Plug seal

Polymers used for seat and plug seals and internal static seals include PTFE (polytetrafluoroeth ene) and other fluorocarbons, polyethylene, nylon, polyether-ether-ketone, and acetal. Fluorocarbons are often carbon or glass-filled to improve mechanical properties and heat resistance. Temperature and chemical compatibility with the process fluid are the key selec tion criteria. Polymer-lined bearings and guides are used to decrease fric tion, which lessens dead band and reduces actuator force requirements. See Sec. 28, Materials of Construction, for properties. 

St. Eouis, H.E. and Trumbull, W. A., Adjustable Plug Seal Mechanism for Heat Transfer Zone Separation in Hoiiow Screws for Extrusion Machines, U. S. Patent 4,355,905 (1982)... 

Small specimens of all products, including reaction intermediates isolated from reaction sequences, and particularly samples of fractions isolated as the result of lengthy chromatographic or other purification procedures, should invariably be retained for reference purposes. The commercially available straightsided specimen tubes with polyethylene plug seals, which are available in a range of sizes, are suitable in the case of solid samples. It is usually advantageous to label them with the name and a code reference to enable physical data (elemen-... 

FIG. 8-67 Cage-guided balanced plug globe valve with polymer seat and plug seal. (Courtesy Fisher Controls International LLC.)... 

Centrifuge tube, glass, 25 ml Centrifuge tube with plug seal cap, polypropylene, 15 ml, rated to 3000 G 50 (30) 50... 

Mechanical pressure, e.g. top, side, internal pressure on a container finish ideally involving a seal between a fairly rigid material and one which is more resilient. Includes screw closures, plug seals, lever lids, etc., which create an interference fit between two materials. 

The multichannel restrictor is fabricated from a short glass plug sealed into a fused-silica capillary tube. The glass plug is permeated by parallel channels 1 -2 pm in diameter. The number, length and diameter of the channels can be varied to produce restrictors with different flow characteristics. 

During reactor vessel dismantling operations, the containment boundary will consist of the main vessel and the underside of the slab. The containment would then consist of the plugs sealing the penetrations left after extraction of the removable components, or airlocks for the transfers into and out of the vessel. 

Multiple screws, variable geometry, inclination from horizontal to vertical, jacketed casings, shaftless and ribbon screws, plug seals , and a host of design variants offer scope for innovative and speciahzed functions. 

An alternative approach is to accept whatever rate of feed reaches the compacting screw and press this against a constant resistance to produce a controllable compacting force. This is done by a form of plug seal screw, either with a fixed form of construction, or with the provision of a variable resistance device to increase or decrease the compacting force. Linking the discharge resistance to the drive unit allows the compaction force to be optimized to the drive capacity. 

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