BSI Standards PublicationGas infrastructure — Pipelines for maximum operating pressure up to and including 16 bar Part 4: Specific functional requirements for renovation... NORME EUROPÉE
General
Choice of renovation techniques to be used on pipework, up to and including 16 bar, shall be made by a competent person
The selection of materials, dimensions and assembling techniques shall be the responsibility of the pipeline operator and comply with EN 12007-1
For comprehensive design guidelines on polyethylene (PE) pipelines in gas infrastructure, refer to EN 12007-2 Additionally, EN 12007-3 provides essential design guidance for steel pipelines used in gas infrastructure.
The pipeline operator is responsible for the uprating of renovated systems, ensuring compliance with the relevant procedures The Maximum Operating Pressure (MOP) for any renovated system must be determined by its weakest point.
Pressure uprating
Renovating gas infrastructure can be integral to a strategic plan aimed at increasing maximum operating pressure Certain renovation methods may reduce the pipe diameter, necessitating higher pressure to sustain the system's flow capacity.
The pipeline operator is responsible for the up rating of the MOP, ensuring that all components of the pipeline can withstand the new pressure level in terms of strength and tightness.
Selection of renovation technique
The following factors shall be considered when selecting a renovation technique These include but are not limited to:
the future structure of the distribution network;
the pressure level at which the pipework will operate after renovation;
the required capacity of the pipework;
the number of gas service lines connected to the section of pipework;
the presence and number of branches, bends, valves;
the current condition of the pipework to be renovated;
the position of the pipework;
EXAMPLE 1 The covering depth of the pipework
EXAMPLE 2 Disruption to traffic and pedestrians
EXAMPLE 3 The location of adjacent plant
EXAMPLE 4 Areas sensitive to break phenomena
the number, type and condition of pipe joints in the section of pipework;
any supply obligations to consumers during and after renovation works
NOTE 1 There is a range of renovation techniques use These are described generally in Annex A Annex A does not represent an exhaustive list of available techniques
NOTE 2 The advantages and disadvantages of the techniques described in Annex A are outlined in Annex B Further details of the different techniques are given in Annexes C to Annex I.
Consultation with third parties
Effective communication with nearby plant owners and street authorities is essential when planning gas infrastructure works Gathering relevant information about adjacent facilities is crucial for successful project planning.
Further guidance is given in EN 12007-1
General
Pipework installation and renovation must be performed by qualified individuals following the specifications set by the pipeline operator or pipework manufacturer For gas infrastructure construction up to 16 bar, refer to EN 12007-1 for general guidance Additionally, EN 12007-2 provides specific instructions for polyethylene pipelines, while EN 12007-3 focuses on steel pipelines.
A detailed procedure for the successive steps of the works should be made Each technique has its specific considerations which are mentioned in the Annex C to Annex I
When renovating with polyethylene pipes, it is essential to ensure that the pipe temperature does not exceed the maximum allowable limit specified by the manufacturer.
Ensuring the safety of personnel involved in gas supply operations and the general public is paramount throughout the duration of the work Special attention must be given to accommodate the needs of elderly and disabled individuals.
Before assembling and installing gas infrastructure components, it is essential to verify the condition of all pipes and fittings for compliance Additionally, existing pipework must be inspected for any unwanted obstructions or blockages.
To minimize environmental impact during the construction of gas infrastructures, it is essential to organize the process effectively For additional guidance on environmental considerations, refer to EN 12007-1.
Lubricants used to aid renovation by pipe insertion shall not have a detrimental effect on the existing or inserted pipe.
Disconnection/reconnection of sections of the gas infrastructure
When disconnecting a section of the gas infrastructure for renovation, it is crucial to ensure that the supplies in other areas of the existing gas system remain unaffected.
It is essential to identify all service lines connected to the gas main section that is to be disconnected, and careful consideration should be given to the renovation of these service lines.
The pipes and fittings shall be correctly stored, handled and transported to ensure continued fitness for purpose as required in EN 12007-1, EN 12007-2 and EN 12007-3.
Excavation and no dig techniques
The determination of excavation position and size must consider the covering depth of the existing pipework, the diameter of the new pipe, and various other factors that may influence the insertion process.
