Why Are D3 & E3 Standards Needed for Molten Metal Suit?

Molten Metal performance levels are classified by testing according to the ISO 9185 norm within the EN ISO 11612: Protective clothing against heat and flame standard. Resistance to aluminum molten is represented by the letter D and is categorized by classes 1, 2 and 3. Similarly, resistance to molten iron is represented by the letter E and is categorized by classes 1, 2 and 3. The lower and upper limits determining the application method and classes of the Molten Aluminum and Molten Iron tests applied in the ISO 9185 test are stated in the tables below.

When examined according to the ISO 9185 test, the main difference between molten Aluminum and molten Iron is the melting temperature of the metals. While Aluminum melts at 780°C, Iron melts at 1,400°C.

This temperature difference creates a potential energy difference between Aluminum and Iron melts. Iron melt, which has a higher temperature and therefore higher potential energy than aluminum, flows much faster than aluminum when poured onto the fabric. Thus, the adhesion force of the Iron melt on the fabric is lower than the Aluminum melt, therefore the damage it causes to the fabric is less. Although it may sound contradictory at first, “as the temperature of the molten metal decreases, the damage it causes on the fabric increases.”

Metal splash events experienced in Iron and Steel factories do not always occur at temperatures of 1,400°C. The temperature of the (secondary) molten iron that spills onto the ground and splashes onto other surfaces decreases due to the impact and the time spent in the air, so the damage caused by these secondary splashes that cool down becomes more effective. In addition, since these secondary splashes are much smaller, at a much higher speed, and in point sizes, they do not reach the grammage that can flow quickly on the fabric and can create point punctures like cigarette burns.

The best precaution to be taken against the damage caused by such point splashes at temperatures lower than 1,400°C is to use clothes made of D3 and E3 class fabrics.

The fact that the fabric is in the D3 and E3 performance classes means that it has the highest molten metal lubricating properties, and this depends on the fiber mixture of the fabric, its weight and weaving type.

In order to achieve optimum user performance, it is important that both sides of the fabric have the same properties, because during use, the inner surfaces of the fabrics in the collar, front placket, cuffs and leg areas may be exposed to molten metal. For this reason, all fibers to be used in the fabric must have molten metal sliding properties. Aramid group fibers such as Para-Aramid or Meta-Aramid, which do not slide metal melts and have high adhesion properties, should not be included in the fabric.

However, the weights of fabrics that can exhibit D3 class performance start from 300 g/m², but the minimum weight required to withstand the high-speed secondary splashes mentioned above is 350 g/m². Even if it is in the D3 class, punctures may occur due to secondary splashes in fabrics below this weight.

In order to prevent the loss of comfort caused by increased weight, it is recommended to use Tencel® derived fibers with high breathability and moisture absorption capacity in the fabric.