Tony,
The straightforward answer to your question is that RTI is a concept developed by UL and is not referred to in the EN standards. The theory is that the EN standards require plastics performance to be assessed at a temperature sufficiently in excess of the temperature at which they are operating to be able to provide a guide as to their long-term performance. One example of this is the ball pressure test which is in pretty well all the EN electrical safety standards.
In practice, a lot of UL's business has historically been based on their expertise at testing plastics in ways which provide repeatable measures of their performance. They are pretty good at it! Much of the data for proprietary plastics is based on UL standards and while there is no formal recognition of the UL plastics performance standards in the EN or IEC system, the information provided by data such as the UL94 or the RTI rating is useful when sourcing parts for products intended for EN compliance so long as you understand what it's telling you.
However, when it comes to testing, third party certification bodies working to the EN standards will want to apply the tests defined in the EN standards for the products concerned and will generally not rely on tests done to qualify the plastics materials separately since, in contrast to UL's approach, this is not, in general, the way the EN standards are structured.
Regards Nick. At 13:45 +0100 2/10/2001, [email protected] wrote:
All, I am having some fun with a lab over RTI ratings on plastics. Basically we have a plastic moulding with a component mounted directly on it. The RTI of the plastic is 60C and the component is getting to around 75C actual. I have always looked at the flammability of plastics 5V, V-0, V-1, etc but never the RTI. Is this a just a UL1950 requirement or is it in EN60950 as well. We have done the thermal stress at 70C and all is OK. They are suggesting doing the ball pressure test at 125C, however, I have only used this for qualifying mains transformer bobbins, etc. Regards Tony Reynolds Pitney Bowes +44 (0) 1279 449479 +44 (0) 1279 449118 [email protected]
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