EXAMPLE 1 The proximity of other buried plant
EXAMPLE 2 The length of the new section of pipe
EXAMPLE 3 The position of service lines to be transferred
Consultation should take place with other utilities before undertaking excavation work, so that adequate measures for the protection of other pipework, cables and underground constructions can be agreed
A qualified individual on-site must guarantee that accurate information regarding the location of existing gas supply pipes and other utility infrastructure is readily accessible Additionally, this person is responsible for ensuring that safe digging practices are consistently adhered to throughout the project.
Proper temporary support must be ensured for pipework, cables, and other equipment during construction, along with permanent support in areas where the ground has been disturbed.
Further guidance on the precautions to be taken when excavating is given in EN 12007-1
During the renovation of gas infrastructures, excavations must be properly backfilled, and surface features like roads and footways should be restored in accordance with the standards established by the Member Countries.
Laying
Laying of pipework
Any new pipe installed shall be laid in accordance with the specific guidance if appropriate given in
EN 12007-2 for polyethylene pipelines and in EN 12007-3 for steel pipelines Further general guidance is given in EN 12007-1.
Cleaning of carrier pipe
When a carrier pipe is contaminated with dust, pitch, or other impurities that may impact the renovation process, it is essential to consider pipe cleaning This cleaning can be performed using mechanical, hydraulic, or pneumatic methods.
NOTE In certain renovation techniques the condition of the internal bore of the carrier pipe is a major factor in determining whether the technique can be successfully applied
During any pipe cleaning care should be taken to:
minimize any damage to the environment;
the presence of pyrophoric dust;
dispose waste material in accordance with national or local legislation.
Inspection of the pipework to be renovated
Before introducing a new pipe in renovation techniques that utilize a carrier pipe, it is essential to conduct an internal inspection This inspection helps identify potential obstructions and deficiencies that could harm the new pipe or impede its passage.
The inspection may be carried out with a camera
Pressure testing procedures to prove the integrity of renovated gas mains and service lines shall be selected from EN 12327
The pressure testing shall be carried out in accordance with minimum test pressure levels given in
General guidance is given in EN 12007-1 Further guidance for polyethylene systems is given in EN 12007-2
Where a tightness test cannot be carried out, for example joint repairs carried out under live conditions at operating pressure, the pipeline operator shall specify the test method
Service line transfer must adhere to the specifications provided by the pipeline operator and the technical requirements of the renovation technique Prior to commissioning the service line, a strength test, tightness test, or a combined test must be conducted on the renovated service line and/or the connection between the service line and the gas main, in compliance with EN 12327.
If pressure testing of the service line pipework cannot be completed before the connection, it must be conducted simultaneously with the new section of the pipeline.
Commissioning and decommissioning shall be carried out in accordance with EN 12327 General guidance is given in EN 12007-1
The establishment and maintenance of a record system for gas infrastructures are outlined in EN 12007-1 Pipeline operators must ensure that relevant details of renovated pipework are incorporated into this record system At a minimum, the record system should include specific data related to the gas infrastructure.
type of pipes, diameters and lengths;
the date of execution of the renovation;
the technique used for the renovation; and
the presence and type of carrier pipe
Figure A.1 — Chart of renovation techniques
Advantages and disadvantages of renovation techniques
Renovation techniques come with several disadvantages, including the necessity for inspection and cleaning of the carrier pipe When steel is used as the inserted pipe, it poses challenges for cathodic protection Additionally, if the maximum operating pressure (MOP) is not increased, there may be a reduced capacity Locating gas leakages can also be difficult, and the process requires specialized equipment and personnel Furthermore, external fusion beads must be removed, and it may be necessary to eliminate bends in the piping system.
The advantages of this method include the requirement of minimal equipment, aside from live insertion, which significantly reduces supply disruption Additionally, the inserted pipe and close-fit pipe do not depend on the integrity of the carrier pipe, ensuring a reliable solution with minimal reduction in capacity.
Techniques Continuous or discrete pipe (Annex C) Close-fit pipe (Annex D)
Renovation techniques come with several disadvantages, including the need for specialized equipment and personnel, which can complicate the process There is a risk of gas leakage between the liner and the support pipe, necessitating thorough inspection and cleaning of the support pipe Additionally, these techniques may have a shorter life expectancy compared to inserted pipework The installation of a sleeve may be required to prevent unacceptable damage to the new pipe, especially in cases where bends in the old pipe pose challenges Reconnecting branches often requires open-cut methods, and fragments from the renovation can potentially damage adjacent utilities or plants Furthermore, significant excavation may be necessary to remove redundant pipework.
