Heat-shrinkable sleeve
Encyclopedia
Heat-shrinkable sleeve is a corrosion
protective coating for pipeline
s in the form of a wraparound or tubular sleeve that is field-applied.
pipeline coatings started to replace bituminous or tape coatings in the oil and gas industry. Back then, the processing for polyethylene to make the sleeve backing was new technology and the adhesives used in sleeves were much the same as those used on pipeline coatings.
The technology used to make sleeves has advanced significantly since then, with new methods of cross-linking the polyolefin
backings and new generation adhesives that are formulated to provide performance under more demanding pipeline conditions.
) that is formulated to be cross-linkable. After extruding the thick sheet, it is taken to the “beam” where it is passed under a unit that subjects the sheet to electron irradiation. The irradiation process cross-links the polyolefin. This improves the molecular structure such that the polyolefin will work as part of a heat-shrinkable sleeve and provide the required level of mechanical protection while in-service. It makes the polyolefin perform more like a tough, heat-resistant, elastic material or rubber, rather than like a plastic material.
After cross-linking, the sheet is stretched by feeding it into a machine that heats it up, stretches it and cools it down. Because the sheet has been cross-linked, after stretching, it will want to recover to its original length when re-heated.
In recent years, many manufacturers had already developed their technologies of extruding and expansion of polyolefin backing. In the past, the production process of backing was done by extruding, cross-linking and expansion. However, in order to increase the production efficiency, some of manufacturers expand the backing during extruding, and then send the backing to e-beam for the cross-linking process.
is then applied to the sheet and various manufacturers use proprietary techniques depending on the type, viscosity
and melting temperature of the adhesive. The adhesive is the key to ultimate performance of the installed system, which is why different adhesive types will be specified depending on the pipeline operating conditions.
The adhesive has many functions; it adheres the installed sleeve to the steel
at the coating cutback and mainline coating, it resists shear forces imparted by soil pressure after the pipeline is buried and provides long term corrosion protection to the steel. (Icon Group, 2008). The choice of which adhesive to use is based on the pipeline design and operating conditions. As an example, for small diameter flow lines operating at ambient temperatures, a soft mastic-based adhesive may be chosen, while on large diameter pipelines operating at higher temperatures, a hard, semi-crystalline hot-melt adhesive is used. The adhesive needs to be chosen based on its corrosion protection properties, adhesion strength, and resistance to shear forces imparted by pipe movement and the effects of soil pressures.
The coated sheet is then cut into individual sleeves suitable for application on a pipeline. As mentioned before, the sheet is stretched and wants to recover when heated, so a sealing strip or “closure” is applied during sleeve installation so that the sleeve will stay in place during and after recovery.
primer. Primers for heat-shrinkable sleeves work in the same manner as an FBE primer does when it is specified on 3-layer polyolefin pipeline coatings and is typically applied between 150 µm and 300 µm thick. Usually, the primer of heat shrinkable sleeve is two components non-solvent Epoxy, one is primer base and the other is curing agent.
As described above, the heat-shrinkable sleeves have an adhesive that sticks the sleeve to the cutback and the factory applied mainline coating and also acts as a corrosion protective layer. The backing provides mechanical protection against abrasion and soil stress forces after the pipeline is buried.
Heat wrap tape may used in addition for pipe bends, or as an alternative method for wrapping the whole pipe.
Corrosion
Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
protective coating for pipeline
Pipeline transport
Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....
s in the form of a wraparound or tubular sleeve that is field-applied.
History
The first heat-shrinkable sleeves were introduced over 35 years ago when polyethylenePolyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
pipeline coatings started to replace bituminous or tape coatings in the oil and gas industry. Back then, the processing for polyethylene to make the sleeve backing was new technology and the adhesives used in sleeves were much the same as those used on pipeline coatings.
The technology used to make sleeves has advanced significantly since then, with new methods of cross-linking the polyolefin
Polyolefin
A polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry...
backings and new generation adhesives that are formulated to provide performance under more demanding pipeline conditions.
Polyolefin Backing
Heat-shrinkable means just that, heat them up and they shrink, or more correctly, they recover in length. A heat-shrinkable sleeve starts out with a thick extruded polyolefin sheet (polyethylene or polypropylenePolypropylene
Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...
