by Dale Evers, Pump Solutions Group
December 17, 2011

Critical design improvements enable the promise of sealless pump technology

Twenty years ago, the managers of a wide range of manufacturing and liquid-storage facilities predicted that the industry was about to enter “the age of the sealless pump.” With stricter federal emissions regulations set to be introduced in 1992, this would have been welcome news for those in the petroleum refining, petrochemical, gas processing and chemical industries in which the use of hazardous/toxic materials or other pollutants was prevalent. Faced with tighter control guidelines for these types of emissions, plant and storage-facility operators needed a pump technology that could deliver the environmentally-sensitive, leak-free operation that they demanded, while also addressing maintenance and cost concerns.

Exploded view of the improved sealless gear pump

Extensive documentation existed to support the thesis that sealless pump technology was the answer in these applications. For example, in June 1990, a management-consulting firm produced a report for a leading manufacturer of industrial gear drives, pumps and compressors that predicted, among other things, that:

  • The best available control technology (BACT) for most refining, petrochemical and chemical plants will be sealless pumps.
  • The chemical industry is moving to use sealless pumps at a faster rate than the petroleum industry.
  • The sealless market will be served two-thirds by magnetic-drive units and one-third by canned-motor units.
  • The long-term answer to the new federal regulations will be sealless pumps.
  • Sealless pumps will take an increased percentage of the market—probably 25 percent by 1995 and 50 percent by 2000.

A year earlier, a report titled “An Overview of BACT Guidelines for Centrifugal Pumps” was prepared by the South Coast (California) Air Quality Management District which noted the No. 1 BACT in terms of efficiency in controlling emissions in liquid-handling applications was sealless pump technology, which was “becoming increasingly important, especially in the handling of toxic and hazardous fluids.”

We now know that 1990 did not signal the beginning of the golden age of sealless pumps.

The technology—as it was designed and constructed at the time—was not reliable enough, with too many instances of failures that were brought about by bearing and load deficiencies that led to seal and leakage issues.

These deficiencies created an operational stigma that many manufacturers of sealless pumps are still trying to overcome today.

However after all that time, innovative sealless pump technology is available that eliminates the bearing and load concerns that affected the performance of traditional sealless designs.

This technology has the capability of creating a new category of sealless gear pump that not only eliminates leakage concerns that can compromise safety for both plant personnel and the environment but also allows the operator to move all types of liquids, from thin to extremely viscous and the hazardous to the benign.

This article will show how a fresh, clean-sheet approach to the conundrums inherent in traditional sealless pump design were confronted and led to the creation of a line of sealless gear pumps.

In short, these pumps increase product sealing reliability while eliminating the unacceptably high ownership, maintenance and environmental costs—as well as the reputational taint—that have dogged past sealless pump designs.

The Challenge

The leakage that occurs in traditional mechanically sealed pumps results in two types of prohibitive costs for plant operators: maintenance and environmental. According to the Hydraulic Institute, as much as 40  to 50 percent of the cost of owning a pump is spent after the pump is purchased due to maintenance issues. The leading causes of high maintenance in conventionally sealed pumps includes that associated with mechanical seal replacement and the premature wear of the bushings and close-fitting metal parts because of insufficient support of the pumping elements.

The environmental cost of leakage includes cleanup and potential local, state or federal fines that may need to be paid in extreme cases. Another non-monetary cost is the resulting bad press and community mistrust after a leak or accident occurs.

Leaks can create several costs:

  • Replacement of the raw materials that are lost and the finished goods that are damaged
  • Paying a firm to clean up the spill
  • Disposal of the material cleaned up
  • Potential slip-and-fall hazards
  • Environmental compliance fines and fees
  • Lowered worker morale
  • The need to replace workers who may choose to seek  employment elsewhere

As mentioned, any pump design that is deemed sealless must overcome the stigma that has been attached to the technology for more than two decades. In fact, while the reports cited above were trumpeting the use of sealless pumps, efforts began almost immediately to discredit the technology's effectiveness and reliability when handling hazardous or toxic materials.