with Nate Sroka, Ipsen Quality Assurance Engineer
The interior brick walls of an atmosphere furnace endure extreme temperatures—sometimes reaching 2200 °F—every hour of every day. Over time, the bricks become brittle, crack, and experience thermal expansion, which can open seams in the mortar.
After years of continuous operation, users may notice exterior walls becoming hot enough to melt insulated cables or components attached to the furnace. When bricks start falling out of place or insulation begins to sag, it’s time to shut down the furnace, assess damage, and plan for repairs.
Typically, furnaces operating for 5-10 years since installation or their last major overhaul require rebricking or relining.
Understanding the Components: Bricks and Boards
Knowing the key components used in the rebricking and relining process prepares you for discussions about repairs
Insulated Fire Bricks (IFB) come in various temperature ratings. A 2300 °F brick is less efficient and durable under extreme heat than a 2600 °F brick, but is often more cost-effective. High-rated bricks typically line the interior, while lower-rated bricks provide an additional insulation layer.
Insulating boards made from calcium silicate form the thermal barrier between the heating chamber and external components. They can withstand temperatures from 1000 °F to 1800 °F and are commonly used in lower-temperature furnaces.
Mineral wool is a fibrous insulating material used to fill gaps around furnace entry points and seams. Made from volcanic rock, ceramic, or slag, it allows for expansion and contraction due to temperature changes.
One key thing to know about atmosphere furnaces is that they’re almost always “on.” In a vacuum furnace, recipes use electric elements that shut off after every cycle, and quenching often happens within the same chamber. However, in an atmosphere furnace, turning off the burners and then restarting the furnace from room temperature the next day is much less energy efficient than running the burners and holding a consistent temperature even when the furnace is empty. Parts from an atmosphere furnace are typically quenched in an oil or salt bath, separate from the heating chamber.
Starting the Rebricking Process – What you need to know
When the time comes to plan for your rebricking and relining process, planning is essential to making sure your operations experience the least amount of downtime.
Preparing for a Quote:
First, review the pre-quote checklist to make sure you have the right information to get an accurate quote.
Pre-Quote Checklist: Important information to have on hand when getting a quote for rebricking or relining your atmosphere furnace
– Furnace model number and serial number
– Heating Chamber Dimensions (w/d/h)
– Archway dimensions from base to top
– Door dimensions and condition
– Drawings or engineering plans outlining any aftermarket modifications
– Typical operating temperatures
– Any additional materials installed to prevent heat penetration
– Photos from as many angles of the furnace as possible.
– A list of any consumable or heavy-wear components that also need to be replaced.
Building a Timeline:
Start collecting quotes at least a year in advance and place a purchase order no less than six months before the planned shutdown.
Scheduling Considerations:
Many furnace operators are looking to have work like this done during either a summer or winter holiday shutdown period. Advanced planning improves scheduling flexibility.
Site Preparations
Before the service team arrives, ensure the workspace is ready:
- Clear space for staging new materials and removing old bricks.
- Provide access to a forklift, a durable waste collection container, a dumpster, and other required tools and resources.
- Confirm power connections near the site for welding and other power tools.
- Review lockout/tagout procedures with maintenance and operations teams.
- Determine the required furnace cool-down time before disassembly and plan furnace shutdown accordingly.
- Identify and disconnect any electrical, process gas, or water-cooling lines as outlined prior to service.
Rebricking Day – What you should expect
During disassembly, consider performing additional maintenance, such as:
- Inspecting and rotating or replacing burner tubes
- Inspecting and replacing pusher chains, and skid hearth sections.
- Checking doors, door hoods, and fan bungs.
- Conducting leak tests and changing the quench oil.
Coordinate these tasks with the service team to avoid disruptions. The rebricking process spans several days, allowing time for concurrent inspections and repairs.
Final Inspection and Testing
Upon project completion:
- Inspect the furnace with the installation team to ensure all work aligns with project specifications.
- Document any changes as a reference for future maintenance.
- Perform a “dry out” procedure and clean the quench tank before refilling the tank. See break-out box below for an example.
- Run the furnace without parts to test for temperature uniformity.
- Carburizing furnaces may need extra burn-in time to “season” the bricks
- Fresh bricks absorb free carbon until fully saturated
- When bricks are properly saturated, furnace atmospheres stabilize
- Time of burn-in is dependent on percentage of carbon-level the system needs to achieve
- Identify potential hot or cold spots that may require further insulation adjustments.
Example Dry Out Procedure
(Follow your service manual for model-specific instructions)
1. Block the front inner door open 4″ to 5″. On furnaces with more than two inner doors, raise the intermediate doors full open.
2. Close inner rear door.
3. Leave the front and rear outer doors open.
4. Set temperature controls at 250 °F to 300 °F and hold at this temperature for 8 hours or overnight.
5. Heat furnace slowly to 500 °F. If violent discharge of steam is noted at any temperature, do not raise the temperature above this setting until all steaming has ceased.
6. Control the furnace at 500 °F until all steaming has stopped.
7. Close the front inner door. On furnaces with more than two inner doors, also close the intermediate door(s).
8. Heat the furnace from 500 °F to 1200 °F at a rate not exceeding 100 °F per hour. Soak for 8 hours, or overnight, at 1200 °F. The furnace is now ready for operation.
Post-Installation Best Practices
A rebrick or reline of a furnace is a significant investment. To get the most from your furnace, make the time to take a proactive approach:
- Establish a daily maintenance inspection for the first week, followed by weekly checks for the first month.
- Resume regular maintenance schedules if no issues arise.
- Schedule independent inspections with an Ipsen Field Service Engineer at three, five, seven, and nine years to proactively assess furnace condition and secure preferred maintenance dates.
By following these steps, atmosphere furnace operators can maximize uptime, streamline service quoting, optimize downtime usage, and ensure efficient future rebuilds.
Contact Ipsen Customer Service at 1-800-GO-IPSEN or email retrofits@ipsenusa.com.