Machine Design

The pumps that could, and did

In 1971, when I was starting my first job in the gear-pump business, among the helpful advice offered by the old timers was that gear pumps would one day be obsolete, and I would be smart to build a career elsewhere.

Robert Dolwick
Parker Hannifin Corp.,
Gear Pump Div.
Youngstown, Ohio

Today, I'm still in the gearpump business, and it's a good business at that. It's not so much that my colleagues were wrong back then. Pumps of that vintage are, for the most part, obsolete. And gear pumps as a technology never were all that bad to begin with. What they didn't foresee were the significant engineering and manufacturing advances over the last 35 years that have steadily improved both the performance and economics that keep the humble gear pump competitive.

Today, the likes of Caterpillar, Volvo, JLG, and many others use gear pumps for critical applications. In fact, some have even switched back to gear pumps after trying other, more "modern" solutions that failed to deliver as promised. How did all this happen to a technology widely believed headed for the scrap heap just a few decades ago?

Part of the answer is that modern CAD technology has revolutionized gear-pump design, making today's products smaller, more efficient, and orders-of-magnitude more reliable. The industry's most advanced versions, dual flank and split gear, owe much of their development to CAD and CAE systems that simply weren't available back then. Neither were the specialized CNC machining centers or hobbing machines that make the complex, computer-designed contours of the housings and generate the gear-tooth profiles.

These manufacturing systems hold tolerances so tight that we couldn't even measure them on a production basis in the '70s, let alone maintain them over a whole production run. And, we know they're doing the job because we watch cpK and Six Sigma deviations to control the processes. Again, technologies nobody knew much about 35 years ago. Steady improvements in materials, surface finishing, heat treating, bearings, and seals have further boosted pump performance.

But let's be realistic: a gear pump is not the right technology for every customer. However, there are situations where a geartype pump is the best choice. Many of these applications are on vehicles of various kinds where compact size, high power density, and reliability are key metrics, all strong points of gearpump technology.

Nothing stands still and gearpump technology is no exception. Today's gear pumps are miles ahead of those made 35 years ago, and tomorrow's will be even better.

Parker Hannifin ( is a maker of industrial automation equipment.

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