The User’s Role in Pump Reliability
This webinar was held April 2, 2015 at 10:00-10:30am CT (8-8:30am PT)
Randal Ferman presented what operations and maintenance can do to improve pump reliability. Pump reliability directly affects process availability. When the cost of pump downtime in terms of lost production is factored in, the real costs of operating and maintaining pumps can be significantly higher than O&M costs alone. While certain O&M costs are built-in at the equipment selection and procurement phases, the pump user can yet play an important role in maximizing pump Mean Time Between Failure and minimizing the total costs associated with pumping equipment.
Please view the full webinar in the video below.
Questions from the above webinar The User’s Role in Pump Reliability:
Q: How can we check for operation in the Preferred Operating Region if there is no flowmeter instrumentation?
A: There are a couple of ways this can be done. One is to take pressure readings and liquid elevation measurements to calculate the Total Head. Rate of Flow can be estimated from the factory performance curve to calculate the velocity head. This may require some iteration but it is not usually a large portion of the Total Head value anyway. From head vs. flow on the factory performance curve the calculated Total Head is used to read a corresponding Rate of Flow value. The field motor input electrical readings can be used in the same way. The motor input power is converted to a motor shaft power using the motor performance curves or nameplate motor efficiencies. The pump shaft power curve is normally provided on the factory pump performance curve and the corresponding Rate of Flow can be read.
These methods are also known as using ‘proxy’ data to make a performance assessment.
Q: What is a good resource for Life Cycle Costing?
A: Optimizing Pumping Systems, A Guide For Improved Energy Efficiency, Reliability & Profitability, Pumps Systems Matter and Hydraulic Institute, 2008.
Pump Life Cycle Costs: A Guide to LCC Analysis For Pumping Systems, Europump and Hydraulic Institute, 2001.
Q: What are your thoughts on cost versus benefit relative to incorporating exotic materials such ceramic matrix composites into pumps as a means to increase reliability of bearings and thrust rings?
A: One should not simply switch to these materials without understanding that other modifications to the design may be required. Ceramic matrix composite parts have different thermal expansion coefficients compared to alloy steels. How they are interfaced and retained on rotating and stationary components calls for design review to ensure they are not at risk of breakage due to expansion or contraction of mating parts.
Q: How can we measure vibration on submersible sewage pumps?
A: Pump and vibration sensor manufacturers do offer devices for submersible sewage pump applications. You should ask about their experience and the reliability of this equipment, since it is immersed and leakage leading to instrument or cabling electrical failure is possible. Electronic devices are also available for monitoring motor current, voltage, input power and insulation resistance. The information derived from such devices is valuable trending and condition monitoring purposes.
Q: Do you consider disposal costs of equipment at end of life as a component of Life Cycle Cost?
A: End of life disposal is part of the Life Cycle. Especially when there is a substantial decommissioning cost involved, then those costs should be included in the LCC analysis. In some cases, the end of life conditions may not be known. For instance, there are pumping installations whose life is indefinite and it might be appropriate to omit disposal and decommissioning costs from the LCC evaluation.
Q: Do you know of any portable flow measuring device that can be attached to the outer pipe in the field for flow measurements at reasonable cost?
A: There are a number of manufacturers that make these devices. I suggest checking out instrument rental companies. Chances are the devices they’re using work well and certainly you can speak to their people about user experiences. An option is to rent one yourself and try it out.
Q: What if the Mean Time Between Failure is short or unpredictable in spite of good pump maintenance and repair practices? In that case isn’t the higher cost of ownership inherently due to a problem pump, as opposed to the User’s O&M practices?
A: Yes. A ‘problem pump’ or ‘bad actor’ pump can drive up the cost of ownership or Life Cycle Cost considerably. For that reason, it’s important to take action early on. Obviously, if the equipment is still under warranty, the OEM should not just repair it, but should also provide a satisfactory explanation and equipment remedy. In any case, it might be worthwhile to bring in an independent third party to help ensure the root cause is found and resolved.
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