π Key Concepts
β’ Self-contained temperature regulating valves use a sensing bulb, capillary, and bellows to move a pilot or main valve as temperature changes.
β’ The temperature set point is changed by altering the spring force that opposes the motion from the temperature-sensing element (bulb/bellows).
β’ In the illustration, notice which parts are clearly sensing elements (bulb or probe) versus which are adjusting screws or nuts acting on a spring.
π Think About
β’ 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?
β’ 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?
β’ 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?
β
Before You Answer
β’ 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.
β’ Find the component that is mechanically connected to the spring labeled near K and clearly has threads/adjusting feature to vary spring compression.
β’ 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.