Exam Question

### (a) Clearances to be checked when lapping valves to seats
When lapping safety valve discs to their seats, the primary objective is to achieve a perfect, steam-tight metal-to-metal seal. However, ensuring correct clearances is equally critical for the valve's proper function, operational stability, and longevity. The following clearances must be meticulously checked:
* **Valve Spindle Guide Clearance:**
* **Description:** This is the radial clearance between the valve spindle (stem) and the guide bush within the valve body. It ensures the spindle moves freely and aligns the valve disc accurately onto the seat.