An actuator can double the value of a valve, or halve it, depending on whether it is complete, identifiable and dry.
Two different products
A bare-stem valve is a mechanical item: body, bonnet, stem, trim and a mounting pad. An actuated valve is a system: the same valve plus an actuator, a bracket, a coupling, a positioner, air tubing, limit switches and often a solenoid. They sell to different buyers at different prices.
The mistake sellers make is to separate them. An actuator removed from its valve loses the bracket and coupling that made it mountable, and a valve separated from its actuator loses the evidence of what it was controlling.
When an actuator adds value
An actuator adds value when it is complete, identifiable and dry. A pneumatic spring-diaphragm actuator with a legible model plate and an intact diaphragm case is a straightforward item. A digital positioner with a known model number and no water damage is a strong item on its own.
It also adds value when the assembly is matched: a valve and actuator that were sized for each other, with the bench set marked, are worth more together than the parts separately.
When it does not
An actuator subtracts value when it is seized, corroded, missing its cover, or so obsolete that no spares exist. In that case the buyer is paying for the valve and taking the actuator as a disposal problem, which is reflected in the offer.
The same applies to positioners stored outdoors with the terminal cover off. Water ingress is the most common reason instrument-level equipment is rejected.
How to store actuated valves
Indoors, upright, with the actuator above the body so any condensate drains away from the instrument. Covers on, air ports capped, tubing coiled and attached rather than cut. If the valve has to be outside, tarp it so that water runs off rather than collecting in the yoke.
Do not test-fire actuators with shop air unless the valve is secured. A spring-return actuator with a stuck stem will damage the stem or the coupling.
What to send us
For each actuated assembly: a wide photograph showing the whole unit, a photograph of the valve nameplate, a photograph of the actuator plate and a photograph of the positioner plate. Note whether the actuator is spring return or double acting, and whether air failure opens or closes the valve.
That is enough to price the assembly as a system rather than as a pile of parts.
Questions sellers ask
Should I remove actuators before selling?
No. Keep them mounted. Complete assemblies are worth more and are easier to handle.
Do you buy bare-stem valves?
Yes, particularly where the mounting pad and stem are intact so the valve can be re-actuated.
Are electric actuators bought?
Yes, when the motor, gearbox and controls are complete and the voltage is identifiable.