Insulating material selection is a critical factor and is dependant on both the Field Heat Treating Process and the geometry of the work piece. Incorrect selection of the insulating material can cause a Field Heat Treating Process Failure, and/or add time delays to the project.
The purpose of Insulating materials is to reduce the heat loss from the work piece, and protect personnel and equipment in the work area.
Refractory ceramic fiber (RCF) blanket insulation is a man-made vitreous (glassy) fiber made by melt-fiberization of kaolin clay with equal parts alumina (Al2O3) and silica (SiO2) fibers. RCF includes fibers in the respirable range Consequently, RCF has been rated as a possible cancer causing agent. When RCF is used it is highly recommended that full-face masks with P-100 Cartridges and full Tyvek suits are used in accordance with a proper decontamination procedure. For these reasons USE of RCF IS NOT RECEOMMENDED.
Non refractory ceramic fiber (non-RCF) blanket insulation is a man-made vitreous (glassy) fiber (MMVF) of an alkaline earth silicate (AES) made by melt-fiberization and spinning of Calcium-Magnesium-Silicate (CalSiMag). Although unspun EAS dust residue is respirable, fibers in the respirable range (diameter less than 3 microns, length greater than 5 microns, and an aspect ratio greater than 3:1) have not been reported. Consequently, AES Blankets are recommended use over that of RCF blanket. Use of respirators are not required for the handling of this material.
These AES Blankets are used for all Field Heat Treating Applications up to the maximum temperature rating of the product.
This product widely known as Cooperknit, has also been marketed under other names is a knitted silica fibre that has shown have great mechanical and thermal properties after repeated uses for operating temperatures of up to 1740°F. Although independent test have shown no respirable fibres in samples taken to 1830°F for 24 hours, respiratory protection is still recommended.
Mineral Fibre Block works as an economical solution for lining the first 4” of a PWHT furnace while the hot face is covered with 2” of an AES Blanket. This non-combustible stone wool insulation board cannot withstand full PWHT temperature but is great the inside layers in a furnace. It has great dimensional integrity and does not slump, shrink or expand.
In field heat treating fire blanket is most commonly used for the set up of welding pre-heats. The fire blanket serves two purposes firstly protect the welder from insulation fibres, and secondly to protect the insulation and heaters from grinding debris when the welding is grinding and cleaning his welds in between passes. We recommend and 17oz Silicone Coated blanket for these purposes.