Field joint coating systems: Identifying the key success factors

Growing energy demand combined with depletion of the “easy-finds” resulted in development of reserves in more remote fields. Traversing longer distances and through harsher environments has become the norm in recent pipeline construction projects. With deeper reserves, many pipelines operate at increased flow temperatures and pressures.

Pipeline engineers select appropriate protective coatings after carefully analyzing a variety of factors. Physical parameters such as pipe diameter, grade of steel, operating pressures and temperatures can be readily determined. More variable factors include pipe shipping logistics, construction techniques, backfill materials and cathodic protection monitoring systems. Understanding the advantages and disadvantages of various pipecoating technologies is critical in making informed decisions.

Mainline Coating Considerations

The selection of mainline coatings has evolved along geographical lines. In North America, fusion bonded epoxy (FBE) has been the dominant coating for large diameter pipe, although increased acceptance of multi-layer coatings is being noted. In Europe, Asia, Middle East and South America, multi-layer polyolefin coatings such as 3-layer polyethylene (3LPE) and 3-layer polypropylene (3LPP) tend to be favoured. A dramatic change from tape to 3LPE has occurred during recent years within the Russian pipecoating mills. Newer technologies such as composite coatings (HPCC) and dual-layer fusion bonded epoxy (DLFBE) are gaining acceptance in various regions.

Pipeline operating temperatures continue to increase. Technologies in the mid-1900's were generally well suited for pipelines operating up to 50ºC. Through 1990’s, few pipelines required coating systems stretching past the 80ºC range. Many recent pipeline projects operate at temperatures greater than 100ºC with some approaching 150ºC. At these temperatures, coating technologies are increasingly challenged to meet the owner’s requirements for long service design life.

Pipe is often sourced and coated a long distance from its ultimate destination. During shipping and construction handling, coating damage is a real concern. The robust nature of 3LPE and 3LPP coatings, compared to FBE, generally results in less handling damage. One example was the substantial coating damage during the shipment of FBE coated pipe from the Asian pipecoating facility to the Caspian-area construction site.

Mainline and Field Joint Coating Differences

Much of the industry’s focus is on developing or updating specifications for the mainline system. Requirements for field joints traditionally receive less broad attention. A joint coating specification is often a listing of previously “approved products” or is recited as “must be compatible with the specified mainline coating”. More progressive companies have teams focusing on generating project-specific joint coating recommendations.

Joint coating requirements differ from those of the mainline coating. Joint coatings are not exposed to the rigours of transportation and construction handling. As a final operation in pipeline construction, joint coatings are often a rushed procedure for both installation and quality inspection resources.

Ultimately, the joint coating is expected to provide corrosion protection and quality consistent with plant applied coating. In an ideal world, the joint coating would be identical to the mainline. For a variety of technical and financial reasons, this is not always possible. A well designed joint coating should mirror the performance of, and be fully compatible with, the mainline coating over the entire design life. Field-applied liquid epoxies, heat shrinkable sleeves and FBE have proven track records on FBE coated pipe. A recent phenomenon of applying liquids on 3LPE is under much scrutiny as long term performance and compatibility questions are being asked. Heat shrinkable sleeves have global acceptance because they mirror the design and performance of the 3LPE and 3LPP systems. Credible manufacturers producing more than one technology are often your best resource for assistance in selecting an appropriate product.

Field Joint Installation Challenges

Unlike the controlled-factory conditions for mainline coating installations, joint coatings are applied in diverse and highly variable field conditions. For instance, field installation conditions in the Middle East are vastly different than those of cold climates common in the northern fields of Russia and Canada. Other key differences between plant and field applications include factors such as equipment requirements, expertise of the workforce and coating technologies.

Ambient temperatures dictate different construction approaches. When temperatures drop below -40ºC, a project may cease until temperatures increase to a point where people and equipment can function. Conversely, when daytime temperatures exceed +45ºC with high intensity sun, the health risk to workers is a concern.

