How to Select the Best Sight Glass Flow Indicator

Discovering what’s flowing through your process pipelines can be time-consuming and frustrating. You stare at your equipment and wonder, “How do I know for certain what’s going on in there? Fortunately, the visible flow indicators make it easy to observe the direction and approximate range of liquid, powder, or gas through a process pipeline, as well as it is color and clarity. A sight flow indicator has a body with one or more viewing windows, usually with gaskets, and a way to mount the indicator to the pipeline.

Sight Glass

Sight glass flow indicators provide a fast, reliable, and economical way to verify fluid flow in industrial process lines. Transparency, color, and fluid flow can be monitored through the window. The type of indicator is specified according to the direction of flow, the flow rate, and the type of fluid. The window can be inserted horizontally or vertically. Visual flow indicators usually consist of a small housing with a flange or thread for direct insertion into a pipe. In addition, the dimensions of the sight window and complete housing can be specified.

Once you’ve decided you need a sight flow indicator, here are simple steps to follow to simplify:

Step 1 Choose the right style for your application.

A visual flow indicator has two opposing windows so an operator can see the intermediate fluid flow illuminated from behind. This design is suitable for ANSI pressure classes, high-temperature applications, and aggressive fluids.

A 360° view, a full view flow indicator passes fluid through a glass cylinder that is visible from all angles. It is ideal for observing process fluid for clarity, color, foam, and other conditions and the presence of moisture. Depending on the model, it may or may not be suitable for high temperatures or pressures.

Sight Glass

A tube-style flow indicator passes fluid through a glass cylinder that is visible from all angles, allowing ample ambient light to illuminate the flow. Although it’s ideal for checking a process fluid for clarity, color, foam, and the presence of moisture, it’s not appropriate for high pressures.

Step 2 Restrict the specific function of the indicator.

Rotary, flapper, flutter, ball, or drip indicators can help you quickly gauge the process material’s direction and speed of flow. Indicators are beneficial with colorless gases and opaque fluids.

Sight Glass

Step 3 Choose a mounting type.

The most common mounting methods are flange, threaded, and sanitary clamp. Sanitary clamp mounting is typically used in bio-pharma and food & beverage applications.

Step 4: Determine the most appropriate materials for the application.

A sight flow indicator comprises metal, gaskets, and glass. Although carbon steel and stainless steel are the two most common metals used, stainless steel offers better corrosion resistance. A Teflon coating is available for particularly aggressive process media. Be wary of low-cost castings that may result in problems down the road. The integrity of the seal is essential to see the performance of the flow indicator. Gaskets are typically made of an enhanced PF material or Teflon. Ensure that the gasket material is compatible with the product with which it will come in contact.

Sight Glass(1)

Standard soda glass is typically used for low temperatures and non-corrosive products or cleaning solutions. For higher temperatures, use borosilicate glass because of its higher resistance to thermal shock, superior corrosion resistance, and increased temperature capabilities than soda-lime glass. For very high temperatures, quartz or sapphire glass is recommended.



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