Degradation Mechanisms Library
Degradation Mechanisms for the Oil and Gas Industry
A key activity carried out during the initial stages of designing an Integrity Management Program is to identify the degradation mechanisms that are possible in the facility. It is fundamental to understand the relevant mechanisms, their likelihood of occurring in the facility, and the impact that they may have on the facility. We have found that a good starting point is to reference API RP571 "Damage Mechanisms Affecting Fixed Equipment in the Refining Industry." This recommended practice describes degradation mechanisms found in refineries, affected materials, critical factors used to identify the mechanism, affected units or equipment, appearance or morphology of damage, prevention/mitigation measures, inspection and monitoring recommendations, and related mechanisms. References are also provided where the reader may be looking for additional information regarding the degradation mechanism.
Ammonite Corrosion Engineering uses API RP571 to identify the degradation mechanisms that are relevant for the client's facility and where necessary expands the list of mechanisms to include those not referenced by API RP571. Photographs are used wherever possible to highlight the mechanisms' description. Information regarding these degradation mechanisms is then captured in a separate document for the client to use as a reference and for training purposes.
We have provided some photographs from our library to illustrate some of the more common mechanisms.
Figure 1- Sand erosion of wellhead piping
Figure 2- Erosion/Corrosion at a pipe elbow
Figure 3- Shackle pin from FPSO mooring chain
Figure 4 - Galvanic corrosion of seawater cooler brass tubesheet connected to titanium distribution grid (bars shown looking through nozzle) and copper nickel cover/nozzle.
Figure 5 - Steam manifold valve, located on ship deck, wet mineral wool insulation.
Figure 6 - Corrosion under insulation (CUI) on steam condensate return line at main deck penetration.
Figure 7 - This design facilitates water entrapment, coating breakdown and accelerated corrosion