š Key Concepts
ā¢ Self-contained temperature regulating valves use a sensing bulb, capillary, and bellows to move a pilot or main valve as temperature changes.
ā¢ The temperature set point is changed by altering the spring force that opposes the motion from the temperature-sensing element (bulb/bellows).
ā¢ In the illustration, notice which parts are clearly sensing elements (bulb or probe) versus which are adjusting screws or nuts acting on a spring.
š Think About
ā¢ Trace the path from the temperature-sensing bulb in the line (lettered on the left) up through the capillary to the internal bellows/spring assembly. Which component directly changes how much that spring is compressed?
ā¢ Look closely at letters A, B, C, M, and L: which ones appear fixed in place once installed, and which one looks like it is meant to be turned (threads, locknut, or screw head) to change a setting?
ā¢ Ask yourself: does changing the set point require moving the sensor location, or just changing the balance between bulb pressure and spring force inside the regulator body?
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Before You Answer
ā¢ Identify which lettered device is clearly the temperature sensing bulb or probe and which are internal valve/pilot parts that do not change the set point.
ā¢ Find the component that is mechanically connected to the spring labeled near K and clearly has threads/adjusting feature to vary spring compression.
ā¢ Before choosing, eliminate any letter that is only part of the process line, body casting, or fixed housing and cannot practically be turned for adjustment in normal service.