Coatings are an important element of a pipeline’s external corrosion protection system. Line pipe is coated in accordance with recognized standards in plants under well-controlled conditions. These plant-applied coatings have an excellent reputation for reliable, long-term performance. In contrast, pipeline coatings applied in the field during construction or maintenance, such as at field welds, are applied under variable and frequently adverse conditions. Rain, snow, extreme cold, steep terrain, remote locations, inexperienced workers, and unsuitable job specifications often present significant challenges. In many cases where external corrosion of a pipeline has been found, it was associated with failure of the field- applied coatings at welds.
To address this issue, the Canadian Standards Association (Toronto, Ontario, Canada) developed CSA Z245.30-141 for external field-applied coatings on steel pipelines. It defines requirements for the qualification, application, inspection, and testing of external oil and gas pipeline coatings applied in the field or shop. Published in October 2014, it became a regulatory requirement in Canada in June 2015. Coated piping addressed by this standard is intended primarily for buried or submerged service in oil or gas pipeline systems. It does not apply to plant-applied pipeline coatings, which are covered in CSA Z245.20,2 and it does not cover the coating system design or selection process.
The standard covers the following types of pipeline coatings: liquid coatings such as epoxy and polyurethane (PUR); single and dual layer fusion-bonded epoxy (FBE); tapes (adhesive and backing); heat shrink sleeves (two and three layer); PUR foam insulation systems; and petrolatum, paraffin-filled, and viscoelastic systems. The standard also defines the responsibilities of each of the parties involved in the field coating process—the coating manufacturer, the coating application company, the individual applicator who applies the coating, the pipeline owner, and the owner’s inspector.
Before a welding procedure specification can be used for pipeline construction, it must be qualified by testing a sample weld made according to the procedure. Welders also must be qualified by demonstrating their capability to deposit sound, compatible weld metal in compliance with the welding procedure specification. The new field coating standard uses these same principles to qualify coating materials, application procedures, and applicators.
A coating manufacturer must qualify its products by testing them against criteria specified in the standard. Coating samples must be applied to pipe in a laboratory under conditions that would be encountered during pipeline construction or maintenance. Qualification tests include cathodic disbondment, flexibility, impact resistance, adhesion, and lap shear. The manufacturer must provide the application company and the pipeline owner with a laboratory test report and certificate of material qualification. The coating manufacturer is also responsible for developing a manufacturer’s qualified application procedure (MQAP), which specifies application methods and requirements such as tools, consumables, and equipment; surface preparation; compatibility with other coatings; preheat methods; substrate temperature; ambient conditions; mixing and thinning; coating thickness; application method; curing schedule; recoat and repair; and time to backfill.
The application company is responsible for the quality of the coating application, including the provision of qualified
applicators, and must have a documented quality management system, such as ISO 9001. Ensuring its applicators are trained is also the responsibility of the application company. The training needs to cover the MQAP, so participation of the coating manufacturer in the training is recommended. Training must include topics such as surface preparation, preheating, application, inspection, repairs, and cold and wet weather techniques. The application company is required to qualify each of its applicators by witnessing them apply a coating sample and confirming the applicator complies with the MQAP. Test samples must be applied to pipe under conditions that approximate pipeline construction or maintenance field conditions. The sample must be inspected to confirm it meets the same criteria applicable to production coating. The company must issue the applicator a qualification certificate. The owner may witness any or all aspects of the applicator training and qualification testing process.
The applicator must maintain a log to document his or her coating application experience. The log needs to include details such as the project name, date, MQAP, and the amount of coating applied. The application company is required to ensure that its applicators are competent. CSA Z6623 defines competent as “qualified, trained, and experienced to perform the required duties.” Competency must be determined by checking the applicator’s qualification certificate and experience log. If these are insufficient, the application company must witness the applicator applying coating, and then inspect it to confirm the coating meets the specified acceptance criteria.
Inspection methods, frequency, and acceptance criteria for production coatings are also defined in the standard. Tests include anchor profile, surface cleanliness, salt contamination, thickness, hardness, adhesion, and holiday detection. The application company is responsible for developing a job-specific inspection and testing plan (ITP) and getting it approved by the owner. It must also prepare inspection reports and provide a certificate stating that
the coating meets the requirements of the standard.
Additionally, the owner’s inspector is required to be competent. Measures of competency include being trained on the MQAP, having an understanding of the inspection methods defined in the standard, and being able to assess test results.
References
1 CSA Z245.30-14, “Field-applied external coatings for steel pipeline systems” (Toronto, ON, Canada: CSA, 2014).
2 CSA Z245.20 SERIES-14, “Plant-applied external coatings for steel pipe” (Toronto, ON, Canada: CSA, 2014).
3 CSA Z662-15, “Oil and gas pipeline systems” (Toronto, ON, Canada: CSA, 2015).
This article was submitted by NACE International member Russell Draper, a senior integrity engineer with Stantec (Calgary, Alberta, Canada). Draper is a NACE Coating Inspector Program (CIP) Level 3-certified Coating Inspector and a member of NACE Specific Technology Group (STG) 04, "Coatings and Linings, Protective: Surface Preparation", and Technical Exchange Group (TEG) 288X, "Nonvisible Contaminants, Identifying Specific Levels: Discussion of Issues." Contact him at e-mail: russell.draper@stantec.com.