This custom high performance butterfly valve assembly operates normally as a modulating fail-close assembly.  As recommended, a filter regulator is used on the input air to the positioner to keep air clean and prevent pressure spikes, helping to extend the life of the positioner.  Using Max-Air’s PEX02 explosion proof positioner w/ external limit switches and a MT46.S4.F07-F10.CH22 spring return actuator, a 4-20mA signal modulates the valve as expected.  However, by closing a 2-way ball valve and turning a 3-way T-port ball valve the inlet plumbing to the actuator is arranged in such a way that the positioner is bypassed and the open/close control is delegated to the auxiliary normal-closed 3-way solenoid valve.  This allows a user to convert this modulating assembly to a simple open/close assembly and vice versa.  In either mode the limit switches provide open/close feedback, regardless of whether the positioner is being used or not. 

Max-Air Technology

Author Max-Air Technology

Max-Air Technology is the worldwide leader in automation technology and process control products; we design automation technologies that provide competitive advantages. For more than 15 years, we have engineered improvements, added flexibility and interchangeability to our products to provide customers with The Best Way to Automate Their Process.

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