Figure 5 (left) – MEML as it mounts between the actuator and ESD valve.
Figure 6 (right) – Disengaged (top) and engaged (bottom). Rotation of
the flag causes engagement of the internal mechanical stop. For remote
operation, a small quarter-turn actuator replaces the manual flag.
sure) and that optional sensors are available to provide feedback for event verification and recording. Additionally, integral PSTDs are optimally sized for each actuator and
require no special mounting provisions.
Typically, color coding is used to identify the correct key
for each MIML (Figures 2, 3 and 4).
Mechanical-External-Manual-Local (MEML): MEMLs
are similar in concept to MIMLs except that the MEML is
separate from the actuator. Suppliers of these devices point
out that MEMLs are actuator independent and are suitable
for new ESD valve installations as well as for retrofitting to
existing valve/actuator packages. Optional remote engagement is offered as are travel sensors for position feedback.
Both MIML and MEML PSTDs are suitable as add-ons
to accessory-based PSTDs as a means to provide hard travel
stops (Figures 5 and 6).
MIAR-type PSTDs provide a pressure-activated, integral
hard stop to prevent spurious shutdown trips. As with accessory-based PSTDs, local manual engagement is optional as
are sensors that provide feedback for predictive maintenance. Suppliers point out that full closure response to an
emergency is not impeded during PST or actuator seal
A CASE STUDY
AUTOMATED INDUSTRIAL PLANT NEEDS
EXTENDED LIFE ACTUATION.
EXTENDED CYCLE LIFE ACTUATORS ARE USED FOR BFV APPLICATIONS UP TO30 INCH. THE
ACTUATORS HAVE PROVIDED OVER 5,000,000 CYCLES OF CONTINUOUS SERVICE RESULTING IN
LOWER OPERATING COSTS AND INCREASED PROFITS. THE ACTUATORS ACHIEVE 90 DEGREE
ROTATION IN LESS THAN 1 SECOND. UNIQUE END OF STROKE DESIGNS REDUCE SHOCK TO BOTH
THE ACTUATOR & THE VALVE EXTENDING THE SERVICE LIFE.
U T YOU ?
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VALVES THAT REQUIRE PROVEN
HIGH CYCLE RELIABILITY?
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