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Peristaltic pumps for metering apps reduce chemical costs as much as 20%

Lakehaven Utility District avoids many of the woes said to be associated with diaphragm pumps

April 01, 2014
KEYWORDS watson-marlow
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Technology advocates never fail to tout early-adopter benefits. These can include capturing the attention of collaborating suppliers and partners, being seen as an industry trendsetter and early access to emerging, productivity-enhancing solutions.

On the other hand, skeptics caution companies not to take chances on “unproven” solutions. For careerists, while waiting may tend to erode competitiveness, keeping to the pack seldom draws attention.

Having pondered the two view points, a fair conclusion might be that, if you’re going to implement a technology solution, be sure you know what you’re doing and why.

It’s also the case that while enterprise software systems involving millions of lines of code often still have glitches when brought to market, innovation and what constitutes a “proven” solution that delivers real return-on-investment is, in industrial pump markets, more succinctly demonstrated.

A case in point is found at the wastewater treatment plant in the Lakehaven utility district in Washington State. The district is an early adopter of Watson-Marlow’s Qdos 30 metering pump for use with sodium hydroxide, a caustic, and poly-aluminum chloride (PAX) applications.

“Water treatment and other process operations often involve chemical metering. Historically it’s been done using a diaphragm pump,” Rick Balek, sales manager, Industrial & Environmental Div., Watson-Marlow Pumps Group, says. Watson-Marlow is known as a peristaltic pump provider. With a peristaltic pump, since the media makes contact only with the tubing, the chemical compatibility issues that often apply with other type pumps are relevant only to the composition of the tubing.

In addition, Balek says, “Diaphragm pumps entail adding and maintaining valves.”

Watson-Marlow says peristaltic pumping technology helped reduce chemical costs at the Lakota plant by as much as 20%, while improving efficiency, ease of use and safety. 

Upgrade for safety

Lakehaven utility district is a municipal corporation serving about 112,000 customers. Its Lakota activated-sludge plant moves about 10 million gallons per day.

“At the plant we were using peristaltic pumps with a traditional tube-element design,” explains Chris McCalib, wastewater operations manager. “They were fine from a dependability standpoint. But to gather feedback of dosage rates, for example, you had to pull the information out of the machine and send it to the plant’s control system. There was no local display or functionality.”

Of paramount importance was protecting operators from any caustic or PAX spill that could result from tubing failure. A Lakehaven safety protocol stipulates peristaltic-pump location in a special Plexiglas-enclosed containment area. 

When he first heard about issues at the Lakota plant, Watson-Marlow sales representative John Simon, of Goble Sampson Assoc. of Salt Lake City, Utah, knew the Watson-Marlow peristaltic pump was a good solution.

“It was a good retrofit opportunity because you were replacing a similar technology,” Simon says. “Given the lay-out, not much engineering was needed. It was a simple drop-in replacement, but also a productivity-enhancing, cost-effective solution. Furthermore, this peristaltic pump offers a further level of operator safety.”

The pump in question

Watson-Marlow says its Qdos 30 pump range, introduced in June 2012, is the first peristaltic specified for chemical-metering applications. The pump is said to deliver accurate, linear and repeatable flow performance from 0.0002 to 8.0 gallons per hour (GPH) at 100 PSI. There are no seals or valves in the flow path to clog, leak or corrode.

Besides reduced valve cost and less maintenance, another reason its peristaltic pumps are a cost-effective chemical metering solution is its “ReNu” pump-head technology, Watson-Marlow says. Quick and easy pump-head removal and replacement minimizes process downtime and requires no specialist tools, training or technicians.

“It means you can rebuild a pump in about 30 seconds,” Balek says. “If the pump head fails, it is double-sealed from atmosphere, so the danger of spills or operator contact with hazardous substances is eliminated. When the tubing exceeds its operational life, the operator is signaled that it’s time to change the sealed pump head.”

Finally, the pump is fitted with a robotic-grade servo motor, for significant accuracy enhancement. “Overfeeding can arise from pump inefficiency,” Balek says. “But this peristaltic pump is so precise — two to four times more precise than other pumps — that savings are derived simply by the fact chemicals are not being wasted.”

Features savings delivery

Following application and performance trials, McCalib reports, “The pump met our criteria for success. In fact it’s been operating flawlessly ever since.”

Lakehaven next used the peristaltic pump for a second application, metering from 250-gallon totes, which was made easy by tapping into the pump’s “barrel-bar” feature — a function that calculates drawdown based on the pump’s metering accuracy and sounds an alarm when a source barrel is getting low.

McCalib says the peristaltic pump was installed here because the plant struggled when pumping from a tote. Operators could not simply shut off pumps mid-process, which made it difficult to know when to change the tote. Occasionally totes would drain completely. At other times an operator would change a tote that was still 20% full. McCalib credits the peristaltic pump’s barrel-bar feature for delivering a 15% to 20% reduction in chemical costs, allowing proper metering without wasting chemical or running dry.

McCalib concludes by indicating that the plant is now looking at peristaltic pumps as replacements for the plant’s older pump technology.

Closing remarks

Key to the peristaltic-pump advantage compared to traditional solenoid- or stepper-motor driven diaphragm-metering pumps is its linear-flow performance regardless of typical fluctuations in suction or discharge pressure conditions.

A peristaltic pump has no internal ball valves to clog or corrode when metering chemicals with suspended solids. It won’t vapor-lock when metering chemicals like sodium hypochlorite. Typical pump ancillary equipment — like backpressure valves, pulsation dampeners, strainers and float switches — is eliminated. 

An easy-to-use, full-color display gives operators access to performance details. Options include manual control; analog speed control and feedback with relay outputs and SCADA level inputs; and PROFIBUS network control. Fitted with an impact-resistant display cover and NEMA 4X enclosure, its maker says this pump withstands the most aggressive chemical environments.

For more than 50 years, Watson-Marlow has been solving fluid-handling problems using state-of-the-art pumping technology. It says its pumps deliver the best combination of pump and drive technology, meeting accuracy and control demands needed for tough applications.

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