What is a common characteristic of the packing used in pumps?

The characteristic of packing used in pumps being designed to wear out recognizes the purpose of packing in a pump system. Packing is typically made from materials such as PTFE, graphite, or other synthetic materials, which are designed to provide a seal around the moving parts of the pump shaft while allowing for some degree of wear over time. This wear is expected and manageable; it allows for adjustments to be made (like tightening the packing) to maintain an effective seal.

The design to wear out also helps in preventing damage to other components of the pump. By sacrificing the packing material, pumps can avoid more costly repairs or replacements of other critical parts. Regular maintenance and replacement of the packing are essential to keep the pump operating efficiently and to prevent leaks.

Waterproofing, expanding under pressure, and being made of metal are not typical characteristics of packing materials used in pumps, as they focus instead on creating an effective seal while being manageable in terms of maintenance and operational efficiency.