Brochure

110
Selection Guides
Pressure and/or Temperature Pilot Operated Steam Regulators
Series 2000
Series 2000 Pilot-Operated Regulators consist of a main
valve that is controlled by a single or combination of pilot
control valves.
There are a number of types of pilot control valves
available:
• Series SPS Spring Pressure Control Pilots – for self-
contained pressure regulation
• Series STPA Self-Contained Temperature Control
Pilots – for control of heated fluids
• Series AP Air Pressure Control Pilots – for remote
pressure control using air pressure
• Series 315 PNT and Series 240 PNT Pneumatic
Temperature Control Pilots – for rapidly changing
load requirement applications
Different types of pilot valves can be used in combination
to control more than one function or as a safety override.
For example, a temperature pilot may be used in conjunc-
tion with a spring pressure pilot to control both tempera-
ture and pressure. Or, a temperature pilot may be used
with a solenoid pilot to provide automatic shutdown when
an over-temperature condition occurs.
Operation of Series 2000 Pilot-Operated Regulator
Main Valve
The regulator main valve is held closed by the pressure
on the diaphragm from an internal main spring. Pilot con-
trol valves control steam flow from the upstream supply
side of the main valve to the underside of the diaphragm
of the main valve. When the pilot valve opens, steam
flows through the pilot and pressure builds in the signal
line, applying pressure under the main valve diaphragm.
This pressure force compresses the main valve spring
and the main valve opens.
Under constant steam demand, the pilot and main valve
remain relatively motionless. As the system approaches
the pilot set point, the pilot valve begins to close. Less
steam passes through the pilot and through the signal
line. Pressure in the signal line decreases as steam
passes through a small bleed orifice on the main valve.
With lower steam pressure under the main valve
diaphragm, the main valve spring forces the main valve to
close.
Bleed Orifice
Port and Seal
Diaphragm
Signal Line Inlet
Hoffman Specialty
®
Selection Guidelines