Refractory castable and plastic linings (as pictured) must be dried-in.
“Drying-In” refractory castables after installation or repair is critical to increase the effectiveness and lifespan of a new refractory lining, but many end users shortcut the manufacturer’s recommended dry-in schedule because of the cost and time involved. Proper refractory dry-in often requires a minimum of twenty-four hours, and speeding up the process can be tempting when production is at stake. However, short-cutting the dry-in process carries risks, as shortcuts can cause catastrophic refractory lining failure due to high steam pressure building up inside the lining.
Why Do Refractories Need to be Dried-in?
Refractory castables are designed to be mixed with water and installed in a fluid state, similar to cement, and they must be cured at ambient temperature after installation. Following curing, some of the water used in the installation process is trapped inside the refractory lining, so the refractory must be “dried-in”, or slowly heated up beyond 212F to operating temperature, to allow the moisture within the lining to gradually escape as vapor through the pores in the lining.
Potential Refractory Failure: Spalling from High Pressure Steam
Refractory installation projects require significant time and costs. By the time the end user has their boiler or furnace back, they are often eager to get the equipment online. End users commonly shorten the refractory dry-in process in order to more quickly reach full operating capacity. However, heating up refractories too quickly poses the most significant risk of failure.
As the water in the lining exceeds boiling temperature and turns to steam, it expands volume over 1600 times. The manufacturer’s recommended dry-in schedule allows ample time for expanding steam vapor to escape gradually from the castable. If the castable is heated too rapidly due to an abbreviated dry-in schedule, then there is serious risk of high pressure steam building within the refractory lining as the steam rapidly expands, causing the refractory to rupture and spall. Thus, shortening the dry-in cycle may not necessarily save time and money, it could result in another shutdown to tear out the damaged lining and reinstall refractories.
Who Can Help with Refractory Dry-in?
Joe Moore & Company is an authorized contractor installer and distributor for major refractory manufacturers. We are trained by the refractories manufacturers to select, install, and dry-in refractories in a variety of applications, including boilers, furnaces, incinerators, and stacks. Call us today at (919) 832-1665 if you need assistance with refractory selection or refractory repairs.
