Gas-tight fans

There are three possible areas where leakage may take place:

• leakage of welds and seals in the casing

• leakage at static interfaces such as flanges and joints

• leakage at shaft seals (dynamic rotating interfaces).

Tightness of the casing volute

An almost absolute casing tightness can only be achieved be­tween metallic materials when the components, such as the scroll and volute sides, are correctly and continuously welded together. This requires close inspection and quality control. It is normally carried out at the same time as the inspection of split­ting flanges. The main areas of concern are the inspection door openings and any removable segments.

Static assemblies

This type of interface has to be capable of disassembly from time to time. The usual joint comprises plane surfaces. Avery common method is to use an “O” ring of some elastic material between two flanges as shown in Figure 8.10. Blind holes are

Recommended and through holes with nuts and bolts should be avoided.

Temperature, corrosiveness and erosiveness of the gas being handled.

Posted in Fans Ventilation A Practical Guide