What type of packing should be used when replacing old packing?

Using "in kind" packing when replacing old packing ensures that the new material matches the original packing in terms of composition and functionality. This is crucial because different types of packing materials are designed for specific applications and conditions, such as temperature, pressure, and the type of fluid being contained.

When replacing packing, maintaining the same type prevents issues such as leaks, improper sealing, or chemical reactions that could arise from using dissimilar materials. The original packing was likely chosen for its compatibility with the fluid system and operating conditions, so matching it ensures optimal performance.

In contrast, using a larger or smaller size may compromise the seal, allowing leaks to occur, while softer materials may not provide the required durability or pressure resistance. Hence, selecting packing that is "in kind" is essential for maintaining system integrity and performance.