Pump reliability is one of the biggest rotating equipment challenges in a process plant. There are literally hundreds of pumps to monitor and maintain. There are three strategies which can be implemented to improve punp reliability, which will be explored here. These are redundant/spare equipment, transmitters with advanced diagnostics and machinery health monitoring.
The easiest way to improve process reliability is to use redundant equipment. If a pump should fail, the spare pump is piped in and the process continues. The failed pump is removed from service and a spare pump is installed. With process automation, the switch can be done automatically. Maintenance will be alerted to replace the pump. While this can be a good strategy for critical pumps, but can also be expensive. It requires at least two pumps in the process and a third spare pump in inventory. The idle pump becomes a liability, not and asset, as it is not producing any work. Moreover, there is not any guarantee the idle pump will work when needed. However, the cost of the redundant/spare pump may be less than other technology presented. It becomes a good solution for standard pump applications.
As the cost and critical nature of a pump increases, another strategy should be considered for pump reliability. Pressure transmitters using statistical process motoring (SPM) as part of their advanced diagnostics is one such consideration. While a conventional pressure transmitter will only provide pressure information, statistical process monitoring can also provide an alert under abnormal process conditions, including pump cavitation. Under normal operation the pressure pulse will be fairly consistent which produces a statistical mean and standard deviation. When the pump starts to cavitate, the pressure pulse as detected by the sensor will be much different. The statistical anomalies will be reported and subsequent action can be taken. Keep in mind pump failure can be the result of abnormal process conditions rather than general mechanical failure. SPMs can assist with root cause failure analysis.
Vibration monitoring has evolved into machinery health monitoring (MHM) which is the third strategy to be considered for pump reliability. It is best suited for expensive and highly critical pump applications. There are several different methods which can be implemented, including online monitoring and portable monitoring. Traditional vibration technology only monitors frequencies below 1000 Hz. However, there is a lot more information available above this frequency. Machinery health monitors using PeakVue technology not only monitors the same frequencies as traditional vibration monitoring, it also monitors higher frequencies. At this level minor problems with bearings will be reported. It also detects loss of lubrication and cavitation in the pump. These two issues are common causes of pump failure. Similar to SPMs, this data will assist in a root cause failure analysis.
In conclusion smaller less critical pumps can be maintained using a redundant model. Spares can also be optimized for these, as the cost of the pump is less than than of the other technology. The next tier of critical pumps is well suited with transmitters that employ statistical process monitoring. It is common to use a pressure transmitter and SPMs add an additional layer of protection. Finally, expensive and highly critical pumps should use both SPM and machinery health monitoring with PeakVue technology. This ensures the best strategy for improving pump reliability. By the way, did I mention the SPM and MHM can all be done with WirelessHART?
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