FOCUS
Hazardous materials The fire point of ester fluids, which represents
the lowest temperature at which the vapour of the fuel will burn for at least five seconds after ignition, is greater than 300°C. For mineral oils, the fire point is 170°C.
A regional fit
Different climates bring different challenges for transformers, and extremes of both hot and cold can cause a failure – and represent a fire risk. In the Middle East, for example, overheating transformers poses a constant threat to utilities. One such event occurred in Saudi Arabia in
July 2017, when a transformer fire at the Saudi Aramco Mobile Refinery in Yanbu was caused by hot weather. On this occasion, the fire was quickly contained, but the extreme temperatures in the region mean that the threat of a far more destructive blaze is ever present. Elsewhere in the Middle East, transformers
in Kuwait are designed for an ambient temperature of 58°C – this is the air that is used to cool the transformer fluid down before it is returned to the transformer. Once back inside, the temperature of the liquid can reach 100°C in a large transformer, or even as high as 130°C in a small transformer – only some 40°C below the fire point for mineral oils. This means that a fault or a hot spot in the transformer
would only need to cause a modest increase in temperature to ignite. With a fire point of more than 300°C,
ester fluids provide a much more sizeable buffer between ignition and the ambient air temperature and therefore a vital protection against fire. Even when inside a transformer in a hot climate, the temperature of ester fluids would have to rise by at least 170°C to ignite – a massive 130°C more than mineral oils.
Insuring the risk
Owing to the fire safety benefits of ester fluids, several transformer manufacturers, insurance companies and end users have concluded that under all possible conditions which could be experienced in a transformer, ester fluids will not burn. Ester fluids generate around 30% less energy than mineral oil, which when combined with the high fire point of the ester fluids, means the fire will not be sustained. Even if the transformer ruptures, the fluid would still not burn, and this has been trialled under test conditions with commercial transformers.
Other benefits
The benefits of ester fluids extend beyond minimising fire risk. Unlike mineral oils, they
30 APRIL 2018
www.frmjournal.com
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