Series 91000
••• Self-Operating Regulators
Operation, Installation & Maintenance Manual
Page 6
SENSING BULB
SENSING BULB LOCATION
The location of the sensing bulb is important.
Use of a thermowell is always recommended, especially in
pressurized systems
. The bulb or thermowell must be totally immersed in an average temperature location
which is representative of the whole volume being controlled. It should not be situated near hot or cold spots,
nor near the outlet of the valve supplying the heated or chilled fluid. If the regulator is to control a corrosive
fluid the bulb or thermowell must be constructed of a compatible material. Never install the bulb with the dead
end up unless it has been specifically ordered from, and constructed by, the factory for this service.
When installed in a pipeline, continuous flow past the sensing bulb must be maintained to obtain continuous
temperature signal to the regulator. If the flow stops, the pipeline may cool or warm to local room temperature
causing false reactions from the regulating valve. On some systems this may require a small by-pass flow line
around the valve to maintain representative system temperatures at the sensing bulb.
SENSING BULB INSTALLATION
To install a union connected sensing bulb, remove the union hub or thermowell from the sensing bulb and install
this hub or thermowell into the process piping or tank. If using a thermowell, liberally coat the sensing bulb with
the heat transfer paste supplied with the thermowell. Now slip the sensing bulb through the hub or into the well
until fully seated. Tighten the coupling nut. Do not over tighten.
Never attempt to tighten, loosen or otherwise rotate the hub or thermowell with the sensing bulb installed.
Always loosen the coupling nut before rotating the hub or thermowell. This will prevent twisting and kinking of
the connecting tubing thus preventing premature failure.
Keep all bends in the tubing greater than 1
1
/
2
” radius. Do not subject the tubing to repeated flexing, vibration,
heat, cutting, kinking or other abuse. Coil all excess tubing and place in a cool location. If motion or vibration
may occur, secure the tubing to the bulb mounting so all moves as one. If vibration or fluid pulsations may be
transmitted to the bulb, it must be housed in a thermowell for protection from fatigue.
