Faulty anchor designs, errors in material selection and improper installation of refractory anchor systems can lead to premature refractory lining failures. Such failures may be highly costly, both in terms of lost production and the direct costs linked to correctional maintenance activities. In this article we will provide an overview of a few essential considerations in refractory anchor system design and installation.
Many specifications call for refractory anchors to be 66% to 75% of the lining depth. However, in general practice the anchor should extend no closer than 25mm of the lining surface.
To a great extent, proper anchor spacing depends on the type of material used, operating conditions and the physical characteristics of the equipment to be lined. Spacing from 75mm on centres to 300 or 400mm is quite common. Some specifications call for spacing the anchor on centres three times the lining thickness. Below are some general guidelines for the spacing of anchors:
The more severe the operating conditions, such as cyclic temperatures, physical stress, abrasion and vibration, the closer the anchors should be spaced.
The lower the physical stress imposed on the lining by the physical characteristics of the unit to be lined, the wider the anchor spacing.
Diamond, square and staggered anchor patterns have been widely and successfully used. The most important fact is that an irregular pattern is achieved by opposing individual anchors. This increases the overall holding power of the anchor pattern, it also helps prevent cracks from extending dangerously in any one direction or from linking together in regular networks to cause weakened areas.
The fixing point of a metal anchor is one of the areas of the anchoring system subject to the greatest load. In refractory installation, anchors are attached to the shell in different ways, in addition to welded connections, screw-in, bolt-on, clip-on and plug-in connections are used. The choice of the type of attachment depends on the type of anchor, the alloy, the installation situation and the amount of anchors to be attached. The more common attachment methods include:
Hand Welding: slower, more costly and requires skilled welders and welding electrodes.
Stud Welding: much faster, cheaper and only requires semi-skilled welders and no welding electrodes are required.
Rotary Kiln Linings: often installed with Kiln Studs or Hand Welded.
Cyclone Linings: mostly Stud Welded.
Ducting Linings: mostly Stud Welded.
Furnaces Linings: VX Hand Welds and Gold Wing hand welds are the most popular.
Custom Designs: manufacture of custom design anchors of any kind, with a CNC machine there is no limit to the designs that can be made.