Sea water lift pump diagnosis, failure to start
Client satisfaction: long-standing mystery in oil and gas industry solved rapidly by Faraday Predictive MBVI (Model-Based Voltage and Current) diagnosis detecting mechanical fault in pump
A massive thank you for the detailed report and a meticulous analysis, and for helping us to get a plausible explanation to an otherwise mystery of a problem.
Our client, an operator of an offshore oil production platform in the North Sea, had a problem with an emergency firewater pump failing to start properly. The problem had persisted for nearly a year, and a team of experts had failed to diagnose the cause. They asked us to help, and by taking readings using the Faraday Predictive P100 we were able to identify a mechanical problem allowing them to plan a way forward.
It’s a great example of the ability of Faraday Predictive MBVI (Model-Based Voltage and Current) systems to give new insights beyond conventional Condition Monitoring technologies.
The machine consists of a diesel engine driving a generator, the output of which directly feeds an electric motor mounted above deck, with the pump which is located below the surface of the sea driven by a 40m long drive shaft.
When called on to start, the diesel engine would fire up satisfactorily and run up to speed together with the generator, but the motor was not speeding up fully. The voltage was low, but the motor was pulling a very high current – way above full load. After a minute or so the system would trip out on low voltage.
There could be a large number of possible causes of this odd phenomenon and before testing we had to consider what tests would allow us to discriminate between them.
The Faraday Predictive system works by measuring the voltage and current being drawn by a motor, or output by a generator – in this case these are the same thing. Our sensors were connected as shown in the diagram, measuring the voltage and current flowing from generator to motor.
Although these measurements are only electrical, the system is able to identify and discriminate a wide range of faults, including mechanical and operational as well as electrical, across the entire machine (supply + motor + transmission + driven equipment + process)
Our results showed that the motor was being asked to provide too high a torque to be able to run up to full speed – this is a problem associated with the typical torque-speed profile of an induction motor:
The test kit used was the Faraday Predictive P100 portable equipment health assessor; just based on measurements of voltage and current its sophisticated analysis of those signals provides a wealth of information on the condition of the entire machine, and diagnosis of a wide range of faults.
Further analysis allowed us to home in on the cause of this problem as a mechanical fault causing high friction loads within the pump, and hence point the way to corrective action.
We presented the findings to the asset leadership and they agreed, with no further challenge. For me personally the findings made perfect sense – it felt like all the various pieces of the puzzle suddenly fell into place.
What to do next
If you are interested in applying Faraday Predictive condition monitoring systems to your plant, give us a call on 0333 772 0748, or email us on info@faradaypredictive.com.
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And if you want to know more about our condition monitoring systems themselves, click here.