Expectations are a large part of the pump selection process. I have users with pumps that have lasted three months and are happy with them. I have other users with pumps that have lasted five years and are upset with the pump’s life. The cost of a pump goes well beyond the purchase price. Maintenance, downtime and the electrical cost to run the pump are important considerations and are as necessary to know and discuss as the pump process conditions.
Let’s start by discussing a pump in the most basic terms. Pumps are devices that move various fluids by mechanical action. With so many possible applications for pumps—transferring liquids, boosting pressure, circulating fluids, etc.—selecting the best one can be challenging, as many factors must be considered.
Installation Location, Requirements & Constraints
Installation location, requirements and constraints of the system should all be considered. These factors include but are not limited to available space, power source and availability, noise level, maintenance frequency, reliability and safety. The system location and limitations affect the design and selection of the pump type, size, material, configuration and accessories. For example, a water pump in a commercial building could be designed with different considerations than a water pump going to a refinery. The conditions surrounding the pump and motor will change the motor selection and general design.
Process Conditions
Process conditions refer to the characteristics of the fluid that needs to be pumped, such as viscosity, density, temperature, pressure, flow rate, corrosiveness, abrasiveness and specific gravity. These factors affect performance and efficiency, as well as the pump’s proper materials of construction. For example, a centrifugal pump is generally suitable for pumping low-viscosity fluids at high flows and low pressures. In contrast, a positive displacement pump is ideal for pumping high-viscosity fluids at lower flow rates and high pressures in most cases.
Discussion & Review
After the process and site conditions have been considered, the sizing and designing of the pump skid can begin. When the pump and skid are selected, a review meeting should be set to discuss the selection between the user and vendor. This will be a time to review the design of the pump, its capabilities and its limitations. During this meeting, I like to discuss accessories and features that are recommended for the pump skid, such as pressure gauges or sensors, temperature switches and vibration monitoring.
Communication Is Key
I started this article by stating that communication is key, and I stand by that. The key to many of my successes and failures in life is communication. When I do not communicate well, I tend to fail. When I do communicate well, I typically find success, and pumps are the same. If I do not know the budget, I may select an unaffordable pump. Without understanding the location and power capabilities, I may choose a pump that requires more power than is available. If reliability or ease of maintenance is the most important factor, I may select a pump at a higher price point with monitors and easy rebuild features.
Evaluating the Pump Selection
Once a pump has been selected and is being reviewed with the vendor or the team at your office, several key points should be considered.
- Does the pump meet the conditions the user provided?
- Does the pump fit the location and meet power and environmental standards?
- Will it meet process conditions?
- Does it have the reliability to meet operation life and maintenance expectations?
The next set of points for review are provided by the vendor and must be reviewed by the user to ensure this is the pump desired for the application.
- Is the pump built with the correct materials of construction for the process fluid?
- Where does the pump run on the curve? Is it left or right of the best efficiency point?
- What is the efficiency of the pump selection?
- What is the net positive suction head required (NPSHr)?
- Does this offer have the proper safety requirements for the site (guard, grounding, relief valves)?
- Is the quality, availability and cost acceptable for the application?