By Lee Hilpert
In the current economic and environmental atmosphere, companies turn to automation in hopes of becoming more competitive and more environmental friendly. In particular, the automation of unattended machines associated with processes can have a very positive impact on the bottom line and the environment.
Automation of unattended machines can be as simple as responding to a single variable in the process, such as a process rate change, or as complex as responding to several thousand variables through model-predictive-control schemes to produce a desired outcome. Either way the result is the same, respond to process variables to maintain or increase process efficiencies.
Efficient operation can mean different things. It might refer to consumption of the least amount of raw material or creation of the least amount of environmental impact or reduction of downtime and required maintenance. Automation of unattended machines often has a positive effect on all of these.
We specialize in horizontal decanting and vertical disk centrifuges used to make liquid/liquid, liquid/liquid/solid and liquid/solid separations. The processes associated with these machines range from removing water from edible oils to cleaning drilling fluids for reuse in oil and gas exploration. These machines typically are equipped with stand-alone controls ranging from simple start/stop controls to fully automated panels with variable-frequency drives, PLCs and industrial communications capabilities. Application of automation to these types of stand-alone control panels can be very beneficial to the end user.
Understanding the end user’s process is critical to success, whether building new or retrofitting an existing machine, and this sometimes can be more difficult than you might first think. You could find that the operators might not truly understand the application of the unattended machine. The operator just starts it up and leaves, assuming that the machine is doing what it was designed to do. The machine might be revisited only if there is an anomaly that results in a shutdown. Often, the only recourse for the operator is to bypass the machine until a skilled technician can travel to the location, troubleshoot the situation and restart the machine. In some situations the application of very simplistic automation could mitigate these shutdowns.
A simple programmable relay and a sensor associated with a critical operating variable such as total load can prevent some of these nuisance shutdowns. The logic simply could be to bypass the machine for a few seconds to let it clear itself and then re-engage the machine into the process. This type of automation can be very effective where the required processing capacity is within the machine’s capabilities but, due to design or the process characteristics, there are brief periods of substantially increased load. In one case we were able to practically eliminate the shutdowns associated with an extractor overload just by returning the feed, via an air-operated knife gate, to the head of the feed stream to allow the machine to clear for a few seconds and then re-engage into the process. Obviously not every automation application is this simple; optimization of unattended machines can be much more challenging.
Applying automation to optimize unattended machines requires a complete understanding of the machine and the associated process. An example of simplistic optimization might be the application of a loop process to speed up or slow down a VFD-driven pump in response to a variable inflow to a tank. By applying the loop process instead of a float switch and a starter, the pump could operate at an average rate that would be less than was required of the original pump. This could reduce the required pump size and also reduce the burden on downstream equipment.
The benefits of applying a little automation to an unattended machine can be significant. So the next time you are visiting a customer facility, be on the lookout for an opportunity to apply this type of automation. You and the customer will both benefit.
Lee Hilpert is president of HilTech in Tomball, Texas.