Alternative packing solutions for manual and modulating valves

Over the past decade or so, die-formed flexible graphite rings, in conjunction with anti-extrusion rings in various configurations, have been established as the valve stem packing material of choice. This is particularly true within the nuclear industry. However, this method is now under review due to advances in materials and manufacturing processes. During the 1980s, the approach and materials for valve stem sealing were altered with the mandatory change from asbestos-based materials to non-asbestos products, such as die-formed graphite contained with anti-extrusion rings. It was a successful transformation. Technology and market needs have now provided the opportunity to implement change. Although not mandatory, many utilities and plants are electing to implement material changes to realize the benefits these advances bring to their plant. The documented and supported advantages of converting or implementing bulk valve packing programs far exceed the disadvantages and will be discussed in this paper. The intent is to provide specific documented information related to the transition from die-formed valve packing materials to those in bulk or spool form without influence to each plant's personal preference. (author)