Liquid applied coatings are very susceptible to temperature changes. Below certain ambient temperatures, epoxies do not cure. At high temperatures common in desert construction, polyurethanes are known to improperly cure. In cold conditions, sophisticated infrared heaters or induction coils may be required for preheating and post heating the joint area. Employing spray-applied systems usually involves hiring of specialized equipment with its requisite factory-trained technicians and operators.

Pre- and post-heating of the field joint is common practice with 3-layer heat-shrinkable sleeve system installations. Installing sleeves at high ambient temperatures is generally easier than in during the cold weather. Canusa-trained installation teams have successfully installed thousands of heat shrinkable sleeves in extremely cold conditions on Sakhalin Island and throughout northern Canada.

Specifiers are cautioned to fully understand the system they are selecting. Recently, a newly introduced heat shrinkable sleeve from a Canusa competitor was selected for a cold weather project in Russia. It passed a number of lab tests, conducted at 23°C, as prescribed by the local jurisdiction. Unfortunately, its adhesive was not designed to bond to the pipe at the ambient construction conditions of -30°C. Hundreds of faulty joints were installed before a proper sleeve system was supplied.

Ambient humidity needs to be considered. Construction in rain forests and areas of high humidity could lead to delays in production. The use of heat shrinkable sleeves is a benefit as they are unaffected by high humidity. Conversely, liquid coatings, most notably urethanes can not be applied during high humidity conditions.

Pipeline contractors often use low cost local employees. These decisions are usually commercially-driven or influenced by local labor content requirements of the host nation. More complicated field joint systems such as spray–applied liquids and FBE require expensive sub-contract ex-pat technicians to be brought in for long periods of time. A strong initial training program augmented with on-going dedication to quality control allows the contractor to use relatively inexperienced local labor to install heat shrinkable sleeves consistently from joint-to-joint.

Though regional in scope, pipeline construction often brings a global community together. Often the owners, specifiers, main contractors and subcontractors are represented by workers from many nationalities and with many different languages. Maintaining clarity in communications, fully documenting procedures and certifying installers can lessen project issues.

Key Success Factors in Field Joint Coatings

The common denominators for successful project installations revolves around specification, product selection, contractor experience and preparedness, equipment, training and ongoing inspection.

Canusa has become the leading supplier of field joint coating systems by helping pipeline engineers and contractors implement these key success factors:
a) The first critical stage is to specify the correct product. In making this selection, issues such as compatibility with the selected mainline coating, intended construction techniques and pipeline operating conditions need to be considered.
b) From this selection, a defined set of installation and inspection plans can be generated. Over the years, Canusa has developed a knowledge base of installation expertise that specifiers have come to rely upon. Transferring this knowledge of product and installation techniques is the critical next step.
c) In pre-qualification trials, the product and processes can be proven and fully documented. This step details procedures that are used to assure project success.
d) Combining this documentation with properly trained installers allows for consistent application. On many projects, Canusa certification with photo identification is a project requirement. This ensures the pipeline owner and inspector that the contractor is using fully qualified, Canusa-trained installers.
e) Depending on the scope and complexity of the installation, our on-site project activities can range from start-up training assistance to full project supervision.

Proper specifications need to account for more than just pipeline operating conditions. Well-informed engineers specify based on many levels of compatibility. As discussed, the field joint technology must be compatible to the mainline system. The field installation techniques must be compatible for the construction environment, the contractor’s expertise and equipment. With proper equipment and training, the prime pipeline contractor can effectively apply the products in the field and the owner can expect performance in line with their specification requirements.

For further information, please contact:

Canusa-CPS 25 Bethridge Road Toronto, Canada M9W 1M7 Tel: + 1 416 734 7111 Fax: +1 416 743 5927 Email: sales@canusa.com	Аргус Лимитед (СНГ) 125040, Москва, Россия Скаковая ул., д.9, этаж 4 тел.: 495–741–4817 факс: 495–741–4818 Email: margcis@arguslimited.com