Feb
20
Work on the WirelessHART specification began over seven years ago. Since that time the WirelessHART specification has been published by the HART Communications Foundation. Also, in 2010 WirelessHART was approved by IEC as an international standard, IEC 62591Ed. 1.0. From the very beginning, the WirelessHART design included the features required for both monitoring and control applications. …
Jan
19
We conclude with a summary on how you can avoid bursts of oscillations, get to setpoint faster, choose the right execution time and filter, coordinate the speed of loops, optimize operations without while protecting equipment, provide a consistent flow response for model predictive control, eliminate limit cycles, and improve analyzer and wireless control loops (all …
Dec
01
We continue this series with some helpful hints for control system design and implementation. This week we look at measurement location and selection. Since a control system deals with change, the prevalent theme is how to improve the detection and correction for change. In the coming weeks we will take a look at control valves …
Sep
01
We have the opportunity to hear the 3 most influential and knowledgeable technical leaders in industry give their assessment of the present state and future of our profession. This will be the first and most likely only time these guys will be sharing their knowledge at the same event, thus covering the complete spectrum of …
Jun
17
The greatest limitation I experienced as a user for process control improvement (PCI) was unmeasured process variables. If we had a high degree of instrumentation, so that only a configuration change was needed we could let our creativity roam free and quickly implement various improvements including new loops and feedforward control. Also, from trend charts …
Jun
17
Every time I see associates retire, I have mixed emotions. I am happy to see them enjoy more R&R, but I am sad to see their expertise go. Very few users have had the time or support to communicate what they have learned the hard way by field experience. When they go out the door, …
Jun
02
Deadtime sets the ultimate limit to loop performance. Deadtime is any delay in the action needed to exceed the threshold for the start of error correction. The loop deadtime is the sum of pure actuation, correction, or recognition delays and the equivalent deadtime from lags smaller than the largest time constant in the loop. For …
May
26
Wireless technology offers the opportunity to select the best electrode for an application. Spare wireless transmitters can be used to test electrodes in lab solutions set to mimic the concentrations and temperatures of the process. The process lab offers a controlled environment to vary the process conditions of interest and keep other conditions constant. The …
May
19
Process efficiency measurements involve the measurement of process flows and utility or raw material flows. The energy efficiency depends upon the utility temperatures and heat transfer coefficient. The raw material efficiency depends upon feed concentrations and the desirable reaction rate to product and the undesirable reaction rate to a byproduct. For simply changing a stream’s …
May
05
Since the ultimate limit to loop performance depends upon deadtime, the effect of deadband, noise, update rate, trigger level (threshold sensitivity), and valve sensitivity-resolution (stick-slip) on the best possible performance can be estimated by the amount of equivalent deadtime these terms add to the loop. The dependence of loop performance on deadtime for unmeasured step …
