Intro to Millwright Practice Exam

Which statement about metallic packing is correct?

1. It is a solid piece of pliable metal like tin.

2. It is always used in high-pressure applications.

3. It is flexible and can change shape easily.

4. It is used exclusively in hydraulic systems.

The correct answer is: It is a solid piece of pliable metal like tin.

Metallic packing is typically a braided or wound material made from various metals, designed to form a seal around a moving part, such as a shaft in a pump or valve. The characteristic of metallic packing that aligns with the answer is that it is indeed made from solid pieces of metal. This construction allows the packing to withstand high temperatures and pressures, making it effective in sealing applications. The quality of being pliable can be somewhat misleading; while it is not flexible like a rubber gasket, it can compress and conform to the surfaces it seals against. Its primary advantage lies in its durability and ability to maintain a tight seal over time, even when subjected to extreme conditions. In contrast, it isn't limited to a single type of metal like tin but can be composed of various alloys to suit specific applications. The other options misinterpret the characteristics or applications of metallic packing. It is not exclusively used for high-pressure applications; rather, it's beneficial in a variety of applications, not just hydraulic systems. Flexibility is not a defining characteristic, as metallic packing does not change shape easily like some other packing materials. Hence, the understanding that metallic packing is made of solid pieces of metal confirms its essential function as a reliable sealing material in various mechanical systems.