How Does Dome Loading Work On The Equilibar Back Pressure Regulator?

Tuesday, July 11, 2023

Equilibar specialise in dome loaded back pressure and vacuum regulator controllers.

The “Dome Loading” process is much simpler than it sounds. Instead of a manual control dial as seen on traditional gas or liquid pressure regulators, this method feeds a one to one loading pressure to act as the set point for the Equilibar BPR. This loading pressure is achieved using a gas, usually air or nitrogen, and is supplied directly to the dome (top plate) of the back pressure regulator. (View our range of Back Pressure Regulators).

Advantages of piloting a regulator/valve

The main 3 advantages of piloting a regulator/valve are:

1. The differential pressure/setpoint pressure is not acting or governed on the working component of the regulator and is not in contact with the process.
2. Higher accuracy as this pilot regulator is not reliant on the sealing areas/moving part to determine the setpoint as it is sourced externally. This is important if there are any potential contaminants in the process which could potentially wear the sealing surfaces.
3. The pilot method only acts of the diaphragm of the Equilibar therefore less moving parts and reduced friction error.

The ‘pilot dome’ regulator can be manual or electronic, depending on the application’s requirements. The most common options have been described below:

Mechanical (or Manual) Method

Some applications only require the setpoint to be set once or are sufficiently simple that an operator can make any changes by hand. As a more cost-effective solution many customers are satisfied by the level of performance achieved by such a mechanical pressure reducing regulator. These regulators can feed either nitrogen or air and should include a self-venting mechanism to facilitate both decreasing and increasing set pressure adjustment.

The BPR will then be set and will perform its required function whether it be positive or vacuum pressure and will not change until manually adjusted again, of course within its specification limits.

Electronic Method

The electronic dome loading method employs a dual valve pressure controlling device. This solution controls the set pressure to the dome of the BPR via local on-board, analog, digital or bus communications.

A Distributed Control System, a laptop, or even the push buttons on the front of the device can be used for fully or semi-automated signal control. This enables the Equilibar BPR to reference its position in line with the dome loading mechanism that is considerably more accurate than the manual control method using mechanical pressure reducing regulators.

A further advantage of using this method is the benefit of remote parameter change, away from the process and the data-logging of any changes made. Furthermore, the use of the associated freeware enables scripts to be written that can vary the set-point over prescribed periods of time within a rolling or finite program.

Electronic Method With Closed Loop Control

This method achieves the highest level of accuracy with superior control characteristics in relation to widely fluctuating flow regimes. Similar to the above this solution includes a dual valve pressure controller, however, a feed-back loop directly monitors the process pressure rather than the dome-loading pressure.

In the diagram below the concept of PID with a feed-back loop is illustrated however in reality this is all “on-board” the dual valve pressure controller itself. The PID system is essentially an automation device which controls and adjusts any variables against a desired setpoint.

Get in touch

We are the distribution partner for these products so please feel free to contact PCT for more information - you can call us on 01953 609930 or email sales@pctflow.com.

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Posted by Andy Mangell, Co-Owner / Sales Director