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When considering
Partial Stroke Testing, plants have two basic methodologies to
choose from: Mechanical
or Electrical. The
D-Stop is a mechanical device and we believe the mechanical
methodology is superior to electrical, and here’s why:
It’s Simple:
When it comes to testing systems, the temptation is to take
what might be an already sophisticated control valve system and make
it even more complex! It
is not necessary to integrate the D-Stop into the control loop or
add ancillary controls, as is the case with electric systems. It’s
simple. In the real world, oftentimes the less complex the system,
the fewer things to go wrong.
True
Safety System Tests: Because the D-Stop requires no extraneous controls, when the
valve is tested all the actual SIS components, controls and elements
used in an ESD or safety valve will be activated.
You have real information about the exact controls that will
be relied upon to protect your plant and personnel.
It’s
Economical: The
basic cost a D-Stop, depending on torque requirement, is typically
hundreds or thousands of dollars less than an electric or
controls-driven system. Instrumentation
personnel and software programmers are not required to install the
D-Stop, so installation costs are lower.
Commissioning or routine calibration of controls is not
required, because there aren’t any.
Most process plants have qualified in-house mechanics or
Valve Automation Centers nearby and, since there are no additional
controls required, installation cost savings can be substantial.
Built for a
demanding, industrial environment:
The D-Stop is vibration resistant.
It is externally corrosion protected with coatings and
independently certified to IP 67 to prevent water ingress.
Stainless Steel trim is used for keys, shafts and sockets.
The D-Stop is permanently lubricated, factory sealed and requires
no routine maintenance.
But most
important…
It’s Safe:
Once the D-Stop is engaged, the drive mechanism prevents the
actuator from causing the valve to stroke past a specified set
point--the partial stroke.
- Theory:
Electronic systems rely on instrumentation, software and
controls to limit valve travel past the set point to closure.
- Reality:
The valve is in a real pipe with real process
flowing through it. If
the valve closes there may occur anything from loss of revenue
to a catastrophic event, depending on the plant and the
application. Obviously if you can tolerate the valve closing, you do
not need a Partial Stroke Test Device.
Solution:
When
performing Partial Stroke Testing:
Keep it safe, keep it simple – specify D-Stop!
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