Sight window for a mixing vessel
Observing mixing homogeneity and level: oblong windows and lighting.
In mixers and agitated vessels the window is responsible for homogeneity: the operator must see the flow pattern, inclusions and the level.
An oblong window covering several zones at once, or a pair of circular windows at different heights, is often more convenient.
Typical conditions
- small or zero excess pressure;
- frequent washing, possibly CIP;
- products that stick to the glass;
- mixing with aeration and foam.
What visibility is required
The window must cover the mixer zone and the free surface. For a long zone — an oblong window; for spot control — a circular one with lighting.
Limits
- sticking products — a mechanical wiper or washer;
- the influence of an oblong cut-out on the wall stiffness;
- gasket materials versus the medium and washing.
Questions for the vessel designer
- which zones require continuous observation?
- is access to the window for maintenance possible?
- which washing is provided and with which agents?
Which classes to consider
At pressures close to atmospheric — non-pressure and low-pressure constructions; with pressure present — circular DIN 28120/28121 fittings. Oblong windows follow the manufacturer documentation.