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STI S.r.l. – Via Dei Caravaggi 15, 24040 Levate (BG) – ITALY www.imi-critical.com
Manual 5100, rev. 06 06/2020 – RTC/RTCS
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DEVICE DESCRIPTION
2.1 General Description
RTC Single/double acting pneumatic low-pressure actuators, are suitable for the operation of quarter turn
valves (ball valves, butterfly valves, plug valves) for ON-OFF and modulating heavy-duty service
The actuator is made up of a weatherproof scotch yoke mechanism transforming the linear movement of
the pneumatic cylinder (on closing or opening) into the rotary movement, which is necessary for valve
operation.
The travel stroke of the yoke is adjustable between -4 deg / +4 deg at both ends by means of the external
mechanical stops arranged into the side-wall of the mechanism body and into the end flange of the
pneumatic cylinder.
Scotch yoke mechanism centerbody cover is machined to provide the assembly pattern for any required
accessories (i.e. positioner, signaling limit switches, position transducer, etc.) by means of proper
matching units. The above mentioned accessories are operated by the actuator drive sleeve.
Actuator centerbody bottom wall is machined with threaded holes to allow actuator mounting on top of
valve top-work either directly or, when required, with the interposition of an adaptor flange or a mounting
bracket.
2.2 Identification of the Main Part
The RTC actuator is composed by three main parts:
1) Scotch yoke mechanism.
2) Pneumatic cylinder.(with internal spring for single acting version)
3) Stopper screw assembly.
4) Stop setting screw kit
Fig. 1: Main parts for RTC/RTCS actuator series
