Food Engineering

Dairy Plant Combines New Capacity With Southern Hospitality

March 27, 2003
Mayfield Dairy Farms' new $18 million, 91,000 sq.-ft. plant on a 20-acre site at Braselton, GA -- 40 miles northeast of Atlanta --adds fluid milk capacity needed to better supply Mayfield's fast-growing markets in Georgia and the Carolinas, and can be easily expanded to serve those areas well into the 21st century.

With capacity to process up to 700,000 gallon of milk per week, the facility supplements Mayfield's Athens, TN, plant -- which had reached full capacity -- and easily accesses company markets ranging south to Macon, GA, and north to Asheville, NC.

The new plant also caters to consumers by hosting public tours through a wide-windowed central hall overlooking operations. Tours start and conclude in a rustic, 4,700 sq.-ft. visitor's center which includes a theatre, ice-cream shop and gift shop.

The building was designed by McClellan & Associates and built by Suitt Construction Co., with process engineering by Mayfield, parent Dean Foods Co. and Tetra Pak. Process design incorporates new technologies such as PMO-compliant mixproof valves, microwave tank-level detectors and optical color sensors. The mixproof valves boost flexibility by allowing simultaneous flow of product and CIP (clean-in-place) solution across the ports, reducing CIP turnaround time and product loss during changeovers. Optical sensors measure solids in CIP flow to reduce BOD (biological oxygen demand) loads to the wastewater pretreatment facility.

The plant manufactures four products: whole milk, 2 percent and skim in gallon and half-gallon blow-molded yellow-plastic jugs plus half-pint gable top cartons for retail markets, and 1 percent chocolate milk in half-pint cartons for institutional and school lunch markets. Eighty-six employees operate the plant, receiving milk seven days per week, producing bottled milk on one 10 to 12 hour shift and cartoned milk on two eight to nine hour shifts four days per week, and loading-out five days per week. Forty employees work in distribution.

Started-up in September 1997, the plant was selected as a runner-up in Food Engineering's 1999 New Plant Of the Year competition.

Construction & sanitation

Process flow is linear from receiving to loadout, with process operations separated from support spaces by the central hallway to minimize the possibility of cross-contamination. Piping and electrical systems are accessed from the second floor of the service core and "walk-on" ceilings over process areas. All equipment is made of stainless steel mounted eight inches above dairy-brick floors for easy washdown. Interior walls are covered with tile and insulated metal panels; doors and frames are made of fiberglass.

Team organization

Employees are organized into eight teams: a management team headed by Plant Manager Valerie Meyers; two production teams, including a process/lab team and a blow-molding/filling team; a sanitation team for night cleanup; two cooler teams which handle loadout and case return; a maintenance team; and a visitor's center team.

Prior to startup, employees were trained in both social and technical skills, says Plant Engineer Mark Howard. Initial training in "soft-skills" such as team organization and problem-solving was conducted by consultants Novomont Corp. and Creative Concepts International. Training in specific plant equipment and process controls was conducted in vendor workshops at Lanier Technical Institute in Gainesville, GA, by experienced operators at Mayfield's Athens plant, and by Mayfield operators and Dean Foods engineers on-site at Braselton. The Georgia Department of Technical & Adult Education, through its QuickStart program, helped fund classroom training at Lanier and production of SOP (standard operating procedures) manuals.

Production teams are gradually assuming more decision-making authority as they gain experience, says Howard.

Process profile

Thirteen functional sections -- such as receiving, CIP, processing, utilities, blow-molding, material handling, filling, waste-treatment -- are each controlled by one of four Allen-Bradley SLC 560 area PLCs and some of 14 operation-specific PLCs via 23 operator control stations. All pumps and major equipment are controlled either through variable-frequency drives or soft-start motor starters located in mezzanine motor control rooms.

Receiving: The receiving station can accommodate two 6,000-gallon tankers simultaneously. After checking temperature, raw milk is routed via Tri-Clover centrifugal pumps, Foxboro magnetic flow meters and APV mixproof valves to one of three 50,000-gal. Walker silos equipped with Endress + Hauser microwave level detectors. (Mixproof valves eliminate the need to disconnect hoses for tanker CIP.) Samples routed to the plant's lab are tested for water, fat and solids content, as well as for pH and antibiotics.

Processing: Raw milk is pumped from silos to the balance tank of a Tetra Laval pasteurizer, which operates at a flow rate of 120 gpm. After preheating in the regeneration section, milk flows through a Tetra Laval separator and cream is added back to the skim milk to achieve the desired fat content. The blended milk then moves through a Waukesha Cherry-Burrell vacuum chamber (to remove air and off-flavor essences), an APV homogenizer, is pasteurized at 175¿ F for 30 seconds, cooled to 35¿ F and routed to one of four 20,000-gallon pasteurized milk silos. Excess cream is returned to one of two 8,000-gallon cream silos. For chocolate milk, magnetic flow meters control a variable-speed pump which proportions chocolate mix to milk in-line ahead of the vacuum chamber. Sprinkman CIP systems sequence cleaning solutions formulated with Ecolab sanitizers.

Filling & casing: Two Uniloy blow molders supply 4,200 gallon-size plastic jugs per hour via conveyors from the blow-molding room to the filling room, where they are labeled on Superior equipment, filled at a rate of 6,600 gph on a 30-valve Federal rotary filler and capped on a 12-head Federal closure machine. Half-gallon bottles, purchased by Mayfield, are filled on another rotary filler at a rate of 9,600 per hour. A four-lane Evergreen machine with capacity of 20,400 units per hour fills half-pint cartons. To minimize the possibility of cross-contamination, filled containers are conveyed through a wall to case packers outside the filling room. Cannon casing equipment loads jugs into plastic cases. Half-pint cartons are conveyed in two lanes to a Cannon caser which packs 50 cartons per plastic case.

Suitt Construction Co., P.O. Box 8858, Greenville, SC 29604. Tel.: (864) 250-5000; Fax: (864) 250-5101