Stud Gasket Assembly

Studded gaskets are a set of two mechanical assemblies consisting of two flanges, fasteners (studs, nuts and washers) and a gasket in between. They are designed to house or allow the transport of a service fluid in a pipe or vessel, ensuring the tightness of the system. In their most practical form, flanges allow the connection of pipes with equipment (pumps, heat exchangers, tanks, etc.) or fittings (elbows, valves, etc.).

The principle of a flanged joint is based on the load applied to the studs, which causes the sealing element (gasket, ring joint, etc.) to flow within the macroscopic and microscopic imperfections of the flange. Thanks to this, the combination between the contact stress and the densification of the sealing material is achieved, which prevents the leakage of the fluid inside the vessel.

The advantage of the flanged joints lies in the fact that because they are joined with fasteners (studs, bolts), they can be quickly assembled and disassembled at the time of repairs or maintenance.

Main components of a bolted gasket

Every bolted gasket consists of three fundamental elements:

• Flanges.
  Sealing element.
  Bolts, nuts and washers.

To understand the integrity of the gaskets it is important to know what each of these elements represents; they will be key when a problem occurs in the flanged joint.

Common Causes of Stud Gasket Leakage

The following are the main causes of leakage in bolted joints:

• Flange misalignment (12%).
• Loose bolts (15%).
• Defective gasket (22%).
• Damaged flange (20%).
• Incorrect installation (31%)

As the above indicates, damaged components, misadjusted equipment and improper gasket assembly cause sealing failures. Despite these failures, the human factor remains the main cause of leakage.

The most common situations that occur due to personnel malpractice are listed below:

• Uneven tension on studs or bolts.
• Incorrect flange alignment.
• Improperly centered gaskets.
• Dirty or damaged flange faces.
• Excessive piping system loads.
• Thermal shock.
• Tamaño y/o tipo incorrecto del empaque.
• Altos niveles de vibración.
• Valores de tensionado no válidos.
• Válvulas en posición incorrecta después del mantenimiento.
• Quiebre del sistema de aislamiento.

Consequences of leaking flanged gaskets with studs

Leakage from flanged joints in industrial installations generates high impacts; when the gaskets do not have good integrity it compromises the rest of the assets around them. Therefore, the gasket designer must achieve a safe, leak-tight and maintenance-free design. If some of these requirements are not met, the package may not work optimally, leading to undesirable events.

Considerations to take into account when installing gaskets

The following are aspects to consider when installing a gasket:

• A lubricant suitable for the type of stud or bolt material should be applied.
• The correct load should be applied to the stud or bolt.
• The flange face should be clean, undamaged and with the correct surface finish for the gasket selected.
• There should be flatness of the flange faces.
• There should be correct alignment.
• Studs or bolts should be in good condition.
• Correct tightening sequence should be used.

Conclusion

Flanged gaskets are a vital element in any industrial plant. The use of good practices for their handling is the best way to avoid the appearance of leaks, which can be harmful to the personnel exposed to them and to the surrounding environment.