NPT Threaded Double Window Sight Flow Indicator Stainless Steel

DOUGLESS flow sight glasses made of steel allow a view of the fluid in the line. They can be manufactured with a 150 PSI NPT threaded connection.


This robust indicator is engineered to cater to a wide spectrum of industrial applications, from water treatment to high-purity pharmaceutical processes. Designed for durability and optimal clarity, it features dual windows that offer a full view of fluid dynamics, enhancing operational safety and efficiency.

Key Features:

  • Available in Carbon Steel, SS304, or SS316 to suit various industrial environments.
  • Threaded connection sizes from 1-1/4″ to 3″ NPT, ensuring a perfect fit for a wide range of piping systems.
  • Customizable with Flappers, Spinners, and Drip Indicators to meet specific monitoring requirements.

Whether it’s for monitoring viscous liquids in chemical manufacturing or ensuring the purity of pharmaceuticals, this Double Window Sight Flow Indicator provides the reliability and versatility needed for critical fluid management tasks. Choose Douglass for unmatched quality and precision in fluid monitoring solutions.

Connection type Flanged #150 / #300
Types of flow indication Free passage, rotor type, fin type, drip type
Working pressure From 0 to 300 PSI
Working temperature 45°C up to 1450°C

Measurement 1” 1-1/2” 2”
A Distance between faces 7” (177.8 mm) 8” (203.2 mm) 9” (228.6 mm)
B Distance between covers 5” (127.0 mm) 5.5” (139.7 mm) 5.5” (139.7 mm)
C Visible process 2” (50.8 mm) 2.5” (63.5 mm) 3” (76.2mm)
D Diameter of covers 4” (101.6 mm) 4.5” (114.3 mm) 5” (127.0 mm)
Total diameter of glass 2.5” (63.5 mm) 3” (76.2 mm) 3.5” (88.9 mm)
Thickness of glass 5/8” (15.87 mm) 5/8” (15.87 mm) 5/8” (15.87 mm)


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