The advantages of this service include the ability to restore service lines without the need for open cuts, ensuring that the capacity of the pipework is preserved Additionally, it allows for the renovation of pipework featuring large radius bends and facilitates the replacement of a pipe with a larger diameter at the same location Importantly, this method ensures that no fragments of the old pipe are left in the ground.
Techniques Cured in place (Annex E) Bursting or splitting existing pipe (Annex F) Pulling or pushing existing pipe (Annex G)
Renovation techniques come with several disadvantages, including a shorter lifespan compared to inserted pipes and the need for regular cleaning and inspection of the carrier pipe Additionally, reconnections of branches require open-cut methods, and the materials used can be sensitive to temperature during application and operation Ultimately, the effectiveness of these techniques depends on the mechanical properties of the support pipe.
The advantages of these techniques include the ability to perform renovations without interrupting gas supply, minimal excavation requirements for certain methods, maintenance of pipework capacity, and the capability to renovate pipework featuring large radius bends.
Techniques Joint repairs (Annex H) Resin lining (Annex I)
Renovation with continuous or discrete pipe
Definition
This technique involves inserting a new gas pipe of smaller diameter into the existing pipe The existing pipework therefore becomes a carrier pipe.
Description
Two techniques are commonly used:
live insertion: where the section of existing pipe to be renovated is not decommissioned prior to and during the insertion work;
dead insertion: where the section of existing pipe to be renovated is decommissioned prior to and during insertion work.
Conditions of application
The choice of insertion technique is influenced by some of the following factors: a) Dead insertion is generally used:
1) when insertion can be done after decommissioning and disruption of the gas supply during the work period; or
2) when it is known or suspected that the existing pipework needs to be cleaned before renovation; or
3) when it is known or suspected that some obstructions in the existing pipework have to be located and/or to be removed b) Live insertion can be used if:
1) the annular space is sufficient to supply consumers while they are still connected to the live carrier pipe; and
The pipe insertion or lining process can be conducted independently from transferring service lines from the old pipework to the new system Live insertion is recommended in specific scenarios.
1) the downstream gas infrastructure cannot be disrupted; or
2) the disruption of gas supply to the consumers concerned has to be limited in time.
Implementation
Preparation
Prior to renovation the following activities are generally carried out:
The length of the sections to be inserted is influenced by various factors, including the positioning of existing connections, bends in the piping, valves, and syphons.
where consumers are affected by dead insertion work, the number of sections to be re-commissioned before the end of each day is determined
NOTE A by-pass can be used to maintain the supply.
Execution
During the insertion process the activities in C.4.2.2 and C.4.2.3 shall be carried out
EN 12327 gives normative requirements for isolation and decommissioning operations
When cutting existing pipework, any dust, pitch, or contaminants must be removed using appropriate cleaning equipment It may be necessary to insert a hauling cable into the pipe to assist with this process Additionally, all contaminants should be disposed of in accordance with local or national environmental regulations after the cleaning is completed.
C.4.2.2.3 Inspecting the pipe to be renovated
A “dummy pipe“, gauging pig or camera is sometimes inserted into the section to be lined to check that:
nothing will damage the new pipe; and
the new pipe will pass freely into the existing pipework
Techniques are available using special controllable devices to allow internal removal of plugs and other obstacles
C.4.2.2.4 Introduction of the new pipe
The new pipe can be inserted into the existing pipework:
by pulling: the hauling cable is attached to the pipe using a suitable hauling device; or
by pushing: care is taken to ensure that the pushing clamp of the machine does not cause unacceptable damage to the new pipe
The tensile or compressive stress imposed on the new pipe is controlled to ensure that it remains below the pre-determined limit
Protective equipment is generally used to prevent unacceptable damage to the new pipework by the edge of the carrier pipe
Testing is carried out according to Clause 6 Pressure levels and test methods are chosen in function of the
MOP of the system and the materials used
A proper pipe cutting tool is essential for accurately cutting the carrier pipe, ensuring the safe transfer of service lines while taking necessary precautions to prevent any damage to the new pipe.
