pneumatic pilot positioners

[gazoo]

anyone have info on how they work for damper actuators and why they are used??

[hvac69]

http://hvac-talk.com/vbb/showthread....lot+positioner

[gazoo]

cant see it. i do not have access to this forum....

[bob_scheel]

Pilot positioners are used for two reasons. The most common reason is to adjust the spring range, ie the pressure at which the actuator is fully open or closed. I've seen them most often on steam line setups where there is a 1/3 capacity valve for fine control and a 2/3 capacity valve.

The other reason is that you can get faster or slower movement because of the direct supply connection instead of going through a control device that might be volume limited.

[gazoo]

any one have a install guide for one??

[Six]

its a controller that acts as a assist to the primary actuator increasing branch pressure to overcome forces acting against the actuator.

I use to see them on large actuators.

It will have a main air line running to it.

also if you dont know their function why are you installing one ?

[gazoo]

not installing one. just saw one and wondering how it works.

[Six]

ah..well there is your explanation. I see less and less pnuematics and pilot positioners.

They're pretty nifty controllers in that you can use them to match spring ranges.

[Control Man]

Here is a tech sheet that should help you out.

http://www.cm3web.com/parts/pdf/F22909-7.pdf

Still lots of them in use from all the major manufacturers

[gazoo]

thanks to all...

[simux]

I've seen people take out pilot positioners and the damper alone can't close or open a set of dampers. You can also use them to stage equipment by changing the start point and end point. For example you can put a heating valve and a cooling valve and stage them where the heat comes on from 3 to 6 psi and the cooling comes on from 8 to 11 psi, this also gives you a deadband from 6 to 8 psi where you have not heating or cooling.