What is typically used to ensure a tight sealing during repacking?

In the context of ensuring a tight seal during repacking, new packing material is typically the most crucial component. This is because packing material is specifically designed to fill the gaps and prevent leaks in mechanical systems. When equipment is disassembled for servicing or maintenance, it is often necessary to replace old, worn, or damaged packing material to restore its sealing capabilities.

Using fresh packing materials, whether it's rope packing, portioned gaskets, or specialized sealing compounds, provides the correct density and elasticity needed to form an effective seal. This is particularly important in systems where pressurized fluids or gases might escape, as even a small leak can lead to performance issues.

The other options—O-ring seals and compression fittings—are indeed valuable sealing methods in various applications but are not as directly related to the specific action of repacking that involves replacing the packing material itself. While each can contribute to achieving a tight seal in different contexts or alongside packing materials, they do not replace the necessity of using new packing material in the repacking process. Therefore, emphasizing new packing material is essential for ensuring an effective and reliable seal, particularly in maintenance tasks.