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Regulator Selection, Installation, and Operation

The primary function of a regulator is to reduce high-pressure gas in a cylinder or
process line to a lower, usable level as it passes from the cylinder to a piece of
equipment. A regulator is not a flow control device. It is used to control delivery
pressure only.
Since there are numerous hazards associated with specialty gases—hazards that
vary with the gas, the equipment used, and with the particular application—it is
necessary to take the proper precautions to assure safety in high-pressure gas
control. 
Before performing any operation with which you are not familiar, seek the advice of
an experienced individual. In addition to adhering to the safety and operating rules
provided here, the user should be aware of the additional safe operating practices
peculiar to each piece of equipment and each application. Consult sales office when
in doubt about correct handling procedures.
Never use any regulator for gases other than those for which it is intended.
The following is applicable to pressure regulators used with flammable, oxidant,
corrosive, inert, or toxic gases, when it is necessary to reduce cylinder supply
pressure to a lower use pressure.
How Regulators Work
Single-Stage Regulators 
High-pressure media enter the regulator through the inlet into the high-pressure
chamber (see Fig. 1). When the adjusting knob is turned clockwise, it compresses
the range spring and exerts a force on the diaphragm, which pushes the valve stem
open. This releases gas into the low-pressure chamber, exerting an opposing force
on the diaphragm. An equilibrium is reached when the spring force on the
diaphragm is equal to the opposing force of the gas in the low-pressure chamber.
In a single-stage regulator, delivery pressure increases as cylinder pressure decays,
because there is less gas pressure exerted on the valve stem. Thus, frequent
adjustment of the control knob is required to maintain constant delivery pressure.
This does not pose a problem, however, with pipelines and liquefied gas products
where inlet pressure is maintained relatively constant.