Types of Devices
Figure 2 – A typical MIML PSTD
Figure 3 – MIML with pin (mechanical stop)
removed to permit full ESD valve travel.
Fig ure 4 – Actuator travel is limited when a pin is inserted.
(MIML): As implied, the MIML type is
an integral, hard mechanical stop that is
manually engaged and provided by the
manufacturer as part of the actuator
assembly. When engaged, the mechanism
positively prevents travel of the valve and
actuator past the preset position.
Engagement and disengagement is
via an operator-stationed adjacent to
the valve actuator. A locking mechanism
is provided to prevent unauthorized
engagement. Communication between
the valve and control room may be via
radio, or there may be electronic messaging from sensors on the hardware to
the control room. As MIMLs are integral to the actuator, they are available
only from the actuator manufacturer.
Suppliers of MIMLs point out that
the hard mechanical stop provides positive assurance against spurious shutdown trips (excessive ESD valve clo-
Half the size. Twice the torque. All the reliability.
An intelligent choice for valves and dampers.
Valvcon ADC Series battery back-up powered actuators are preferred over
spring-return operators in critical and emergency shutdown applications.
• Compact and reliable they are easier to install and to maintain.
• Efficient and solid state they provide up to 4 times the torque per weight.
• Extra battery capacity allows multiple cycling and constant monitoring.
• Costs less, can be solar powered, and goes up to 5
years without servicing.