Exam Question

### (a) Clearances to be Checked When Lapping Valves to Seats
When overhauling and lapping an auxiliary boiler safety valve, the primary goal is to restore a perfectly steam-tight seal between the valve disc and seat. However, after reassembly, it is critical to verify several mechanical clearances to ensure the valve can operate freely, lift to its designed height, and reseat correctly. Failure to maintain these clearances can render the safety valve inoperative.
**1. Valve Spindle to Compression Screw Clearance:**
* **Description:** A slight axial and radial clearance exists between the top of the central spindle and the compression screw that sets the spring pressure.