Technical Committee Analytics
- Determination of the oxidation stability of otto fuels - Safety technology test on an apparatus according to DIN EN ISO 7536
In the determination of the oxidation stability of otto fuels under accelerated conditions according to
DIN EN ISO 7536, the induction period until reaching the „breaking point" is measured. For this
purpose, a fuel sample in an oxidation bomb is exposed to oxygen using elevated pressure and
temperature. Any potential pressure decrease in the oxidation bomb is recorded. During the test period
there exists an explosive mixture of fuel vapor an oxygen inside the oxidation bomb, which can
detonate when ignited.
In the past there has been an accident in a pilot plant under similar conditions to those in the oxidation
bomb of this test procedure. Therefore, the German standard test method DIN 51 780 was withdrawn,
and an additional warning was added to the new test method DIN EN ISO 7536 standard. The Federal
Institute of Materials Research and Testing (BAM) has carried out safety test on behalf of DGMK, using
a modified oxidation bomb made by Petrotest Instruments. These tests, using conditions very close to
real practice, were carried out by igniting mixtures of fuel and oxygen, recording the pressure response
and mechanical changes to the apparatus.
It was shown that the modified apparatus was able to resist securely the explosion pressure peaks. No
lasting deformations could be measured on the apparatus. When in the case of an explosion the
bursting disk at the distributor head opens, this leads to a considerable recoil and to the ejection of a
fuel jet which can ignite in form of a shooting flame. For safety reasons it must therefore be assured
that the bursting disk can only blow into a direction where it cannot cause any harm to the operator.
The test has shown that the apparatus was able to resist the explosion pressure without the use of a
bursting disk. It is therefore questionable if the use of a bursting disk really leads to a reduced risk
during operation of the apparatus.