Sight flow indicators provide a quick, reliable and economical way to verify the flow of fluids through industrial process lines.  Fluid clarity, color, and flow can be monitored through the window.  The indicator type is specified based upon flow direction, flow rate, and media type. The window can be inserted horizontally or vertically.  Sight flow indicators usually consist of a small housing with a flange or thread for direct insertion into a pipe. Dimensions of the sight window and/or complete housing can be specified.  Wipers may be included to clean the viewing area or internal parts with high viscous fluids and/or suspended solids.

Plain sight flow indicators often include only the window and the housing; there are no moving parts to indicate flow.  This type is used with easily visible fluids to detect color clarity of turbulence of fluids.  A ball float may be included to indicate low flow or level for low light applications.

Visual indicators like flappers or propellers are used to indicate flow direction and flow rate. The type of process material may be a factor in choosing this type of indicator.  For example, some slurries may interfere with the moving part.  Flappers are used to indicate when media type is flowing.  Flappers can be used when flow is in two directions.  The vane points to the direction of flow.  A propeller, paddle wheel, or rotor type sight flow indicator turns when media type is flowing. This type of sight flow indicator is designed for clear, translucent, or dark fluids.

Drip tube allows the liquid drips into the indicator through a small opening in the end. Units are designed for vertical application only with downward flow. They are recommended for intermittent gravity or extremely low flow rates.

Full view and armored sight flow indicators are cylindrical so that the media can be seen from more than one angle.  Armored indicators include supports on either side of the cylinder; viewing may be blocked by these supports.  

Maximum flow rates may be identified for the indicator type.  Body, seal material, indicator material, and window material may be important based upon application.  For example, Viton seals are often chosen for high temperatures or the indicator may be Teflon lined for transporting and viewing corrosive materials.

Sight flow indicator features may include single or double window.  Double windows can be located on the front and back of the indicator to observe the clarity or color of a liquid.  Dual windows, two glass discs held in position by a metallic housing, internal shims and gaskets, provide added protection in applications where there is external mechanical impact, high pressure or corrosion / erosion.  FM Approval means the indicator meets Factory Mutual System standards.  Sanitary applications may require FDA or other approval.