36 ” min π www . valve-world . net Valve World March 2024
STEAM REGULATORS
Why are electric PRVs replacing self-piloting steam regulators ?
A trend has been gaining steam . Electric modulating pressure-reducing valves ( PRV ) are increasingly replacing traditional selfpiloted regulators in steam systems .
By Robert Workosky , Warren Controls
The adoption of this “ smart ” technology is part of the overall trend of digitally connecting all components to building automation systems ( BAS ) for greater visibility and control and for lower energy consumption . Sometimes the shift to electric PRVs is driven by more basic considerations . For example , PRVs with electric actuators can be more compact , allowing them to fit in spaces too confined to install — and maintain — a pilotoperated steam regulator . Moreover , an electric PRV can be set up to automatically calculate the downstream steam flow rate , without the need to install a traditional flow meter . This is an important benefit in locations that lack a sufficient straight run of pipe to accommodate a traditional flow meter .
Pressure reduction increases efficiency
Steam is usually produced at high pressure by a steam boiler , to avoid the production of wet steam among other reasons , and then distributed to one or more points of use that require lower pressure for safe and efficient operation . Steam pressure-reducing stations perform the critical function of reducing the pressure to a desired set point . The control of pressure can also be an effective means of controlling temperature because the temperature of saturated steam is closely related to its pressure . A single facility may have several pressure reducing stations . Hospitals , for example , require PRVs to deliver steam for many different uses , including heating , humidification , hot water , sterilization , kitchen , and laundry functions , with varying steam usage requirements based upon the process , the time of day , weather , etc . Pressure reducing stations also facilitate costeffective distribution . Significantly smaller pipe diameter can be used where the steam is under high pressure . Therefore , on university campuses where the steam plant serves many buildings spread over a large area , the pressure reducing stations may be located close to the points of use to save on the installation cost of piping and fittings . This benefit needs to be weighed against the energy savings achieved from reducing radiant heat loss when distributing steam at lower temperatures . The goal is not only to deliver steam below the maximum allowable working pressure ( MAWP ) of each piece of equipment , but to maximize energy efficiency for financial saving and environmental sustainability . The most significant energy savings from pressure reduction comes from delivering the optimal pressure at the point of use . Lower pressure results in increased enthalpy of steam and the availability of more latent heat . In other words , more BTUs can be delivered per pound of steam when the pressure is reduced .
Traditional pilot-operated regulators
Originally invented in the 1880s , pilot-operated steam regulators are a tried-and-true method
110VAC Emergency Power
Note
BACnet Communications to BAS
ILEA Electric Actuator |
FT |
PI |
PT |
High Pressure Steam |
|
|
|
3,561 lb / hr 100 psi |
6 ” |
6 ” |
Low Pressure
Steam 15 psi
|
PRV
Schematic of a connected system engineered by Warren Controls
36 ” min π www . valve-world . net Valve World March 2024
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