🔍 Key Concepts

• Blow down is the difference between the pressure at which the safety valve pops and the pressure at which it reseats • On a spring-loaded boiler safety valve, set pressure is adjusted by changing spring compression, while blow down is adjusted by changing the position of the nozzle/adjusting ring around the seat • Parts at the top of the spring usually affect set pressure or lifting gear, while parts near the seat and nozzle ring affect blow down

💭 Think About

• Look at which labeled part is closest to the valve seat and discharge nozzle rather than the spring compression hardware at the top • Ask yourself: which part, if moved slightly up or down, would change the flow path and reaction of the escaping steam around the seat, thus affecting when the valve closes? • Compare: which parts are clearly related to the compression of the main spring (set pressure) versus the parts that shape the steam discharge path (blow down)

✅ Before You Answer

• Identify which letter corresponds to the nozzle/adjusting ring assembly around the seat area rather than the spindle or spring plates • Confirm that the part you pick is not the main compression screw or locknut that changes set pressure • Mentally trace the steam path from inlet to outlet and verify that your chosen part, when repositioned, would realistically change the pressure at which the valve reseats (closes)