Magpie Sealing Technology Insight
Valve Packing Seals: Wear and Lubrication in Packing Seals
The service life and reliability of packing seals are closely tied to wear and lubrication.
Friction-induced wear is a prominent issue in packing seals. In rotary or reciprocating motion, not only does the packing material wear, but the shaft or rod it seals against can also experience significant abrasion. The extent of this wear is influenced by several factors, including the wear resistance of the packing and shaft (or rod) materials, the shaft's rotational or reciprocating speed, the effectiveness of lubrication and cooling, and the quality of the packing installation.
Due to the uneven axial distribution of radial contact stress, even properly installed packing tends to wear more at the gland area, with the wear gradually decreasing inward. Poor installation may result in abnormally high-stress zones, leading to accelerated and severe wear of both the packing and the shaft within a short period.
In addition, if the valve stem does not move along a consistent axis, or if it lacks proper coaxial alignment with the stuffing box and packing rings, it can cause uneven circumferential wear. As a result, wear is one of the primary causes of packing seal failure.
Lubrication plays a critical role in reducing wear and directly impacts the packing's lifespan and sealing performance. Most braided packings are impregnated with self-lubricating and high-temperature-resistant lubricants. In some applications, lubrication can also be provided externally or even through the process fluid itself.
Besides minimizing friction, lubricants help dissipate heat generated during operation, reducing thermal wear on the packing. For extreme conditions such as high temperature, high pressure, or high speed, forced lubrication and cooling become especially important to maintain the integrity of the seal.
Moreover, in valve stem packing assemblies, it is common to install lantern rings (spacer rings) within the packing set. These rings can serve multiple purposes: facilitating lubricant injection, enabling leak monitoring, and in cases of excessive leakage, allowing for the injection of sealant to maintain sealing performance.
At Magpie Sealing, we provide innovative solutions for low-leakage sealing systems. If you have any technical questions about sealing technologies, we welcome your comments and inquiries. Thank you for reading! In the next issue, we'll continue with an introduction to different types of sealing gaskets. Stay tuned!