Video: Flow control & small delta-P

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13 July 2021

Flow Control by PCS

The precision control technology that is behind the pressure control products of PCS & Equilibar has proven to be a powerful basis for the control of other process parameters, such as flow. As a result of increasing customer demand, PCS has specialized more and more in innovative flow control solutions that match complex system requirements for the most demanding process conditions.

How Equilibar ® technology can improve flow applications

Equilibar dome-loaded control valves are uniquely designed to hold pressure over an extremely wide flow and pressure range. This is achieved by balancing three-way-pressure around a diaphragm inside the valve that seals the multiple inlet- and outlet orifices. When the diaphragm sealing the orifices is pushed onto the body, the flow is blocked. By modulating the pressure against the diaphragm, the flow changes.
One of the main characteristics and a unique feature of the Equilibar valve is its neglectable amount of pressure drop. It is exactly this feature that makes the Equilibar valve also suitable for flow control. See our How it Works page including video if you want to explore this operating principle further and/or explore our expertise: Flow Control by PCS.

Flow control, pressure differences & flow control stability

To explain the unique capabilities of our back pressure technology for the purpose of flow applications, we zoom in on a recent question we got from a customer, let’s call him John for ease of reading.

John needed a flow controller to dose a liquified gas into a reactor, starting at atmospheric pressure. “How stable could this flow be controlled despite a (small) difference in the upstream and downstream process pressure?”, John asked us. Furthermore, he wondered what the minimally required pressure drop would be over this Coriolis mass flow controller: “What if the pressure delta is very small; would it endanger the flow control stability?”.

Set-up for testing and validation

As a reply to John and to demonstrate the excellent accuracy and stability of our flow control solutions, we built a test set-up and shot a video of it. This video set-up consists of:

  • 1 Coriolis flow sensor combined with an Equilibar back pressure regulator with integrated proportional valve (in this case an ML120 with U3L1 Equilibar valve).
  • 1 Equilibar back pressure regulator controlled by a dual valve electronic pressure controller.
  • 2 delta-P sensors.


The set-up is depicted in this schematic:


Test video

In the video, we see how the total delta-P over the mass flow controller is not even 1 bar. This pressure drop is mostly caused by the Coriolis sensor. More specifically, the pressure drop over the Coriolis sensor is 77 mbar when dosing at a flow of 30 gr/h of air.

This mass flow controller is capable of controlling over a range of 0.1…200 gr/h of liquid or gas, with a delta-P of 200 bar down to 1 bar. The Coriolis measuring principle is media-independent and very accurate, which means you can control almost every liquid, gas, or liquified gas (like for example C2H4, C3H6 or CO2) with this combination. The Cv rangeability of the Equilibar dome loaded control valve is 0,07 down to 10E-8, making it a “One-Size-Fits-All” mass flow controller.

In our experience, a picture says more than a thousand words. To see how accurate and how stable this flow with a small pressure delta could be controlled, we recommend that you watch this short video:

Key features

Flow control solutions by PCS are available also for higher pressures and/or for very low flows (0…200 gr/h). Our flow control products can operate over a delta-P range from 200 bar down to almost 0 bar pressure drop.
Through the use of Coriolis mass flow controllers, we can control liquids, gasses supercritical or liquified gasses and our unique Equilibar control valves can handle a Cv range from 10E-8 to 0,07, allowing us to control multiple media with one MFC.
We can achieve an accuracy of 0.2% reading for liquids or liquified gasses and 0.5% for gasses. Products are available in SS316 as well as Hastelloy and are thus suitable for the most demanding process conditions.

Want to know more?

Feel free to contact our engineers if you want to discuss possibilities for your flow control application. We’ll be happy to share our expertise and propose a “best match” product solution for your particular process requirements!