BOOK_CONTENT
From Control Valves

Packing Arrangements

SINGLE PACKING

This is an economical seal for many applications. Single packing consists of a stack of packing at the top of the packing box supported by either a spring or gland follower. Spring packing can be accomplished by having the packing follower drawn against the bonnet to compress the spring. (This is a variation on the live loaded packing discussed later in this section.) Figures 19 and 20 show single packing arrangements for sliding stem and rotary valves.

This type of packing is not adjustable. Springs are not available in all alloy materials. If a special alloy is required, packing with lantern rings should be specified. The packing with lantern rings is also called "jam-type" packing. Jam-type packing will have a gap between the packing follower and bonnet. Single packing arrangements are available in these materials:

  • PTFE V-ring
  • Ribbon-style graphite
  • Graphite ribbon/filament

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DOUBLE PACKING

Double packing arrangements provide a more rugged seal than single arrangements and generally have more packing above than below the lubricating/ lantern ring connection. Figure 10-21 shows a double packing arrangement.

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LEAK-OFF PACKING

These are specifically designed for applications that require a means of purging packing leakage without allowing process fluid to leak through to the top of the packing box. To meet this criteria, leak-off packing arrangements have the packing above and below a bonnet leak-off connection. There is at least one full set of packing (minimum packing stack height of 1 1/2 stem diameters) below the leak-off connection. There is at least one full set of packing on the valve side of the connection. The smaller amount of packing above the leak-off connection ensures that the adjustment force applied to the packing follower is more completely transmitted to the lower set of packing without creating excessive compression and stem friction in the upper set. Figure 10-22 shows a leak-off packing arrangement.

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© 1998 Instrument Society of America

Products & Services
Hydraulic Valves
Hydraulic valves contain and transfer the flow and pressure of hydraulic fluid in hydraulic power systems. They range from simple shutoff valves to precision control valves.
Valve Actuators
Valve actuators mount on valves and, in response to a signal, move a valve to a desired position using an outside power source.
Manual Valve Actuators
Manual valve actuators do not require an outside power source. They use a handwheel or lever to drive a series of gears whose ratio results in a higher output torque compared to the input (manual) torque.
Pneumatic Valve Actuators
Pneumatic valve actuators adjust valve position by converting air pressure into linear or rotary motion.

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