm (1.0 in) to allow adequate clearance during installation. The use of
metallic components in isolation spacers should be avoided.
NOTE 2 Additional information is given in NACE/SP 0286.
End caps should be installed on the carrier pipe to keep debris and deleterious material from entering the
carrier pipe and to aid in smooth push/pull operations.
The casing shall be visually inspected where possible and practical and, if necessary, cleaned immediately
prior to installation of the carrier pipe to remove any debris or foreign material.
All coating damage on the carrier pipe shall be repaired prior to insertion into the casing in accordance with
the applicable specifications and manufacturer’s recommendations.
NOTE 3 The requirements on handling pipe are also applicable to the installation of uncoated carrier pipe.
The carrier pipe shall be installed by the boring sled, a crane, or side-boom tractor using slings or belts
that do not interfere with the isolators or damage the coating. The push/pull operation shall continue in a
smooth motion until the carrier pipe is properly positioned.
The alignment of the carrier pipe and casing shall be ensured both prior to and during insertion of the
carrier pipe into the casing. During the installation operation, it shall be ensured that there is no isolator or
spacer displacement or damage to the carrier pipe coating.
NOTE 4 Isolators can slide along the carrier pipe during installation if not installed properly, if the casing is bent, or
if the installation is out of line. Inadequate support of the carrier pipe allows the carrier pipe to sag and make metallic
contact with the casing.
The cased crossing shall be inspected in accordance with Clause 6 to confirm that the casing and carrier
pipe are electrically isolated.

ISO/DIS 16440:2025(en)
The carrier pipe and casing or tunnel liner plate shall be cleaned as necessary for the installation of the end
seals in accordance with design specifications and the manufacturer’s recommendations.
NOTE 5 One procedure is to fill the annulus with water after carrier pipe has been pulled in temporarily for test
purposes. All water used for this purpose shall be removed by air pressure from the high end vent to push free water
to the bottom vent until as free of water as possible.
A CP drainage test is executed to verify the condition of the carrier pipe coating. Acceptance procedure is
described in ISO 15589-1.
5.3.3 Casing end seals
Isolating end seals shall be installed on both ends of casing.
Particular attention should be paid to the selection process, application method and applicator skills when
installing casing end seals.
Failure of end seals is a major cause of unwanted water and soil ingress into the annulus between the carrier
pipe and the casing. The end seal may be a pressure and watertight seal or a simple seal to prevent debris,
deleterious material and water from entering the annular space between the casing and carrier pipe. The
selection of the seal should consider:
— the position of the carrier pipe at the end of the casing;
— operating temperature;
— end seal materials;
— pressure rating of the seal.
NOTE 1 Annex A gives additional guidance on casing end seal selection.
NOTE 2 Most watertight seals, such as modular mechanical seals require that the carrier pipe be positioned in the
centre of the casing (centralized), whereas most simple end seals allow for some amount of off-centred position.
5.3.4 Test leads
Test leads for cathodic protection testing shall be installed on the carrier pipe and should be installed at
both ends of the casing. The leads shall be attached using pin brazing or thermite welding or other approved
process.
One test lead wire shall be installed at each location. When required by design, an additional test lead wire can
be installed, e.g. in order confirm the integrity of the leads and as a contingency in case of test lead damage.
The test lead connection to the carrier pipe shall be coated. The coating shall be compatible with the carrier
pipe coating, the test lead insulation and conform to the shape of the test lead/carrier pipe connection.
Damage to the carrier pipe or coating shall be repaired. The coating shall be made in such a way as to
eliminate any voids that may permit the ingress of moisture. There shall be no strain on the test lead that
might dislodge the protective coating. Any coating damage shall be repaired with a compatible repair
coating to return the coating to a holiday free condition.
To prevent electrical shorting, test leads shall not be wrapped around the vent pipe or the casing.
Test leads shall be installed on the casing when
— required by the documents or specifications,
— no vent pipes are installed,
— non-metallic vent pipes are installed, or
— metallic vent pipes are installed using mechanical couplings/fittings.

