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What the future holds for magnetic drive pumpsThe push for cleaner air was the catalyst to a magnetic drive revolution in the United States pumping industry, but cleaner air is not all these pumps have to offer. Keith Thompson of Sundyne Corporation explains how the magnetic drive pump gained a strong foothold in the process industries and what’s next on the cards for this environmentally sensitive machine.

Magnetic drive pumps have come a long way since their introduction in the 1940s.

Although early designs were somewhat special and limited in capability, industrial users found magnetic drive technology to be very attractive for solving problems associated with leaky seals in services such as lethal chemical and hot oil transfer. After years of evolutionary development, current magnetic drive pump designs conform to industry standards and have vastly increased application capability. More significantly, in many process plants, the technology continues to drive the paradigm shift away from conventionally sealed pumps to sealless pumps

Compelling need

Magnetic drive technology has been available for many years, but the mainstream popularity of magnetic drive pumps did not come about until the 1990s. It was at this time that one key event, the passage of the US Clean Air Act, thrust magnetic drive technology into the limelight. The US

Clean Air Act was enacted to control pollution into the environment. Among other pollution sources identified in the act, conventionally sealed pumps were listed as a major contributor to air pollution. With conventionally sealed pumps, small amounts of chemicals, known as fugitive emissions, leak into the surrounding environment. Many countries had enacted laws to control emissions in the 1980s, but it was not until 1990 that the US followed suit. Subsequent amendments to the Clean Air Act promised steep fines, expensive monitoring, and complex reporting procedures for sealed pumps.

For the US chemical processor, the need to find an alternative to sealed pumps became compelling. Pump manufacturers around the world responded to this need with sealless technology, both magnetic drive and canned motor, because sealless pumps were exempt from the cumbersome requirements of sealed pumps.

The growing demand for magnetic drive pumps during this period was also accompanied by many

technological improvements in both bearing materials and magnet strength. These improvements enabled pump manufacturers to expand their offerings into larger pump sizes with greater horsepower capability. However, the most significant effect of the technological advances was that manufacturers were able to offer magnetic drive pumps in compact sizes that were dimensionally interchangeable with the conventional ANSI sealed pumps that were the workhorse of the chemical process industry. The flange-to-flange interchangeability with ANSI pumps enabled even more users to take advantage of sealless technology without expensive piping changes. Subsequently, the American National Standards Institute (ANSI) recognized the more widespread demand and application of magnetic drive technology when it published the B73.3 Standard for magnetic drive pumps in 1997.

A new realization

Many magnetic drive pumps were purchased and installed in anticipation of ever tightening emissions requirements. Over time, it became apparent that enforcement of the new law was being handled inconsistently. Individual state laws had different interpretations of the pollution control requirements, and enforcement varied greatly and was generally less pervasive than originally anticipated.

But during this period driven by legislative compliance, companies began to realize that in addition to the avoidance of fugitive emissions, and the associated fines and monitoring costs, magnetic drive pumps provided greater reliability and a smaller overall life cycle

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Figure 1. The components of a Sundyne Ansimag sealless non-metallic magnetic drive pump.

Shaft support/Thrust ring

O-ringOutermagnet

Close-coupledadapter

Driver

Driver frame

Rear casing/Rear casing supportImpellerCasing

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cost than many of the pumps they just replaced. With magnetic drive pumps, companies could not only be safer and more environmentally responsible, they could save money too.

While magnetic drive pumps are now accepted by many of the world’s largest companies, there are still many who have yet to explore their benefits. Much of this hesitation may be due to old misconceptions regarding pricing, a steep learning curve for operating the pump correctly, or horsepower and hydraulic range limitations. The reality of the situation, however, is that modern magnetic drive pumps can economically meet nearly every process pumping condition’s needs without requiring any special operating procedures. Demanding process conditions, such as temperatures of 850 F, system pressures exceeding 3,000 psi, and power requirements in excess of 500 hp, can all be handled with magnetic drive pumps.

