Sight-glass, application in compressed air systems.

Sight-glasses are used in many applications in many industries, and all have to do with the fact that it's necessary to visually monitor the liquid level inside a container that has walls that you can't see through.

When we are talking about compressed air applications, usually the sight-glass is used on the outside of an opaque filter or lubricator bowl.

A sight-glass will be plumbed vertically along side the outside of the bowl or the tank or whatever vessel is being used, with an inlet into the sight-glass through the wall at the bottom of the vessel, and another at the top.

The drawing shows the sight-glass on the left of the filter bowl.

Different manufacturers have different style sight-glasses, with some being completely attached to the side of the bowl.







The drawing shows the sight-glass "standing off" the bowl, for clarity.

It's called a sight-glass since originally the vertical tube was made of glass - for visibility, of course.

Current sight-glass materials may be synthetic plastic composites that offer the clarity of glass, but without the same potential for breakage.







Here's more info on compressors in general sight-glass.

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