There are conditions under which Skydrol will burn.
Skydrol fluids are "fire resistant."
Traditionally the term "fire resistant" has been used to describe phosphate esters, as opposed to mineral oil
based hydraulic fluids, because they are very difficult to ignite at room temperature. In standardized testing, a fine mist spray of Skydrol cannot be ignited with a burning propane
torch. The same fine mist spray of a mineral oil
hydraulic fluid, such as MIL-H-5606 or MIL-PRF-83282, produces a large fireball when touched by a propane
The basic parameters of fire resistance include: 1) resistance to ignition, and 2) resistance to propagation of the flame from the source of ignition. The test methods followed by the industry are described in AMS 3150 and various ASTM test methods. For more detail, please ask for our Publication No. 9118 on fire resistance.
Skydrol fluids must be heated to high temperatures before they will sustain combustion.
The fire point of Skydrol LD-4, for example, is 360oF. This is the temperature the fluid must be heated to in order for it to be ignited in the ASTM D92 cup apparatus. The autoignition temperature of LD-4 is 880oF. This is the temperature at which the vapors will ignite spontaneously.