Page 1
THE OPERATING CYCLE OF A SPENCE TEMPERATURE REGULATOR
The Type ET134 has been selected to illustrate the operation of a SPENCE Pilot Operated T emperatur e Regulator.
This presentation describes the successive steps in the mechanical cycle of the Regulator.
1
MAIN VALVE is normally closed. On placing
Regulator in service, initial pressure fills the
passages shown in red.
3
CONTROL LINE connects Pilot Diaphragm
Chamber to Delivery piping.
4
PRESSURE SPRING
forces Pilot Valve open.
5
CONNECTING TUBING conducts steam from
Pilot to Main Valve Diaphragm and Bleedport.
When Pilot opens, steam flows through Pilot faster
than it can escape at Bleedport, creating a loading
pressure (orange) which forces Main Valve open.
6
HEATER, Delivery Pipe and Control
Line are now being filled with steam
flowing through Main Valve.
As delivery pressure (yellow) rises, it
overcomes the force exerted by Pressure
Spring and Pilot throttles. This, in turn
allows Main Valve to throttle just enough
to maintain the set delivery pressure.
7
THERMOSTAT ELEMENT (vapor tension type) is connected into heater outlet.
The rising temperature of the fluid (blue) being heated creates a vapor pressure
(green) on the Temperature Diaphragm. When this pressure has reached a point
sufficient to overcome the Temperature Adjusting Spring, it applies a force on the
Lever so as gradually to decrease the spring loading on the Pressure Diaphragm.
This produces a stem-by-step reduction in the delivery pressure as the temperature
rises through several degrees.
If the desired temperature is exceeded, the vapor pressure on the Pilot
Temperature Diaphragm overcomes the forces of the Spring. This allows Pilot and
Main Valve to close tight.
2
PILOT receives
initial pressure
through Nipple and
Union Connection.
KEY
INITIAL STEAM PRESSURE
LOADING STEAM PRESSURE
DELIVERY STEAM PRESSURE
VAPOR PRESSURE
FLUID HEATED
- 13 -
OPERATING CYCLE
TEMPERATURE
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