What are Flow sight glasses?
Flow sight glasses are industrial sight glass fittings that are equipped with standard process connections and can be mounted in pipelines like other fittings. Most designs are available with flange connections, screwed connections, or welding ends.
The simplest variant, seen in the first image on the right (or online with a detailed 3D view as ACI Type 530), consists of a straight housing with two opposite viewports. Based on this basic shape, three-way or four-way sight glass fittings as well as variants with multiple viewports are also available,
With appropriate structural design and material selection for housing, glass, screws, and gaskets, this type of sight glass fitting is suitable for applications up to 400 °C or 400 bar.
For even better observation of the processes and media in the pipelines, tubular sight glasses can be used.
This type of sight glass fitting offers a 360° all-round view and is additionally almost dead space-free. As a result, this design is particularly suitable for applications that place high demands on hygiene but operate at comparatively low pressures (up to 16/40 bar). The low dead space in the interior also significantly reduces the flow resistance in tubular sight glasses. Since the open glass area is larger than in other flow sight glasses, an impact protection made of acrylic glass is often additionally installed here, as also shown in the first image above.
Due to the design, the maximum possible working pressure for classic tubular sight glasses of the Type 620 – as shown in the diagram – decreases significantly, especially for large nominal sizes compared to other flow sight glasses. For higher pressures, ACI has developed the Type 670 and Type 671.
For high temperatures and pressures, there are also tubular sight glass fittings in intermediate flange design, which are available as variants, among others, with quartz glass. Such a sight glass is shown in the first image on the right in the mounted state.
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