The new pipe is connected to the existing gas infrastructure using a procedure provided by the pipeline operator prior to commissioning EN 12327 gives requirements for the commissioning of pipework
C.4.2.3.1 Introduction of the new pipe
The pipe to be renovated can be divided into sections Each section allows the “live insertion“ of a new pipe in one operation
The new pipe can be assembled to the required length prior to insertion
Where required in the procedure, the external beads of the butt-fusion will be removed with care
The new pipe is inserted into the existing pipe through a gland assembly There are two methods commonly used for live insertion:
The initial step involves the introduction of gas into the inserted pipe while it is being placed into the carrier pipe using a specialized nose cone Throughout this operation, the inserted pipe remains filled with gas.
The second method involves an inserted pipe that contains air under atmospheric conditions Once the insertion is complete, gas is introduced into the pipe after establishing the final connection to the existing system.
Small diameter pipes can be inserted by hand by using manual clamps For larger sizes hydraulic or pneumatic pushing machines are used
To ensure smooth insertion of coiled pipe, a straight pipe is butt fused to the beginning of the coil, preventing any obstruction caused by the natural bend of the coiled pipe.
On completion of the insertion procedure the pipe end is sealed by the application of an approved foaming product into the annular space
After removing the gland assembly the new pipe is connected to the existing gas infrastructure using a technique approved by the pipeline operator
Before installation, a strength and tightness assessment is performed on the new pipe, following Clause 6 The pressure levels and testing methods are selected based on the system's MOP and the materials utilized.
The transfer of service lines from the existing pipework to the new inserted pipe is limited by the necessity to keep supplies flowing to service lines that are still temporarily linked to the original gas main.
Generally the service lines furthest from the source of gas into the annular space are transferred first, working methodically towards the source of supply
To isolate the flow, an approved foaming product is injected into the annular space upstream of the service line after disconnecting it from the existing pipe This process can be performed at the connection point of the service line to the existing pipe.
To facilitate the fusion or mechanical connection of the service line to the new pipe, a suitable length of the existing pipe is cut, following the procedure outlined by the pipeline operator.
For testing, see Clause 6 and Clause 7
Testing is carried out according to Clause 6 Pressure levels and test methods are chosen with reference to the MOP of the system and the materials used
Lining with close-fit pipe
Definition
These techniques temporarily deform the PE pipe to facilitate its insertion into the pipe to be renovated
The pipe being renovated acts purely as a carrier pipe and the new PE pipe is not physically attached to it.
Description
There are a range of techniques which can be used These include but are not limited to:
Thermal-mechanical deformation is a technique that can be performed either hot or cold, involving the process of pulling polyethylene (PE) pipe through a die to achieve a reduced diameter.
In the hot procedure, the material is heated to a permissible temperature before being extruded through the die The pipe is then tensioned as it is pulled into the existing pipework to ensure a reduced diameter The reversal process is executed using the correct method.
Mechanical deformation is a technique that reduces the diameter of PE pipes by forcing them between two hemispherical rollers This process involves a reversal that depends on time and temperature To expedite the reversal, the pipe can be filled with water and subjected to internal pressure, which can be further increased within the limits set by the pipeline operator.
The memory effect of PE pipes allows previously extruded pipes to be reshaped under mechanical and thermal influences, resulting in a reduced outside diameter These pipes are typically sold in this altered form Once inserted, the pipes return to their original shape through thermal and/or mechanical pressure, expanding back to their circular cross-section This process restores the original polymer morphology before reshaping, ensuring optimal performance and functionality.
Conditions of application
The techniques in D.2 can be used:
to renew all types of old pipes for diameters between 100 mm and 600 mm; and
for the different pressure levels used in the distribution system The use of PE pipe can enable the Maximum Operating Pressure (MOP) of the gas infrastructure to be increased
For each method the pipe to be renovated is decommissioned in sections The number and length of the sections will be determined by practical factors
EXAMPLE The number and distribution of consumers supplied from the pipe to be renovated.
Implementation
Materials
The materials and components used shall conform to the requirements given in relevant standards.
Preparation
For close fit insertion techniques the following points should be considered:
The length of the pipe to be inserted must align with several critical factors, including the tensile stresses it will endure, the available space for implementing the technique and necessary equipment, and the duration for which the gas supply can be safely isolated.
the position and size of excavations required; and
the different types of materials which comprise the pipework to be renovated
Execution
For each of the techniques the phases are as follows: a) Isolation and decommissioning
EN 12327 gives normative requirements for isolation and decommissioning operations b) Cleaning the pipework
When cutting existing pipework, it is essential to clean any dust, pitch, or contaminants using appropriate equipment A hauling cable may be introduced into the pipework for this purpose After cleaning, contaminants must be disposed of in accordance with local or national environmental regulations Additionally, inspecting the pipe designated for renovation is crucial.
