Dome loaded back pressure controllers are often used in processes where constant pressure is needed in a (chemical) reactor. Electronic pressure controllers are very effective when it comes to automating such processes.
‘We use the latest Bronkhorst electronic pressure controller for our Equilibar dome loaded back pressure controllers. This allows us to regulate two control valves,’ says Armand Bergsma, owner of Pressure Control Solutions in Veenendaal (NL).
Dome loaded back pressure controllers
The process pressure is set by applying the required pressure to the reference side of the controller at a one-to-one ratio. The reference pressure can be applied using a manual reduction device, or for process automation, you can use electronic pressure controllers.’
‘Until recently, we used single-valve electronic controllers to get the right pressure levels, then to reduce pressure, we added artificial leaks. Although this works very well in practice, the downside is that this solution requires us to continuously use inert (high-pressure) gas.’
‘This configuration is fine for low-pressure applications using a compressed air network, or high-pressure applications where the customer provides a centralised high-pressure network. However, it can be a problem if such facilities are not available.’
‘If there is no centralised high-pressure network, you can use 200 or 300-bar gas cylinders. The reactors used to test catalysts usually only need a pressure of 150 to 180 bar, so you should not use more than 50 to 20 bar respectively from a 200-bar nitrogen cylinder in order to maintain maximum process pressure. If you want to work for an extended period, you will have to find another way to limit the consumption of dome gas.’
(Industrial) Process Pressure Controller
‘Together with Bronkhorst Nederland, I looked for a solution to reduce the consumption of dome gas. We now combine our Equilibar dome loaded back pressure controller with the new Bronkhorst EL-PRESS Process Pressure Controller. This device features an integrated PID controller, which means we can now regulate two control valves, reducing the consumption of dome gas by quite a lot.
This pressure controller opens the control valve located upstream of the pressure sensor. Meanwhile, the downstream valve remains closed, which causes the reference pressure to increase. Gas consumption during the pressure build-up is negligible. The control valve located downstream of the pressure sensor is only opened once the pressure is lowered. Naturally, the upstream valve remains closed when this happens. By choosing the right valve (orifice size) and PID settings, we can quickly or slowly increase and/or reduce the dome pressure, depending on our needs.’
Pressure control with two control valves for dome loaded pressure controllers
The Bronkhorst Process Pressure Controller (PPC) doesn’t just reduce gas consumption, it also offers excellent stability. Thanks to the clean pure gases that are used, processes that combine an Equilibar precision dome loaded pressure controller and the PPC can control pressure stability at a rate that is even better than 0.1%.
‘The process side of the dome loaded pressure controller is often used to process aggressive reactants and by-products at high temperatures. For these severe applications, the Equilibar can be manufactured from chemically inert materials such as SS316, Hastelloy, Zirconium and Monel. The multiple-orifice design is capable of controlling gases and liquids as well as multi-phase flows.’