ISO/DIS 16440:2025(en)
Test leads shall be labelled, or colour coded in accordance with the design and pipeline operator requirements.
Key
1 test station
2 vent pipe
3 carrier pipe
4 casing
5 insulated test panel inside test station
6 pipe test lead
7 casing test lead
8 ground level
Figure 1 — Typical Test Station at cased Crossing
5.3.5 Backfilling
The carrier pipe and casing shall be supported to prevent settlement during the backfilling operation. The
method of support, for example, earth filled bags or compacted earth, shall be approved by the pipeline
operator.
The backfill material shall be free of debris and deleterious material.
Caution shall be exercised to prevent test lead damage, which is a common cause of shorting.
Inspection as described in Clause 6 shall be performed upon completion of the backfilling operation.
5.4 Split-sleeve type casing extensions and installations
Extension of existing casings or construction of new casings on existing pipelines often involves installation
by the split-sleeve method.
NOTE This method is used if the pipeline cannot be taken out of service and the subsequent blow down (gas), or
drain-up (liquid), and cutting out of the crossing to allow a casing to be slipped over the pipeline is not feasible or cost-
effective.
Split-sleeve casing extensions should be specified to match the size of the existing casing. If required by
the configuration of the existing pipeline, an oversized casing extension may be installed. In this case, an
eccentric or concentric reducer should be used to achieve the size transition.
The carrier pipe section to be cased shall be excavated and supported to prevent sagging.
The carrier pipe shall be cleaned and the coating shall be inspected and repaired as needed.

ISO/DIS 16440:2025(en)
Existing end seals and vents shall be removed and the vent pipe hole shall be capped with a steel plate. To
prevent coating damage, the carrier pipe shall be protected during cutting and welding operations with an
insulating shield of non-flammable material.
The existing casing ends shall be prepared for welding in accordance with the owner company/operator
specifications.
Isolators shall be installed in accordance with the pipeline operator's specifications.
The pipe to be used in the casing extension shall be specified to provide metallurgical and physical
compatibility with the existing casing.
If a manufactured split casing is not used, splitting of the casing shall be performed in a manner that
minimizes warping or disfigurement. Hinges may be welded to the casing to maintain proper alignment
of the two halves during installation. Carbon steel backing strip of 2 mm to 3 mm may be used for the long
seam welding of the casing pipe over the existing carrier pipe.
The split casing shall be positioned over the existing carrier pipe in a manner that avoids any damage to
the pipe, coating, or spacing materials. Seam welding shall be performed in accordance with applicable
specifications. The casing seams may be tack welded at intervals prior to the continuous welding operation
to prevent warping. During the welding operation, non-flammable, insulating backing material shall be used,
where needed to protect the carrier pipe.
The installation of new vent piping and test leads, if required, shall be performed in accordance with 5.3.1
and 5.3.4.
Backfilling shall be performed in accordance with 5.3.5.
6 Inspection and monitoring
6.1 General
The inspection and monitoring of cased pipelines should include:
— integrity inspection of carrier pipe;
— monitoring of carrier pipe and casing;
— leakage survey.
Inspection and monitoring shall be performed throughout the life of the pipeline. Monitoring shall also be
undertaken immediately after the installation of the casing to verify its status.
6.2 Integrity inspection of carrier pipe
If available, integrity inspection data (such as in-line inspection or Guided Wave data) should be used to
determine the presence or absence of steel defects (such as pitting corrosion) in the carrier pipe.
NOTE Some in-line inspection techniques are capable of detecting the presence of a casing around a carrier pipe but
are unable to accurately detect metal-to-metal contact between the casing and carrier pipe or carrier pipe metal loss.
6.3 Monitoring of carrier pipe and casing
Carrier pipe and casing shall be monitored on a periodic basis to determine the condition for continuing
suitability and electrical status using the following method: potential survey.
The electrical status of carrier pipe and casing shall be assessed using one or more of the following methods:
— internal resistance test;
— four-wire IR drop test for cased crossing;

