Static seals

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. 

Shaft-sealing elements can be split up into two groups. The first type may be called pusher-type seals and includes the 0-ring, V-ring, U-cup, and wedge configurations. Figure 10-116 shows some typic pusher-type seals. The second type is the bellow-type seals, which differ from the pusher-type seals in that they form a static seal between themselves and the shaft. 

Materials Springs and other metalhc components are available in a wide variety of alloys and are usually selected on the basis of temperature and corrosion conditions. The use of a particular mechanical seal is frequently restricted by the temperature limitations of the organic materials used in the static seals. Most elastomers are hmited to about 121°C (250°F). Teflon will withstand temperatures of 260°C (500°F) but softens appreciably above 204°C (400°F). Glass-filled Teflon is dimensionally stable up to 232 to 260°C (450 to 500°F). 

For sieve or valve plates, h = h , outlet weir height. For bubble-cap plates, h = height of static seal. Tbe original references present vaH-dations against laboratoiy and small-commercial-column data. Modifications of tbe efficiency equation for absorption-stripping are also included. 

Static seals are standard provision from many suppliers therefore seals for the moving elements in pumps will be discussed. For centrifugal pumps, both stuffing box and mechanical seals will be considered and the discussion will be extended to reciprocating and rotary machines. 

Where such seals are unfavourable, for example, with horizontally split compressor housings, structural measures, such as the use of vertically split barrel housings, are used to guarantee a reliable seal. The clamping and sealing of diaphragms for diaphragm pumps and compressors requires special static seals [5,29],... 

These compressors are free from leakage to the same extent as are static seal systems. The leak-free integrity of the system is maintained even in the event of a diaphragm or diaphragm seal failure. 

Faults in sandstones deformed at depths greater than 1 km tend to deform by cataclasis. Permeability and entry pressure of such faults can be predicted from estimates of matrix properties. Static seal capacities of cataclastic faults depend on the minimum sealing properties, which are related to the fault displacements. 

The fault has its minimum displacement (ca. 75 m) where it branches with Fault 3. In this area the SGR is just below 20% or higher, and by analogy with Fault 1, the potential for having a trapped HC-column at the extension of G Central is good. In addition, a gas column is more likely to be present rather than an oil column, increasing the possibilities for a static seal. 

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