Tray-packing sates school lunch crunch

The Clark County School District (CCSD) in Nevada serves a large and growing number of students lunch every day, providing breakfast as well to a large percentage of the student population. Currently, the district produces about 32 million meals each year. That number is growing at the rate of 2 to 4 million a year as the county, which contains booming Las Vegas, continues to add more to its population.

Those meals are prepared in a central kitchen and packaging facility that incorporates a high-speed packaging line rivaling those of major food packagers in speed, volume and complexity. That is why CCSD and other large school districts with central lunch facilities—in Pittsburg; Flint, Michigan; and Los Angeles, for have turned to Food Equipment Manufacturing Co. (FEMC) [www.femc.com]) to create customized systems that meet their individual needs.

“In addition to expertise in packaging machinery,” notes CCSD foodservice director Charles Anderson, “We needed a company that was accustomed to dealing with large organizations, high-speed production and complex systems.”

Planning for growth

In the 1970s, CCSD was already producing school lunches in a central kitchen and packaging them by hand in a 5,000-sq-ft facility. By 1996, administrators saw the demand that was coming as Las Vegas/Clark County's accelerated growth began. Clearly, packing lunches manually in a cramped facility would not be adequate to meet future needs.

Continuing to pack lunches by hand would mean a sizable workforce. To avoid that, it became critical to install an automated packaging line.

There followed an extended period of planning and subsequent readjustment, as accelerating population growth continually changed the project's requirements.

FEMC was chosen as the primary supplier based on its history of designing and manufacturing high-speed automated packaging lines for large food companies and its experience with Heinz, Nestlé, General Mills and Kellogg.

Anderson says CCSD worked closely with FEMC, designing and revising a packaging system that could meet such changing requirements. Points out FEMC sales manager Dan Auvil, “One advantage is that the system could take advantage of some of the latest developments in servo-motor technology. As a result, the system combines servo-driven elements with mechanical drive systems, which results in more precise control than we could have achieved with mechanical systems throughout.”

Adds Anderson, “FEMC also took on the role of project manager, sourcing the elements of the system they did not manufacture themselves. This was a turnkey operation, including installation, startup, on-site training and ongoing maintenance.”

The filling operation

The filling and packaging line incorporates most of the operations found in a comparable line at a food-manufacturing plant, including denesting, multiple filling stations, heat sealing and metal detection. Not included are the coding and marking systems required of packaged foods entering the retail food chain.

In place of the palletizing and stretch wrapping of a conventional manufacturing operation, an automated basket loader places filled, sealed trays into stainless-steel wire baskets for easy handling during delivery to the various schools.

The line operates on a 55-ft, dual lane FEMC conveyor that extends through to tray denesting, filling and sealing operations. It begins with two types of denesters: two FEMC Eccentric Peel denesters that can drop paperboard trays (used for hot foods) on the conveyor belt and dual universal-screw denesters that handle plastic trays (used for cold products such as breads, fruits and salads) that vary in configuration, depending on the contents. This dual setup enables the line to fill both types of trays interchangeably, without the need for time-consuming changeovers.

The filling station on the line begins with two FEMC Angular Dial Volume Accurate™ fillers that dispense uniform-sized particulate or IQF (Individually Quick Frozen) products into trays. The trays are next fed from a single overhead hopper continuously filled by a KLEENLine (www.kleenline.com) inclined conveyor before a Grote (www.grotecompany.com) pendulum slicer cuts the sandwich meats and places the slices into the trays progressing down the line.

Two FEMC four-out piston fillers follow, capable of dispensing measured amounts of liquid and semi-liquid products, such as mashed potatoes, puddings and apple sauce. Supporting these piston fillers is a Unifiller Systems (www.unifiller.com) Hopper Topper that transfers product to the hoppers that feed them.

Matching line speeds

The piston fillers feature traveling heads that move to match line speeds and maximize fill time and also have sealed ports that ensure accurate, uniform fill rates.

The fillers also offer the option, which CCSD selected, of tracking containers so that filling only takes place when tray presence is detected.

Each piece of equipment has a function in filling trays with the varied and nutritious meals specified by CCSD's resident nutritionist. But clearly, not every piece of equipment is active in every packaging run.

Denesters handle either paperboard or plastic trays depending on the product being packaged, and liquid or solid fillers come into play as those products change.

“The result,” points out plant manager Mario Saenz, “is that we can easily change over from one lunch menu to another without physically changing out equipment.”

Coordinating the line is an Eaton (www.eaton.com) Cutler-Hammer Panelview Pro human/machine interface (HMI) and Allen Bradley controls and logic from Rockwell Automation (www.rockwellautomation.com). This single HMI provides on/off control of each piece of equipment in the operation.

Specific controls for the non-FEMC equipment in the line are integral to the individual machines, and the FEMC piston fillers also have individual controls managing pneumatic functions not driven by the HMI. But these individual controls rarely need attention, Saenz says, having been set initially by FEMC during installation to coordinate with the speed of the line.

The maximum rates of speed of individual pieces of equipment vary, from 150 containers/min to 400 cpm. “The maximum overall production speed of the line is 200 cpm,” says Charles Anderson.

Sealing, metal detection

Once filled, the two lanes of containers pass into an FEMC 10-ft-long rolling-head Heat Sealer that places film on the trays and seals it to the container lip. Containers next pass through a Mettler-Toledo Safeline (http://us.mt.com) metal detector and are now ready to be packed for transfer to the schools.

At the end of the line, two operations meet as empty baskets returning from schools arrive through an incoming dock area and enter a custom FEMC basket washer/dryer line. A metal wire belt carries the baskets through a hot, high-pressure wash and a cold rinse. The baskets then air dry as they travel on a second conveyor to the basket-loading area.

The sealed food containers move by conveyor to an AMF (www.amfautomation.com) Intellipac basket loader, where vacuum grippers load them, 10 at a time, into the clean baskets coming from the basket washer. The loaded baskets are then stacked on carts and removed to trucks for delivery to the schools.

A long recess

An unexpected challenge arose once the FEMC elements of the system were manufactured and the sourced elements assembled, in 2004. CCSD didn't have an existing building that could adequately house the new central lunch preparation operation. It was going to be necessary to expand and reconfigure a 338,000-sq-ft warehouse/freezer building, adding 45,000 sq ft of administrative office space.

As a result, FEMC kept the packaging system at its Ohio facility until the new building was ready for occupancy. “That was the best alternative,” says Auvil. “Like any complex machinery, a system like this should never be 'put in storage,' but kept active. Having it in our plant let us run it periodically and do regular maintenance to keep it in tip-top shape.”

High marks

On completion of the expansion construction, the system was shipped to Las Vegas in three large trucks and set up in August 2007. The line went into production operation full-time only one month later, as the school year began.

“This system was designed and specified long before I was with CCSD,” points out Saenz, “But I have to say that, given the size and complexity of this system, I was amazed at how smoothly the installation and startup went. There were very few hitches, and nothing we couldn't smooth out almost immediately.”

Anderson continues, saying that during startup and presently, FEMC specialists maintain regular contact with CCSD to ensure that the system continues to deliver. Currently, the CCSD Central Kitchen facility plans, prepares, packages and delivers 133,000 lunches and 41,000 breakfasts for each school day. The packaging line that makes that volume possible running at its maximum speed of 200 cpm, with minimal downtime for maintenance and changeover, and has been doing so since September 2007, without missing a day.

“That,” says Anderson, “is the reliability we were looking for.”