I can still remember the day I was told: “the pipe failed its thickness testing – but don’t worry we are going to use a pipe clamp so we can keep using it”. I had just attended my API 570 and 510 courses to learn all about process equipment inspection protocols. Not once did I hear about any “enclosure” that we could put around a leak or a failed inspection component so that we could continue to run until shutdown/turn-around. But little did I know, there is actually a practice for this very reason. Agree with it or not, in some situations shutting down the process can increase risks and have far-reaching economic impacts. And once I was shown the level of detail this practice has built into it, I was actually impressed – but I still limited the practice and required a very detailed MOC hazard review process based on where this engineered pressure enclosure was to be used. The FIRST and by far the MOST IMPORTANT fact that EVERYONE INVOLVED MUST AGREE to is:
Engineered Pressure Enclosures (EPE) can remain in place ONLY until the degraded or damaged pressure-retaining component can be PROPERLY AND PERMANENTLY REPAIRED OR REPLACED. They are TEMPORARY leak containment devices and at the VERY FIRST OPPORTUNITY to shut down the line, it is shut down, drained/purged, isolated, and repaired/replaced per API 570!!!!
I say this as I have found EPEs during audits that had been in place for so long that the current management/supervision/engineering had no idea it was in place!!
The use of an Engineered Pressure Enclosures (EPE) to contain a leak or to reinforce a degraded or damaged pressure-retaining component is considered to be a TEMPORARY ALTERATION (i.e. a Temporary MOC is required) of pressure equipment. We limited the time frame EPE’s could be used on PSM/RMP covered process equipment to one (1) year. We also treated our process “critical utilities” when the PHA showed that if we were to lose them, it would lead to an LOPC event as if the pipe contained an HHC/EHS.
Corrective action to properly and permanently repair or replace damaged pressure equipment MUST be taken in accordance with the facility’s risk management assessment/analysis. All personnel involved MUST UNDERSTAND that the use of EPEs to contain leaks could introduce new damage mechanisms in the area under the EPE which may significantly degrade, damage, crack, corrode or cause the piping to fail catastrophically. In addition, the use of an EPE may develop operating and residual stresses due to constrained differential expansion. It is the owner’s responsibility to assess and address the impact of damage mechanisms, failure modes and the possible addition of operating and residual stresses when an EPE is used.
In most plants, an EPE is PROHIBITED from being used on:
- Boilers,
- Boiler proper and/or boiler proper piping,
- ASME Section VIII, Division 1 vessels
- ASME Section VIII, Division 2 and 3 vessels,
- Any pressure relief device or flanged joints connecting a pressure relief device
- Any pressure equipment having a crack where crack propagation cannot be eliminated (Refer to PCC-2)
In some states (and Canada) the use of an EPE may require a special permit from the AHJ where it may be a two (2) step process:
- EPE fitting design registration; and
- Risk assessment, Root cause analysis, Installation procedure, Maintenance & monitoring, and Removal (RRIMR) procedure registration
Both the EPE design registration and RRIMR registration will be obtained prior to starting any work. A submitter of an EPE design is responsible to communicate to the owner any applicable conditions and/or limitations of design registration.