by Matt Migliore
|In this side-by-side cooling tower application, a process pump equipped with an intelligent VFD system ran on 32 less horsepower and 230 RPM slower than its twin fixed speed pump. The energy savings, at .06 cents per kilowatt hour, is $12,000 annually. In a, the lower speed translated into increased MTBR because of less wear and tear on pump components.
Photo courtesy of ITT Monitoring & Control (www.ittmc.com)
The key advance in pumping technology over the last decade has been the emergence of “smart” pumping systems. Using variable-frequency drive (VFD) technology in conjunction with system performance and feedback controls to monitor the process, the latest generation of smart pumping technologies offers the promise of improved efficiency, de-materialization of the process loop, and protection from process upsets. Yet, by some accounts, the end-user community has been slow to employ such technologies.
Understanding the Benefit of Intelligent Pumping
“Smart pumping systems have been around for years, and solid-state VFD technology has advanced dramatically along with reliability, wireless system monitoring, space-age metallurgies, permanent magnet motors, premium-efficiency induction motors, etc.,” says William Livoti, senior principal engineer for the Power Generation & Fluid Handling segment of Baldor Electric Company (www.baldor.com) and vice chair on the Board of Directors for the Hydraulic Institute’s Pump Systems Matter (www.pumpsystemsmatter.org) program. “[But] technology comes at a price,” he says. “The OEMs spend a great deal of money on R&D; the question is, will the end-user pay for the technology?”
According to Livoti, many end-users have been reluctant to invest in smart pumping technology due to the relatively high initial cost of such systems. He believes this is an unfortunate trend, as it has limited the uptake for intelligent systems and, subsequently, prevented end-users from realizing some pretty significant long-term cost savings via improved process efficiency and reliability. “We have the technology developed that will provide improved efficiency and reliability,” says Livoti, “However, industry has been slow to embrace the ‘changes,’ [particularly] in North America.”
Nicolas Ganzon, P.E., general manager of ITT’s Monitoring and Control (www.ittmc.com) business unit, also sees intelligent systems as the most significant recent advance in pumping systems technology. “From the design perspective, computational fluid dynamics has provided us the ability to significantly enhance both the efficiency of pump designs, as well as their ability to manage process upsets, such as the presence of clogging materials,” says Ganzon. “Manufacturing advances have also allowed us to build pumps with greater degrees of precision, which ultimately translates into more efficient and longer lasting equipment.”
From an end-user perspective, Ganzon says the maturation of variable-frequency drives is providing the most visible benefit to pumping systems. “By running pumps slower, pumps are consuming less energy, and, even more importantly, dissipating less unnecessary, and damaging, energy into the surrounding system,” he says.
Keys to Pumping Efficiency & Reliability
By using technologies such as computational fluid dynamics (CFD) to design more robust pumping systems and arming those systems with capabilities such as intelligent variable-speed operation, pump manufacturers are essentially trying to failure-proof the pumping system. However, while the technology is growing more and more intelligent and capable of operating under a wider range of operating conditions, there is still plenty of room for the end-user to play a role in the efficiency and longevity of their pumping systems.
According to Livoti, there a several common application issues he encounters when working with end-users. They are:
• Oversized pumps (typically 25 percent)
• Misapplied pumps (incorrect type)
• Incorrectly installed pumps (base plates, piping, valves)
• Poorly controlled systems
• Users expect the pump to operate reliably at numerous points on the curve at fixed speed
Ganzon views oversized pumps as the most prevalent issue with end-user applications, and he says the issue is largely solvable with current-generation variable-speed technology. “Oversizing of pumps during the application phase is still a very common problem, especially in the process-related industry,” he says. “While many end-users are considering the use of variable speed, few take the sizing advantages associated with it.”
According to Ganzon, variable speed should be considered on almost every new pump installation. He says while many users consider variable speed only for variable-flow applications, it can also have profound benefits in constant-flow applications and even some applications with high static heads.
Design Best Practices
Livoti recommends end-users pay particular attention to their installation practices when designing pumping systems. Further, he says, end-users would be wise to revisit their current pumping systems to ensure the integrity of the installation. Typically the root cause of most problems on existing systems is due to incorrect specifications and installation,” says Livoti. “This results in poor process and operation of equipment.”
For new designs, Livoti says the end-user must first develop a proper specification to ensure the long-term success of the process under consideration. He says it would be helpful to end-users if there were a recognized standard for pumping systems design. “If the appropriate standards organizations (HI, ASME, ISO, ANSI) developed a system standard with energy efficiency and reliability as the focal point, I believe we would eliminate the ongoing issues [of incorrect specification and improper installation],” says Livoti. “We need a paradigm shift to change the status quo; we cannot continue to design systems on a first-cost basis.”
Improving Existing Systems
For existing pumping systems, Livoti offers a few recommendations to ensure pumping systems efficiency. They are:
• Use flow modeling software
• Make sure the pump/primary base plate and piping are installed correctly (per HI standards)
• Use VFD if system requirements dictate
• Size pump to system requirements (+10)
• Size motor to system requirements (1.0 service factor)
• Install controls to manage system (i.e., feedback controls to VFD)
• Consider the lifecycle cost of the system rather than just the initial cost
Ganzon views sizing adjustments as a valuable modification for existing pumping systems. “Right-sizing the pump to the system demand is the best way to improve the overall efficiency and reliability of your system,” he says. “The best technology to do this is a good ole-fashioned impeller trim.”
Regarding maintenance, Livoti says he sees some common mistakes among end-users. Those are:
• Poor alignment of pump to motor (soft foot, angularity motor to base and pump to base)
• Failure to change oil in bearing housing and failure to maintain proper oil level
• Bypass line left in open position
He says, many maintenance issues can be avoided by employing some best practices, including:
• Perform precision alignment to correct above referenced issues
• Check the pump on daily basis
• Verify valve positions
• Install wireless monitoring (vibration, temperature, etc). There is an initial cost, but the return on investment is high
Ganzon recommends that end-users take the time to understand their pump performance curves, their system curves, and how the two interact. “In the age of computerized system analysis and pump selection, this fundamental step is often overlooked and can easily result in oversized systems,” he says.
Regarding maintenance specifically, Ganzon says end-users should work with their suppliers to properly perform root cause analysis. “The most common mistake we see are customers not working with their suppliers to help identify and correct the root cause of their failures,” says Ganzon. “Most reputable companies want to have long term relationships with their customers; to accomplish this, we need our customers to be profitable.”
Matt Migliore is the editor of Flow Control magazine. He can be reached at firstname.lastname@example.org or 610.828.1711.