Michael Brown has introduced an online control loop optimisation and tuning consultation service designed to help plant engineers all over the world understand why their loops are not behaving the way they should. Here’s how it works:
Figure 1.
Figure 2.
Figure 3.
1. Michael will loan the Protuner loop analysis and tuning software to install in one of the plant’s own computers, which will then be connected to the control system via an OPC link.
2. One of the plant technicians or engineers will operate the system and share his screen with Michael via a Zoom link.
3. Michael will direct procedures over the link.
4. A full report will be provided after each session.
Several plants in various countries have already taken advantage of this service in troubleshooting and tuning some difficult loops, with excellent results achieved to date.
To illustrate this, consider how the wayward behaviour exhibited by this slurry flow loop at a platinum concentrator was tamed through a combination of practical insight and the implementation of good tuning practices:
1. When looked at with the initial ‘as-found’ tuning parameters, the system was taking nearly an hour and a half to fully respond to a 10% change in set-point (Figure 1).
2. When the correct tuning coefficients were substituted, the loop went wildly unstable (Figure 2).
3. It was quickly established that there was a 9-times incorrect scaling factor in the P gain term of the PLC controller module. When the gain was reduced by a factor of 9, the response was beautiful – getting smoothly to set-point in just 15 seconds (Figure 3).
Expert online help is now available to all plant personnel struggling with similar problems.
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If nonlinearity occurs it means that if one is to carry on controlling with the same response to changes in load or setpoint, then the tuning of the controller will also need to be adjusted to meet the new conditions.
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