Customizing mass flow and pressure controllers: brilliant to baroque

Customizing mass flow and pressure controllers: brilliant to baroque

Posted by: Dan Yount

Many customers, even our most loyal ones, don’t realize that we customize just about EVERY Alicat instrument order. That’s because all our instruments are built when you order, and configured and programmed to best suit the application and conditions for which you’re buying them. Customizations can range from having a meter automatically tare itself every 24 hours, to engineering new limits of what our pressure controllers can handle! To give you an idea of how we work out your new requests, here are some simple and helpful customizations we produced on request.

Local Valve Drive Percentage

Resulting from a customization created at a customer’s request, the Local Valve Drive (LVD) option lets you monitor the work your valve is doing—because it can help you assess whether your process is in trouble. The LVD parameter appears on the large, multivariate display screen of an Alicat mass flow controller (or pressure controller), right above the main parameter output in the center. The LVD option reports the proportion of power being applied to the valve to maintain the setpoint. Valve drive percentage is something our devices normally track internally, and is a useful data point in troubleshooting, should you ever need it (our free lifetime support, available by phone or email, can help you with any troubleshooting you need). The value to the customer is that it serves as an indicator of the overall health of their chemical reactor vessel’s inputs and outputs. A significant change in the valve drive may indicate several possible failure conditions. Here’s a quick video showing this simple and smart customization at work:

Our “Local Valve Drive” (LVD) customization allows you to see how much drive is being given to a valve from your controller. One of our customers wanted a quick way to diagnose if their reactor’s output was dropping. Given steady pressures and flow rates, the valve drive will consistently be within a certain range. Our customer knew that at 30 PSIG inlet pressure with 10 SLPM of flow, the valve driver would be somewhere between 35-40% full power typically. If they saw the valve drive creeping much higher than this, then they would know that they were losing pressure differential in the process, since the valve was needing to open the valve wider than usual to create the same amount of flow. It may be that something is clogging the valve, making it open wider to allow flow to pass through. If they saw the valve drive percentage at 100 this would indicate that the valve was 100% open, or it was at least trying to be that way. They’d know that their reactors were creating such little output that it wasn’t possible to generate enough flow to satisfy their setpoint.

Local Valve Drive is now an option you can ask for, if your application calls for it.

Controlling pressurization speed

A customer wanted to use a pressure controller to maintain a certain pressure within a leak test chamber. However, they also wanted to make sure that the chamber would not pressurize too quickly.

MCD-Series bidirectional mass flow controller, shown with IPC option

MCD-Series bidirectional mass flow controller, shown with IPC option

To assure this, we built them a dual-valve mass flow controller in our MCD Series. A dual-valve mass flow controller can be programmed to fill with one valve and vent with a second valve. Like all our standard MFCs, it can be set to control flow based on pressure, rather than mass flow, (while still measuring mass flow!) Our dual-valve mass flow controller is also able to measure mass flowed in either direction. The MCD series of mass flow controller can be perfect for dispensing gases into a closed volume without overshooting or overpressurizing, or as an instantaneous pressurized leak test, with a built-in pressure relief valve for quickly changing the devices under test.

The customer used pressure control mode so that the setpoint was in pressure units, not mass flow units.

Finally, we created a custom software feature: a “Mass Flow Limit” function, configurable through the front screen. This would operate as a governor on the flow rate. It tells the valve to not open any further, once a certain mass flow rate was reached. This effectively limited how quickly the unit was allowed to pressurize their system.

Custom Configuring: a Stainless, IP-rated Dual Valve Pressure Controller

Customization can come in the form of unique combinations of options. Like this PCDS–it’s a dual valve pressure controller with a lot of options added on:


  • Stainless flow bodies and corrosion-resistant seals for using aggressive gases
  • A remote pressure sensor port (it’s on the backside of the flow body with the display), so that the pressure control will be based on a remote volume, independent of the valve lines.
  • IP-65, a liquid ingress prevention rating, means all the connectors are sealed with gaskets, and the display panel doesn’t have our menu buttons
  • The second valve is remote. The cable is the right length to mount the “relief” valve in a different location of the process flow.
  • Modbus industrial protocol on board. Without interface buttons to program the device, remote commands are necessary. But the display will provide a visual confirmation of the operation of the device for any technicians on the scene.

Altogether, it’s a very unusual device.

What’s your application?

When you place an order, our apps engineers always ask a lot of questions, like “What is the application? What are the operational parameters, and what are you trying to do?” This guides them in recommending things like custom tuning of valves (no extra charge!), or the selection of a particular sensor, or communications options. We do our best to make the device perform at its very best in your hands. Sometimes that means custom engineering, sometimes just custom configuring of existing options. Alicat prides ourselves in our ability to accommodate many custom configurations, or invent a solution!

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: