Pressure Regulation Terminology
Types of Pressure Regulators
Single Stage Regulator: a regulator with only one pressure reduction point.
Dual Stage (or Two Stage) Regulator: a regulator with two pressure reduction points; the first is usually fixed and the second is usually adjustable within the range of the primary spring.
Back Pressure Regulator: most regulators are used to regulate the downstream pressure; this type is used to regulate the upstream pressure.
"Line" Regulator: typically this is a high flow regulator installed somewhere between the gas source and the final point of use, and often limited to inlet pressures below 500 PSI.
"Point of Use" Regulator: this is usually a high performance regulator that is installed in a gas stick or Gas Isolation Box very near the point at which the gas(es) will enter the system.
Performance Definitions:
Creep: the rise in oulet pressure as flow is terminated (sometimes referred to as "lock-up"). Creep is minimized by decreasing the area around the poppet that needs to be sealed; and creep increases as inlet pressure decreases.
Droop: the deviation between the outlet pressure at a low flow condition and the outlet pressure at a higher flow condition. The higher the range, the higher the droop. The larger the diaphragm, the less the droop. Pilot Operated ("Dome Loaded") regulators also have lower droop.
Hysteresis: the difference in the presure at a given reference point between an increasing flow condition and a decreasing flow condition.
Repeatability: how closely a regulator returns to a given set pressure after terminating and resuming a specific flow rate.
Sensitivity: the minimum pressure increment that can be set repeatably on a pressure regulator.
Transient Response: a plot of the outlet pressure vs. time when switching between two different flow rates.
Supply Pressure Effect: the change (decrease) in outlet pressure caused by a change (increase) in inlet pressure. If you need to minimize this effect, use a Dual Stage Regulator.
Tied-Diaphragm: (sometimes called "Linked-Poppet") this is when the diaphragm is attached to the poppet to prevent runaway flow condition. It is primarily useful a safety measure when flowing hazardous gas(es).
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