MOC for Fixed Equipment Mechanical Integrity | RefinerLink

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MOC for Fixed Equipment Mechanical Integrity

By John Reynolds of

Apr 13, 2015

Advice on when to involve asset integrity specialists in your MOC process.


Management of Change (MOC) for fixed equipment mechanical integrity (FEMI) issues is one of the most important of the 101 essential elements in pressure equipment integrity management.


There are a multitude of incidents in the refining and petrochemical industry that can be traced to changes made in hardware or process conditions without effective MOC, many eventually causing a breach of containment. 


Changes to the hardware are typically easier to recognize and deal with through proper MOC. Changes to the process that might affect FEMI are more difficult to recognize. Both must be included in the comprehensive MOC process to assure its effectiveness. 


Unfortunately, many who are involved more in the operation and process side of our business sometimes make changes to equipment and process variables, assuming that any change in material degradation will be found in the next inspection.  That’s simply not the way the inspection process works.


An effective MOC process is vital to the success of any FEMI program. It allows the inspection group to anticipate changes in corrosion or other damage mechanisms, anticipate other potential effects, and alter the inspection plan if necessary to account for those changes. Even when MOC is triggered, if knowledgeable people are not involved, then the MOC process for avoiding breaches of containment could be flawed.


It is vital that the FEMI discipline be interlocked with the PSM group on the MOC process.  If the two disciplines are not close coupled, then critical MOC issues that affect FEMI can be missed, sometimes until a breach of containment occurs.


While operators, process engineers, and others outside of the FEMI discipline may be able to readily identify most physical changes that require the MOC process, such is not always the case with process changes. 


It is vital that someone knowledgeable in corrosion and damage mechanisms, i.e. a corrosion and materials SME, be involved in assessing ALL process changes for their potential impact on FEMI.


The MOC process for FEMI does not work well enough if the FEMI discipline is called upon when someone else thinks they need to be involved, or worse yet the FEMI discipline simply receives action items from the MOC process without their involvement.  This whole MOC process for process variable changes is completely dependent upon having a comprehensive list of Integrity Operating Windows (IOWs) for each process unit.



Some Examples to Consider


While most physical changes are somewhat obvious to those outside of our FEMI discipline, some are not.  Here are just a few examples of physical changes that should not be overlooked for MOC applications:


  • Recommisioning of equipment that has been out of service for a while
  • Installation of temporary equipment or temporary repairs
  • Re-pumping of clamps or boxes
  • Re-rating of equipment or resetting of a PSV set pressure
  • Deletion or addition of insulation
  • Shutting down a cathodic protection system for buried piping
  • Continued operation when piping supports have changed
  • Changes in equipment numbering that will require record updating


As mentioned above, process changes that require MOC for pressure equipment integrity reasons are not as easy to identify for those who are not knowledgeable in process corrosion mechanisms.  Here are just a few examples of some less obvious process changes that should instigate an MOC:


  • Continued operation outside of established boundaries or IOWs
  • Continued operation of equipment that is leaking
  • Operating with furnace tube or refractory lined equipment hot spots
  • Continued operation when chemical injection, wash water or neutralization injection systems are down for maintenance
  • Continued operation with steam tracing leaks under insulation
  • Postponing a turnaround or an inspection due date
  • Opening or closing bypass lines that might change process conditions
  • Changing composition of crude or other raw materials
  • Creating a dead leg by closing a valve or blinding off some piping
  • Revising start-up procedures
  • Changing equipment from continuous operation to intermittent operation or vice versa
  • Changing heating or cooling rates of equipment, especially heavy walled equipment
  • Changes in process velocity, fluid phase, or flow regime
  • Carry-over of liquid streams into areas not designed for them
  • Introduction of air or moisture into unintended process steams
  • Process changes that might shift the dew point location


There are dozens more examples of physical and process changes that might affect pressure equipment integrity.  For each of those changes listed above, there are numerous FEMI incidents that occurred because adequate MOC was not implemented. Inadequate MOC is one of the most common root causes of FEMI incidents in our industry.


In-kind replacements are another potential MOC trap, as they are explicitly excluded from the OSHA PSM regulation in the US. 


If someone not familiar with process corrosion issues replaces a piece of carbon steel piping in-kind that has suddenly experienced accelerated corrosion, then it certainly should not be done without the involvement of competent corrosion and materials SMEs.  The same problem that caused the accelerated corrosion will likely still be present.


There is also the argument for conducting a MOC when staffing changes in the FEMI discipline.  The site needs to completely understand the upside and downside of eliminating an inspector position, increasing inspection workload, deleting normal Inspection/NDE contract services, changing PEI staffing for turnarounds, or decreasing the amount of available engineering support.


How closely involved is the FEMI discipline at your site in the MOC process for FEMI issues? Are competent, knowledgeable FEMI persons involved up front to help decide what changes need to be put through the MOC process?  Do you have an indisputably good track record for assessing changes that might impact FEMI at your site?


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