Pump It Up

Emerging technologies keep fluids in motion with lower maintenance and longer service lives

Paul Studebaker, editor in chief

It's not an easy thing to do in today's plant environment, but give it a shot. Kick back, put up your heels and think for a moment about the ideal pump. Imagine a strong, new machine smelling of fresh oil and paint, eager to be bolted up and start working on whatever fluid you have to move. Ponder its willingness to be forgotten and abused, yet serve trouble-free for years beyond its anticipated life.

What technological developments would be manifested in this wondrous engine of fluid motivation? Pump guru Bill McNally lists more than 50 specific features he'd seek at http://mcnallyinstitute.com/09-html/9-3.html. He and other experts emphasize high-performance seals, long-lasting bearings and advanced pump designs and materials, all properly matched to the application. Indeed, those are the areas pump-makers have been focusing their product developers on during the past several years.

Advanced materials at work
The past few years have witnessed an explosion in the performance and availability of ceramics, polymers, composites, exotic corrosion- and wear-resistant alloys and surface treatments originally developed for cost-is-no-object applications in aerospace, military and semiconductor fabrication. These materials underlie significant increases in maintenance intervals and service lives of many common pump components.

Not long ago, titanium was viewed as an unobtainable, exotic material for most industrial applications. Now the fall of the Iron Curtain and advances in refining and manufacturing technology have brought it into the mainstream. "There is plenty of excess worldwide capacity to meet demand," says Rick Porter, corrosion engineer, RMI Titanium, Niles, Ohio. "The Russians have no concept of supply and demand, they just make as much as they can."

"Titanium offers unique opportunities for many industrial applications," says Lev Nelik, president, Pumping Machinery (www.pumpingmachinery.com). "Among the highlights are elevated strength-to-density ratio, low densityroughly half the weight of steel, nickel and copper alloyswhich translates into significantly improved dynamics of titanium rotors, exceptional corrosion resistance excellent elevated temperature properties (up to 600F) and excellent properties at low temperatureASME allows using of Titanium Grade 1 and Grade 2 to -75F."

Where abrasion-resistant alloys and surface treatments were once reserved for rotating parts, Viking Pump, for example, now offers three hardened material options for high-wear stationary components on its abrasive liquid pumps (see Figure 1). New material options include hardened cast iron, austempered ductile iron and tungsten carbide-coated cast iron. Service life on highly abrasive liquids has been extended by more than 50%.


Figure 1: Hard case
In abrasive service pumps, wear-resistant materials once reserved for rotating parts are now being used for stationary components as well.

But most experts identify seals and bearings as the traditional limiting components when it comes to pump life and maintenance, and those areas are where advanced materials are making the most significant improvements.

Long live the seals
Process-pump sealing technologies continue to move from wet/contacting to dry-running designs. "Dry-running, non-contacting gas seals, common in compressors and turbines, are becoming more standard in process pump and slower-shaft-speed applications such as mixers," says Mike Kraus, market development manager, John Crane Inc. (www.johncrane.com).

In traditional seals, mating faces run against each other, resulting in friction and wear and requiring lubrication. Non-contact seals are designed with an engineered pattern on the face so one surface lifts off from the other. Air or gas forms the seal. Friction and its associated wear and heat are significantly reduced, which extends seal life for longer maintenance intervals.

These seals are effective even for highly regulated or hazardous fluids. "We continue to have increasing success using high-pressure gas seals and nitrogen gas to seal hazardous materials," says Tom Bennett, marketing manager, Flowserve (www.flowserve.com). "This approach increases mean time between failure and helps us reach our goal, which is to save customers downtime."

For dry-running seals, where faces are in contact and there is no fluid for lubrication, there are new materials and designs that reduce heat and wear. Some offer improved wear resistance for both wet and dry running and for unloading operations, for example, where there may be nobody there to turn off the pump when the freight car or tank is emptied.

In one example, the traditional soft face/hard face combination (i.e. carbon graphite/silicon carbide) is being replaced with designs where both faces are made of the same silicon carbon/graphite composite, which combines the lubricity of carbon graphite with the wear resistance of silicon graphite. The result is a seal with improved abrasion resistance and dry-running capabilities.

In another application, seals made of a sintered composite of silicon carbide and graphite were able to withstand five hours of dry running on an agricultural chemical pump. "Over 100,000 pairs of seals based on this new material have been supplied for the past two seasons for many tough applications, including trailer-mounted pumps," says Joseph Boylan, vice president, market engineering, Morgan AM&T (www.mamat.com). "And, according to the users, not one seal has yet failed," he adds.