5 Signs a High-Temperature Expansion Joint Needs Replacement

5 Warning Signs That May Require Expansion Joint Replacement

The following conditions indicate that a high-temperature expansion joint should be inspected and may require repair, redesign, or replacement.

1. Fabric Shows Cracking, Fraying, or Burn-Through

Visible damage is one of the clearest indications that an expansion joint requires attention.

Inspect the fabric and surrounding assembly for:

• Cracks, tears, or holes

• Frayed or broken fibers

• Charring or localized heat damage

• Burn-through

• Abrasion or thinning

• Damaged stitching or seams

• Cracked, peeling, or delaminated coatings

• Exposed or damaged reinforcement

Damage can develop where the joint experiences repeated flexing, abrasion, contact with adjacent equipment, or concentrated thermal exposure. Seams, corners, attachment areas, and other high-stress areas deserve particular attention.

Not every surface defect requires complete replacement. However, damage that affects the joint's structural integrity, insulation, flexibility, or ability to contain hot gases should be evaluated by a qualified engineer or maintenance professional.

2. Expansion Joint Has Become Brittle or Lost Flexibility

A high-temperature fabric expansion joint must remain sufficiently flexible to accommodate the movement for which it was designed.

If the material has become unusually stiff, brittle, or difficult to flex, its ability to accommodate thermal and mechanical movement may have changed.

Potential causes include:

• Prolonged elevated-temperature exposure

• Excessive peak temperatures

• Repeated thermal cycling

• Chemical exposure

• Mechanical fatigue

• Abrasion

• Exposure outside the material's intended operating range

A loss of flexibility can increase stress on the expansion joint and connected components. During inspection, compare the current condition with the original design and expected movement requirements.

3. You See Excessive Movement, Vibration, or Mechanical Wear

Expansion joints are designed to accommodate controlled movement. Excessive displacement, vibration, rubbing, or contact with adjacent components can accelerate material fatigue and abrasion.

Look for:

• Abraded or thinned fabric

• Wear at contact points

• Torn or exposed reinforcement

• Distorted fabric or assembly geometry

• Broken stitching

• Damage around mounting hardware

• Evidence of repeated rubbing against adjacent equipment

• Changes in movement or vibration compared with normal operation

The correct construction still depends on the application. A higher-strength fabric does not automatically compensate for excessive movement, incorrect joint geometry, poor installation, or operating conditions outside the original design.

4. You Detect Unexpected Heat Loss, Hot Spots, or Leakage

An expansion joint can deteriorate even when obvious fabric damage is not visible.

Unexpected changes in surface temperature may indicate deterioration of the thermal insulation system, gaps between layers, damaged fabric, degraded insulation, or changes in operating conditions.

Potential warning signs include:

• Hot spots detected with infrared inspection

• Higher-than-normal surface temperatures

• Increasing heat loss

• Damaged or displaced insulation

• Visible gaps in the assembly

• Leakage around the expansion joint or adjacent connections

• Changes in nearby equipment temperature

Thermal performance should be evaluated against the actual application rather than relying solely on the nominal temperature rating of the outer fabric.

For example, a material's continuous operating temperature and peak temperature are not interchangeable specifications. Radiant heat exposure, direct contact, thermal cycling, insulation thickness, and the construction of the complete assembly can all affect performance.

5. Performance Degrades During Thermal Cycling

Thermal cycling is a particularly important consideration for expansion joints.

During startup, operation, shutdown, and process changes, connected components can repeatedly expand and contract. The expansion joint must accommodate this movement while maintaining its flexibility, structural integrity, insulation performance, and sealing function.

Recurring problems after thermal cycles, such as cracking, distortion, leakage, excessive movement, or increasing heat transfer, can indicate that the existing construction is no longer suitable for the operating conditions.

This may happen because:

• Operating temperatures have increased

• Thermal cycling has become more frequent

• Equipment movement has changed

• The process configuration has been modified

• The original material construction has reached the end of its service life

• The expansion joint was not originally specified for the current conditions

For systems with demanding thermal and mechanical requirements, replacement is also an opportunity to reassess the complete construction rather than simply replacing the outer fabric with the same material.

