Dome-loaded pressure regulators can deliver highly stable outlet pressure. In these devices, the required outlet pressure is regulated by means of a gas cushion instead of a spring. The gas technology specialists at WITT have perfected this technology, the company claims. But how does it work exactly, and where are the differences?
Text courtesy of WITT
Dome-loaded pressure regulators are of enormous importance for the quality of the gas supply. They control the gas pressure constantly even with fluctuating upstream pressures or flow rates and can also allow high flow rates even with small pressure differences. Stable outlet pressure means a stable process downstream.
In conventional devices, a simple spring provides the necessary counterforce to reduce the inlet pressure to the desired outlet pressure. In dome-loaded regulators, the required counter-force is generated by gas pressure.
The so-called pilot gas forms a kind of gas cushion and presses on a diaphragm, whose movement adjusts the main valve. The gas flowing through acts behind the valve seat as a counterpart to the pilot pressure on the diaphragm. The pilot pressure and the outlet pressure compensate for each other and achieve a stable equilibrium. The outlet pressure thus remains constant, even if the flow rate is fluctuating.
Pilot and dome pressure regulator in a single fitting
In dynamic systems, a separate pilot pressure regulator is usually used. The user simply adjusts the pressure applied to the dome pressure regulator at any time via the pilot pressure regulator, thereby controlling the required outlet pressure.
WITT has now integrated the pilot – and dome pressure regulator into a single device, a complete solution that can be installed in any position and includes pressure gauges. “The compact regulator is fully assembled, tested and ready for immediate use. This means minimal space requirement, as well as rapid installation and low maintenance needs, with the corresponding time and cost savings for the user”, WITT states.
In addition, WITT regulators have some special features: a separate gas source is not required as the control gas is used for the control pressure. WITT’s dome-loaded pressure regulators sense the working pressure via their so-called “Pilot Control Tube” in their outlet. In other words, exactly at the point that is relevant for accurate outlet pressure control. In addition, their “Balanced Seat Design” balances the valve position by means of the pressure on each side. Even with upstream pressure fluctuations, the outlet pressure remains constant for the user.
Furthermore, the diaphragm does not rest di-rectly on the valve seat but transmits its stroke movement via a special diaphragm plate. This is key to their highly precise pressure regulation, WITT states.
Constant pressure curve
WIIT says that with other dome pressure regulators, the pressure curve usually drops off,
i.e. the higher the flow, the greater pressure “droop”. With WITT domes, the outlet pressure remains practically unchanged over the entire possible flow range. Readjustment is not necessary.
“WITT dome pressure regulators also compensate extraordinarily quickly for changes in the upstream pressure. Fluctuations of the outlet pressure or the notorious “fluttering effect” seen in other designs do not occur. The pressure loss or the pressure difference are also minimal. Even with a pressure difference of only 1 bar between upstream and downstream pressure, exact regulation is possible. This means that both very small and very large pressure differences can be controlled. The regulators are designed and cleaned for O2 according to EIGA/CGA guidelines.”
Advantages for many applications
The advantages of WITT dome-loaded pressure regulators can be seen in numerous applications. Whenever high degrees of pressure stability, high flow rates and low pressure drops are required, dome-loaded pressure regulators are the best choice, WITT states.
For example, in CO2 systems for the supply of welding gases. Here, strongly fluctuating flowrates often occur, depending on how many tapping points are currently being used. With WITT dome pressure regulators, the working pressure remains stable.
The regulators are also frequently used for industrial gas supplies with high pressures, for example downstream of a tube trailer, a tank or cylinder bundle. The low pressure drop of the regulators allows maximum emptying of the contents, providing logistics costs’ savings.
