With significantly reduced toxic smoke and corrosive gases emitted in the event of a fire, low-smoke zero halogen (LSZH) cables have become the industry standard for safety critical installations. However, these cables aren’t “set it and forget it” solutions. Their unique compounds, while great for fire protection, react and respond differently to PVC cables and need careful ongoing monitoring and maintenance to ensure electrical functionality and the most critical aspect for end-users, the low smoke characteristics, is maintained in hospitals, tunnels, airports, high rise buildings and industrial automation control systems.
At Hulk Electric, we are here to make sure your facility manager and engineer can maintain a reliable halogen-free cable installation for many years. This guide highlights considerations based on experience from real-life applications with LSZH cables in challenging applications.
Why Inspection and Maintenance Matter for LSZH Cables in Safety-Critical Installations
The purpose of the LSZH cable is to release very little smoke and no halogen acid gases when exposed to fire, allowing more time to allow occupants to evacuate and sensitive electronics to avoid corrosive damage. They are typically needed in escape routes, control rooms, data centers, and other areas where risks are high, like in IEC 60332, IEC 60754, and IEC 61034.
But, most LSZH jackets have a high concentration of mineral fillers to give them the flame retardant and low-smoke properties. This formulation renders them slightly more vulnerable to mechanical stress, fatigue from flexing and extreme heat and cold, and some environmental elements than conventional cables. Properly designed and maintained cables will provide electrical integrity and fire-safety performance over their service life through regular inspection.
Common Failure Modes and Material Pain Points in Halogen-Free Cables
Maintenance teams can detect problems early by knowing the common issues that can occur with LSZH cables.
Mechanical Damage and Jacket Cracking
The excellent fire performance of LSZH can also be obtained through its high filler content, which can lead to reduced flexibility. Excessive pulling tension on installation, repeated motion or abrasion against sharp tray edges can cause the jacket to crack. In outdoor or high temperature fluctuating environments, these cracks can be observed following relatively brief exposure.
Cracked jackets allow water to enter the cable and can ultimately impair the cable’s fire resistance.
Insulation Damage, Moisture, and Aging
Mechanical damage of insulation, absorption of moisture, thermal aging or overheating. These factors reduce the insulation resistance and hence the likelihood of faults, which can be critical in safety related circuits where reliable operation is crucial.
Reduced Heat Tolerance in Extreme Conditions
LSZH cables have good performance over a large temperature range, but some formulations may soften or be degraded at lower temperatures than some halogenated alternatives. Where heat levels are very high, the routing, protection and periodic review is important.
Inspection Checklist for LSZH Cables in Safety-Critical Circuits
Establish a specific inspection program based on the risk level of your facility.
Visual and Mechanical Inspection
- Inspect cable jackets for cracks, cuts, abrasions, deformations, and discolorations particularly at bends, terminations, and tray/support contact areas.
- Check bend radii to ensure they are within manufacturer’s specifications – LSZH cables are sometimes more prone to tight bends than PVC.
- Look for sharp edges or unsecured fittings on supports, clamps, and conduits which may lead to continued abrasion.
- Check for any areas that have sun or harsh environmental exposure that may show signs of UV damage, chalking or surface roughness.
Insulation and Electrical Health Checks
- Regularly test insulation resistance of critical circuits.
- Look for any abnormal hot spots, increased leakage currents or continuity changes.
- Check cables for performance with data, control or emergency systems.
Environment and Exposure Review
- Evaluate moisture, chemical, temperature fluctuation and physical shock.
- Ensure that conduit or trunking will still provide protection for outdoor or harsh-environment runs.
- Record any changes in the surrounding installation which might impact the cables.
Maintenance and Repair Practices That Preserve Safety Performance
If problems are identified, follow disciplined procedures.
Fault Handling and Repair Process
Isolate the circuit, find and diagnose the fault, repair or replace the faulted area of the circuit and retest the circuit after repair or replacement before it is returned to service. In safety critical applications, quick fixes without proper documentation and testing are not acceptable.
Replacement and Upgrades
Replace damaged LSZH cable with properly certified LSZH Equivalent. Ask for third party testing reports for compliance of IEC 60332 (flame retardance), IEC 60754 (halogen content), and IEC 61034 (smoke density). Avoid replacing with non-halogen-free cable during emergency repair.
Installation Practices to Extend Service Life
Properly instruct teams on recommended bend radii and pulling tensions. Protect against stress on cables with the use of suitable lubricants and protective sleeving or conduit. The best initial installation will yield minimal maintenance costs over the years.
Practical Recommendations for Facility and Maintenance Teams
- Consider LSZH cables as safety assets – conduct visual and electrical checks frequently on all escape route, riser and control area cables.
- Keep an eye out for cracking in the jacket, tight bends, and degradation by the environment, things that LSZH materials can have a higher tendency for than traditional cables.
- Record detailed inspection, fault, repair and test data for audit and ongoing improvements.
- Only use source replacement cables from manufacturers that offer complete certification and traceability.
- Provide technicians with training to understand the unique characteristics of the handling of halogen-free cables to avoid damage to cables in the installation process.
- Work with knowledgeable suppliers for periodic audits or specific testing of your LSZH installations.
It is critical to ensure that halogen-free cables are inspected and maintained properly year after year, to maximise their safety value. Our team at Hulk Electric (Dongguan) Co., Ltd. brings a wealth of experience to the table, excelling in designing and customizing halogen-free cables for longevity, even in the most challenging environments. From existing installations to new custom LSZH solutions, our team is always at your service to keep your safety-critical systems protected.
