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PRESSURE-REDUCING VALVES
Should steam pressure be too high for a specific process, a self
contained pressure-reducing valve (PRV) may be used to reduce
this pressure, which will also increase the available latent heat.
These valves may be direct-acting or pilot-operated
much like temperature control valves. To maintain set pressure,
the
downstream pressure must be sensed either through an internal
port
or an external line.
The amount of pressure drop below the set pressure that causes
the valve to react to a load change is called droop. As a general
rule,
pilot-operated valves have less droop than direct-acting types.
To
properly size these valves, only the mass flow of steam, the inlet
pressure, and the required outlet pressure must be known. Valve
line
size can be determined by consulting manufacturers’ capacity
charts.
Due to their construction, simplicity, accuracy, and ease of
installation and maintenance, these valves have been specified
for most
steam-reducing stations.
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