Going to the Well for Peristaltic Pumps

By Chuck Treutel

• Watson-Marlow Bredel explains why rugged hose pumps on drilling rigs process the toughest applications on -- or in -- the Earth, making them ideal for groundwater management in such cases to prevent contamination of potential drinking water.

Watson-Marlow SPX pump on side of Rig Source drilling system[Web Exclusive - Industrial WaterWorld - Sept. 1, 2009] -- If you were an industrial pump, chances are you wouldn't want to be used in the environmental and geotechnical drilling industry. That's because few applications exist where a pump is worked harder, beat up more and forced to process harsher, more abrasive materials.As an example, consider a clay-like substance called bentonite. In many drilling applications, slurry walls are constructed to contain contaminated groundwater, diverting it from the drinking water intake, directing uncontaminated groundwater flow, and providing a barrier for the groundwater treatment system. The slurry, usually a mixture of bentonite and water, is pumped into the trench, which prevents native soil from caving into the excavation. Even heavily diluted, this concoction is extremely viscous and can not only clog the pump but significantly shorten its useful life.

Mike Crimaldi understands difficulties associated with pumping bentonite as well as anyone. His company, Rig Source Inc., is dedicated to assisting drilling contractors with a range of support services, including new and used equipment sales; equipment rental, maintenance and repair; and different drilling supplies. Having spent the last 25 years working in the drilling industry, the founder and president of the Elburn, IL-based firm is also well versed in abuse his pumps must withstand.

The Rig Source drill in action

"The pumps installed on our drilling equipment are used to process a variety of materials, some more abrasive and corrosive than others," said Crimaldi, who started out as the "clean-up kid" at a family-run drilling business in the Chicago area. "When we provide a rig to a customer, we have to ensure the pump is capable of handling the specific fluid or material the customer will be working with. If not, the entire job can go south in a hurry."

For this reason, Crimaldi relies heavily on SPX high-pressure hose pumps from Watson-Marlow Pumps Group, the world's largest manufacturer of hose pumps with over 75,000 positive displacement hose pumps in operation. These pumps are used as primary and secondary fluid pumps for drilling and grouting. They're found more often than not assembled on the company's Diedrich D50 and D120 drill rigs, used mainly for auger drilling and, occasionally, soil sampling.

Familiar with Watson-Marlow products during his days in the field as a drilling contractor, Crimaldi's choice of Watson-Marlow is no mystery. Positive displacement pumps like the SPX are typically used for moving viscous and corrosive fluids -- or, due to their slow-moving, smooth action, sensitive materials that require gentle handling. Diaphragm and progressive cavity pumps make up about 85% of the pumps in this category.

Differing slightly in operation, most positive displacement pumps share a common trait: moving parts that come in contact with the material being processed. In diaphragm pumps, ball and check valves shift up and down, while progressive cavity devices feature rotors and stators. Despite mechanical differences, a source of concern connects the two types of pumps: whenever abrasive materials rub against moving parts, especially metal parts already rubbing together, the result will be substantial wear and tear.

SPX high-pressure hose pump & showingcutaway of positive displacement designThankfully, the SPX is one pump solution in the positive displacement pump category designed specifically with these abrasive materials in mind, whether as a hose pump or peristaltic pump. Peristaltic pumps address the two primary concerns associated with other pump types -- wear and tear, and clogging -- with a mechanism that's considerably different from other positive displacement pumps. The peristaltic design utilizes a rotor that remains outside the pumpage zone; thus, the pump's rotor never actually touches the product being moved. Therefore, rotor erosion is virtually non-existent.

"You wouldn't believe the damage we've seen some materials cause in the rotor," said Crimaldi. "There isn't a rotor on earth that can handle all the abuse our equipment faces. That's why the concept of keeping material away from the rotor is so critical -- it's the only way to virtually guarantee rotor life."