A "dummy pipe", gauging pig or camera may be inserted into the section to be lined to check that:
1) nothing will interfere with or damage the pipe;
2) the new pipe will pass freely into the existing pipework
Techniques are available using special controllable devices to allow internal removal of plugs and other obstacles d) Preparing existing pipework
To introduce the new pipe, sections of the old pipe are removed from existing connections, and special bridge tees or tapping sleeves are welded into the new line, incorporating spacers for proper alignment.
The new pipe can be seamlessly integrated into the existing pipeline through a pulling or pushing method If necessary, the external beads from the butt-fusions will be carefully removed during the process.
During thermal-mechanical deformation, if the draw-in process is halted, the reversal process will commence immediately upon the release of the tensile force, and it is essential that this process proceeds without interruption.
The drawn-in PE pipe conforms to the inner wall of the existing pipe, but it does not create a gas-tight seal between the exterior of the new pipe and the internal diameter of the renovated pipe Testing is essential to evaluate the integrity of this installation.
Testing is carried out following Clause 6 Pressure levels and test methods are chosen as a function of the
MOP of the system and the materials used g) Service line transfer
Using an appropriate pipe cutting tool is essential for accurately cutting the carrier pipe, ensuring the safe transfer of service lines while taking necessary precautions to prevent any damage to the new pipe.
Service lines and connections are directly attached to the new PE pipe, utilizing specialized techniques to create a window in the carrier pipe, thereby minimizing potential damage to the new installation.
For testing, see Clause 6 and Clause 7 h) Commissioning
The new pipe is connected to the existing gas infrastructure using a procedure provided by the pipeline operator prior to commissioning EN 12327 gives functional requirements for the commissioning of pipework
Lining with cured-in-place pipe
Definition
This renovation technique utilizes the inversion method by inserting a hose into the existing pipe The hose is constructed from plastic or reinforced with textile fibers for added durability.
Description
The hose is pressurized to cover the entire inner surface of the pipe, and it is securely bonded to the existing pipe using a curing resin that was applied to the hose beforehand.
The lining systems are designed to remain leak proof, fracture resistant, and be properly bonded to the support pipe.
Conditions of application
This method is applicable for renovating various types of old pipes, as long as the changes in the internal diameter of a section of the gas main remain within the manufacturer's specified limits.
The lining systems are designed:
to be generally free of wrinkles and blisters;
to perform satisfactorily at operating temperatures in the range 5 °C to 25 °C in addition to any further range specified by the manufacturer of the system.
Implementation
Preparation
For lining techniques using cured in place pipe the following points should be considered:
The length of the pipe to be renovated must align with several key factors, including the diameter-length ratio, which influences the air pressure required for hose inversion, as well as the available space and the duration for which the gas supply can be safely isolated.
the inside diameter of the pipe to be treated and particularly any changes in pipe type or diameter is determined;
the pipeline operator ensures that the condition of branches is such that no additional excavations will be necessary and that in particular they are not leaking;
the position and size of the excavations required.
Execution
The operation includes the following phases: a) Isolation and decommissioning
EN 12327 gives normative requirements for isolation and decommissioning operations b) Cleaning the pipework
Effective cleaning of pipes requires the use of appropriate equipment, such as a hauling cable, to facilitate the process After cleaning, an inspection of the pipe's interior is essential, as any residue or moisture can hinder the adhesion of the lining material Grit blasting may be necessary to achieve the required cleanliness level Additionally, it is crucial to dispose of contaminants properly, adhering to local and national environmental regulations.
A thorough internal inspection of the pipe is essential to assess its diameter, identify any variations, locate branch connectors, and ensure that no obstructions could harm the hose Advanced techniques utilizing specialized controllable devices enable the internal removal of plugs and other impediments This process is crucial for the effective introduction of cured-in-place pipe solutions.
Before installing the cured-in-place pipe, all branch connections in the renovation area are sealed off Once the lining process is finished, the plugs are taken out, and the connections to the liner are reestablished.
A polymerisable resin-coated hose is inserted into the existing pipework, where air pressure inverts the hose and securely bonds its outer surface to the interior of the existing pipes.
