To prevent leakage at the point where the shaft protrudes through the case, which is used to seal the space between the shaft and the case?

The sealing of the space between the shaft and the case is critically important for maintaining the integrity and functionality of a system. Packing rings are specifically designed for this purpose. They are made from materials that can compress and fill the gap around the shaft, effectively preventing leakage of fluids.

Packing rings operate by creating a tight seal that prevents water or other fluids from escaping. They are installed around the shaft within the stuffing box of pumps and other rotating equipment. The ability to adjust the tightness of packing as it wears over time is another advantage, allowing for consistent sealing performance.

In contrast, lantern rings enhance packing arrangements by promoting lubrication and assisting in leakage control but do not directly seal the shaft. Shaft sleeves provide a protective surface for the shaft but are not used specifically for sealing. Mechanical seals are more advanced sealing solutions that utilize rotating components to achieve their sealing function, often at the expense of simplicity and ease of maintenance associated with packing rings. Each of these alternatives serves various functions, but packing rings remain the most traditional and effective method for sealing shaft protrusions against leakage in many applications.