Mechanical seals - technology

The ever-changing technical and economic requirements of the industrial world are leading to the increasingly widespread use of dynamic seals. This article complements the article "Mechanical seals" [B 5 420] .

Continuously improved mechanical seal technology ensures maximum sealing reliability for a wide range of products under increasingly severe operating conditions (with service lives of up to several thousand hours):

• high pressures: over 150 bar ;

• high temperatures: over 400 °C ;

• high speeds: over 10,000 rpm ;

• large diameters: over 500 mm.

Mechanical seals meet the needs of all sectors of activity, including the chemical, petrochemical, oil, paper, processing, food, agri-food, textile and pharmaceutical industries. A wide range of products are sealed: clear or filled products, mixtures, syrups, bitumens, paper pulp, cements, powders, liquefied or non-liquefied gases, etc.

The mechanical seal is therefore an essential component of any rotating machine, such as pumps, compressors, mixers, gas turbines, centrifuges, clarifiers, refiners, reactors, etc. In this respect, the various studies carried out by all industrial maintenance departments show that the mechanical seal solution is the most economical overall, since it offers the best compromise between reliability and cost.

The components used in mechanical seal technology are based on high-precision mechanics and the expertise of the manufacturer. The constituent parts of a mechanical seal can be classified into four groups: friction faces (primary seal), secondary seals (gaskets, diaphragms, bellows, etc.), springs (or bellows or other), and other connecting components (liner, cover, screws, supports, etc.).

Selection of the type of mechanical seal and the materials used is based on the manufacturer's theoretical and practical knowledge (calculations, research, tests, experiments, etc.). All materials used for mechanical seal components in contact with the fluid to be sealed must :

• withstand extreme temperatures without significantly losing their characteristics or deteriorating over time;

• have sufficient mechanical characteristics to withstand the stresses generated by operating conditions (pressure, speed);

• be able to withstand any specified chemical attack.

The complete study of the subject includes the articles :

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