Shaft seals seal materials

API Std 614 Lubrieation, Shaft-Sealing, and Control-Oil Systems for Speeial-Purpose Applieations API Std 670 Vibration, Axial-Position, and Bearing-Temperature Monitoring Systems ASME BPV Seet 11 Materials... 

Pumping of liquids is almosl universal in chemical and petrochemical processes. The many different materials being processed require close attention to selection of materials of construction of the various pump parts, shaft sealing, and the hydraulics of the individual problems. A wide variety of qqtes and sizes of pumps have been developed to satisfy the many special conditions found in chemical plant systems however, since all of these cannot be discussed here, the omission of some does not mean that they may not be suitable for a service. 

The sealing systems for the shaft are quite similar to those for the centrifugal however, internal shaft seals are not necessary between stages. The materials of construction are similar to those for the centrifugal compressor. 

Cast iron is the standard material used to construct the cylindrical housing, but other materials may be used if corrosive conditions exist. The rotor is usually a continuous piece of steel that includes the shaft and is made from bar stock. Special materials can be selected for corrosive applications. Occasionally, the rotor may be a separate iron casting keyed to a shaft. On most standard air compressors, the rotor-shaft seals are semi-metallic packing in... 

Both physical and process-material considerations influence the choice and use of shaft seals in the industry. It is essential that the seal material is compatible with any process material and the operating variables. 

Nitrile rubbers, including fiber-reinforced varieties, are used both as radial shaft-seal materials and as molded packing for reciprocating shafts. They have excellent resistance to a considerable range of chemicals, with the exception of strong acids and alkalis, and are at the same time compatible with petroleum-based lubricants. Their working temperature range is from —1°C to 107°C (30°F to 225°F) continuously and up to 150°C (302°F) intermittently. When used on hard shafts with a surface finish of, at most, 0.00038 mm root mean square (RMS), they have an excellent resistance to abrasion. 

Silicone rubber as a shaft seal and backing material has a number of special applications. It can be used over a temperature range of —60°C to 260°C (—76°F to 500°F) in air or suitable fluids. Its abrasion resistance is good with hard shafts having a 0.000254 mm RMS surface finish. Commercial grades of silicone rubber are compatible with most industrial chemicals up to 260°C (500°F). In lubricating oils, the limiting temperature is 120°C (250°F), but special types have been developed for use up to 200°C (392°F). 

Minor parts that are not identified (sueh as nuts, springs, washers, gaskets, and keys) shall have eorrosion resistance at least equal to that of speeified parts in the same environment. Gasket or seal material between the shaft and the shaft sleeve under the paeking or meehanieal seal shall be verified by the vendor as being satisfaetory for the serviee conditions. 

As in all medium-pressure agglomerators that use rollers for the densification and extrusion of moist and/or plastic materials, the primary cause for roller rotation is friction between the roller surface and the material to be processed. The roller is mounted on a shaft with sealed antifriction bearings and is brought to close proximity... 

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