Following installation the resin cures by polymerization over a period of time laid down in the manufacturer’s specifications
Special attention should be paid to check if the polymerization of the entire lining has occurred as desired The pipework should be inspected with a camera e) Testing
Testing is carried out following Clause 6 Pressure levels and test methods are chosen as a function of the
MOP of the system and the materials used f) Service line transfer
The hose is pierced from the inside to commission the service line
For testing, see Clause 6 and Clause 7 g) Commissioning
The new pipe is connected to the existing gas infrastructure using a procedure provided by the pipeline operator prior to commissioning EN 12327 gives functional requirements for the commissioning of pipework
Renovation by bursting or splitting existing pipe
Definition
This method involves bursting or splitting the current pipe and installing a new pipe within the space created The replacement pipe can either match the diameter of the original or be larger.
Description
The technique consists of creating a void in place of the existing pipework to enable it to be replaced by a new pipe
The existing pipe may be:
burst, where the material is brittle;
EXAMPLE 1 Grey cast iron pipe
split, where the material is ductile
Conditions of application
During pipe bursting or splitting there is a risk of causing unacceptable damage to the new pipe A protective sleeve can be used to prevent this damage
Other utilities equipment should be precisely located to avoid damage by the fragments of the old pipe, displacement of the surrounding soil or vibrations
Damage by vibrations to buildings in the vicinity should be avoided
The type of soil should be known to assure displacement into the surrounding soil is possible.
Implementation
Preparation
For bursting or splitting the following points should be considered:
the material and condition of the pipe to be renovated is known;
When replacing a grey cast iron pipe through bursting, it is advisable to identify the locations of any repairs made with different materials that cannot be burst.
the length of pipe to be inserted is compatible with factors such as the space available and the time during which the gas supply can be disrupted;
The locations and dimensions of the excavations are established based on the depth of the pipe being replaced, the specifications of the new pipe, and additional operational considerations.
EXAMPLE 2 The use of discrete or continuous pipe
EXAMPLE 3 Making the connections using arc welding for steel or butt fusion for PE pipes
EXAMPLE 4 The use of a sleeve.
Execution
EN 12327 gives normative requirements for isolation and decommissioning operations b) Cleaning the pipework
When cutting existing pipework, it is essential to clean any dust, pitch, or contaminants using appropriate equipment A hauling cable can assist in this cleaning process After cleaning, contaminants must be disposed of in accordance with local or national environmental regulations.
Prior to the operation all excavations required for launch and reception of the new pipe, together with any excavations required for any service connections are carried out
Existing service lines and branches which are on the section to be renewed are cut off prior to the operation
A pneumatic-driven bladed cutting head is utilized to replace pipes by cutting, fragmenting, and expanding the existing pipe as it moves through The resulting fragments are displaced into the surrounding soil.
A sleeve is drawn behind the splitting or bursting head to stabilize the ground and protect the new pipe from damage caused by fragments of the old pipe Service connection windows are cut into the sleeve, and once completed, the new pipe is inserted through it.
Testing is carried out following Clause 6 Pressure levels and test methods are chosen as a function of the
MOP of the system and the materials used e) Service line transfer
For testing, see Clause 6 and Clause 7 f) Commissioning
The new pipe is connected to the existing gas infrastructure using a procedure provided by the pipeline operator prior to commissioning EN 12327 gives functional requirements for the commissioning of pipework
Renovation by the pulling or pushing of the existing pipe
Definition
This technique involves either pushing or pulling the current pipe to replace it with a new one positioned in the created void The new pipe can match the diameter of the existing pipe or be larger.
Description
The technique involves removing the existing pipe by creating a void, allowing it to be pulled or pushed into a receiving trench Once in the trench, the pipe is cut into sections for complete removal and proper disposal.
Conditions of application
During pipe pulling or pushing there is a risk of causing unacceptable damage to the new pipe A protective sleeve can be used to prevent this damage
The route of the pipe needs to be checked for presence of bends
The location of underground pipework and cables should be determined to reduce the risk of causing damage.
Implementation
Preparation
When using this technique, it is essential to consider the compatibility of the pipe length to be replaced with factors such as imposed stresses, available space, and the duration for which the gas supply can be safely isolated.
