Factory applied external pipeline coatings for corrosion control
|Publication Date:||1 May 2017|
This recommended practice (RP) has been prepared to facilitate the specification and execution of coating application work. The RP covers the application of specific types of linepipe coating systems as referred to below. The use of this RP implies the involvement of purchaser in quality control aspects, including review of procedures and inspection/testing plans for coating application, witnessing of qualification tests (PQT) for coating and acceptance of documentation of quality control (daily log formats and index for Final Documentation) prior to start of production in order to ensure that the produced coating meets all requirements of this RP and ISO 21809-1.
The requirements to design and quality control are in compliance with ISO 21809-1, but with some additions. This means that compliance with this RP ensures full compliance with ISO 21809-1.
This RP covers the process of applying external coating systems for corrosion control of submarine pipelines at the coating plant, and includes the qualification, implementation and documentation of this process. The following coating systems are covered:
1) Single layer fusion bonded epoxy*).
2) 3-layer coating based on an inner layer of fusion bonded epoxy (FBE) applied by spraying, an intermediate adhesive layer applied by spraying or extrusion, and an outer jacket of polyethylene (PE) applied by extrusion*).
3) 3-layer coating based on an inner layer of FBE applied by spraying, an intermediate adhesive layer applied by spraying or extrusion, and an outer jacket of polypropylene (PP) applied by extrusion.
4) Glass fibre reinforced asphalt enamel coating*).
5) Polychloroprene (vulcanised rubber) coating (sometimes applied for thermal insulation in addition to corrosion control and mechanical protection).
*) Primarily for use in combination with a concrete weight coating.
Pipeline operators (and installation contractors if applicable) should consider the need to carry out qualification of generic coating systems for specially demanding applications; e.g. resistance to bending during installation by reeling and/or long term (>10.000 hrs) thermal degradation of critical coating properties associated with high operating temperatures. Purchasers of linepipe coating should further consider pre-qualification of the coating manufacturers prior to the issue of purchase document (see definition in Sec.3).
This RP covers primarily the process of applying coating to ordinary straight pipe joints (including any joints designed as buckle arrestors). It may also be used for coating of certain pipeline components (e.g. bends, tees and reducers), or for coating of linepipe for onshore pipelines, using the same or similar coating systems. The user shall then duly consider the needs for amendments and deviations for such applications.
Some of the coating systems for field joints as defined in DNVGL-RP-F102 may be better suited for coating of pipeline components than those covered by this RP.
The following activities associated with linepipe coating are not covered in this recommended practice:
- requirements for the qualification of manufacturer specific coating materials and applicator specific coating systems for general purposes (i.e. not project specific, see guidance note to [6.6.3])
- application of internal coating
- application of thermally insulating coating
- application of concrete weight coating.
The coating systems as defined in CDS 1, 2 and 3 are applicable as substrate to a thermally insulating coating or concrete weight coating.
Considerations related to safety and environmental hazards associated with either pipe coating work or properties of the coating in the as applied condition (reflected by national and multi-national regulations) are beyond the scope of this document.