In this issue of Process Cooling, our cover story looks at using nondestructive testing to detect leaks, thinning vessel or piping walls, or moisture within (and corrosion beneath) insulation. The damaging effects of corrosion under insulation are particularly perilous in ammonia refrigeration systems.
As author Jim Kovarik notes, “In a properly designed, operated and maintained closed-circuit refrigeration system, ammonia is a safe refrigerant. This chemical is a threat to public safety, however, when system containment fails, and the refrigerant is released.” Plant upsets and valve leaks at seals, among others, are cited as common causes of ammonia releases by the Environmental Protection Agency and others.
Corrosion under insulation presents a hidden hazard. It occurs when moisture becomes trapped in the insulation surrounding pipes, vessels and valves. Over time, that moisture causes corrosion on the surface of the material, which begins to weaken the integrity of the components.
Nondestructive testing methods, as Kovarik explains, provide a way to survey pipe, vessel and valves without disturbing the insulation system. Testing can help ammonia refrigeration system users to assess the material conditions and plan for preventive maintenance. Having an “inside view” before the insulation is even removed can help identify valves or fittings in need of replacement long before failure imminent. What’s more, having advance insight allows the facility to anticipate and prepare for system maintenance during the next shutdown.
In any maintenance operation, the goal — it nearly goes without saying — is “Fix it right the first time.” The rate at which a plant accomplishes that, however, may not be a metric normally monitored. Perhaps it should be.
While the first-time fix rate is a term more often applied to service industries, it has applicability in the process industries. Nondestructive testing can help illustrate how. The first-time fix rate, or the number of problems or service requests that are resolved during an engineer or technician’s first visit to the site of the problem, is the result of an interconnected series of behaviors. For instance, failing to properly diagnose a problem at the time that an alarm condition is noticed can lead to efforts that may resolve an existing issue. Yet, at the same time, those efforts may do nothing to address the root causes of the alarm.
One factor affecting first-time fix rate is inadequate access to field-based parts. Without a proper diagnosis and triage of the problem, the technician may not be equipped with the parts and tools he needs. As a result he is unable complete the repair.
Having knowledge of and access to data such as the service history for the equipment in question can provide insights. Likewise, predictive maintenance technologies such as nondestructive testing as well as IIOT-enabled sensors for temperature, vibration, pressure and flow, among others, can provide early indicators of the need for maintenance. The data generated by smart controls also can be analyzed for trends and long-term degradation, and for clues to the root causes of poor performance or nuisance alarms.
Do you measure your first-time fix rate?
Linda Becker, Associate Publisher and Editor