Chances are, the pork sausage on your breakfast plate came home from the grocery store frozen. And if it is one of the big-name brands, chances are equally good that it was not processed by the company whose name is on the package. Instead, it was likely processed by a co-packer — a company that specializes in that particular product.
One of the larger co-packers in the Midwest produces tons of frozen pork sausage every day in a continuous process that includes blending the meat and spices, stuffing the casings or forming the patties, cooking the sausages and, finally, freezing the ready-to-eat product. That final critical step is accomplished in a sophisticated waterfall pouch chiller using a food-grade propylene glycol/water mixture at -5°F (-20°C).
Because the glycol/water mixture comes into physical contact with the product — and because nothing is perfect, including packaging — the chiller is equipped with bottom-mounted screens. The filters catch any bits of sausage or packaging materials that may get into the liquid and keep them out of the heat exchangers. This function is critical to the process because the glycol/water mixture must be maintained within a narrow temperature range to meet strict food safety regulations.
If the screens get clogged, the flow of glycol/water through the heat exchangers is reduced, and the temperature in the processing area rises. If the temperature exceeds food-safety guidelines, then the entire batch of sausage — and the potentially contaminated glycol/water mixture — would have to be entirely discarded. (If damage was minor, the product might be “reworked.”)
“That happened two or three times a year, on average,” explains Jeff Simpson, a fluid process and industrial wastewater engineer at Crane Engineering in Kimberly, Wis. “The cost of replacing the process fluid alone was about $20,000 per incident. Over and above that, maintenance costs were running in the $40,000 to $60,000 range per year, and they still weren’t preventing the overtemperature incidents.
“The customer was walking a fine line between the cost of labor and downtime to clean the screens and sumps, and the cost of lost production when the chiller was out of operation while [the screens] were being cleaned,” he says. “They clearly needed a better solution, so they invited us to their facility to review the process and make a recommendation.”
While the situation clearly called for a more effective filtration system, handling the 1,000 gal/min flow of glycol/water through the system presented an unusual challenge. That task was made even more difficult by the customer’s request for a solution that did not require the system to be shut down for filter maintenance.
The standard alternatives were:
- A multi-filter system with enough extra capacity to handle the flow while one of the filters was offline for maintenance.
- A self-cleaning filter that did not require downtime for maintenance.
While the self-cleaning filter offered significant cost benefits, the volume of glycol/water that needed to be filtered was greater than the capacity of then-available standard models.
“We decided to pursue the self-cleaning alternative,” Simpson continues. “To prove the concept, we installed an Eaton DCF-800 self-cleaning filter on a side-stream. That particular filter is rated for 60 gal/min. In several months of operation at maximum flow, it never clogged or required any maintenance.”
The filter consists of a cylindrical stainless steel housing that holds a filter media. Fluid enters inside the element and flows through it to the outlet, depositing any contaminants on the inside wall of the element.
A spring-loaded cleaning disc moves up and down, wiping the filter element clean and depositing the contaminants at the bottom of the housing, out of the flow path. Cleaning frequency can be based on time, differential pressure, manual selection or any other application-specific criteria. Because it remains in service while being cleaned, the filter satisfied the co-packer’s no-maintenance-downtime requirement.
“With the concept proven, the next hurdle was finding a self-cleaning filter with enough capacity to handle the full 1,000 gal/min flow of glycol/water in the system,” Simpson says. When the filter manufacturer added a larger version of the filtration system to its line, the co-packer could be outfitted with a filter sized for its production flow rate.
Crane was able to procure one of the first larger filters produced, and the company installed it in the co-packer’s chiller circuit. The stainless steel filter is rated at 1,100 gal/min while filtering up to 100 microns. It can be equipped with slotted-wire strainer elements ranging from 50 to 1,140 microns to meet a range of application requirements.
The unit installed on the co-packer’s chiller uses a 75 micron strainer to provide minimum flow restriction. The output then is routed through a stainless steel bag filter housing with a 10 micron needle-felt bag filter for the final cleaning before the glycol/water mixture enters the heat exchanger.
“The first Eaton DCF-3000 filter ran for 3.5 years with no maintenance and no downtime,” Simpson says. “The customer still uses the screens at the bottom of the chiller to backstop the system, but they no longer plug up because the [filtration system] keeps the entire glycol/water stream so clean.”
Simpson added that the co-packer has installed similar filtration systems in two of their other packing plants. With reduced downtime helping ensure full production output, that breakfast sausage you like so much is just a trip to the grocery store away.