Kilns and Firing Schedules Questions and Answers

Answer: A

Correct answer: is loaded, fired, cooled and emptied in cycles

An intermittent kiln does one load at a time: it is packed cold, taken up to temperature, cooled and emptied. A continuous kiln holds a steady temperature profile along its length while the ware travels through it, so the zones stay hot indefinitely. The intermittent kiln suits short runs and varied schedules; the continuous kiln suits volume.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the cause. In an intermittent kiln the brickwork, the insulation and the furniture are all heated to peak temperature and cooled again on every cycle, and that heat is lost each time. A continuous kiln heats its structure once at start-up and then only the ware passing through - which is why it can be several times more efficient per tonne fired.

Answer: C

They suit small batches, frequent changes of product and firings that need an unusual schedule or atmosphere. Efficiency is only one consideration, and a continuous kiln that runs half empty is worse than an intermittent one that is full.

Answer: D

Cars carrying the ware travel against the gas flow, so each piece experiences the schedule as it advances. The zones stay at constant temperature, which is what allows the kiln to run indefinitely. Only the ware experiences a changing temperature.

Answer: A

Correct answer: driven rollers that span the kiln width

A roller hearth kiln carries the ware directly on driven rollers, with no kiln car and no setting furniture. That removes the mass which would otherwise be heated and cooled with the ware, so the cycle can be very short - under an hour for wall tile, against a day or more in a tunnel kiln. The limitation is that the ware must be flat and reasonably uniform to travel on rollers.

Answer: B

Both are true and the reason gives the mechanism: thermal mass sets the rate at which any kiln can be cycled, and removing the car leaves little but the ware itself to heat. The saving is in what is not heated rather than in better insulation.

Answer: C

Twenty-four hours is 1,440 minutes, and dividing by 40 gives 36. Cycle times of this order changed the economics of tile making completely when they were introduced. Faster firing also cut work in progress and floor space dramatically.

Answer: D

Correct answer: the early heating while binder and water leave

The early stage is the slowest because residual water, organic binders and lubricants must all leave through a body that is still relatively impermeable. Driving them off faster than the vapour and gas can escape builds internal pressure and bloats or cracks the ware, so the schedule creeps upward until that material is gone. The peak hold is usually measured in minutes and the early rise in hours.

Answer: A

Correct answer: False

A firing curve has distinct segments, each set by something happening in the body: a slow rise while water and binder leave, a hold to burn out carbon, a faster rise through the inert region, a hold at peak for the reactions to complete, and a controlled cooling with its own caution around the quartz inversion. A straight line would be either needlessly slow in the safe regions or dangerously fast in the critical ones.

Answer: B

The change from alpha to beta quartz is rapid and reversible and involves a volume change of about one per cent. Both heating and cooling are slowed through the range, and the cooling passage is the more dangerous of the two.