Supply-pressure effect (SPE) or dependency is a ratio describing the change in outlet pressure per 100 psi (6.8 bar) change in inlet pressure. In other words, for every 100 psi (6.8 bar) drop in inlet pressure, the outlet pressure will increase by X psi. X is the SPE. For standard pressure-reducing regulators, the outlet pressure increases as supply pressure decreases. The opposite is true as supply pressure increases. This effect can also be realized on system startup or shutdown. The regulator should be set to the “off” position before turning the supply pressure on or off to prevent overpressurization of regulator diaphragms, outlet pressure gauges, or other equipment downstream. When selecting an antitamper model, it is important to make sure that SPE will not cause excessive overpressurization on opening and closing of the supply pressure.
In a live technical webinar on January 17th, customers of Swagelok Northern California will receive a 30 minute briefing from Swagelok field engineer and regulator expert Eric Kayla. Kayla will discuss how to properly select and size a pressure reducing regulator and cover:
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Related articles:
Webinar Replay: The Theory and Operation of Pressure Reducing Regulators
Related downloads:
Technical Bulletin and Article on Pressure Regulator Flow Curves
Slide Deck: The Theory and Operation of Pressure Reducing Regulators
Q&A from The Theory and Operation of Pressure Reducing Regulators
Swagelok Pressure Regulators Catalog