If you were an industrial pump, chances are you would not want to be used in the environmental and geotechnical drilling industry. That’s because there are few applications 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 ground water, divert contaminated ground water from the drinking water intake, direct uncontaminated ground water flow, and provide a barrier for the ground water treatment system. The slurry, usually a mixture of bentonite and water, is pumped into the trench, which prevents the native soil from caving into the excavation.

Pump clogging

Even heavily diluted, the bentonite-water concoction is extremely viscous and can not only clog the pump, but can also significantly shorten the pump’s useful life.

Mike Crimaldi understands the difficulties associated with pumping bentonite as well as anyone. His company, Rig Source Inc, is dedicated to assisting drilling contractors with a wide range of support services, including new- and used-equipment sales; equipment rental, maintenance and repair; and a full range of drilling supplies.

Having spent the past 25 years working in the drilling industry himself, the founder and president of the Elburn, Illimois, USA- based Rig Source is also well-versed in the abuse that the pumps installed on many of his drilling equipment must withstand.

"The pumps on our equipment are used to process a wide 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 that the pump is capable of handling the specific fluid or material that the customer will be working with. If not, the entire job can go south in a hurry."

For this very reason, Crimaldi relies heavily on SPX High-Pressure Hose Pumps from Watson-Marlow Bredel, the world's largest manufacturer of hose pumps with over 75000 positive displacement hose pumps in operation. The SPX pumps are used as primary and secondary fluid pumps for drilling and grouting. They are found more often than not assembled on the company’s Diedrich D50 and D120 drill rigs, which are used mainly for auger drilling and, occasionally, soil sampling.

Crimaldi’s choice of Watson-Marlow Bredel is no mystery, given his familiarity with the company’s products during his days in the field as a drilling contractor. And given the overall performance and advantages of the SPX, Crimaldi’s satisfaction with its performance is no mystery either.

To begin with, the category of pump in which the SPX resides (positive displacement) is highly favourable versus other pump types. They are typically used for moving viscous and corrosive fluids or, due to their slow-moving, smooth action, sensitive materials that require gentle handling. Within the realm of positive displacement pumps, there are various types: diaphragm pumps and progressive cavity pumps make up approximately 85percent of the pumps in this category.

While they differ slightly in operation, most positive displacement pumps share one thing in common: 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 their mechanical differences, one source of concern connects the two types of pumps: every time abrasive materials rub against moving parts, especially metal parts that are already rubbing together, the result will be substantial wear and tear.

Abraisive materials

Thankfully, the SPX is one pump solution in the positive displacement pump category designed specifically with these abrasive materials in mind. As a hose pump, or peristaltic pump, the SPX stands head and shoulders above other positive displacement technologies. Peristaltic pumps address the two primary concerns associated with other pump types – wear and tear, and clogging – with a mechanism that is considerably different from other positive displacement pumps. The peristaltic design utilises a rotor that remains outside the pumpage zone; thus, the pump's rotor never actually touches the product that is being moved. Therefore, erosion of the rotor 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 that our equipment faces. That’s why the concept of keeping the material away from the rotor is so critical – it’s the only way to virtually guarantee rotor life."

High-viscosity

In terms of benefits, this is barely the tip of the iceberg. Peristaltic pumps don’t require expensive ancillary equipment – no check valves, sealing water flush systems, or run dry protection. What’s more, they are suitable 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.

The 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 the need for check-valves when the pump is not running.

Once it became evident that the peristaltic pump was ideally suited to Rig Source's applications – and given Crimaldi's connection to Watson-Marlow Bredel – the only decision left was which model to select.

According to Crimaldi, the purchase of the SPX pumps was initially catalysed by a few clear but

hard-to-meet criteria.

"We had been using other pumps, but we needed a pump 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 of our parameters."

The compact size of the SPX means that less deck space is used. The pumps are less expensive, and maintenance is much easier. In fact, completely rebuilding an SPX is a simple operation; all that is required is to drain the lubricant, unbolt the flanges, and replace the old hose.

In addition, the SPX pumps are extremely easy to drain and preparted for winter.

"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, the 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 that is directly tied to its success is the pump's direct-coupled design. The SPX combines the small footprint of

close-coupled pumps with the reliability and ease of maintenance of long-coupled designs. Although

close-coupled pumps are extremely 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 the 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."

The SPX direct-coupled design contains heavy duty rotor bearings within the pump rotor, eliminating any overhung load. Ultra-compact SPX high-torque planetary gearing then aligns directly to the pump housing and is fully protected by an innovative buffer zone. No other pump achieves the same reliability, simplicity, and compactness as the SPX.

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 who are involved in some pretty challenging applications."

Perfect compression

The machined hose element is the single most vital component for the performance, durability, and efficiency of the hose pump. To ensure perfect compression and consistent, reliable performance, Watson-Marlow Bredel manufactures hose elements 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, the company does offer other pumps on some of their drilling rigs. However, his preference is for the SPX pumps

"We also use the SPX along with some other pumps," he said. "In some applications, 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."

For more information, visit www.watson-marlow.com