Atmosphere pusher furnace

A pusher plate drives the carrier, or the loaded saggar, through preheat, firing and cooling in sequence. The loading method and the push interval follow from the residence time the process requires.

The original design uses a corundum-mullite high-temperature chamber with alumina bubble insulation. Heating arrangement and exhaust method are matched to the specific process.

Selection check: when a pusher furnace fits, and when it does not

It fits when: the plant runs continuously and the load sits in a saggar, pushed forward plate by plate at a fixed interval; output demand is high and the product mix is stable; the process temperature is high — this model reaches 1800 °C, the top of the range alongside the elevator furnace; the process needs vacuum or a controlled atmosphere and still has to run continuously.

It does not fit when: the product mix changes often — interval, pusher plate size and saggar format are one linked set of parameters; the load is thin, tall or unstable — the inertia of each push knocks it over; the building cannot accommodate the return section for the in- and outfeed.

The one-line test: a pusher furnace trades rhythm for output. Once the rhythm breaks, the whole line breaks.

How the specification is fixed: work back from the material

1. The saggar section sets the chamber section. Fix the saggar first and the chamber second — the same logic as the roller hearth.
2. Pusher plate material follows temperature and atmosphere. In the high-temperature section the plate has to carry load for long periods without softening.
3. The interval comes from hold time ÷ number of positions in the furnace. This is a hard constraint. More output means a longer furnace or a second line; it does not mean pushing faster.
4. Automatic return in- and outfeed decides labour input and run stability. This is the core value of a pusher furnace compared with a batch furnace.

Common questions

Q: Pusher furnace or roller hearth — how do we choose? Temperature, load, and whether vacuum is needed. The roller hearth tops out at 1500 °C, does not offer vacuum and suits flat parts in continuous flow. The pusher furnace reaches 1800 °C, can be built for vacuum, and suits saggar-based continuous production. When both can run the same load, compare output and saggar format.

Q: Will the plates jam? Jamming usually comes from three causes: a deformed pusher plate, debris on the track, or an interval that does not match the temperature profile and causes local over-firing and sticking. The design provides access ports; operation requires track cleaning to procedure.

Q: How much can one line produce? It depends on saggar load, interval per plate and the number of positions in the furnace. Only after those three are fixed can daily output be calculated. Any "tonnes per day" figure without a saggar specification is meaningless.