During the past 40 years in the refractory industry, I have seen, and been part of the continuing effort to develop monolithic refractories as the go to product for most of the heat intensive industries. However, there are still applications where brick is a better choice.
During my “early years” on the Onex construction team, 100# bags of castable containing plenty of cement was the car deck refractory choice of the day. A mortar mixing tub and a cement hoe was “good enough” because the “liberal” use of water made mixing easy. A quick hit with a pencil vibrator and off you went. We called them “utility castable” in those days.
After the recession in the early 80’s, castable and other monolithic such as plastic ram and dry vibes became even more important because the tradesmen programs run by big steel companies faded away and the work to install refractories needed to be made simpler for the semi-skilled worker in the mill. Mix it, dump it or ram it.
Over the years, product improvement efforts have mostly revolved around improving the properties of castable products paying attention to particle sizing, raw material sourcing and cement content/quality. These changes have led to increased product density’s, increased hot and cold modulus of rupture (MOR), higher abrasion resistance, higher temperature performance moving these products closer to the performance of pressed and fired brick shapes.
It is important to note that castable properties look great on a data sheet, but the variables associated with casting such as weather conditions, water content, mixing time, vibration time, air curing and final firing can have a marked effect on your actual finished properties and performance. To cold, too much/too little water, not vibrated properly, not cured and fired properly, or not mixed long enough can lead to substandard properties, not those stated on the data sheet.
Even with the great strides the monolithic manufacturers have made, there is still a place for brick. The advantages of using a brick product that has been mechanically pressed and high fired and has the properties as indicated on a data sheet should not be overlooked in those tougher/troublesome applications or when the installation of a castable is not possible.
Sure, the use of brick will require the need for skilled tradesmen (masons). But when installed correctly, the refractory brick can help you keep equipment up and running any time of the year. Brick products are available in many chemistries for numerous applications as well as numerous shapes to fit a specific area or diameter. When to consider refractory brick as part of your maintenance program:
• During colder times of year when the casting environment is not ideal
• As a Just-In-Time (JIT) material available on site that doesn’t have a shelf life issue
• Need a product that is not susceptible to negative material property deviations that have the potential to occur during casting process (untrained crews
• The furnace lacks the abilities to properly cure and fire castable material in a slow and controlled manner
• Movement of the castable to the area requiring repairs is difficult or impossible
• A composite lining makes sense such as an insulating firebrick sub-hearth and cast hearth
• You’ve tried every castable you can to no avail.
Brick should be part of any plant’s refractory maintenance planning and design consideration (in addition to castable, plastic ram and dry vibe). A professionally installed brick lining could be the answer to some particularly tough applications. Give brick some consideration when you talk to your supplier about the best refractory design for your problem areas. And don’t forget, the mortar used with the brick is key, so don’t go cheap. Utilize a mortar that complements, or exceeds, the chemistry of the brick.
I am happy to assist with questions you may have and here to help you wind your way through any refractory issues you may be experiencing.
Michael Ducato/Onex, Inc.