Shaft seals carbon

Graphites (natural or synthetic) are black semireinforcing fillers used almost exclusively in rotary shaft seal applications where surface lubricity and abrasion resistance must be enhanced (see Carbon, natural graphite). 

Garter spring a helically coiled spring, typically made of carbon steel or stainless steel wire, formed into a ring, and used in a shaft seal to help maintain contact between the sealing lip and the shaft. 

Many induced flotation units, particularly mechanical flotation units, operate at pressures within a few ounces of atmospheric pressure. The walls are thin and have numerous penetrations for motor shafts and observation hatches. As a result of the simplicity of design, air can easily enter the units around the paddle or if observation hatches are left open. Oxygen in the water treating system increases the corrosion rate in the unit as well as all downstream carbon steel equipment and can cause the formation of a reddish precipitate resulting from oxidation of dissolved iron in the treated water. To avoid corrosion and the precipitate, care should be taken to avoid oxygen ingress. Hatches should be left closed as much as possible, and the integrity of shaft seals should be maintained. 

Gaskets, turbine carbon packing, and mechanical seal parts can be purchased from local sources. Shafts, sleeves, cast parts can be purchased from... 

A floating shaft can cause chattering, which results in chipping of the seal faces, especially the carbon element. Ideal mechanical seal performance requires a uniform wear pattern and a liquid film between the mating contact faces. 

Note Bushings must be sized to allow for thermal growth of the shaft. The clearances in Table 2-4 are based upon carbon bushings at pumping temperature. Other materials may require other clearances. Axial space limitations may make it impractical to fit floating bushings on dual seals. 

The additional cost of the material for a larger-diameter shaft is rarely a major factor for carbon or stainless steel, but may be sizeable for special alloys. The additional cost of a larger mechanical seal, for pressurized applications, may add considerable cost regardless of the shaft material. 

The system operating pressure is contained by a double-row cooled and lubricated carbon mechanical seal between the casing and rotating shaft in the vapor space at the upper end of the centrifuge assembly. 

Fig. 5. Rotating electrode unit. A, Nylon block shaped to fit conical joint, B C, electrode bearing housing (brass) D, rotating electrode mounting shaft (glass) E, ball bearings F, PTFE seal G, working electrode H, brass slip ring I, carbon brush J, drive motor connecting point. (Reproduced with permission from ref. 15.)...

A mechanical seal s principal components are two smooth rings carbon and a hard metal alloy. One ring rotates on the shaft while the other is stationary and connected to the pump. The two faces are forced together with a spring. When a seal leaks, it is usually because these faces become separated or are no longer smoothly rotating against each other. 

These seals operate in a different way to standard oil seals. They are used axially. A seal nose of bronze, carbon or Teflon is mated to a much harder material (i.e. a hardness of 500 brineU) and held in position by a spring. The harder material can be a tightly fitted collar inserted on the shaft or it can be a part of the shaft. The mating surfaces must be true or at high speeds, or the surfaces may break contact and leakage could occur. A mechanical seal and its application are given in Figures 2.13 and 2.14. 

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