Tips for Selecting the Right Pump
The Pump Selection Problem
Why cheaper isn’t always less expensive
When selecting a pump, hydraulic fit and efficiency are often the first factors engineers consider, weighing them above all others. This approach often saddles end-users with pumps that are either oversized or underperforming in their designated application because the spec process fails to account for overall operating cost, maintenance, and reliability. Overlooking all aspects, both technical and commercial, of the pump selection process will inevitably result in higher costs and more inefficiencies. This article will demonstrate how to avoid the common pitfalls of pump selection by detailing a thorough process.
Smart Pump Selection
Answer these questions before buying
Pump selection is based on two broad categories of considerations: Technical and Commercial.
Technical aspects of a pump are important for obvious reasons. To obtain information about a pumping system’s technical requirements, an engineer should complete a complete analysis of the system, taking care to note the following:
Net Positive Suction Head (NPSHa) - What is the NPSH? Quite frequently, NPSH is never examined, which can lead to pump cavitation and corresponding total pump failure. NPSH available (NPSHa) should always be .5 m more than NPSH required (NPSHr). This is specified by the pump manufacturer. For more information, read this article on understanding NPSH.
- Fluid Type and Specification - What is the solids size- if any, temperature, corrosive and abrasive property, level of toxicity, and flammability of the fluid being transferred? Before selecting a pump, understanding the fluid type being pumped is essential.
- Criticality of the Application - If a spare pump needed? Spares are necessary where a pump failure would be detrimental to the overall system.
- Sealing Requirement - Is the fluid hazardous or sterile? If leakage is an unacceptable option, mechanical seals may be required.
- Construction Requirement - Is there a space constraint or lack of clean water? This determines not only the pump size and configuration, but also whether or not oil lubricated pumps are recommended.
- Efficiency - What is the efficiency rating? Pumps are one of the largest consumers of energy; energy efficient pumps can reduce the harmful effects of CO2 emissions and reduce the cost of energy bills. Although high-efficiency is important, it is also important to note that the pump with the highest efficiency is not necessarily the best pump for the job.
- Drivers - How will the pump be powered? Steam Turbine, Diesel Engine, and Electric Motor are all examples.
Commercial considerations emphasize pump costs to the end user, whether in time, money, or lost opportunity. These considerations are equally as important to consider as technical aspects.
- Capital Costs - Buyers frequently purchase oversized pumps, adding unnecessary safety margins and resulting in huge capital cost for the end user.
- Operating and Maintenance Costs - Lower initial investment does not always translate to a lower operating cost. Cheap, unreliable pumps can increase downtime, resulting in increased power consumption, lost revenues, and increased maintenance fees.
- Efficiency - Higher energy efficiency translates to higher energy savings. Better operational fit should not be sacrificed for higher efficiency, however, as the benefits may not always outweigh the costs.
Other factors to consider when selecting a pump are the service history, manufacturer, spare parts availability and cost, and end-user proximity to the service center. When these factors are all weighed without a specific focus on only one or two, end users can properly select the best pump for their application.