Monday, December 31, 2007

Sometimes elegance takes a backseat

As an engineer I take satisfaction in designing an elegant solution to a problem. Elegance in engineering design is somewhat hard to define. Appearance contributes to elegance but is not essential. Elegance in an engineering sense is developing a solution to a design problem the requires as few components as possible. An elegant solution often has components that serve multiple functions.

A recent project of mine entailed designing an airlock for introducing a sample into a furnace. The furnace operates at 1600 C. The airlock is to prevent introducing air into the furnace chamber. Prior to introducing the sample into the furnace, the airlock is pumped down to a vacuum and then backfilled with inert gas.

My initial design used a thermal shutter just above the furnace to minimize the heat load on the vaccuum gate valve. The thermal shutter was simply a flapper made of refractory material. The vacuum gate valve was a commercial component.

In my search for an elegant solution I thought why not combine the gate valve and thermal shutter into a single unit?

Some reflection provided ample reason not to do this. The gate valve could no longer be a commercial component. It would require active cooling. The most critical requirement would be allowance for thermal expansion. The valve and its seals would have to operate with the furnace temperature ranging from room temperature to 1600 C.

It might have been possible to design a new valve from scratch capable of operating over this range but the design would not have been trivial. Thermal loading and thermal expansion would have to be analyzed.

The project did not have the time or money to design this.

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