Mechanical seals

Mechanical seal. Element used to prevent leaks of fluids and gases at the point where the shaft passes from the wet end to the dry or atmospheric end, mechanical seals are used in pumps, compressors and other types of rotating equipment.

Summary

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  • 1 Elements that make up the mechanical seal
  • 2 Type of mechanical seals
  • 3 Materials with which they are manufactured
  • 4 Operation
  • 5 Selection of mechanical seal
  • 6 Variation of track materials
  • 7 Difference between a single and a double mechanical seal
  • 8 Use of single and double stamps
  • 9 Sources

Elements that make up the mechanical seal

  • Tracks or faces (rotating track and stationary track).
  • O’rings-boards (dynamic and static).
  • Compression mechanism (springs, bellows, blades, etc).

Type of mechanical seals

·         Simple

·         Double

·         Internal

·         External

·         Stationary

·         Rotary

·         Balanced

·         Unbalanced

·         Component seals

·         Cartridge stamps

·         Mono-springs

·         Multi-springs

Materials with which they are manufactured

Mechanical seals can be made of various materials, which makes the metal parts of a seal, commonly they are made of stainless steel , in seals of lesser manufacture, we can find cast iron, exotic alloys such as A276, A20, are also used. etc. Moreover, the materials of tracks or faces, may be carbon , stainless steel, bronze , carbide of silicon carbide, tungsten , ceramic , etc. Finally, the materials of the joints and O’rings must be considered: Ethylene Propylene , Nitrile , Buna , Viton, Aflas , Teflon , Grafoil , etc. Both metal part and track materials and O’rings-gaskets should be selected based on the type of fluid and gas to be sealed.

Functioning

A mechanical seal has a static part and a dynamic part, the dynamic or rotating part is the one that rotates together with the shaft, there is the rotating track, the static part is the one that is subject to the fixed parts of the equipment and in Where the stationary track is housed, the tracks of a mechanical seal work with each other: one turns on the other, both must be flat and free of irregularities, the mechanical seals have three sealing points:

  • The primary seal (between the tracks).
  • The secondary seal (the dynamic O’rings).
  • Static joints or O’rings.

Selection of mechanical seal

Mechanical seals are manufactured and designed depending on the fluid or gas to be sealed, so that mechanical seal manufacturers can select the appropriate mechanical seal, they need to know the following data: Fluid or gas, RPM, temperature, working pressure.

  • When talking about fluid and gas, the products that compose it, PH, etc. must be indicated.

Variation of track materials

The manufacturing materials of a mechanical seal are selected based on the fluid and gas to be sealed. The mechanical seal tracks are classified into hard tracks and soft tracks: silicon carbide, tungsten carbide, ceramic, among others, are classified as hard tracks and as soft tracks, carbon, bronze, stainless steel, etc.

Difference between a single and a double mechanical seal

Simple Cartridge Seal

Constructively, single mechanical seals have one set of tracks (called internal tracks) and double mechanical seals have two sets of tracks (internal tracks and external tracks). The single mechanical seal is lubricated with the fluid and gas itself being sealed (lubrication is sometimes used from an external source) while a double mechanical seal is lubricated with an external fluid.

Use of single and double stamps

Double Cartridge Seal

When fluids must be sealed at low temperatures, non-toxic, non-abrasive, non-polluting, etc., a simple mechanical seal can be used. When it is necessary to seal abrasive fluids (fluids with suspended solids), dangerous fluids – flammable, toxic, polluting, among others – fluids at high temperatures, fluids that crystallize and carbonize in contact with the atmosphere, etc., mechanical seals must be used. of the double type. However, there are different designs and types of mechanical seals, so it may be necessary to use a simple mechanical seal to seal a fluid with a high temperature, etc.

Both the seal model (single – double, cartridge – component, rotary – stationary, balanced – unbalanced, etc.) as well as the materials of the tracks, metallurgy and O’rings-seals must be selected based on the type of fluid and gas to be sealed.

 

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