How this positive displacement technology improves energy efficiency and production rates.
by Mark Pyk
December 12, 2018

The need for more industrial operations to satisfy the demands of a constantly growing population can collide with edicts that manufacturers reduce their utility and overall operating costs while simultaneously operating in a more environmentally friendly manner. This has forced operators in the industrial sectors to reconsider the types of equipment they have been using in their facilities and operations, with an eye on upgrading to systems that can reliably provide both environmentally safe and cost-effective production.

A Positive Outlook

First, a bit of background. Positive displacement (PD) pumps were developed long before centrifugal pumps. Greek mathematician Archimedes is said to have invented the first screw pump around 225 B.C. The operation of PD pumps is signified by the displacement of a known quantity of liquid with each revolution of the pumping elements, which can include vanes, lobes, gears, rotors, screws, etc.

The liquid is displaced through the spaces that are created between the PD pump’s specific pumping elements. After the liquid is collected in this space, the movement of the pumping elements transports it to the discharge port. In general, this method of operation allows PD pumps to handle liquids with viscosities up to 1,320,000 centistokes (cSt)/6,000,000 Saybolt Seconds Universal (SSU); capacities up to 1,150 cubic meters per hour (m3/hr) or 5,000 gallons per minute (gpm); and pressures up to 700 bar or 10,000 pounds per square inch (psi).

a chemical processing facilityImage 1. The operational and energy-efficiency capabilities of positive displacement sliding vane pumps, like those seen above in a chemical processing facility, can help operators successfully overcome processing issues. (Images courtesy of Blackmer)

Today, according to the Hydraulic Institute, pumps account for nearly 27 percent of total electricity use in the industrial sector. While centrifugal-style pumps remain the most-used technology in industrial fluid-handling applications, there is no “one pump fits all” solution. This opens the door for operators to consider the benefits PD pumps can offer from an efficiency and energy-savings perspective, even in applications that have traditionally relied on centrifugal pumps.

When making the final choice in pump type, several crucial factors need to be taken into account, including required flow rate, suction and differential pressure, temperature, viscosity, weight and corrosiveness of the liquid being handled. In addition, facility managers too often choose oversized pumps as a fallback under the erroneous belief that such equipment will address future capacity needs.

These decisions ignore the added energy costs that are inherent in continuously operating oversized pumps.

A mechanical efficiency comparison between sliding vane and gear pumpsImage 2. A mechanical efficiency comparison between sliding vane and gear pumps shows that from the lowest to highest viscosities, sliding vane technology delivers the highest level of mechanical efficiency, which equates to the lowest overall energy consumption.

While the majority of the world’s pumping tasks may be performed with centrifugal-style pumps, PD pumps can become a top-of-mind choice when facility operators are apprised of the functionality PD pumps can offer users, including: