Regulators: Which To Choose?
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Regulators: Which To Choose?
 
Article Introduction
Regulators are highly technical, highly specialized fluid handling components. So before installing regulator, it is very necessary to consider various factors for proper functioning of application

Article Description
Regulators are one of the essential tools in industrial application. Regulators are available in various size, types and designs. Hence, while choosing a regulator it is very important to give consideration to the gases, phases, pressures, and temperatures. For example a stainless steel regulators should be considered in any application having even a small presence of corrosive gases or liquids or hostile environmental conditions.

As regulator controls pressure, they are used as the pivot points between high and low pressure. Regulators control pressure in such a way that there is higher pressure on one side, and lower pressure on the other side. On the high-pressure side, the regulator mechanically controls a pressure drop, so that on the low-pressure side, pressure will remain relatively constant. Regulators like pressure-reducing regulator allows inlet pressure to undergo a mechanically controlled pressure drop, resulting in a relatively constant pressure at the outlet. While in some cases, a backpressure regulator would be used to mechanically control the outlet pressure, so that a relatively constant pressure maintained at the inlet.

Types of regulators
There are five types of regulators. These are vaporizing regulators, one-stage regulators, two-stage regulators, diaphragm regulators, and piston regulators.

Vapourising regulators
A vapourising regulator is pressure- reducing regulator used for controlling or inducing a phase change. In certain cases, a sudden and rapid pressure drop may result in the joule-Thompson effect (A process in which gas loses heat to undergo to a complete or partial phase to become liquid) leading to freezing of regulator. In such circumstances, Vapourising regulator applies heat at the point of pressure drop, preventing the phase change and freezing. In other cases, a liquid may need to be analyzed in a vapour form, typically in gas chromatograph applications. In this case the regulator applies heat to vapourise the liquid to a gas.

One-stage pressure reducing regulatorsIn case of One-stage pressure reducing regulators, inlet pressure is relatively constant. But on-stage regulators are sensitive to a phenomenon known as supply pressure effect (SPE) (SPE is the ability of a regulator to adjust to changes in the high-pressure supply to the regulator). Therefore in applications where the high-pressure supply is subject to large variations, a regulator with a low SPE will provide the most stable low-pressure delivery. Therefore, a one-stage regulator will generally deliver a stable outlet pressure when the high-pressure supply is stable.

Two-stage regulator
A two-stage regulator consists of two one-stage regulators in series and combined into one component. The first regulator reduces the high-pressure supply to an intermediate point between the inlet pressure and the desired outlet pressure. The second regulator reduces the intermediate pressure to the desired outlet. One-stage regulators are located off each cylinder. An additional regulator is located at the entry point to the system, so at all times the gas is passing through two regulators.

Sensitised action
Daiphragm regulators generally are the quickest to respond, if there are some changes in pressure, especially in low-pressure applications. Depending on their type, they may be used in pressure up to 248 bar. In a diaphragm regulator, a thin metal diaphragm flexes as the high-pressure inlet varies. This flexure causes the regulator poppet to move in and out of the regulator seat. This compensating action is what causes the downstream pressure to remain constant.

Piston regulators
Piston regulators are usually used in higher-pressure applications. In a piston regulator, pressure is controlled by means of a spring-loaded piston, which is a stainless steel, inflexible disk that lies flat in the vertical cylinder of the regulator, that is a piston. The piston sticks against the cylinder walls by means of an elastomeric O-ring seal. The thickness of the piston, along with the O-ring seal, allows a piston regulator to achieve higher working pressures than diaphragm regulators.


Conclusion
Selection of a regulator should be done based on application type and different parameters like gas/liquid content, temperature, and flow rate. Once the type of regulator has been chosen (backpressure or pressure reducing, piston or diaphragm, one-stage or two-stage), other factors such as regulator construction, quality of the shell seal, ease of stem adjustment, diaphragm/piston seal, integral filtration, and poppet seating should be considered. Most importantly, quality and type of materials should be checked to ensure safe and proper functioning of the regulator over time.
Posted : 11/19/2005

 
 
Regulators: Which To Choose?