Holnam Inc.'s Holly Hill, S.C. operation was brought on-line in May 1966, when it was called Santee Cement, with a production rating of 350,000 tpy. With the ever-increasing demand for cement in a rapidly developing market, an expansion was soon undertaken, and the overall capacity increased to more than 1.2 million tpy. In 1978, Santee Cement became a subsidiary of Dundee Cement of Michigan, and in 1990 it became the Holly Hill plant, operated by Holnam.

In 1966, Santee started its packing operations with the installation of two, four-spout, in-line, hand-operated packers and manual palletizing of the bags. To keep the packing output in step with market demands, the size of the pack house staff kept increasing until, in 1985, it reached 51 employees packing product around the clock, seven days a week to handle 16.3% of the total capacity of 1.22 million tpy. Maintenance of equipment was reserved for breakdowns only, and the packing was averaging 1,240 man-hours per week.

First upgrade In 1986, the Santee subsidiary of Dundee Cement upgraded its packing and palletizing system by installing a complete system that included a 10-spout Haver Roto-packer equipped with automatic weight adjustments and an automatic bag placer.

This unit was coupled to a Beumer 2400PD fully automatic palletizer with PLC controls. This equipment selec- tion was based upon the company's requirements for machinery to maximize production while being capable of handling a variety of bag sizes and weights.

The installed system included a vibrating screen to remove foreign material and agglomerates from the air slide systems that deliver the cement from the multiple storage tanks feeding the packing system. A surge tank was provided in the system to ensure the uninterrupted supply of cement to the packer, which was equipped with a variable-speed drive to compensate for variations in the densities of the materials and make it adaptable to the range of bag types.

The packing system included an automatic Radimat bag placer with a large magazine storage section. The placer was adaptable to handling the variety of bag sizes without requiring any manpower. The system also included a check weigher that automatically adjusted individual packing nozzles of the Roto-Packer when either over- or underweight bags were sensed. Prior to the check weigher, a bag-cleaning and broken bag-removal system was installed that included a cement return system that collected spillage from below the packing spouts of the Roto-Packer as well.

A conveyor belt delivered the bags to a Beumer 2400PD automated palletizer rated at 2,000 bags per hour. The palletizer was equipped with adjustments that allowed it to handle the wide variety of bag sizes. The palletizer produced stable pallet stacks that were compressed between each layer and delivered to a pallet pick-up section that allowed for dual side-by-side forklift handling. This cut in half the time for delivering the pallets to trucks or storage. The entire palletizing system was controlled by a PLC that provided all adjustments and sequencing required by the entire palletizing area and interfaced with the Roto-Packer to maintain complete system integrity.

As a result of this installation, the facility was able to handle 19% of a 1.58 million-mtpy plant output, and the pack house staff was reduced to five workers per shift working three shifts per day, five days per week. This staff of 15 not only operated the new system but also handled the loading of the full pallets on the flat-bed trucks as well as all rail bulk loadout.

The combination of the more attractive and cleaner package, along with the ability to fulfill client needs, resulted in a large upswing in packaged shipments. In fact, a record was established in 1987 of 6.3 million bags. In addition to the reduction in work hours and cost of packaging, other economic advantages of the new packing and palletizing system included Santee's ability to reduce the cost of the bags by decreasing the bag size.Also, the pallets were more uniform and easier to load on to trucks. During these years, the plant would manually place protective bag covers over the full pallets prior to loading on to trucks and shipment to clients. These covers were used at many customers' request.

Second upgrade In 1998, the Holly Hill managers decided to upgrade the plant's packing and palletizing system after more than 12 years of successful operation. The goal this time was to further increase production rates of this system and satisfy the ever-increasing demands of the market. To do this, it was decided to retain the present Roto-Packer with upgrades to increase its capacity, replace the palletizer with a more versatile machine rated at a higher capacity, and add an automatic stretch-hood placer to replace the manual operation.

The Haver Roto-Packer was fitted with a new and faster Radimat bag placer, which allows the Roto-Packer to operate at a higher capacity and make the changeover from one type of material to another much faster. New PLC s were added to the packer drive, thereby increasing the packers speed and capacity and giving the floor personnel more control over the unit and its output.

The requirements for the replacement palletizer were for a unit capable of being retrofit into the existing system; a capacity rating equal to or greater than the upgraded output of the Haver Roto-Packer; and the flexibility of not only being able to handle the variety of bag sizes used at the plant but also capable of stacking the smaller 47-lb bags that are becoming more popular throughout the industry.

A Beumer FVSQD 3000.8 fully automatic, totally electric palletizer was selected. In addition to fitting the previously mentioned criteria, the system also has an operating capacity of 3,000 bags per hour. The past reliability of the previous 2400PD unit also weighed heavily in the selection. The new machine fit into the allotted area and retained the basic profile of the earlier system. The basic machine is equipped to handle full-size bags on a single turning post and is equipped with a secondary turning post, used when the smaller 47-lb bags are handled at a higher rate.

All layer pattern formations are done on the upper section of the palletizer, while the alternating layer pattern of the stack is accomplished on the elevator turntable. This rotating elevator also allows for compression between layers, which stabilizes the stack for shipping. The entire machine is fitted with automatic layer-size adjustment and either drivers with frequency inverters or servo-motors that gain high speed and assured accuracy of movements.

An automatic Beumer Stretch Hood unit was added to the line and eliminated the need for manually placing the stack bag covers. The machine not only provided a cover but also offered additional stability for the stack. This is accomplished because the machine uses a tubular gusseted film that is measured to fit each individual pallet as the stack is fed into the machine (Figure 1). The tube is then opened to a rectangle by clamps that positively define the position of the corner points, cut and welded to form the cover, stretched open, and bi-axially stretched and lowered over the pallet stack. The film is drawn down the stack and forms an underwrap on the pallet, thus forming not only a cover for the bags but also a structural support for the stack.

Holnam had the option to ship the pallet stacks uncovered in some cases but elected to place a hood over all pallet loads, thus assuring a clean, neat, and stable pallet of cement or mortar.

The pallets from the stretch hood unit are then picked up at a tandem station when two pallets at a time are transferred to warehouse storage or directly to truck loading.

Results Many benefits have been realized from this most recent modernization, including greater customer satisfaction at receiving materials in a cleaner, neater looking shipment; Holnam better serving its clients faster and more accurately; and the entire packer/palletizer/stretch-hood area of the pack house is handled by only two employees per shift.

The primary duties of these workers are to change over the product types, keep the magazine of the Radimat bag placer full, keep the empty pallet storage of the palletizer full, take the full loads away from the stretch hood unit, and load out the pallets onto truck transportation. With these changes and the growing demand for product in the marketplace, Holnam shipped more than 7 million bags of cement in 1999.

When the reduction of work hours is taken into consideration, the reduced time required to turn out the required production and the acceptance by clients of the shipments makes this a solid investment by Holnam. All totaled, Holnam experienced a 96% reduction in manhours and a 52% reduction in production time, while surpassing old shipping standards, which has accounted for extensive savings.