Two pressure controllers are better than one in extreme environments

Some industrial and analytical applications, especially applications with mixed phase fluids, corrosive media or extreme temperatures, can be better handled by purely mechanical classic industrial regulators than electronic pressure controllers. Purely mechanical regulators don’t usually have the same susceptibilities to these types of conditions that electronic pressure controllers do.

However, there is a trade-off. While the process gains toughness, it loses high speed control, user friendly electronic interface, onboard PID and the accuracy and resolution of pressure control that make Alicat electronic pressure controllers highly accurate, fast and easy to use.

Why don’t we have both?

One of Alicat’s partners, Equilibar, is a manufacturer of high performance mechanical industrial back pressure regulators. The Equilibar back pressure regulator (BPR) features a flexible diaphragm as its only moving part to provide frictionless, stable operation. Equilibar’s dome-loaded, multiple orifice design offers precision, as well as compatibility with mixed phase fluids, corrosive media and extreme temperatures.

One requirement of the Equilibar back pressure regulator is that a reference pressure be provided to the “dome” in order to tell the larger regulator what back pressure to control to.  This can be handled in a number of ways:

  1. Using a sample pilot pressure pneumatically routed to the dome. The limitation here is that the setpoint is subject to change as the pilot pressure changes.
  2. Pressure is provided to the dome with a mechanical pressure regulator.  While this may do a fine job in some applications, a mechanical regulator feeding the dome on another mechanical regulator still does not attain the precision and functionality of an electronic solution.
  3. Utilizing an Alicat Dual Valve Pressure controller (PCD) to perform the precise pressure manipulation of the diaphragm inside the dome.  Alicat’s sub 100ms control speeds and precision of control allows high resolution control of the Equilibar BPR diaphragm control mechanism. Alicat’s PCD series, optimized for closed volume pressure control, essentially becomes the brain of the Equilibar BPR, giving end users the ability to automate control through a computer terminal– or simply with the push button display on the Alicat PCD.

Alicat and Equilibar

When Alicat and Equilibar began working together, Equilibar had been looking for a solution to precise closed-volume pressure control for their domes that could control the pressure on the diaphragm reliably from 0 to 3000PSIG. This would give The Equilibar back-pressure user who needs 3000PSIG back pressure control, the advantages of using an electronic pressure controller.

The Equilibar BPR and the Alicat PCD3 3000 both have high resolution, so each is able to take advantage of the other’s high precision control.

  • Alicat’s sub 100ms control speeds and precision of control allows high resolution control of the Equilibar BPR diaphragm control mechanism.
  • Equilibar’s unique construction using a thin, supple diaphragm as the only moving part delivers near-zero hysteresis and will accurately repeat the high resolution pilot signal from the Alicat into a corresponding high resolution pressure within the application.
  • Alicat’s active PID control and dual valve system allows for fast and adaptive response to changing operating conditions without the need for user interference or adjustment.
  • An Equilibar back pressure regulator allows the Alicat to control pressure in applications with extreme temperatures, severe chemistry or mixed phase fluids because the Equilibar will faithfully reproduce the pilot pressure signal in these complex process conditions.
  • The Alicat PCD series allows users to automate communication. And adds the features of a lab style instrument to the Equilibar back pressure regulator.

Sometimes two technologies are better than one. Pairing Alicat’s feature-rich electronic pressure controller with Equilibar’s resilient mechanical pressure controller allows for the best of both worlds in processes that require accuracy, speed and durability.


Reference: click here.

D&D Engineering – “W’ere YOUR Sensor Guys”
3835 E. Thousand Oaks Blvd. Suite 464 Westlake Village, CA 91362  – Voice: (818) 772-8720 Fax: (818) 772-2477 Toll Free: (888) 333-6474
Email: Website: