Equipment Pumps

Pumps Unload FOG

EP Editorial Staff | June 1, 2023

Progressing cavity (PC) pumps provide sufficient transfer power to handle and store a variety of bulk liquid products, including diverse flow types, temperatures, and abrasiveness.

Fluid mixes of animal fat and kitchen oil are easily pumped from rail cars with progressing cavity pumps.

A major U.S. terminal operator, with a site located in the Gulf of Mexico region, required dependable transfer power to handle and store a variety of bulk-liquid products. Using progressing cavity (PC) pumps from NETZSCH Pumps USA, Exton, PA (, the facility now reliably unloads as many as 80 rail cars/day filled with a fluid mix of animal fats and used kitchen oils.

For many years, the company used gear pumps to handle petroleum, biofuels, commodity/specialty chemicals, and vegetable/tropical oil products produced by refineries and chemical plants. As oil prices strained the biofuel industry, the terminal operator was increasingly being asked to transfer fluid mixes of fats, oil, and grease (FOG) for which gear pumps were not designed.

The progressing cavity pump uses a metal rotor turning inside a rubber stator to better handle solids than metal-on-metal gear pumps.

PC pumps

The terminal operator contacted NETZSCH through one of its distributors, Voigt-Abernathy, to address the issue of unloading the FOG-filled rail cars which, in many cases, included solids such as chicken parts and other small items.

With engineering firm input during the design phase, it was concluded that a PC pump’s large cavities would better handle the mixtures. PC pumps have the capacity to convey viscous products temperature extremes (summer and winter) and when solids are present.

The pumps have technical features such as a sealed heavy-duty universal joint, extreme wear-resistant coating on the rotor, and a stator design that allows operation over a wide temperature range. Experts also provided on-site training for engineers and the maintenance crew.

The PC pumps offered several advantages over gear pumps that, in the early phases, were also considered for this application:

The low-speed capability of the PC pump and capability of conveying solids is significantly more productive for these applications while the total cost of ownership, considering future maintenance interventions, would be attained with the PC pumps.

The pump design, with a conical stator inlet, is an interference fit between the rotor and stator and can be operated bi-directionally (to aid pipe layout), which lowers the NPSHr value to only 1 ft.

A metal rotor turning inside a rubber stator offered an advantage over metal-on-metal gear pumps for handling solids.

For this project, the potential solids in the fluid were the major concern and a stator with NEMOLAST S261 was offered. This elastomer is a special BUNA-elastomer formulation that handles abrasiveness more efficiently. The pump manufacturer’s control of its state-of-the-art, in-house production of pump rotors, stators, and other major parts ensures that any component will perform with the same operational excellence when the pump is serviced in the future.

PC pumps transfer the material through 50 ft. of hoses on the suction side and much further on the pressure side to the storage tanks. If the material makes it into the cavity, the pump will operate effectively and efficiently.

Six pumps were supplied and installed. Five were complete pumps and one was a spare bare-shaft pump. The spare was installed as a backup should any of the operating pumps be down for maintenance. The pumps have been performing well since start up. EP

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