Oilers/Plant Tenders (HHC) Civil Service Practice Exam

Which statement is true about packing in a centrifugal or reciprocating pump?

1. It must be installed to completely stop leakage

2. The packing material is always resistant to wear

3. It needs to be replaced after every use

4. It does not need to be installed to stop leakage

The correct answer is: It does not need to be installed to stop leakage

In the context of packing in a centrifugal or reciprocating pump, the statement that it does not need to be installed to stop leakage is accurate. Packing is a crucial component used to create a seal around the shaft of the pump, preventing fluid from leaking into the atmosphere. While it is ideal for packing to minimize leakage, it is generally installed to allow for some controlled leakage for several reasons. This small amount of leakage cools the packing, lubricates the shaft, and can prevent overheating. The installer's goal is to find a balance between effective sealing and reducing wear on the packing and shaft. The other statements fail to capture the practical realities of packing in pumps. For example, while some packing materials are designed to resist wear, not all materials guarantee complete wear resistance. Moreover, requiring the replacement of packing after every use would be impractical, as packing is typically designed for longer service life and should only be replaced when it shows signs of wear or a significant increase in leakage. Lastly, installing packing specifically to stop leakage entirely contradicts the operational principle of allowing some leakage for lubrication and cooling.