Dwyer 38R - Manual (Page 17)

Page 17
Option 3 “FAIL-SAFE” – Installation & Maintenance
The valve body assemblies on these models are identical to those
previously described and there is no difference in their servicing.
However, the actuators are different and larger bellows are used to
develop adequate thrust with the limited pressure differential available
below atmospheric pressure. If the “Fail-Safe” tube system becomes
damaged and inoperative, the valve will move toward the
hot position within the listed working conditions. If subjecting the
thermal bulb alternately to temperatures above and below the
instruments range does not produce any valve stem movement,
the system is dead and requires replacement or factory service.
FACTORY SERVICE
If you are unable to obtain proper operation of the regulator, we
suggest you contact the nearest W.E. Anderson representative. If
necessary, the regulator will be sent to the factory on a “Check and
Report” basis and the regulator will be thoroughly inspected and tested.
Option 3 – SPECIAL INSTRUCTIONS
Option 3 Actuator Stem
The actuator stem in an Option 3 actuator does not turn. When removing or attaching the valve stem to the
actuator stem on an Option 3 Actuator turn the valve stem only.
• On a cooling valve the sensing bulb must be heated in a bucket of hot water to extend the stem to
displace the valve plug off of the valve seat to prevent damage to the valve seat.
• On a heating valve the sensing bulb must be cooled in a bucket of ice to retract the stem to displace
the valve plug off of the valve seat to prevent damage to the valve seat.
Option 3 Actuator Stem Locknuts
When setting the stem locknut dimensions the Direct-Acting valves used on Option 3 Actuators are to be
set
1 / 4 ” shorter than shown in Figure 6. Reverse-Acting and three-way valves are set the same as tabulated.
Over Range Protection
The Option 3 Actuator does not incorporate over-range protection. Do not exceed the maximum temperature
shown on the instrument.
Series 38R ••• Self-Acting Temperature Control Valves Operation, Installation & Maintenance Manual
Option 3 shown