The design of the anchoring system to be used in the shape is of tremendous importance.  In addition to the normal considerations of alloy type and anchor size, the precast shape design must also consider all alternatives for attaching the shape to the structure.  Numerous methods can be used, including threaded stud attachments through the wall, welded fixtures, or bolted assemblies.

Perhaps most importantly, the proper refractory material must be selected to suit the demands of the application.  Factors such as the desired temperature profile through the lining, expected mechanical stresses, potential chemical attack on the lining, erosion mechanisms, and expansion allowance must all be understood prior to selecting a material to be used in the precast shape.

A well-equipped precast manufacturing facility should include high-energy, large capacity mixers, automated mixing stations with conveyors for material delivery, vibration tables, digitally-controlled water addition, mixing time controllers, and adequate lifting capabilities for large shapes.  Firing of shapes is accomplished with a digitally-controlled furnace with burners capable of firing to at least 1300 deg. F.  In-house mold/pattern fabrication capabilities and CAD-generated drawings for design assistance should also be expected

In service, linings comprised of precast shapes often see less stresses and cracking, due to the independent, “floating” nature of the lining.  The performance of the lining can also be more predictable, resulting in better opportunities to plan for maintenance and repairs.

Other major benefits to be gained from the use of precast refractory shapes are related to simplified installation and repair logistics, which can lead directly to reduced costs and shorter down times.  With the use of precast shapes, forming labor, materials, equipment costs, actual placement time and expense, and associated costs during form removal, curing, and cleanup are all eliminated.  These costs are shifted back to the manufacturer of the shape, who can absorb them much more efficiently when spread over his overall production capacity.  

Whenever any portion of refractory repair work can be completed prior to crews being on site, costs are automatically reduced.  Installation contractors have also found that the use of precast shapes can often give them a substantial advantage in competitive bid situations.  With the use of precast shapes, crew sizing can be minimized.  Speed of installation is another obvious benefit to both the installer and the owner, resulting in reduced costs due to shorter job duration.  Material usage is also reduced, when compared to other installation methods such as guniting, where as much as 45% extra material is required to compensate for rebound and other job losses.  Environmental hazards such as dusting and tripping hazards associated with equipment and hoses are also reduced substantially, if not eliminated.    

Future repairs also become much more economical and quicker to accomplish.  Repair areas can often be isolated to just the immediate wear area within the boundaries of a shape.  Anchor attachment points can typically be reused.  Replacement shapes, purchased early and kept as spare parts on site, can be easily installed in a fraction of the time required for conventional repair methods.  Repairs become more of a mechanical maintenance job, rather than a refractory installation job requiring a specialized crew and equipment.  

TFL, Incorporated is a supplier of refractory materials and related services located in Houston, Texas, and is a leading manufacturer of
REDI-SHAPE

Web site:  www.tflhouston.com