VFI Standard Threaded Sight Flow Indicator

Standard Inline Flow-Indicator Sight Glass with Threaded Connection

The most common style of flow indicator for industrial application allows visual observation of process flow through a pair of sight glasses mounted on a casted metal body.

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All standard threaded models in the L.J. Star Incorporated line of sight flow indicators carry full ANSI rating and are available in several applications- specific configurations. ANSI designed for 150# or 300# service, threaded units are available in sizes from 1/2” to 2”.

Indicator Types

  • Plain Style – installed in any position
  • Drip Tube Style – well suited for vertical lines with downward flow direction.
  • Flapper Style – monitoring either horizontal or vertical lines with upward
  • Rotator Style – may be installed in any position to indicate flow in any direction.
  • Full ANSI Class Rating


  • Standard alloys
  • 316 Stainless Steel; Carbon Steel
  • Standard gasket materials
  • Neoprene; Gylon®
  • Tempered borosilicate glass
  • Investment cast surface finish
  • In-stock delivery

Sight flow indicator model options.

150 psi Standard Threaded Model

Pipe Size Dimension

A                  B                  C

Approx. Wt. (Lbs.)
1/2″ 3-3/4” 1-1/4” 3-7/8” 6
3/4” 3-3/4” 1-1/4” 3-7/8” 6
1” 4-1/4” 1-1/4” 4-1/8” 11
1-1/2” 5-1/2” 1-3/4” 5-3/8” 12
2” 6-1/4” 2” 6-1/8” 17

The specifications contained herein are subject to change without notice and any user of said specifications should verify from the manufacturer that the specifications are currently in effect. Otherwise, the manufacturer assumes no responsibility for the use of specifications which may have been changed and are no longer in effect.