A valve positioner is a device that communicates to the actuator to move the stem position
based on a desired set point. In this video, we’ll talk about why you might want to use them,
how the three main types of positioners work, and the options that Kimray provides.
If we were to simplify and say that a positioner controls the actuator on a valve, it may sound
like the same function as the Kimray pilot on a control valve package. While they do perform
similar functions, the pilot does not offer the same feedback and control. For example, it will
not tell you the actual percentage open that the valve is or be able to give you any diagnostics.
With a positioner installed, it intercepts the signal to the actuator and outputs a
corresponding signal, either pneumatically or electrically,
which provides optimal control over the process variable.
A positioner offers more precise control than the actuator on its own because it
knows the valve’s exact position. And because it allows for faster
response time to changes it minimizes operating time above or below setpoint.
There are 3 primary types of positioners depending on the type of control signal and
communication: Pneumatic, Analog, or Electro-Pneumatic, and Digital
A Pneumatic Valve Positioner receives a pneumatic signal from a controller
and then supplies the valve actuator with the correct air pressure to provide an
accurate valve stem or shaft position proportional to the pneumatic input signal.
An Electro-Pneumatic, or “EP” Positioner uses a mix of both air pressure
and electricity. It receives an electric signal from a controller
and sends a corresponding pneumatic signal to a pneumatic valve actuator.
EP Valve Positioners are also called
analog positioners because the electrical input is an analog signal.
Since many processing units use electronics with a 4-20 mA DC signal to modulate control valves,
the positioner must convert the electronic current signal into a pneumatic pressure signal.
This is also known as an I/P positioner or transducer, such as Kimray’s YAK2.
A Digital Valve Positioner also receives an electric signal from a controller,
but it’s digital as opposed to analog. It then
sends a corresponding pneumatic signal to a pneumatic valve actuator.
It also differs from an EP because it uses a microprocessor to convert the control signal
and perform the position control rather than a mechanical beam,
cam and flapper assembly found in an EP.
This electrical input allows more advanced capabilities for the user.
These digital “smart positioners” also collect data to automatically alert
users about valve performance, diagnostics and maintenance.
The Siemens PS2 is one example of a digital valve positioner that can
remotely monitor and control any pneumatic valve.
Kimray is a proud reseller of this product, and we offer it
with different communication protocols and enclosure options to meet your needs.
The PS2 may be operated manually or electronically. It’s simple to program,
with only three buttons and a two-line display and it can be calibrated in minutes. They feature
low air consumption compared to the industry average and only use air when required so
you'll quickly reduce costs incurred by air generation, maintenance and material.
One Kimray-designed solution that combines the positioning capabilities we’ve talked
about in this video and more is the Electric Valve Controller.
The Electric Valve Controller is a compact, easy-to-use, versatile solution
for oil and gas automation, including remote monitoring and control of your production.
You can use the Electric Valve Controller for back pressure control, suction control,
pressure differential or hi-low gap control all through a simple 3-button interface.
For more details about the EVC package and its functions,
check out the video in the description below.