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STI S.r.l.
– Via Dei Caravaggi 15, 24040 Levate (BG) – ITALY www.imi-critical.com
Manual 5400, rev. 05 02/2018
– RTQHS
3
2
DEVICE DESCRIPTION
2.1
General Description
RTQHS single acting hydraulic actuators, are suitable for the operation of quarter turn valves (ball valves,
butterfly valves, plug valves,...) for ON-OFF and modulating heavy-duty services.
The actuator is made up of a weatherproof scotch yoke mechanism transforming the linear movement of the
hydraulic cylinder (on closing or opening direction) or the linear movement due to the force of a spring (on
opposite direction to the hydraulic cylinder) into the rotary movement, which is necessary for valve
operation.
The travel stroke of the yoke is adjustable between ± 4 degree at both ends of the nominal travel by means
of the external mechanical stops arranged into the end flange of the spring cartridge and into the end flange
of the hydraulic cylinder.
The cover of the centerbody of the scotch yoke mechanism is machined to provide the assembly pattern for
any required accessories (i.e. positioner, signalling 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.