What Causes High-Temperature Expansion Joints to Fail?

The service life of an expansion joint depends on more than its age. The actual operating environment is often the more important factor.

Thermal Cycling

Repeated heating and cooling can place mechanical and thermal stress on fabrics, coatings, seams, insulation, and reinforcement.

Excessive Temperature

Exposure above a material's recommended operating range can accelerate degradation. Peak temperature and continuous operating temperature should both be considered during material selection.

Mechanical Movement

Vibration, flexing, displacement, rubbing, and repetitive movement can cause abrasion and mechanical fatigue.

Chemical Exposure

Process chemicals, oils, solvents, vapors, and other contaminants can affect certain fibers, coatings, adhesives, or other components.

Moisture and Weather Exposure

Outdoor installations may require resistance to moisture, weathering, UV radiation, and other environmental conditions.

Inadequate Material Selection

Temperature resistance is only one part of expansion-joint design. The selected construction may also need appropriate mechanical strength, flexibility, abrasion resistance, chemical resistance, moisture resistance, and insulation performance.

How to Extend the Service Life of a Fabric Expansion Joint

A preventive inspection program can help identify deterioration before it becomes a larger system problem.

During inspection, evaluate the complete expansion-joint assembly, including:

• Fabric layers

• Coatings and laminates

• Seams and stitching

• Wire or other reinforcement

• Insulation layers

• Flanges and attachment hardware

• Adjacent piping and equipment

• Areas exposed to abrasion or rubbing

Also document changes in operating conditions, including temperature, movement, vibration, pressure, chemical exposure, and thermal cycling.

If the process or equipment has changed since the original expansion joint was specified, reassess the design requirements. A joint that performed adequately under the original conditions may not be appropriate after a change in temperature, movement, equipment configuration, or process duty.

Standards and Engineering Considerations

Expansion-joint requirements can involve several different engineering disciplines. The applicable standards depend on the piping system, equipment, material, installation, and design authority.

For process and power piping, engineers may need to consider standards such as ASME B31.3 and ASME B31.1, respectively. These piping codes address broader system design and engineering requirements rather than serving as material specifications for a fabric expansion joint.

For metallic bellows, EJMA guidance is relevant to the design and application of metallic bellows expansion joints. It should not be treated as a design standard for fabric expansion joints.

Thermal-insulation and coated-fabric test methods such as ASTM C177, ASTM C518, and ASTM D751 can provide useful material-performance information where applicable. However, test results for an individual fabric or insulation material should not be interpreted as certification of a complete expansion-joint assembly.

The final design should account for the actual combination of:

1) Temperature
2) Pressure
3) Movement
4) Vibration
5) Thermal cycling
6) Insulation
7) Reinforcement
8) Sealing requirements
9) Chemical exposure
10) Installation conditions

Tip: Always verify the current edition and applicability of any code or standard with the responsible engineer, AHJ, or specification authority before using it as a design or procurement requirement.

Related Articles:

ASTM & ISO Test Standards for High-Temperature Fabrics

What Has Changed in NFPA 1970 Firefighting PPE Standards

How to Choose ISO 11612-Compliant Safety Apparel

Conclusion

A high-temperature expansion joint should be inspected as an engineered assembly, not just as a piece of fabric.

Cracking, fraying, burn-through, loss of flexibility, excessive mechanical wear, unexpected heat transfer, leakage, and recurring problems during thermal cycling can all indicate that an expansion joint needs closer evaluation.

When replacement is required, reassess the application's current operating conditions rather than automatically specifying the same material used previously. Temperature, movement, thermal cycling, abrasion, chemical exposure, insulation requirements, reinforcement, and installation conditions all influence material selection and service life.

Need a custom high-temperature expansion joint? Contact Newtex Industries to discuss your operating conditions, material requirements, and custom fabrication requirements.