STI RTQ Series, Instruction Manual, Page: 25 / 44

STI S.r.l. – Via Dei Caravaggi 15, 24040 Levate (BG) – ITALY www.imi-critical.com
Manual 5300, rev. 09 06/2020 – RTQS 21
9.3 Special maintenance
Under normal working and environmental condition, the actuator doesn’t need special maintenance.
It is however recommended to inspect the actuator every six years.
If leaks in the pneumatic cylinder, or a malfunction in the mechanical components are found, the actuator
must be disassembled and seals and/or any other damaged parts must be replaced.
Important In order to correctly schedule the special maintenance activities, the following aspects
must be considered:
-
replacement of seals of the cylinder can be done in field without removing the
actuator from the valve;
- replacement of tie rod of the cylinder can be done in field without removing the
actuator from the valve;
- replacement of seals or mechanical part in the scotch yoke mechanism requires
the removing of the actuator from the valve and disassemble it in workshop;
- any malfunction that could be attributed to the spring package requires the
removing of the actuator from the valve and disassemble it in the workshop;
spring package cannot be opened except for demolition following the next
paragraph 14.3.
Warning
Before performing any maintenance activity use always wear protective gloves,
footwears, clothing, high visibility jacket, eyewear and any other protective device
prescribed by the Local Rules depending on the working conditions.
Warning
RTQS actuators are fail safe units; before to start with any maintenance activity
it is therefore mandatory to make sure, using the specific documentation (i.e.:
operating diagram, …), that the actuator is in his safety position: i.e. close for
fail to close version or open for fail to open. Following steps must be followed:
- Disconnect any operating lines providing air pressure, electric power, or a control
signal to the actuator. Attention: during these activities the actuator could
suddenly open or close the valve.
-
Exhaust the residual pressure from the actuator cylinder and from the control unit,
to ensure safety of maintenance staff.
- Pay attention to the residual load due the internal springs: to release the spring
tension, the stop screw at the end of spring cartridge must be remove
before the cylinder tie rods are opened.