A U.S. Department of Energy study on pump life cycle costs notes that maintenance and energy costs make up the vast majority of lifecycle costs. Pumps that are critical to the operation of the process typically are installed with online condition-based monitoring (CBM) systems to help prevent failures and provide early warning to allow repairs to be made before slowdowns or shutdowns occur. In complex processes such as oil refining, 10% of the pumps may have these monitoring systems.
In a new whitepaper you can request, Three Innovative Ways to Improve Pump Reliability, basic and advanced monitoring techniques are shared. For many of the pumps not deemed critical, monitoring has historically been done through manual rounds and time-based preventive maintenance schedules.
These methods do not always catch degrading performance in time. These pumps have not had CBM systems in place due to the expense and installation challenges associated with wiring. Technology advancements have reduced some of these challenges and costs with wired monitoring solutions to where possible applications include:
- Pumps with repeat failures
- Pumps without spares
- Pumps that can cause a fire or environmental incident
- Pumps that can lead to a significant process disturbance, process shutdown or slowdown
The three methods the whitepaper shares are pump seal monitoring, cavitation monitoring and vibration monitoring. I’ll provide a quick overview of each and point you to the whitepaper for specifics in instrumenting and monitoring.API Standard 682: Pumps—Shaft Sealing Systems for Centrifugal and Rotary Pumps was updated to its fourth edition in May of 2014. This standard specifies requirements and gives recommendations for sealing systems for centrifugal and rotary pumps used in the petroleum, natural gas, and chemical industries.
API 682 now shows a preference for level and pressure transmitters instead of level and pressure switches in order to provide the signal to annunciate the level or pressure alarms. The use of transmitters for pump seal monitoring provides an improved view of the pump seal flush reservoirs. A level signal also allows for monitoring the rate of change of a reservoir level for earlier indication of potential seal failure.
Cavitation is “…the formation of vapor cavities in a liquid… when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to higher pressure, the voids implode and can generate an intense shockwave.” These shock ways damage the pump over time.
For high head multistage pumps that cannot tolerate cavitation even for a brief time, the pumps can be instrumented to monitor discharge flow and pressure, the integrity of the level instrument on the suction vessel, and the differential pressure across the suction strainer to help prevent cavitation from occurring.
Wireless vibration transmitters provide vibration monitoring to help detect the presence of any one of many common causes of pump failure, such as worn bearings, worn shaft coupling, misalignment, impeller damage, cavitation, foundation or frame faults.
Request the whitepaper for details on pump seal, cavitation and vibration monitoring for the pumps not already protected with online condition-based monitoring systems.