In Search of Middle Ground

Intermediate heavy-duty process pumps bridge the gap between expensive API pumps and less-sophisticated ANSI pumps in many flammable and hazardous applications

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Mitsubishi Polyester Film in Greer, S.C., has been using non-API heavy-duty, high-temperature process pumps successfully for many years. The pumps transfer Dowtherm glycol-water heat-transfer fluid through heat exchangers to stabilization systems for processing polyester-resin pellets. These pellets are sold to manufacturers that extrude them to produce plastic sheets for packaging applications.

Tom Caudill, staff maintenance engineer at Mitsubishi, says Dowtherm liquid is circulated through the system at about 536F. Mitsubishi has had 10 of these pumps in its stabilization unit for about six years, with five on-line simultaneously and five reserved for backup, according to Caudill.

As good as API pumps

Although the pumps at Mitsubishi are not true API-style pumps, they have provided the company with a performance comparable to that of API-610 pumps, at a substantially lower cost. Many factors are responsible for this successful track record, most of them focused on pump design and construction features that are similar to those of API-610 pumps.

For the most part, their lower costs are directly attributable to the elimination of testing, documentation, software and traceability requirements on the part of pump manufacturers. The new API-610 Ninth Edition fundamentally minimizes many of these previous requirements for those pump users who do not actually need them.

More choices

The original API standards were intended to establish a minimum set of mechanical criteria for refineries to enhance operating safety and reliability through the design and construction of more rugged, reliable pumps. Although the Ninth Edition calls out specific performance standard requirements, it includes two key statements that now permit user discretion with regard to pump selection.

Specifically, "Section 1 ," Scope" of the revised API standard ("centrifugal pumps for petroleum, heavy-duty chemical and gas industry services") ," is technically equivalent to International Standard Organization (ISO) 13709 and contains the following statement:

"Process and utility services exist within most facilities that do not require pumps of the robustness and intrinsic reliability of those covered in this standard. For such services that do not exceed ANY of the following limits, i.e., less rigorous services, the user may want to consider pumps designed in compliance with other standards such as ISO 5199 or ANSI/ASME B73.1M."

Many other organizations also are applying non-API pumps in flammable and hazardous service successfully and have been doing so for years. A word of caution: In the author's opinion, when employing non-API pumps in traditional API services, users should not over-specify construction, performance and software requirements in an attempt to obtain a pump with API characteristics at a lower, non-API cost.

Conclusion

The API-610 Standard Ninth Edition ," and the availability of many suitable pumps to meet its requirements ," gives chemical pump users the option to consider lower-cost alternatives. The intermediate heavy-duty process pumps also offer design, construction and performance advantages over ANSI-type pumps for many applications ," without the added expense of a virtually comparable API 610 pump.

D'Alterio works for the Dean Pump Div. of Met-Pro Corp., Indianapolis. Contact him at gdalterio@met-pro.com.

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