Spec the right pump, save the system
- 8 hours ago
- 5 min read
All too often, inefficiency, downtime and ballooning maintenance costs trace back to a simple misstep: the wrong pump was chosen for the job. Caleb Summers, a leading application engineer at Unibloc Hygienic Technologies, says the root of the problem is often avoidable.
“With so much at stake, engineers may not want to blindly trust a vendor’s recommendation,” he cautions. “You need to understand your system, your product and your pump - and how all three interact.” During a recent online event Summers outlined some of the most common pump selection pitfalls offering a practical, experience-based framework to help to avoid them.
Push or pull
“Pull” refers to a pump’s suction-lift capacity - its ability to draw product into itself - while “push” describes how well it overcomes discharge pressure. “Certain pumps are going to be better at certain applications than others,” said Summers. AODDs and centrifugal pumps excel at suction lift, while lobe, screw and piston pumps perform better at higher discharge pressures.
He illustrated this with a real-world example: “A customer bought one of our lobe pumps from a distributor and tried to use it to lift product out of a 210-litre drum.”
“It wasn’t working. Once we looked at it we realised he was using one of our load pumps to pull product up which it was simply not capable of doing - it was the wrong pump for that application.” Understanding pressure limitations is also crucial. “Centrifugal, AODD and gear pumps are generally limited to 100–150 PSI. Lobe pumps can go up to 500 PSI and piston and screw pumps beyond that,” he said. But it’s just as important to take into account the pump’s pressure rating as well as the connection pressure rating.
“We’ve worked extensively with pumps in the meat industry, where systems often run at very high pressures. In one case, a customer kept experiencing failures with his tri-clamp fittings—not because the pump couldn’t handle the pressure, but because the connections weren’t rated for it. What he needed wasn’t a higher pressure pump, but higher pressure-rated fittings to match the system demands.”
Bigger pump or bigger pipe
According to Summers, many operators looking to boost flow rate, productivity and efficiency often assume that simply installing a bigger pump will solve the problem. “It sounds logical - more pump, more product. But the pump isn’t always the limiting factor,” he said. “In many cases, it’s the pipework that restricts flow, not the pump itself.”
A prime example was of a customer who added an additional filler line to their facility wanting more flow. “They were using an existing pump to unload product to their original filler line and when they added a new filler line, they extended pipework from the same pump. The flow rate was acceptable, but they wanted to improve it more.”
After running friction loss calculations, Summers found line size was just too small, creating high friction loss and preventing the pump from operating at full displacement. A bigger pump wouldn’t have helped - they’d still be limited by the same undersized pipework.
“Instead of a new pump, we kept the existing pump in place and they maintained the current flow rate as it was the most cost-effective solution since upgrading the pipework wasn’t feasible.”
Even a slight increase in pipe diameter can yield dramatic benefits. “The cross-sectional area of a pipe increases exponentially with its diameter. Go from 50mm to 100mm and you’re looking at a 300% increase in flow area.”
This principle came into play for a customer with a 430m oil transfer line. The initial motor spec didn’t account for the friction loss of such a long run. “In this case, it was cheaper to upgrade the motor than replace all that piping,” said Summers.
Redline vs. idle
Using a car as an example Summers explained that running a pump at its maximum rating was a bit like redlining one’s car. “Just because a car can run at 80 000 RPM, doesn’t mean it should. You would spend more time in the workshop than on the road.”
“Pumps are no different. Operating a pump at its maximum displacement may seem efficient, but it leads to increased maintenance, faster wear and ultimately shortens the pump’s service life. Running at full capacity all the time is rarely the smartest or most cost-effective choice.”
He said a customer recently called wanting to purchase a pump rated for 150 liters per minute. “But he needed to move about 144 litres of product. On paper, it seemed like a perfect match. But the product had significant viscosity and he was trying to pump it 6 metres vertically and 9 metres horizontally, while still expecting full flow.
Under those conditions, expecting the pump to maintain 150 litres per minute simply wasn’t realistic. “Even if it could achieve that flow rate, the added strain from pumping a viscous product over a 6-metre vertical and 9-metre horizontal run would lead to excessive wear, constant maintenance and frequent part replacements.”
He said a good rule of thumb was to run low-viscosity products at around 75–80% of the pump’s maximum speed. As viscosity increased, operating speed should be reduced. “High viscosity and high pressure go hand in hand,” he explained. “The thicker the product or the higher the system pressure, the slower you want to run the pump otherwise, you’re setting yourself up for excessive maintenance and premature wear.”
Not all liquids are equal
“Rheology matters,” said Summers indicating that different fluids behaved differently being pumped making it imperative to know how fluids flow and deform under force, particularly how their viscosity and other flow properties change under different conditions. “Viscosity can dramatically affect pump performance. Knowing the viscosity in centipoise is needed to size a pump.” He said with most pump curves based on water making it important to know that anything that does not act like water will perform differently.
The whole picture
Sometimes, a small tweak to the process system can lead to major gains - improving efficiency, cutting costs or both. “It’s important to take a step back and look at the big picture,” said Summers. “Where is the product coming from? Where is it going? Can you shorten the distance?
A shorter pipe run often means smaller pipes and smaller pumps, which immediately reduces cost. And don’t overlook how maintenance factors into the system as a whole.”
When it comes to selecting new pumps, this broader perspective is essential. “Sit down with your supplier, keep an open mind, and assess the entire process system,” Summers advised. “There’s real value in holistic system design. It’s never just about the pump - it’s the pipework, the cleaning, the power requirements, the flow rates. It all matters.”
Unibloc Hygienic Technologies,
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