Refractory dryout services help to ensure that newly installed or repaired refractory linings are completely cured and dry prior to being put into high temperature service. If the refractory is not properly dried, it can experience thermal shock and damage that will result in costly repairs or early lining degradation.
What is the dryout of refractory castables?
Refractories are abrasive, chemically aggressive, highly porous and prone to spalling if exposed to the wrong conditions. This is why it’s important to follow all recommended refractory dry out schedules as provided by the refractory materials manufacturer and/or refractory installation contractor. Failure to do so can lead to thermal shock, cracking, fracturing, shrinkage and other costly problems that will shorten the life of the lining and impact operational performance.
Dryout is the period of time required after conventional castables have been placed to allow a hydraulic bond to form between the refractory and the concrete substrate. There are two types of water remaining on the castable after this process: free water (physical water), which is simply in the pores of the refractory, and chemically combined water tied up in various cement hydrate phases. It is the chemically combined water that comes off en masse during a drying process and must be driven off quickly and controlled to avoid excessive internal pressures in the refractory that could cause it to spall or break down.
Refractory drying is accomplished by slowly heating the refractory using heaters located around the area of the lining being dried. The hot water is fed through nominated man ways, nozzle locations or furnace doors while the cool air is drawn out through these same nominated points. The combination of the warm air and the cold air provides a controlled environment for driving off the chemically combined water that is in the refractory.