Selecting the proper positioner is critical. The wrong decision can lead to unnecessary costs on one end of the spectrum and the need for a replacement on the other. Thus, it is not a decision that should be entered into lightly. There is not a one-size-fits-all solution out there, and simply going by a company’s “good, better, best” approach is suboptimal.
You have to understand the features of the positioner and how they may or may not be of help to your needs, which can typically be summed up through two distinct categories: control and communication.
How much precision do you need controlling the valve?
The valve needs to perform as well as possible. Pneumatic positioners do a reliable job when basic control is all you’re looking for. However, when you need something that is just a bit more robust, microprocessor-based models may be a better solution. They have advanced internal algorithms that perform more comprehensive tasks.
How much communication do you need?
This is kind of an interesting question as it relates to the topic of control. In many instances, operators are not too concerned with control if the communication system is robust. Furthermore, the topic of communication has far more depth.
In the past, most positioners relied on one-way communication, acting on an analog signal from the controller. Today, however, many positioners feature two-way communication where the device not only receives the signal from the control system, but also relays back digital information on the actual valve position.
As positioners continued to evolve, more advanced diagnostics became available to the operator. This allows a window into the internal components of the positioner and its external behavior, alerting operators when a valve is acting unexpectedly.
The key, of course, is understanding how much information is beneficial to YOU in YOUR PROCESS. Is this kind of communication critical? If so, then the options are there and likely worth the investment. However, if its clear that having this type of feedback doesn’t provide any crucial, actionable information, then it doesn’t make too much sense to implement the technology. You don’t want to over specify and thus, overspend on unnecessary technology or features.
Want to learn more about the nuances of communication available with positioners? I put together an in-depth piece for Chemical Processing Magazine, which you can read in its entirety
here.
Give us a call at
(855) 737-4714 the next time you need a positioner. Let us walk you through your options so you can make the most informed decision.
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