Another benefit, peristaltic pumps don't require expensive ancillary equipment -- no check valves, sealing water flush systems, or run dry protection. What's more, they're ideal for high-viscosity or shear-sensitive product, and are capable of processing abrasive slurries, corrosive acids, and gaseous liquids as easily as water. They can run dry indefinitely without damage and have only one wetted component -- the hose element. Consequently, there are no seals, ball-checks, diaphragms, glands, immersed rotors, stators or pistons to leak, clog, and corrode.

Operation of peristaltic pumps is elegantly simple. Fluid is drawn into a pump, trapped between two shoes or rollers (depending on the brand), and finally expelled from the pump. The complete closure of the hose, which is squeezed between a shoe and the track, gives the pump its positive displacement action, preventing backflow and eliminating need for check-valves when the pump isn't running.

According to Crimaldi, the choice of pumps was initially catalyzed by a few clear but hard-to-meet criteria once it became clear the peristaltic pump was ideally suited to the application.

"We were using other pumps but needed one that took up less space, was easier to maintain and provided the same performance for a lower cost," he said. "When we saw the SPX, it became evident very quickly that it would meet all our parameters."

Its compact size means less deck space required. It's less expensive, and maintenance is much easier. In fact, completely rebuilding one is a simple operation, requiring only draining of the lubricant, unbolting the flanges and replacing the old hose. And it's extremely easy to drain and winterize.

"The added space we get from the SPX is a huge advantage for our customers," said Crimaldi. "Plus, they have minimal downtime. Thanks to these features and others, feedback from customers has been extremely positive. Most times, frankly, we hear nothing about the pumps, which is the best indicator of all."

A critical design element of the SPX directly tied to its success is the pump's direct-coupled design. It combines the small footprint of close-coupled pumps with the reliability and ease of maintenance of long-coupled designs. Although close-coupled pumps are very compact, this out-of-date technology relies on the gearbox to seal the pump housing and support the heavy overhung load of the pump rotor. And while close-coupled pump companies offer optional long-coupled pumps to improve gearbox and bearing life, this comes at the cost of substantially increased footprint and added complexity of coupling alignment and maintenance.

"Close-coupled pumps and long-coupled pumps each have distinct disadvantages," said Crimaldi. "The direct-coupled design provides the benefits of each without any of the downsides."

Watson-Marlow's SPX 40 to 100 pump lineThe SPX direct-coupled design contains heavy duty rotor bearings within the pump rotor, eliminating any overhung load. Ultra-compact high-torque planetary gearing then aligns directly to the pump housing and is fully protected by an innovative buffer zone. Few if any other pumps achieve the same reliability, simplicity and compactness. And when a pump does need to be changed, it's a remarkably simple process.

"No pump lasts forever, even the SPX," said Crimaldi. "When our customers do have to change out a pump, it takes almost no time. The feedback overall on the SPX has been extremely positive. We've heard about no problems and, as I've mentioned, we have customers involved in some pretty challenging applications."

The machined hose element is the single most vital component for hose pump performance, durability and efficiency. To ensure perfect compression and consistent, reliable performance, SPX hose elements are manufactured from high quality compounded rubbers, reinforced with four individual layers of braided nylon and finished by high precision machining. Perfect compression eliminates slip which, in other pumps, can destroy shear sensitive product, reduce metering accuracy, or allow abrasive slurries to wreak havoc on wetted parts.

According to Crimaldi, Rig Source does offer other pumps on some of its drilling rigs. His preference for the SPX pumps, though, is obvious.

"In some applications," he said, "the SPX are right alongside other pump types, including progressive cavity. Our customers actually have a choice of which pump they want when they purchase a new or rebuilt rig. But I can tell you for a fact that the SPX pumps have fewer maintenance issues and simply outperform the others."

For him, the choice of the SPX pumps was an easy decision for a very tough application. IWW

About the Author: Chuck Treutel is marketing manager at Watson-Marlow Bredel Pumps, based in Wilmington, MA. Contact: 608-883-6851, [email protected] or www.watson-marlow.com

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