Food Engineering

Sine of the times

February 4, 2002
Lower maintenance, improved quality of finished goods realized from pump upgrade.


Powerful suction lift and pulse-free laminar flow are delivered by sine-wave pumps. Source: Sundyne Corporation.


Hoopeston Foods’Al Johnson (right) observes a sine-wave pump in operation at the Denver plant. The pump is transferring tomato-based sauce for tamales from a holding kettle through a metal detector. Source: Sundyne Corporation.

Sine-wave has been called the ideal waveform for the transfer of AC power, so it shouldn’t be too surprising that Hoopeston Foods Denver Corp. found sine-wave positive displacement pumps from Sundyne Corp.to be the ideal replacement for the rotary-lobe pumps to move pumpable products between cooking kettles and canning lines.

A copacker of more than 300 varieties of chili, stews, soups, tamales and other products, Hoopeston relies on batch processes to produce high-viscosity canned products.

With rotary lube pumps, “the company’s finished product all too often did not meet customer expectations,” recalls Al Johnson, the plant’s production manager. Impellers on the rotary-lobe pumps consistently sheared product. Pump cavitation occurred every few days, further contributing to product degradation.

Repair and maintenance were significant headaches, as well. By switching to sine pumps, quality improved and payback was achieved within a year.

Downtime and repair costs were a problem, with shafts requiring replacement twice a year, bearings every two to three months and seals and O-rings weekly.

“Ceramic seals, at $170 each, would occasionally be dropped and broken during daily cleaning of the pumps,” Johnson adds, “and when seals wore out, they would leak product on the floor, requiring additional clean-up time.”

Dairy Engineering Co. provided a MR-135 sine pump for fluid handling. The plant’s experience with that unit led to the purchase of four more as replacements for rotary-lube pumps as they wore out.

Introduced in the mid-1980s, sine pumps employ a sinusoidal rotor to create four symmetrical compartments in the pump housing. As the rotor turns, the compartments provide a positive displacement of product from suction to discharge. A sliding scraper gate inside the pump prevents discharged product from returning to the suction side of the pump. As a result, the pump’s volumetric displacement is constant, regardless of the rotor’s position. Pulsation and axial thrusting are eliminated because of the constant pressure, thereby extending the service life.

Major maintenance is performed once a year, compared to two annual overhauls with the old lobe pumps, he adds. Seal and O-ring replacement is much less frequent, and maintenance is easier, thanks to the accessible single shaft and single seal. There are no timing gears to set, parts stand up better to daily sanitation procedures and the cavitation problem of the old pumps has been eliminated.

“Customers no longer complain of damaged and cosmetically unappealing meats and vegetables,” says Johnson. “Foods now are gently passed through the pumps, compared to being torn apart and pushed through.”

Sundyne Corporation, 14845 West 64th St., Arvada, CO 80007