{"id":1182,"date":"2026-02-14T22:10:53","date_gmt":"2026-02-14T22:10:53","guid":{"rendered":"https:\/\/hydrocarbon.sbs\/?p=1182"},"modified":"2026-03-24T22:36:38","modified_gmt":"2026-03-24T22:36:38","slug":"repair-and-fitness-for-service-study","status":"publish","type":"post","link":"https:\/\/petrostreet.com\/main\/repair-and-fitness-for-service-study\/","title":{"rendered":"Repair and Fitness-for-Service Study"},"content":{"rendered":"\n

All sort of static equipment at any petrochemical, oil & gas, refining or energy industry require periodic inspection and to some extent at least one repair in their life time. It has been estimated that any equipment installed for 30 years of design life happens to be under question by at least one degradation mechanism against which some sort of action is required. That action can be a repair made or a fitness for service study to keep the equipment running with mitigation in form of regular inspection monitoring. However, there still are chances that an equipment can never have a history of finding hence no action required whatsoever during its life time.<\/p>\n\n\n\n

Talking about those ones which happen to get damaged due to one degradation mechanism or other, a decisive action is required in order to mitigate the effect of degradation mechanism and bring back equipment to its original specified shape to function normally. The one major factor which originally control the functionality of a static equipment (pressure vessels, heat exchangers and tanks) is the health of its pressure boundary. Anything happening inside would also be important (even to a larger extent) but the one major thing to be taken care of is the pressure boundary envelope. This pressure boundary envelope can be attacked externally or internally or it can have an inherent defect as well which may open up over the course of its continuous operation and yet masked in its operational history.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Graphic 1: <\/strong>Static Equipment under Question<\/p>\n\n\n\n

Pressure boundary of a static equipment can be attacked externally by atmospheric corrosion mechanism if uninsulated or by corrosion under insulation if insulated. This Corrosion Under Insulation (CUI) can act as external chloride stress corrosion cracking in case of pressure boundary made up of stainless steel. Internally, there are a lot of damage mechanism which can attack the pressure boundary depending upon the factors like the operating fluid, its temperature, other chemical properties, pH, corrosivity and the material of construction.<\/p>\n\n\n\n

Question arises when there is an inspection finding on this pressure boundary either from the external side or internal. And the question is that what to do if the pressure boundary has been attacked and the failure is in the form of corrosion where the metal has been eaten up or the form of failure is something like stress corrosion cracking affecting the health of pressure boundary? Should at this point a repair be done or fitness-for-service is demanded? Before looking for an answer to this, the first thing to be seen is whether the active damage mechanism is the one list in Risk Based Inspection (RBI) or something not foreseen? After this, comes the significance of fitness-for-service evaluations. With current scenario and foresight of industrial operations in oil & gas, petrochemical and refining, the question of performing fitness-for-service has gotten a greater value as we talk about savings on inspection, maintenance and operational costs of our assets. In cases where the damage is well within the acceptable limits, there is obviously no need to do repairs but that judgement of acceptable limits has to be adjudged by some qualified personnel. What has been done previously in most of the industries and which is still in practice at many locations, is that where repair will fix the issue and make the equipment as-new would be the first choice of inspection personnel and they will recommend the same without an earlier step of Fitness for Service (FFS) assessment. What seem more logical and appropriate is that if fitness-for-service proves that the defect is within permissible size and dimensions, the repair work should not be performed.<\/p>\n\n\n\n

This approach is being shown in Graphic 2 where a flow chart is representing a case of an equipment undergone a damage in the form of corrosion and an action is required over that:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Graphic 2:<\/strong> Approach to Repair or No Repair<\/p>\n\n\n\n

If the active degradation mechanism causing the defect is different than the one listed in RBI, then a quick Root Cause Analysis (RCA) session shall be done which should identify the root cause of failure. If not identified then putting back the equipment in service would be just being blind about its health. Once identified, root cause must be addressed and eliminated which would then follow a fitness-for-service study. However, if the active damage mechanism has been the one ascertained in RBI data already then there is no action required and moving straight to the next step which is performing FFS identifying whether the defect is within the permissible limits or not is the way forward. And if FFS study supports that the defect is within the permissible limits than a decision of repairing the defect would neither be correct nor cost effective.<\/p>\n\n\n\n

It is to be noted here that this case is true only in those cases where a careful FFS assessment can be made in-house or is not costly if done through outside resources. If that\u2019s not true then repairing the defect with appropriate repair methods to bring back the equipment in its normal operation is the recommended option.<\/p>\n\n\n\n

How FFS plays a role in defining what to repair demands an in-house qualified resource which can perform these assessments within no time to avoid delay during shutdowns and turnarounds. A facility lacking FFS resource would be investing resources in repairing the static equipment all the time even when it is not necessary to do so.<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

All sort of static equipment at any petrochemical, oil & gas, refining or energy industry require periodic inspection and to […]<\/p>\n","protected":false},"author":1,"featured_media":2174,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_uag_custom_page_level_css":"","_ppp_document_settings_meta":"{\"product_ids\":[{\"label\":\"Repair and Fitness-for-Service Study - 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