10 most common failures in industrial seals and how to avoid them

Joint leaks remain among the main causes of operational losses, fugitive emissions, unscheduled stops and safety risks in industrial facilities.

Although often industrial seals are identified as responsible for the problem, Industry experience and technical literature demonstrate that most failures are related to flanged union assembly.

A ASME PCC-1 – Guidelines for Pressure Boundary Bolted Flange Joint Assembly consolidated decades of field experience by establishing procedures for the correct assembly of flanged joints.

In the same way, renowned manufacturers, like to KLINGER, emphasize that sealing performance depends on the interaction between gasket, flanges, screws, lubrication, assembly tools and procedures.

In this article, we present the 10 most common failures in industrial seals, organized according to the importance attributed by ASME PCC-1 and best international practices.

1. Inadequate screw load

The main function of screws is to generate compression necessary for the joint to produce an efficient seal.

When the applied load is less than necessary, the gasket cannot completely fill the irregularities on the flange faces, allowing fluid to pass.

On the other hand, excessive load can crush the seal, cause permanent deformation or even damage to screws and flanges.

According to ASME PCC-1, Correctly controlling the bolt load is the most important factor in ensuring the tightness of a flanged connection.

How to avoid

• Use specified torque or load values
• Use calibrated tools
• Consider the coefficient of friction of the lubrication used
• Check the final load on all screws

2. Uneven load distribution between bolts

Even when the applied torque is correct, differences between individual screw loads can cause uneven joint compression.

This situation creates regions of low contact pressure that become preferential points for leaks..

PCC-1 recommends that tightening be carried out in cross sequence, in several successive passes, to equalize the load around the entire joint.

How to avoid

• Strictly follow the tightening sequence
• Perform multiple torque passes
• Perform the final uniformization pass

3. Inadequate assembly procedures

Most leaks occur because assembly procedures are not followed correctly.

Among the most frequent errors are:

• Tightening in just one step
• Lack of surface cleaning
• Miscalibrated tools
• Lack of lubrication
• Assembly carried out by untrained personnel

A ASME PCC-1 dedicates a large part of its content precisely to the standardization of these procedures.

How to avoid

• Adopt written procedures
• Train assemblers
• Use calibrated equipment
• Record the assembly steps

4. Incorrect selection of the sealing gasket

No seal is universal.

Each application has specific requirements related to pressure, temperature, fluid, flange finishing and connection type.

An inadequate joint can suffer chemical degradation, loss of elasticity, extrusion or mechanical failure.

How to avoid

• Check chemical compatibility
• Consider design pressure and temperature
• Consult the manufacturer's recommendations
• Meet regulatory requirements

5. Inadequate condition of flange faces

Even the best seal cannot compensate excessively damaged flanges.

Corrosion, deep risks, Warping and inadequate roughness significantly reduce sealing efficiency.

Visual and dimensional inspection of faces must be part of the maintenance routine.

How to avoid

• Inspect surfaces before assembly
• Check warping
• Confirm the recommended roughness for each type of joint
• Repair or replace damaged flanges

6. Screw problems, nuts and lubrication

The applied load directly depends on the fixing set conditions.

Corroded screws, Damaged threads or inadequate lubrication significantly alter friction during tightening, causing the applied torque not to result in the desired load.

How to avoid

• Inspect all fasteners
• Use suitable lubricants
• Replace damaged components
• Avoid mixing incompatible materials

7. Misalignment of flanges or piping

It is relatively common to try to correct misalignments using the screws themselves..

This practice introduces external loads that reduce the uniform compression of the joint and accelerate the appearance of leaks.

PCC-1 recommends that flanges are aligned before gasket installation.

How to avoid

• Correctly align the piping
• Eliminate external efforts
• Never use screws to bring together misaligned flanges

8. Relaxation of the joint and screws

After assembly, there may be a gradual reduction in residual load due to the accommodation of materials, joint creep, thermal cycling or relaxation of screws.

The loss of this load reduces the joint contact pressure.

How to avoid

• Select suitable materials
• Consider the effects of temperature
• Use retightening procedures when technically permitted

9. Gasket reuse

After being compressed, many joints suffer permanent deformations.

Reuse significantly reduces its sealing ability and increases the likelihood of leaks.

For this reason, to KLINGER recommends replacing the gasket whenever the connection is disassembled.

How to avoid

• Use new gaskets in each intervention
• Follow the manufacturer's recommendations
• Maintain adequate inventory for maintenance

10. Operation outside design conditions

Even correct assembly can fail when the equipment operates beyond the expected limits.

Pressure overloads, excessive temperatures, intense thermal cycles and vibrations can reduce seal life.

How to avoid

• Respect project limits
• Monitor operating conditions
• Review seal selection when process changes occur

How to avoid failures and increase the reliability of industrial seals

Experience accumulated by the industry shows that the majority of leaks in flanged connections are not related to the quality of the connections. industrial seals, but to the way the flanged assembly is designed, assembled and maintained.

A ASME PCC-1 reinforces that the seal must be treated as an integrated system composed of flanges, screws, nuts, junta, lubricant, assembly tools and procedures. Negligence in any of these elements compromises the performance of the set.

Invest in standardizing procedures, in team training, Inspecting components and controlling bolt load is the most effective strategy to increase the reliability of industrial seals, reduce maintenance costs, minimize fugitive emissions and increase the safety levels of industrial facilities.