) that is formulated to be cross-linkable. After extruding the thick sheet, it is taken to the “beam” where it is passed under a unit that subjects the sheet to electron irradiation. The irradiation process cross-links the polyolefin. This improves the molecular structure such that the polyolefin will work as part of a heat-shrinkable sleeve and provide the required level of mechanical protection while in-service. It makes the polyolefin perform more like a tough, heat-resistant, elastic material or rubber, rather than like a plastic material.
After cross-linking, the sheet is stretched by feeding it into a machine that heats it up, stretches it and cools it down. Because the sheet has been cross-linked, after stretching, it will want to recover to its original length when re-heated.
In recent years, many manufacturers had already developed their technologies of extruding and expansion of polyolefin backing. In the past, the production process of backing was done by extruding, cross-linking and expansion. However, in order to increase the production efficiency, some of manufacturers expand the backing during extruding, and then send the backing to e-beam for the cross-linking process.
Adhesives and Functions
An adhesiveAdhesive
An adhesive, or glue, is a mixture in a liquid or semi-liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials...
is then applied to the sheet and various manufacturers use proprietary techniques depending on the type, viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
and melting temperature of the adhesive. The adhesive is the key to ultimate performance of the installed system, which is why different adhesive types will be specified depending on the pipeline operating conditions.
The adhesive has many functions; it adheres the installed sleeve to the steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
at the coating cutback and mainline coating, it resists shear forces imparted by soil pressure after the pipeline is buried and provides long term corrosion protection to the steel. (Icon Group, 2008). The choice of which adhesive to use is based on the pipeline design and operating conditions. As an example, for small diameter flow lines operating at ambient temperatures, a soft mastic-based adhesive may be chosen, while on large diameter pipelines operating at higher temperatures, a hard, semi-crystalline hot-melt adhesive is used. The adhesive needs to be chosen based on its corrosion protection properties, adhesion strength, and resistance to shear forces imparted by pipe movement and the effects of soil pressures.
The coated sheet is then cut into individual sleeves suitable for application on a pipeline. As mentioned before, the sheet is stretched and wants to recover when heated, so a sealing strip or “closure” is applied during sleeve installation so that the sleeve will stay in place during and after recovery.
Epoxy Primer
A final component is an optional epoxyEpoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
primer. Primers for heat-shrinkable sleeves work in the same manner as an FBE primer does when it is specified on 3-layer polyolefin pipeline coatings and is typically applied between 150 µm and 300 µm thick. Usually, the primer of heat shrinkable sleeve is two components non-solvent Epoxy, one is primer base and the other is curing agent.
Use
When steel pipelines are built, they commonly consist of 10~12m long sections of steel pipe that has had a corrosion protective coating applied to it in a factory. The factory will leave an uncoated area at each end of the pipe called a “cutback” so that when welding the pipe sections together, the coating is not damaged. Heat-shrinkable sleeves are applied onto the cutback at the field weld or “field joint” during the construction of a pipeline.As described above, the heat-shrinkable sleeves have an adhesive that sticks the sleeve to the cutback and the factory applied mainline coating and also acts as a corrosion protective layer. The backing provides mechanical protection against abrasion and soil stress forces after the pipeline is buried.
Heat wrap tape may used in addition for pipe bends, or as an alternative method for wrapping the whole pipe.
Companies offering heat-shrinkable sleeves
- CCL Label Decorative SleevesCCL Label Decorative SleevesCCL Label Decorative Sleeves is a UK based company founded in 1979. The company manufactures heat shrink sleeves for product marketing sectors including, food, beers, soft drinks, spirits, wines, dairy products, household products, cosmetics, toiletries etc...
- RaychemRaychemRaychem Corporation was founded in Menlo Park/Redwood City, California in 1957 by Paul Cook, James B. Meikle, and Richard W. Muchmore. The original name of the company was RayTherm Wire and Cable and later formed a subsidiary named RayClad Tubes. The company changed names to avoid confusion with...
- Canusa-CPS
- DensoDENSOis a global automotive components manufacturer headquartered in the city of Kariya, Aichi Prefecture, Japan. Established December 16, 1949 as , in 1996 the company became DENSO Corporation worldwide...
, - TIAL,
- Dasheng CJDS
- Stepko
Main Standards and certificates
- DVGW,
- ISO 21809-3,
- EN 12068,
- DIN 30678,
- NACE SP 0303,
- Shell standard