Execution
EN 12327 gives functional requirements for these operations b) Introduction of the new pipe
Prior to the operation all excavations required for launch and reception of the new pipe, together with any excavations required for any service line connections are carried out
Existing service lines and branches which are on the section to be renewed are cut off prior to the operation
A guide system is installed using rollers for PE or guide rails in the case of metallic pipe in discrete lengths
Pulling rods or cables are inserted into the pipe that needs replacement When using pulling rods, they are attached to the old pipe with an anchoring plate at the starting point, which can also serve as an expansion cone during the insertion process if needed.
The new pipe or sleeve is attached to the anchoring plate, while the pulling device is set up in the receiving trench along with cracking wedges in both the receiving and intermediate trenches The pulling rod connects to the pulling device, enabling the existing pipework to be pulled or pushed toward the receiving trench, where the cracking wedges break the pipework It is essential to collect and properly dispose of the resulting broken pieces of pipework.
After the old pipework is fully removed, the new pipe is installed, often within a protective sleeve If a sleeve is utilized, access windows are created for service connections, allowing the new pipe to be inserted through the sleeve upon completion Testing follows to ensure proper installation.
Testing is carried out following Clause 6 Pressure levels and test methods are chosen as a function of the
MOP of the system and the materials used d) Service line transfer
For testing, see Clause 6 and Clause 7 e) Commissioning
The new pipe is connected to the existing gas infrastructure using a procedure provided by the pipeline operator prior to commissioning EN 12327 gives functional requirements for the commissioning of pipework
Definition
This technique consists of the repair of leaking pipework joints.
Description
These techniques require access to the pipework, either internally or externally, in order to repair pipework joints.
Conditions of application
General
Repair techniques for leaking lead/yarn, mechanical, and welded joints in cast iron, ductile iron, and steel pipework can be effectively utilized Most repairs are performed under live conditions at the system's operating pressure, although certain methods necessitate decommissioning the pipework before the repair process.
The article discusses various sealing techniques, including internal methods like emulsion sealing, anaerobic spraying, Mono-Ethylene Glycol (MEC) spraying, and internal clamps It also covers external methods such as anaerobic injection, encapsulation, and leak clamps.
Internal methods
H.3.2.1 Commissioned pipework − MEG and anaerobic spraying
The effectiveness of these techniques is constrained by the system's MOP, the dimensions of the connections to the pipework, and any major directional changes in the piping layout.
The process is designed to internally seal screwed joints on iron or steel pipework It will not be successful on a pipe that has been subjected to extensive corrosion
This method effectively seals large diameter lead/yarn and mechanical joints Clamps can be installed using either remote techniques or through manned entry, requiring access to one end of the pipework for remote equipment and both ends for manned entry.
External methods − Commissioned pipework
These techniques focus on externally sealing the joint, with encapsulation and leak clamps requiring full access to the joint for effective sealing In contrast, anaerobic repair methods only necessitate access to the top of the joint.
Implementation
Internal repairs
H.4.1.1 Commissioned pipework − MEG and anaerobic spraying
A small diameter hole is created in the pipework to allow for the insertion of equipment This can be accomplished by either drilling and tapping the pipe or by attaching a saddle or tee through clamping or welding methods.
The equipment is engineered for operation under live conditions and is introduced into the gas main via a pre-drilled hole in the pipework There are two primary methods for applying internal joint sealing: the first method involves spraying the sealant directly into the joint, while the second method atomizes the sealant into the gas stream.
Where the equipment has been designed to spray into the joint, such as anaerobic spraying, a joint location method is used to ensure that the joints can be located accurately
EXAMPLE TV camera, electronic joint location instruments
When the joint has been located a measured amount of fluid is sprayed into the joint b) Spraying into the gas stream
The equipment is moved at a controlled rate through the pipework during the spraying process The fluid is carried by the gas stream and deposited into the joint, causing the yarn or rubber gasket to expand.
Before applying these techniques, ensure that the pipework is disconnected from the gas supply, as outlined in EN 12327, which specifies the functional requirements for these operations Additionally, disconnect any meters, filters, regulators, valves, and branches that are not meant to be treated from the gas supply.
When cutting existing pipework, the presence of dust, pitch, or contaminants may necessitate the use of specialized cleaning equipment Additionally, proper disposal arrangements for any contaminants may be required after the operation.
