Not a trick question; however, I bet it made you stop and think for a second. There are many stories/scenarios involving LOPC events where a pressure gauge was not maintained or not read properly. This year we got involved in an LOPC event and testing done on the critical pressure gauge showed it was way off in its reading. Of course, the gauge was over 20 years old, had never been calibrated/inspected/tested, and had recently been moved to a new location and service. Unfortunately, the gauge was removed from a non-chemical service to a PSM/RMP-covered process and was not even compatible with the HHC/EHS; but chemical compatibility did not seem to factor in the failure of the gauge, as the internals and seals did not fail. But the gauge was “way off” in calibration. And as you can imagine, our causal analysis has opened Pandora’s compliance box as OSHA (and maybe EPA) are leaning on issuing citation(s) referencing the gauge manufacturer’s recommendations as one RAGAGEP and ASME B40.100, ASME Pressure gauges and gauge attachments as another applicable RAGAGEP that covers “Reuse of Pressure Gauges”. Here is what the manufacturer says about the maintenance of their gauge, as well as what ASME B40.100 says about reusing gauges in different services and locations.
(emphasis by me)
|
4.1 Frequency of inspection – This is quite subjective and depends upon the severity of the service and how critical the accuracy of the indicated pressure is. For example, a monthly inspection frequency may be in order for critical, severe service applications. Annual inspections, or even less frequent schedules, are often employed in non-critical applications. 4.2 In-service inspection – If the accuracy of the gauge cannot be checked in place, the user can at least look for (a) erratic or random pointer motion; (b) readings that are suspect – especially indications of pressure when the user believes the true pressure is 0 psig. Any gauge which is obviously not working or indicating erroneously, should be immediately valved-off or removed from service to avoid a possible pressure boundary failure. 4.3 When to check accuracy – Any suspicious behavior of the gauge pointer warrants that a full accuracy check be per- formed. Even if the gauge is not showing any symptoms of abnormal performance, the user may want to establish a frequency of bench-type inspection. 4.4 When to recalibrate – This depends on the criticality of the application. If the accuracy of a 3-2-3% commercial-type gauge is only 0.5% beyond specification, the user must decide whether it’s worth the time and expense to bring the gauge back into specification. Conversely, if the accuracy of a 0.25% test gauge is found to be 0.1% out of specification then the gauge should be recalibrated. 4.5 Other considerations – These include (a) bent or unattached pointers due to extreme pressure pulsation; (b) broken windows which should be replaced to keep dirt out of the internals; (c) leakage of gauge fill; (d) case damage – dents and/or cracks; (e) any signs of service media leakage through the gauge including its connection; (f) discoloration of gauge fill that impedes readability |
As shown above, if the gauge is deemed critical (as was the one involved in the incident), the inspection frequency should have been monthly. In hindsight, the gauge was never in the MI/PM inspection/testing program. I could maybe make an argument that not every pressure gauge in the PSM/RMP process may not be deemed “critical”, but I tend to always assume they are all critical until we can logically document otherwise. For example, a pressure gauge that plays a role in the procedures to “avoid or correct a deviation from the safe upper/lower pressure” would absolutely be a critical gauge. Even a gauge that is used during “rounds” to validate process pressures would be deemed “critical” to process safety. These gauges should be inspected MONTHLY and any issues noted and resolved via the CMMS.
Now let us talk about reusing a gauge. Reusing a gauge from an entirely different service must be AVOIDED. In the incident we got involved with, a gauge on the chemical process was found damaged and a Replacement-In-Kind gauge was not available. So a unit supervisor took one off an old air system that was no longer in service and replaced the damaged process gauge with the old air system gauge. This was done due to the critical need for a working pressure gauge at this location in the chemical process. So yes, the gauge was deemed “critical” by the facility. This was “intended” to be a very temporary change – just until the new gauge arrived. However, due to supply change issues, the new gauge had a 4-month lead time, and by the time it had arrived, no one remembered what it was for, so it was entered into inventory. NO MOC (permanent or temporary) was done on this change.
Everything from gauge range, chemical compatibility, temperature compatibility, etc. MUST be considered in any REUSE of gauges. But there is a RAGAGEP that actually calls out this practice. ASME B40.100, ASME PRESSURE GAUGES AND GAUGE ATTACHMENTS section 4 states:
(emphasis by me)
|
4.4 Reuse of Pressure Gauges 4.4.1 Consideration for Reuse. It is NOT recommended that pressure gauges be moved from one application to another for the following reasons: (a) Chemical compatibility The consequences of in-compatibility can range from contamination to explosive failure. For example, moving an oil service gauge to oxygen service can result in explosive failure. (b) Partial fatigue The first installation may involve pressure pulsation that has expended most of the gauge life, resulting in early fatigue in the second installation. (c) Corrosion Corrosion of the pressure element assembly in the first installation may be sufficient to cause early failure in the second installation. 4.4.2 Other Considerations When reusing a gauge, all guidelines covered in this Standard relative to application of gauges should be followed in the same manner as when a new gauge is selected. |
The discussion with the engineering group for this organization led to the question: can we move a pressure gauge within the same process?
We settled on NO, it is not worth it, based on the costs and availability (now that they maintain an inventory) of these gauges. But there is some concern that now they have 19 gauges that have been identified as “critical” and will be inspected monthly, that their replacement frequency could increase substantially. But only time and a well-managed inspection and testing program will tell.