Recognizing a need for a sealless pump specification for heavy-duty services in refineries and related industries, the American Petroleum Institute (API) introduced the API 685 standard in 2000. API 685 was based upon the widely specified and popular API 610 standard, which provides guidelines for the design and construction of conventionally sealed pumps for heavy-duty services. API 685 not only provided further credibility to the advancement and application of sealless pump technology, it also brought sealless technology further into the mainstream of pump specification and selection. Today, because of API 685, magnetic drive pumps are successfully being used in refineries for heat transfer fluids, acids, caustics, aromatics and sour water.

Outside of the chemical and hydrocarbon processing industries, where service temperature or pressure is not so severe, magnetic drive pumps have found growing acceptance as new, non-metallic materials have further lowered the total cost of ownership. Magnetic drive pumps lined with fluoropolymers such as ETFE or PFA have proven to be a cost effective alternative to higher alloy metallic designs in highly corrosive applications. Non-metallic containment shells, the fluid-containing barrier within

the magnetic coupling, do not have the energy consuming “eddy-current loss” characteristics of their metallic counterparts, enabling a more energy efficient pump design. As energy costs continue to rise, pump efficiency has become an ever more critical decision criterion in the selection of pumps. Non-metallic containment shell designs have enabled magnetic drive pumps to compete with conventionally sealed pumps on an equivalent efficiency basis. Consequently, users have adopted non-metallic magnetic drive pumps as standard technology for services such as sulphuric and hydrochloric acid, sodium hydroxide, and sodium hypochlorite.

Reliable operation

The application of magnetic drive pumps has dramatically expanded as pump users have also been attracted to the pump’s simplicity and overall reliability. Simplified designs and years of maintenance free operation have led to the realization that magnetic drive pumps can be the most reliable pumping solution. A major consideration in overall reliability is the ability of the pump to withstand process interruptions or upsets that might lead to dry run operation. In dry run operation, the pump does not receive the fluid necessary to provide adequate bearing lubrication and heat removal. Over the years, magnetic drive pump reliability has increased as manufacturers have experimented with new materials that possess some dry running capabilities, and end users have adopted pump monitoring as a key strategy to improve total system reliability. Monitoring magnetic drive pumps is typically simpler than monitoring most conventional pumps with complex seal plans. One simple, inexpensive, and easy to operate power monitor is all that is usually needed to protect against the

vast majority of pumping conditions that might lead to pump failure.

Beyond acceptance

Whereas seal failure, leakage, and legislative action were once, and still are, primary drivers for the adoption of magnetic drive pump technology, the overall reliability and cost of ownership have become equally powerful drivers for its acceptance. There is little doubt that with all the growing attention over global warming and other environmental concerns, the emission-free aspect of magnetic drive pumps is likely to continue to gain momentum and become a larger factor when specifying pumps. Nevertheless, it is even more likely that the ever-widening acceptance of magnetic drive pumps – in areas far outside the pollution control arena – will be a significant driver of this technology in the future. More recently, standard industrial and municipal industries that treat water and wastewater are utilizing magnetic drive pumps for chemical transfer and scrubbing. Agricultural companies involved with ethanol and biodiesel and other processing have adopted these pumps to control their operating and maintenance costs.

Customer feedback data suggests that most companies that try magnetic drive pumps continue to use them and even expand their application within their plants. Manufacturers have responded to this need by expanding hydraulic coverage and adding positive displacement, self-priming and vertical pump designs to their magnetic drive pump catalogues. As pump manufacturers continue to develop and expand their magnetic drive pump capabilities in response to customer driven needs, the technology will continue to attract new fluid transfer uses as it moves beyond acceptance and fuels the paradigm shift towards sealless pumps as the preferred technology for the future. ■

CONTACTKeith Thompson Ansimag business development manager Sundyne Corporation 14845 West 64th AvenueArvada, CO 80007Tel +1 303 425 0800E-mail: kthompson@sundyne.comwww.sundyne.com

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Figure 2. Sundyne HMD/Kontro sealless magnetic drive metallic pumps.