HVAC Hoses: Ageing Test Done for High-Temperature Silicone Hoses

Hvac-hoses-ageing-test-for-high-temperature-silicone-hoses

With the EURO-VI regulations, the working temperatures and pressures for Coolant Hoses have become very demanding. To resist these rising under-the-hood working parameters, HVAC system providers are moving to Silicone Hoses, instead of the erstwhile popular EPDM Hoses.

However, Sodium 2-ethylhexanoate, Potassium 2-ethylhexanoate,  and ethylhexanoic acid are not compatible with Silicone Rubber.
Because of mis-guidance, some OEMs/Tier-1s resort to Silicone Hoses lined with Fluorosilicone. But as per our experience, Fluorosilicone is also permeable to the OAT gases!

In the above picture you can see sections of different hose constructions. The hoses have been aged for 32 days at 115 degrees centigrade, with Organic-Acid bases Coolants inside the hoses.

 

  • On the left you can see that the OAT gases which contain EHA acid, have eaten into the Fluorosilicone.
  • On the right is the hoses Shore Auto Rubber Exports Pvt. Ltd. has developed, with a special impermeable liner, to replace Fluorosilicone. No visible damage to the specially formulated liner developed by Shore Auto Rubber Exports Pvt. Ltd.

Although the hoses have shown similar pressure ratings following the ageing, the deterioration of the Fluorosilicone can be clearly seen. We are continuing the ageing tests to observe the long-term impacts.

You can get the following options for regular Ethylene Glycol or Organic-Acid based Coolants at SHORE AUTO:

  1. EPDM hoses (sulphur cured) for low temperature applications if reinforced with Polyester. Hoses reinforced with Aramid/Kevlar show better ageing properties when exposed to OAT coolants.
  2. Upto 150 degrees celsius EPDM hoses (peroxide cured) with Aramid reinforcement, for higher temperatures , and good for coolants including OAT coolants that contain EHAs (ethylhexanoic acids).
  3. Silicone Hoses with Aramid reinforcement. These are for even higher temperatures upto 215 degrees celsius, and good for coolants including OAT coolants that do not contain EHAs.
  4. Silicone Hoses with Aramid reinforcement and inner lining of impermeable liner. These are for even higher temperatures upto 225 degrees celsius, and good for coolants including OAT coolants that contain EHAs.

Please contact us for more information.