If the stuffing box bore on a pump is 63.5 mm and the shaft diameter is 50.8 mm, what size packing should be used?

The size of packing for a pump's stuffing box is typically determined by understanding the difference between the bore of the stuffing box and the diameter of the shaft. The goal is to achieve a proper sealing effect, and one standard practice is to use packing that is generally one-eighth of the stuffing box bore size.

In this case, the stuffing box bore is 63.5 mm. Dividing this measurement by 8 gives approximately 7.93 mm, which can be rounded to a more easily available packing size. Since the options provided are in specific measurements, the closest effective size for packing that aligns with the one-eighth rule would be 6.35 mm, as it offers an acceptable balance between sealing effectiveness and ease of installation.

Selecting the correct packing size is critical for maintaining the efficiency of the pump and preventing leaks, which can lead to both operational issues and potential damage to the equipment. Using packing that is too large can cause excessive friction and wear, while packing that is too small may not provide adequate sealing. Therefore, choosing 6.35 mm packing aligns with these considerations for optimal performance in the stuffing box.