Important Factors To Consider When Installing Refractories

Proper installation of the refractory is as important as selection of the right material for the service life and safe operation of the furnace. 

 

If the material is inadequately compacted during installation, voids or areas of low density may form, creating a weak spot. Maintaining proper expansion gaps, correct dimension of bricks and monolithics, fixing anchors etc. all are very important to achieve better life of refractories. 

 

There are some of the important factors to consider in respect to laying of refractory bricks, their dimensions, selection of mortars, expansion joints and many other important things.

 

Bond

Bond is an arrangement by which the joints between the bricks are staggered in all directions in a pre-determined manner. This ensures stability in construction as well as air tightness. An all header construction is recommended in the hot face of a furnace. 

 

Wall Thickness

Structural stability should be taken into consideration while deciding the wall thickness. As a good engineering practice, furnace walls lined with 115mm thickness bricks should not be constructed beyond a height of one meter without proper anchorage. From the stability point of view minimum thickness should be around 230mm, which may be suitably increased as the height goes up. Use of metallic sheets with anchoring arrangements, improves the stability of the wall where basic refractories are used. Such anchoring of walls with the furnace structure should have sliding arrangement to take care of the movement of refractories during heating up and cooling down.

 

Joints

Joints are considered as important design elements that have various functions and classified according to construction and design requirements. Although joints form a small part of the furnace lining, they play a important role. They can assemble the pieces (bricks or blocks) together, absorb thermal expansion and limit the stresses generated in the masonry. The joints may be either mortared joints or dry (without mortar) joints. In either case, the stress/strain behavior of the joint interface differs considerably. 

 

Structural Support

Refractories are normally held in position with steel shell or a structural framework by tie rods as failure of structural by other reasons will cause partial failure or limit the total collapse of refractories. Their alignment, shape etc should also be equal concern. Also important is that the structural should not get overheated, and should be adequately insulated wherever required.

 

Anchor

The anchor's length, diameter, spacing, and orientation are all critical factors that must be closely examined. The number of anchors to be used is dependent on the operating conditions, the refractory materials used, and the lining thickness. The choice of anchor material, shape, number, and size all have a significant impact on the cast refractory lining lifespan.

 

Once the installation of refractories is over, it is important to heat the lining before starting the actual operation.