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.
Transcript
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
Material Selection
Ammonite Corrosion Engineering provides consulting services regarding the selection of materials (metals and non-metals) for the oil and gas industry. We have extensive experience through our monitoring and inspection services with the operating phases of wells, pipelines, gas plants, refineries, upgraders, and petrochemical plants. This experience allows us to provide sound, life-cycle cost solutions for the design of new and replacement equipment.
Preferential corrosion due to different materials being welded together
Inspectors (AP 1510, 570, 653)
Ammonite Corrosion Engineering can provide inspectors for:API- 510The in-service inspection, repair, alteration, and rerating activities for pressure vessels and the
pressure relieving devices protecting these vessels. API-570Piping inspection for inspection, repair, alteration, and repairing of in-service piping systems.API-653Tank inspection, repair, alteration, and reconstruction.
Thermographic image of solids in a separator
Public corrosion awareness: paper No 121/03/2011 By CES Information Dept Leave a Comment
Corrosion – The chemical or electrochemical reaction between a material, usually a metal, and its environment that produces a deterioration of the material and its properties. Corrosion intrudes itself into many parts of our lives. Far too many have seen rust holes even in new automobiles, outdoor deterioration of garden appliances and steel house-hold, rust in water systems ant etc. That these effects are caused by “corrosion” is well known. Corrosion processes have great impact in deterioration of industry utilities and it is one of the main risks for major accidents in oil-gas facilities. The economic costs of corrosion in the United States of America alone have been estimated between $70 billion and $126 billion per year.
For induction of corrosion three components needed: water, corrodent and metal. To reduce corrosion it is enough to effect on one of the components.
Corrosion and its control is an important, but often neglected, element in the practice of engineering. Corrosion engineering seeks to minimize corrosion costs for a particular owner or operator. Because of the distorting influence of taxation on these costs, it does not necessarily minimize total corrosion costs for society as a whole. Selection of a material for use in a corrosion situation must be based on sound economics. Both the cost of the material and the ongoing cost of preventive measures
must be included. As mentioned above corrosion could cause catastrophic accidents in oil-gas industry, as examples some of this accidents shown in pictures.
Corrosion of supports beneath fireproofing
External corrosion
Top-of-line corrosion
External corrosion in splash zone
Corrosion under insulation
Stress corrosion cracking
Internal corrosion of supports
External corrosion under insulation
Statistic reports show that corrosion is the main cause of failures in oil industry. Below is the statistic of onshore pipelines for European oil.
Corrosion typesCorrosion can be categorized in some common types
dealloying hydrogen damage intergranular corrosion Uniform or General Corrosion The metal loss is uniform from the surface. Often combined with high-velocity fluid erosion, with or without abrasives. Pitting
Corrosion The metal loss is randomly located on the metal surface. Often combined with stagnant fluid or in areas with low fluid velocity. Galvanic
Corrosion Occurs when two metals with different electrode potential is connected in a corrosive
electrolytic environment. The anodic metal develops deep pits and groves in the surface.. Crevice Corrosion Occurs at places with gaskets, bolts and lap joints where crevice exists. Crevice corrosion creates pits similar to pitting corrosion. Environmentally induced
cracking Brittle fracture of a normally ductile alloy in the presence of an environment that
causes minimal uniform corrosion. Usually accompanied by tensile and cyclic stresses, chlorides, nitrates and so
on. Dealloying Occurs when an alloying element is active (negative electrochemically) to the major
solvent element. Metals lose its mechanical properties and not fit for the service. Hydrogen Damage Reaction of hydrogen ions in steel to form H2 results in voids and surface blisters Often results in surface damage or cracks.
Microbial Corrosion
Sulphate reducing bacteria (SRB) produce the ‘corrodent’ hydrogen sulphide (H2S) as part of their metabolism. The resultant acidic environment leads to rapid pitting – up to 10mm/yr.
Location: stagnant areas, dead legs, bottom of the vessels, under deposits Mitigation measures in place: Use of highly resistance alloys, analyses of fluids and
coupons for the presence of bacteria.
To be continued in the next paper!!! CES E-Journal, Jan 2009.
Author: Rufat Azizov //CES E-Journal
CUI - CORROSION UNDER INSULATION
CUI - Corrosion Under Insulation is the one of the greatest concerns in the oil, gas, and petrochemical industries where highly dangerous liquids and gases are processed throughout plant pipelines. For many years thermal imaging has been successfully used in the petrochemical industry for inspecting and monitoring system performance and the integrity of insulated pipelines and vessels.
De-salter vessel showing water intrusion under the insulation
Most of the insulation defects we associate with pipelines and vessels occur through poor initial installation or subsequent damage to the insulation material during its lifetime. Damaged insulation will allow water to saturate the materials nearest to the metal where corrosion will eventually begin to occur.
Thermograpghy allows us to scan large areas of insulated pipelines quickly and safely whilst identifying areas where the integrity of the insulation has become subject to water ingreaa. These areas can then be removed and reinstated once a more detailed study of the pipeline using other NDT techniques has been carried out to measure the extent of the Corrosion Under Insulation (CUI).
The areas shown in red are where the insulation has become saturated and is conducting heat from the process pipework to the outside of the cladding. The particular survey took one week to complete and resulted in a number of anomalies being found and a programme put in place to remove and reinstate the damaged insulation.
