Low shearing and self-priming make this technology ideal for chemical, oil and food applications.
by Paul Cardon
Eccentric disc pumps consist of a cylinder and pumping element mounted on an eccentric shaft. As the eccentric shaft is rotated, the pumping element forms chambers within the cylinder, which increase in size at the intake port, drawing fluid into the pumping chamber. The fluid is transported to the discharge port where the pumping chamber size is decreased. This action squeezes the fluid out into the discharge piping.

In contrast with other pump technologies, the eccentric disc design enables self-priming, which ensures strong suction even after the pump runs dry. When other pumps run dry, they continue to operate even after the material has been transferred to clear the lines. As a result, the pump’s components can potentially burn and seize, resulting in costly damage to the pump internals. Eccentric disc pumps, by comparison, have the ability to run dry for a limited time without the risk of pump damage.

The eccentric disc design also ensures gentle product handling with low shearing and has the ability to self-compensate for mechanical wear, guaranteeing consistent flow rates over time. Petit’s eccentric disc pump design features high vacuum and compression effects for strong line-stripping ability and a reduced number of components for quick and easy disassembly and reassembly. The eccentric disc principle allows these pumps to continually run in reverse, which enables the back pumping of liquids.

International Expansion
While eccentric disc pumps offered the gentle handling, reliability and operational efficiency needed on a global landscape, the technology remained relatively unknown outside Europe. Launched in 1965, a series of eccentric disc pumps quickly built a reputation for robustness, delivering up to 40 years of virtually maintenance-free service in some of the most demanding applications in the chemical, food and oil industries. For years, the pumps remained a Western European technology. Technological advancements in evolving industrial applications necessitated design enhancements, and those design enhancements have enabled the pumps to enter the international market.

To prepare these pumps for use in global markets, a critical modification was made to the pumps’ flanges. Previously only available with non-standardized flanges, their new design was equipped with ISO PN16/ANSI 150 flanges. Using flanges certified by the International Organization for Standardization (ISO) and American National Standards Institute (ANSI) enables the pumps to meet all applicable global operating standards.
Another critical part was the pumps’ mechanical seals. The mechanical seal is positioned behind the piston to provide shaft sealing. Previously, operators could only use the pumps with specific mechanical seals, but they can now be equipped with standardized seals. This helps expedite installations because end users no longer have to wait for the delivery of specialized seals.

From a performance perspective, the redesigned pumps have doubled their maximum differential pressure from 5 bar (73 psi) to 10 bar (145 psi), allowing them to be used in many new applications. The pumps are now available in ductile-iron construction. Previously, they were available in cast-iron construction only. This material enhancement is critical because more companies in the petrochemical industry are moving away from cast-iron construction.
The redesigned pumps enable product transfer up to 150 C (302 F) and the use of heating or cooling jackets with products that can solidify at ambient temperatures. The pumps are ATEX-certified and can run dry for up to three minutes in potentially explosive environments.

True greatness can be achieved by pursuing a dream that no one else can see. Andre Petit chose to pursue greatness and designed the eccentric disc principle in pump operations, a technological development that provides efficiency, reliability and durability. The technology improves end users’ liquid-handling operations and gives them peace of mind.