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Technical Articles

3-Position Valve Assures Filling Accuracy

By Barry Sutphin, Plast-O-Matic Valves, Inc.

A chemical manufacturer was filling 55 gallon storage drums positioned on a weight scale. When the desired weight was achieved, a power signal was sent to a motorized control valve to close. Electrically actuated ball valves had been used but closed too slowly for the accuracy and repeatability desired, and often resulted in costly overflows.

  4-20 mA Control Not Available

A modulating valve was recommended, however the fill system was not sophisticated enough to provide a modulating control signal. A simple control valve solution was needed.

Plast-O-Matic provided the Basiks® S20.14 Smart Actuator with a 3-Position option, mounted on a Series EBT, Grade 1/Type 1 PVC Ball Valve designed for corrosive liquids. The Smart Actuator is unique in that in addition to the standard “open” and “closed” positions, a third position can be ordered with a simple electrical signal – no electronic positioning required. In this application, the position was pre-set at 30º.  

Power to the actuator is controlled by two SPDT switches. The actuated ball valve, mounted on a dispenser sub-assembly, now moves to a partially closed position as the scale approaches the desired weight, slowing the flow as the drum approaches capacity. When the desired fill weight is reached, the next signal closes the valve completely. The valve then reopens automatically when the operator resets the scale. 

The overfill problem has been eliminated, and the accuracy and repeatability have improved considerably.

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Barry Sutphin is Northeast Regional Manager for Plast-O-Matic Valves. Barry holds a Bachelor of Science Degree in Chemical Engineering from the University of Akron and has 15 years of experience with control valves, air release valves and process piping systems. He is a member of ISPE and has presented at multiple state AWWA, Rural Water, and WEA conferences, as well as teaching CEU courses for PRWA. Barry currently resides in Wheeling, WV.