ISO/DIS 16440:2025(en)
— cycling the rectifier;
— casing depolarization test (see Note);
— pipe/cable locator;
— Panhandle eastern method.
Details of test methods are given in Annex B and Annex C.
NOTE Results from these measurements allow the verification of the CP effectiveness according to
ISO 15589-1:2015, D.4.2.
WARNING — If cathodic protection is applied to the casing, the cathodic protection system shall be
disconnected from the casing and allowed to depolarize before any tests are conducted. The presence
of direct-connected galvanic anodes on the casing during the test can negate the test results.
6.4 Leakage survey
Leakage surveys should be carried out for the pipeline and the casing at the frequency required by the
applicable pipeline code.
The casing vent and the area in the vicinity of the end seals should be observed for evidence of product
leakage such as product, product odour, or dead and dying vegetation.
Leak-detection instruments, such as combustible gas indicators, may be used to analyse the atmosphere
within a casing for the presence of combustible hydrocarbons.
The results of pressure tests and leak detection systems may be used if available.
6.5 Corrosiveness of the annular space
The corrosiveness of the annular space may be evaluated by inserting electrical resistance probes into the
annulus to estimate the rate of corrosion at holidays in the carrier pipe coating and on the inside of the
casing pipe wall.
7 Maintenance and repair
7.1 General
If inspection and monitoring of a steel cased pipeline indicates risk to the integrity of the carrier pipe, the
presence of a shorted casing or a product leak, then maintenance shall be undertaken using one or more of
the following actions:
— post-lay coating evaluation shall be carried out by competent persons and a determination made as to
whether or not the levels of coating damage are acceptable.
— eliminating metallic contact;
— removing the casing;
— repositioning the carrier pipe in the casing;
— repairing or replacing the carrier pipe;
— providing supplemental cathodic protection to the casing;
— filling the casing with a dielectric or non-dielectric (conductive) material;
— installing a new crossing;
— monitoring the electrical condition of the casing;

ISO/DIS 16440:2025(en)
— coating or recoating the carrier pipe;
— replacing end seals;
— removing electrolyte from inside the casing.
NOTE Typical examples of maintenance and repair situations include:
— corrosion or other damage to the carrier pipe or casing is indicated by inspection;
— casing extension or removal is necessary;
— the casing is in metallic contact with (shorted to) the carrier pipe;
— the casing becomes filled or partially filled with electrolyte and an electrolytic contact develops.
7.2 Maintenance of vents and test leads
The maintenance of casing vents should include coating at the soil/atmosphere interface and painting,
repair, or replacement of vents and, if necessary, vent caps.
Test leads shall be checked periodically in accordance with ISO 15589-1 to determine their integrity.
7.3 Clearing of shorted casings
Metallic contact between the carrier pipe and the casing (such as contact with the metallic portions of end
seals, isolating spacers, bond wires or straps, test leads, debris, or the casing itself) should be removed.
NOTE 1 The casing could have come into electrical contact with the carrier pipe in several ways:
— the carrier pipe moved in the casing, causing it to come into metallic contact with the casing at some point; such
contact often occurs at the ends of the casing;
— spacing materials failed during or after the original installation of the pipeline;
— the carrier pipe was inadequately supported within the casing, allowing it to sag and come into metallic contact
with the bottom of the casing;
— the carrier pipe was intentionally shorted or installed without isolators;
— a foreign object, such as a shovel or other metallic material present at the construction site was accidentally left in
the casing;
— a metallic short developed between the test lead and the vent pipe or the test leads.
— a vent extension sank through the dirt and made contact with the pipeline.
Established construction techniques shall be used to realign the carrier pipe, permanently maintained in
the aligned position after realignment to eliminate metallic contact.
NOTE 2 Equipment typically used in this situation includes hydraulic jacks, tripods, air bags, side-boom slings and belts.
The carrier pipe and casing shall be permanently maintained in the realigned position by the use of supports,
such as compacted earth, sandbags or isolated concrete piers.
The carrier pipe should be coated with ARO coating when installed on an isolated concrete pier. The concrete
should have an FRP shield installed between the pipe and the pier and be bonded to the pier.
If the casing and carrier pipe cannot be realigned, elimination of a metallic contact may be accomplished by
removing a portion of the casing.
Once metallic contact is eliminated, spacing materials, end seals, vents and test leads should be reinstalled
as necessary.
ISO/DIS 16440:2025(en)
CAUTION — Engineering, metallurgical and operational concerns and regulatory requirements shall
be considered before moving the carrier pipe.
Annex D gives further guidance on clearing of shorted casings.
7.4 Filling of casings
If required, casings may be filled with awax or petrolatum filler, or corrosion inhibitors in an attempt to
eliminate a corrosive environment. Alternatively, a non-dielectric (conductive) material (e.g. concrete, sand,
flowable fill, etc.) can be used to allow CP current to flow from the casing to the carrier pipe.
NOTE Information on casing f
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