Cutting packing will always results in some waste. This could be rings that are too long or short but also can be rings whose ends have unraveled or blossomed to the point at which they could result in a leak path. One of the easiest ways to sidestep errors in cutting is to order cut rings from the packing supplier. Besides no scrap, there is also a considerable time savings from not having to cut the rings. The drawbacks to using cut rings everywhere is having good documentation of the actual size of the packing beforehand to know what to order. This can be a bigger hurdle than first thought since a major paradigm shift needs to occur regarding creating a database of equipment dimensions.
A couple of other simple ways to create a good environment that will result in a better cut ring are first to order (or get a machine shop to create) accurate mandrels for all stem and shaft sizes. The other is to have in the cut ring area some good knives and access to a knife sharpener.
Next Month: What factors should be considered for stainless steel fasteners in bolted flange connections?
Pumps & Systems, November 2011