In industrial environments, heat is a constant enemy of rubber and plastic hose assemblies— even for hoses designed for high temperatures.
It’s a common oversight: a hose may be rated for 100°C fluid, but is installed next to a furnace or a superheated manifold. This gradually leads to material failure at the molecular level.
At IzoflexHose, we want to look beyond the temperature rating label – even in a high-temperature hose, like our Altair Wash Food rubber low-pressure steam hose for foods – and explain what is truly happening inside your hoses, and why strict, regular inspection is the only way to stay safe in high-temperature applications.
What happens to hoses at high temperatures? The molecular breakdown
Rubber (Elastomers) and Plastic (Thermoplastics) hoses are made of long-chain polymer molecules. When these materials are exposed to excessive or prolonged heat, they undergo irreversible processes that compromise the hose’s physical integrity:
Material Type |
Molecular Process |
Effect on the Hose |
|---|---|---|
Rubber (Elastomers) |
Cross-Linking / Embrittlement |
Heat accelerates the creation of new bonds between polymer chains. The material hardens, loses its vital elasticity, and becomes brittle. The cover and tube may crack or crazing when flexed, leading to immediate failure under pressure. |
Plastic (Thermoplastics) |
Chain Scission / Softening |
Excessive heat breaks the polymer chains, weakening the material. The plastic will typically soften, lose its rigidity, and can discolor or melt. This drastically reduces the hose's ability to hold its rated pressure. |
Running a hose at its maximum temperature and maximum working pressure can can reduce service life by more than 50%. The combination of heat and pressure accelerates material fatigue.
The hidden danger for heat resistant hoses: Radiant heat
It’s not just the fluid temperature you need to worry about. Ambient heat and radiant heat are silent hose killers:
- Radiant heat: This is energy transferred via electromagnetic waves (like sunlight, or heat from a hot engine block, furnace, or molten metal). A hose can be damaged by a heat source a foot away, even if the ambient air temperature is mild.
- Insulation damage: Radiant heat can quickly degrade the outer cover and reinforcement layers, leading to internal component failure before the inner tube even shows distress.
If a hose assembly is consistently exposed to ambient or radiant temperatures that approach its rated maximum, even the highest-quality heat resistant hose will degrade rapidly. For every 8°C (18°F) above the maximum rated temperature, the hose life can be cut in half.
Safety checklist: Why regular inspection is critical for high temperature hoses
Due to this accelerated, often invisible degradation, heat resistant hoses used in high-temperature environments require a non-negotiable, frequent inspection schedule.
Look For |
What it Means |
Action Required |
|---|---|---|
Cover Crazing/Cracking |
The rubber has hardened and lost elasticity (embrittlement). |
Immediate replacement. |
Cover Dryness/Charring |
Exposure to excessive radiant heat. |
Immediate replacement, and installation of heat shielding. |
Soft Spots or Swelling |
The plastic or rubber liner is breaking down and softening. |
Immediate replacement. |
Hose Frozen in Shape |
Loss of elasticity; the hose is now stiff and brittle. |
Immediate replacement. |
Coupling Leaks |
Gaskets/seals have hardened or degraded from the heat. |
Replace seals, inspect hose for associated degradation. |
PTFE hoses are recommended for sustained high-temperature use
If heat is unavoidable, we recommend selecting hoses with superior heat-resistant materials (like silicone or PTFE hoses) and incorporating thermal protective sleeves or shields during installation. For demanding applications, consult to our expert team to ensure proper selection and protection.
