Annealing Ovens

When an annealing oven is not available, even quite large pieces of equipment can be annealed by flame. Apparatus assembled on the bench can often only be annealed by a flame. As a general principle each joint should be annealed as it is completed, unless a further join is to be made, or another operation is to be performed immediately in the same region or so near to it that the whole of the first joint can be kept hot—then the whole is annealed together. 

Glass-working shops that are called upon to make large or intricate apparatus should be equipped with an annealing oven. With some ingenuity a home-made one can be built using Nichrome wire and fire-brick. 

The annealing ovens, termed in France carquaises, are very large, and have several fire-places. The bed or floor is made of bricks, presenting in its whole extent a perfectly level surface. Sand must be sprinkled over the bed, that the plates may slide freely upon it, and encounter no impediment in shrinking or contracting. 

Of the three options, the second and third are limited by available equipment. Without a polariscope and/or glass annealing oven, you cannot do them. If you do not have this equipment, play it safe and use the first option. 

The floor area of the workshop will depend on the amount and nature of the work to be undertaken. Not less than 40 m (400 ft ) will be necessary if no limit is to be put on the glassblowing service required. The floor bearers should be strong enough to support a glassworking lathe and an annealing oven, if such equipment is to be installed. 

Fireclay outer protecting tubes are used for protection in kilns, glass and steel furnaces, annealing ovens, etc. Usually they are mounted vertically in the top of the furnace and may be cemented in place. Small fireclay insulating tubes are used on base-metal couples. 

Table-blown glassware of the laboratory may also be given an annealing with advantage in a small annealing oven heated by a gas flame. A convenient brickwork chamber for the laboratory or small workshop is one about 2 feet square in area and about i foot deep. It should be provided with a small chimney outlet with a sliding... 

After the centrifuge has stopped, the segments of the mould wall are separated so that they cannot shrink onto the blank during the annealing process. The casting mould with the blank is then driven into the annealing oven and set onto the base slabs of the oven. The transport vehicle then travels back out of the oven again. 

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