Running on autopilot

by Suzi Fraser Dominy
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When Sietsema Farm Feeds LLC, Howard City, Michigan, U.S. built its new 6,000 tonnes per week feed mill, the company sought the latest in control systems to deliver efficient and economical operation.

Sietsema worked closely with main contractors Wagester & Lease and control systems specialists, Comco, to develop a ‘Functional Requirements Document’ that dictated how the facility was going to operate and be controlled. From this document, the control system was developed. Comco designed and built the PLC, which includes panels that contain an Allen Bradley SLC 505 PLC and remote inputs/outputs. Five PCs running Windows XP Pro are used as workstations for batching, receiving, pellet mill, loadout and one for the manager.


The mill is fully automatic with one truck-receiving pit that feeds 24 grain and ingredient bins. A hammermill can grind into three ground grain bins. The main ingredient bins feed a major scale and a minor scale with the salt bin feeding both for better accuracy. There is a separate scale that can be fitted with up to four tote bags.

Two micro systems each have 12 bins for small additions. A soy flush facility cleans out the micro scales transfer conveyor. Manual additions feed directly into the five tonne mixer.

Up to five metered liquids are controlled into the main mixer and after mixing, batches are transferred to one of two pellet bins or two bulk mash bins.

The pellet mill is a normal arrangement of feeder, conditioner, pellet mill, cooler and crumbler. The control system is fully integrated and fully automatic; the operator only has to click on the start button on the graphics and if it is a product that has been made before, click on confirm start.

All control of pelleting is fully automatic with all parameters checked 10 times per second to monitor for plugs, temperature, amps etc.

The downstream fat coater is also fully automatic as the fat level is taken from the formula. Pellets are then routed to one of 16 finished feed bins with automatic swap from bin to bin on high level.

Sietsema employees are able to operate the facility through hand held wireless pocket PCs, a unique feature of the AutoPilot4Feed control system. This allows the operators to maximize the running time of the facility and monitor ongoing operations without being attached to the control room.


Loadout orders are automatically sent from the office commercial computer. Although there is a loadout operator, loadout is controlled as automatically as possible.

A moveable 4-tonne weigh truck is moved to one of three positions, automatically filled and then moved to the truck hopper for discharge. Filling and discharging the moveable weigher is repeated for larger loads. On completion, AutoPilot4Feed sends the weight information back to the commercial computer, which prints out the loading tickets and declaration. All information transfer is seamless.

Four of the loadout bins have variable speed dischargers and this gives the facility the ability to blend two base products together into the weigher. For this, AutoPilot4Feed has a product type called ‘blended’ which is defined as X% of product A and Y% of product B. As AutoPilot4Feed controls the whole mill, quality is ensured by its accurate weighing, optimized pellet mill control and by minimizing any operator mistakes.

The control system has built-in redundancy should a PC fail and a modem allows 24 hour support should it be needed. The modem may also be used to install modifications, thus minimizing

the cost of any changes.

A maintenance package that seamlessly ties into the I/O used in the control program, called Asset Master NT, was also installed at the Sietsema Farms facility. It records live details of all monitored equipment as well as tracking sub assemblies, suppliers and maintenance details. Reports can be produced for preventative maintenance schedules based on the actual usage of the equipment. Over time a history of each item can be built up as maintenance is done and repairs are made to estimate and adjust its efficiencies. There is also the ability to log spare parts. WG For more information on Comco: