When less is more

When building a cleanroom, getting the entry airlock right is important. Florian Dittel, Dittel Engineering, looks at why, when designing airlocks, smaller can often turn out to be more expensive.

The airlock system that allows personnel to pass through from a non-controlled environment into a cleanroom is for many cleanroom operators an unwelcome cost. While the cleanroom itself provides a measurable economic benefit, the airlock seemingly only provides access to the controlled area and requires maintenance, while not obviously adding to the bottom line profit. The common consequence is often the decision to make personnel airlocks as small as possible. This can, however, work out more expensive in the long run.

This point is well illustrated by Florian Dittel, chief technical officer of Dittel Engineering, in an academic paper that won him the Albert Tichelmann prize for Best Diploma from the German Association of Engineers – the VDI. In his thesis, Dittel developed a formula to calculate the optimal size of personnel airlocks for cleanrooms from an economic point of view.

“The idea is to minimise the footprint of airlocks as much as possible for reasons of cost. But to keep both the operating and capital costs of an airlock low, it is necessary to identify all the factors that may impact on operation and cost in the early stages of conceptual design, and then to evaluate and incorporate these into the planning,” says Dittel.

Although such an airlock is essential for many cleanrooms, and represents a significant cost factor, until now there has been no available mathematical model for their efficient design, construction and operation. Dittel has shown that the airlock size can have a decisive influence on cost-effective operation, and this can be calculated exactly.