Carel has been chosen by e2v technologies, a specialist developer and manufacturer of high-technology electronic components and sub-systems, to control humidity in clean rooms.

e2v technologies, based in Chelmsford, Essex, has been operating its close control clean rooms for a significant period of time using open-end electrode boilers to produce steam for humidity control. Over the years the open-end electrodes have provided a reasonable level of control, at about ± 5%rH, but in order to maintain this, the boiler cylinders, supplied with hard mains water, have had to be replaced every 7-10 days. With about a dozen units installed on the site this has produced an unwanted maintenance overhead running into many thousands of pounds per annum.

Therefore, the decision was taken this year to replace the electrode boilers and the alternative chosen was the Carel heaterSteam resistance heater steam humidifier.

There were several benefits that the change was able to provide. Firstly, the units could be operated using the existing site-generated Reverse Osmosis water supply. This would not have been acceptable to the open-end electrode system, as there has to be a nominal water conductivity to allow the electrical current to flow between the electrodes.

Secondly the heaterSteam units use elements that are cast into Aluminium Alloy housings, which provide a significantly increased surface area in contact with the water. There are two additional benefits to be derived from this, in that the larger element area produces a very fast response time when heating, even with single phase units, and also the surface of the casting, having been coated in non-stick Teflon, can resist the build up of any possible scale that may develop in the boiling vessel.

The third and possibly the most significant advantage that the heaterSteam units provide is that they can operate long term without the output being interrupted by periodic drainage. This was immediately evident at e2v as on start up, with no changes to the basic operating format, the units filled with water, boiled within a few minutes and settled into uninterrupted operation with a control tolerance of ± 1%.

Maintenance on the heaterSteam units should be reduced to little more than an annual inspection and the increased cost of the units could be paid back in a very short period of time when the original cost of replacement cylinders is considered. e2v is also counting on the time benefit of having one maintenance engineer released from the full time occupation of cylinder monitoring and maintenance

for other more cost effective activities.

Source: Carel