Case Studies:
The Pet Food Factory

The Customer

The customer was responsible for the factory data systems in the production facility for a large pet food manufacturer. The pet food factory is highly automated. The tanks of raw ingredients, mixing equipment, ovens, cooling units, conveyor belts, canning and packaging systems are all remotely controlled and monitored via devices called PLC's. These devices regulate the functions of the manufacturing components and communicate with other computer systems in the office area of the company. Many computers in the office areas have the capability of monitoring any aspect of the factory, but they are not typically all in use at one time and most users are only monitoring a portion of the factory at any given time.

Problem

The control and monitoring systems were bogging down and losing connections, sometimes to the point of compromising production.

Analysis

After an initial check of interface errors and general traffic levels, we started monitoring the data going to and from one of the the monitor/control units (PLC) and established a baseline of the traffic flow characteristics. The baseline showed us that the data rate was very constant between the monitoring systems and the PLC.

Then we igradually increased the number of systems that were monitorinng this particular PLC and observed what happened to the performance characteristics. We saw that the PLC had a maximum data rate it could achieve that was independent of the number of systems that were monitoring it. Although this bandwidth was divided equally among the monitoing system, when 11 or more monitoring system were monitoring an individual PLC, the PLC's bandwidth was no longer sufficient to kepp up with the monitoring and the system would started to break down. At around 13 systems monitoring, the degradation would become noticeable.

Now that we knew the maximum capability of the PLC's, we monitored the user load on several of the PLC's and saw that typically there were 5 - 9 systems monitoring a PLC at any given time, but there were times when the number of system potentially be as many as 24 systemsIn this original design of the system, there were potentially 24 stations that had the monitoring software tat might monitor any particular PCL, but they weren't usually all actively monitoring at any one time.

Solution

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