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Pump systems play a critical role in keeping our world in motion. However, specifying parties can often overlook opportunities to improve pump system reliability and efficiency. This can happen when designers or engineers fail to consider new demands placed on the system since installation or understand the benefits of available options. Often, the most significant opportunities missed stem from neglecting to see the big-picture savings and efficiencies to be gained.
There are certain criteria to consider when specifying a pump, whether for a new system or replacing an old one. The usual checklist includes process liquid, flow, pressure, size and power, efficiency, space capacity, reliability and cost. But there are many nuances to pump selection that can make big differences in performance, reliability and cost-saving energy efficiencies. Here are five factors to always keep front of mind in pump selection.
1. Footprint Matters
Space availability and the pump system’s footprint are an important factor in the selection process. Given the accessible space, a frame-mounted (pump has its own bearing frame), close-coupled (motor bearings carry pump loads) or inline pump may be appropriate based on the power and speed requirements. However, these options will not have an interchangeable footprint.
Compared to frame-mounted pumps, commercial close-coupled pumps may be limited to 100 horsepower to 150 horsepower but offer space savings of around 20 percent. Alternatively, the use of inline pumps where applicable can dramatically reduce footprint.
Similar to valves, inline pumps are designed so the flow enters and exits on a single axis, requiring minimal floor space. As a result, inline pumps can occupy one-third of the floor space a typical frame-mounted pump occupies. So, if space is at a premium, the pumps that can help maximize it and the choices around it can impact other criteria.
And remember — it’s not just about horizontal space. Suitable vertical space for installation and maintenance is also required. This is more important for inline pumps that typically have a vertical motor above the pump.
2. Carefully Assess Flow Requirements, Fluid Properties
Fouling, corrosion and erosion of pumps and pipe over time can be attributed to biological, chemical and abrasive factors. Understanding fluid properties can be critical to avoid failure or the need for continuous and costly maintenance. Additionally, viscosity and temperature also are critical considerations in the pump selection process.
Amid the global pandemic of COVID-19, many manufacturers drastically increased and continue to increase production volume to meet supply chain demand. Detergent, solvent, plastic and gel manufacturers required greater volumes of olefins and aromatics. Should another similar scenario occur in the future, it could be advantageous for these manufacturers to re-examine the flow rate and pressure ranges that influence control methodologies to grant them greater flexibility.
For example, positive displacement pumps are often used in the industrial and petrochemical sectors and many applications with viscous product. These pumps come in many designs but generally deliver consistent volume with every rotation of the shaft, efficiently handling viscous liquids and providing a nearly constant flow against low or high pressures.
In another example, a conventional surface water treatment plant can have 10 to 20 different pumping processes. Each requires specific pump designs to handle the various liquid stream properties that range from clean water, water laden with solids, sludges, to chemicals for disinfecting. The plant designer must understand the demands of each of these processes, the characteristics of each process liquid, and an understanding of the appropriate pump designs and materials of construction suited for the application.
In short, pump systems and application needs can vary wildly. Because of the complexity of such systems, proper assessments may be required. These procedures provide a host of results to justify costs for improvements to the system’s design, control, operation and maintenance.
Improvements to pump systems for ultimate optimization can result in reduced system head pressure, reduced system flow rate or operating time, more efficient equipment or controls, and improved maintenance or operation procedures. The assessment team should be comprised of personnel from cross-functional backgrounds, including the following individuals:
• Host organization representative that has management support and overall responsibility and ownership;
• Assessment engineer with broad pump system analysis competencies;
• Specialists in system processes, operations and functions;
• Specialists in maintenance practices and history;
• Specialists who can provide the team with cost data.
3. Make Energy Efficiency Part of the Cost Assessment
Pump systems can account for 40 percent of industrial fluid system use and are often overlooked as energy- and cost-saving sources. A variety of factors for different settings can affect energy savings, resulting in the long-term potential for significant cost savings. Upfront costs can often deter purchasers from considering overall savings throughout a pump’s lifecycle.
For a typical pumping system, 65 percent of the total cost of ownership (TCO) is related to energy and maintenance, while the initial cost only accounts for 10 percent. For example, a double-casing between bearing multistage pump (BB5) will cost more than an axially split multistage pump (BB3), but the BB5 is designed for high reliability in high pressure and temperature applications. Trying to reduce cost upfront by extending the pressure and temperature range of the BB3 pump could result in a higher TCO due to misapplication.
Enhancing the energy efficiency of pumps can go a long way to save on utilities. To help identify the most efficient pump for the system requirements, the Hydraulic Institute offers an Energy Rating Program for select pump types 200 horsepower and below.
When it comes to prioritizing energy efficiency, there is no time like the present. There is a growing bipartisan expectation that a historic infrastructure investment/job creation bill will be a priority for the Biden administration and the 117th Congress in 2021.
Increased funding for water infrastructure will be one of the centerpieces of this legislation. Federal funding for Clean Water Act and Safe Drinking Water Act infrastructure, including pumps and pumping systems, will be increased from $2.5 billion annually to more than $12 billion annually. Committees in both the House and the Senate support green infrastructure set-asides of up to 15 percent — including energy-efficient pumps and pumping systems.
4. Think Smart
Often, there is an opportunity to improve the performance, efficiency and reliability of a system. For example, using smart pumps that integrate a variable-frequency drive with the pump performance programmed in from the factory instead of retrofitting with a separate VFD. Both solutions reduce the pump speed to meet a designed set point for greater efficiency and cost savings.
However, the more conventional approach of installing a separate VFD requires the additional legwork of installing the VFD near the pump, installing instrumentation and connecting it, then programing the VFD, which also can create opportunities for error.
A pump system assessment will be beneficial in understanding the energy of installing a VFD to control the pump system. While a level-one assessment (a paper audit) includes a pre-screening, information-gathering for pumping systems and design review, a level-two assessment entails physically measuring the system for a set time to provide a snapshot of system operations. Neither offers a picture of potential variations over a lengthier period.
A level-three assessment is a longer-term measurement that establishes how the system operates over time, forming a complete picture of performance. This type of evaluation is accomplished using in situ monitoring combined with any available historical site data.
5. See the Big Picture, Employ the Tools for Change
No matter the application, approach the process with the notion that a pump is selected to meet system requirements, and not the other way around. Defaulting to the traditional tried-and-tested solutions may not always yield the most effective option to improve performance, efficiency and reliability. By designing for excellence across a complete system instead of addressing challenges in silos, engineers will be better positioned to maximize the impact of any improvements.
Of course, maintaining the critical balance and correlation between the spend on a pump system and its output is essential to measuring performance, optimization and value. However, if the pump system can minimize utility costs via reduced consumption of water and energy in a way that does not compromise reliability or output, it is worth making the extra considerations that will eventually generate cost savings.
To encourage this approach, HI has launched several digital resources to assist utilities in establishing and maintaining incentive programs that work toward common goals of achieving greater energy efficiency.
Additionally, HI also launched the Pump Savings Calculator, a tool to assist specifiers and purchasers in determining the most energy and cost-efficient pump systems. It factors in the impacts of potential energy savings, based on the HI Energy Rating, alongside other variables such as initial cost, installation, maintenance, etc.
Additional details on HI’s Energy Rating Program, utility resources and Pump Savings Calculator are available at www.pumps.org/energyefficiency.
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