Why does packing seal leak when in use, but some pumps still choose packing as the sealing material ？

Sometimes customers ask, when using packing seals, it is required that water leak out at the sealing point to cool the shaft, which would cause the pump installation site to be unclean. 

Then why is there still a requirement to use gland packing seal as the centrifugal pump shaft seal?

Despite the risk of leakage, packing seals are still widely used in some centrifugal pump types, mainly for the following reasons: ‌

 Cost and maintenance advantages ‌ : The packing seal has a simple structure, low manufacturing cost, and is easy to replace on site, making it suitable for applications with low sealing requirements. ‌

 wide applicability ‌ : The packing materials are diverse (such as flexible graphite, carbon fiber), can adapt to high temperatures and corrosive media (such as acids, alkalis, steam), and have high reliability under specific working conditions. ‌

 Strong fault tolerance ‌ : Packing seals have relatively low requirements for the machining accuracy of the shaft and allow for a small amount of initial leakage to achieve lubrication, making them suitable for pumps transporting media containing particles or prone to crystallization. ‌

Therefore, the selection of packing seals needs to weigh their advantages such as leakage risk, cost, and applicability, and they are usually used in low-pressure, non-critical or easy-to-maintain scenarios.