Limit Switches for Valve Positioning

What are the type of limit switches used for valve positioning opening and closing feedback?

Is proximity limit switches suitable and well functioned?

Wayne Ulanski can spelled it out pretty well:

http://www.svf.net/resources/How_to_Select_Automation_Accessories_for_Valves.pdf

Proximity switches seem to becoming the standard for valve position.
They are well sealed from the weather and are vibration resistant.

I've used a Turck DSU-35 dual sensors in a pharmaceutical plant. They can be mounted on any standard valve. I believe that Turck also offers an analog version too.

http://www.clrwtr.com/PDF/TURCK/TURCK-Valve-Position-Sensors.pdf

I have had used just about every kind of switch I can think of for valve position indication. I don't think any one particular style or type is necessarily better. In most cases it probably just doesn't even matter.

Sometimes the application dictates that one solution is better than another. Sometimes people just have a preference for one particular solution over another with no real reason.

For quarter turn valves especially in hazardous areas the top mounted enclosed types work very well. All the wiring comes to one enclosure including a solenoid valve is optional. There are many manufactures and I have attached a brochure of one example.

http://www2.emersonprocess.com/site...ocuments/ES-05726-1 R1 TW_D-SerASCOInside.pdf