The pipe is filled with emulsion sealant in accordance with the manufacturer specification After the required curing time the product is drained and removed
The pipework to be repaired should be disconnected from the gas supply and EN 12327 gives functional requirements for these operations
Proper cleaning of internal joints requires the use of appropriate equipment Following the cleaning of the pipework, it is essential to inspect the interior of the joint, as any residue can hinder the adhesion of the clamp To achieve the necessary cleanliness, grit blasting may be required Additionally, manned entry into the pipework may be necessary for thorough inspection and maintenance.
For safe manned entry, it is essential to have the necessary safety equipment and communication methods on site Once the joint is identified, it should be cleaned using the correct tools for the job The clamp must be installed following the manufacturer's specifications, and remote fitting of clamps should also be considered.
After location of the joint, cleaning should take place and the clamp should be fitted in accordance with the manufacturer’s specification.
External repairs − Commissioned pipework
Access to the joint needing repair is essential, and there must be adequate space around it for the installation of encapsulation and clamping systems Typically, for anaerobic injection, only access to the upper section of the gas main is necessary.
All equipment must be designed for operation under live conditions, with repairs conducted according to the manufacturer's guidelines It is essential to clean the joint for encapsulation and clamps For anaerobic injection methods, access to the lead/yarn or rubber gasket of a mechanical joint is necessary, which can be accomplished by drilling a small diameter hole through the lead seal, backing ring, or the back of the joint.
Testing
Testing is carried out following Clause 6 Pressure levels and test methods are chosen as a function of the
MOP of the system and the materials used.
informative) Resin lining
Definition
This technique consists of completely coating the inside of the pipework with a resin.
Description
The process involves injecting epoxy resin into the pipework, followed by the use of a pig to evenly distribute the resin across the entire inner surface, creating a complete film that coats the walls Other methods may also be employed to achieve a uniform film over the inner surface of the pipes.
This film provides a gastight lining in the existing pipework
The resin lining is designed to remain ductile and properly bonded to the existing pipework which remains as a support pipe.
Conditions of application
This technique can be used to renovate corroded metal pipework, provided that any corrosion hole or crack does not exceed the limits given in the manufacturer’s specification
Fittings, such as elbows, plugs, tees and valves, can influence the lining process The pipework system is normally taken out of service.
Implementation
When utilizing this technique, the following steps are undertaken:
the pipework to be treated is normally disconnected from the gas supply;
fittings, meters, filters, regulators and valves are removed if necessary;
each branch, not intended to be treated, should be disconnected or plugged off
EN 12327 gives functional requirements for these operations b) Cleaning the pipework
When cutting existing pipework, it is essential to check for dust, pitch, or contaminants, as these require cleaning with suitable equipment Any residue or moisture on the internal pipe wall can hinder proper bonding After cleaning, an internal inspection may be necessary using appropriate systems Additionally, contaminants must be disposed of in accordance with local or national environmental regulations.
1) to check the diameter and any variations in diameter for selection of the lining pig;
2) to check that nothing will interfere with or damage the resin lining
Techniques are available using special controllable devices to allow internal removal of obstacles such as protruding ends of plugs, internal welding beads etc d) Injection of the resin
Resin is injected into the pipework, and if needed, a suitable lining pig is introduced to facilitate the treatment process This pig is then pushed or pulled through the pipework to ensure even distribution of the resin Any excess resin collected at the end of the pipework must be disposed of properly to prevent environmental contamination.
EXAMPLE Preparation by mixing of two component epoxy resin
Following completion of the work, fittings, meters and other ancillaries are reconnected
Testing is carried out following Clause 6 Pressure levels and test methods are chosen as a function of the
MOP of the system and the materials used
The treated pipework is integrated into the existing gas infrastructure following a procedure outlined by the pipeline operator before commissioning According to EN 12327, there are specific functional requirements that must be met during the commissioning of the pipework.
Technical changes between this European Standard and
Title Change of "recommendation" in the title to
"requirement reflecting the main character of the text
General Change of recommendations in the text to requirements where technically appropriate
General Update of normative references
5.2 Rephrasing of the paragraph with reference to EN 12007-1, -2 and -3
6 Deletion of the “example: leakage survey’
Annex B ,Table B1 Addition of a disadvantage of bursting or splitting existing pipe; ‘fragments can damage adjacent utilities or plant’
[1] CEN/TR 13737 (all parts), Implementation Guide for functional standards prepared by CEN/TC 234 Gas infrastructure