Jam Style PTFE Packing Arrangements – In some applications, a jam style packing arrangement is preferred to the spring-loaded design. A double, jam style, PTFE packing arrangement is shown in Figure 26. Note that the two sets of packing are separated by a lantern ring.
Jam style packing is commonly specified for sour hydrocarbon services and other applications that must conform to NACE guidelines. Because the NACE guidelines limit material hardness, and because material hardness is a required property for a good spring material, suitable springs are simply not available for spring-loaded packing.
The major disadvantage of the jam style packing is the requirement for periodic adjustment of the packing flange nuts to ensure that sufficient loading is applied to create a tight seal.