Sight Glasses

Flow indicators are used in steam and condensate systems for visual confirmation of flow, checking steam trap operation, and identifying continuous discharge, blockage, or unwanted live steam carryover. They are typically installed upstream or downstream of the steam trap, in condensate return lines, steam tracing circuits, manifolds, and auxiliary lines where local diagnosis is required without dismantling the pipework.

This category includes double-window, single-window, tubular, and ball-type flow indicators, with series such as ARI BR660 and Noris 020, 025, 050, 108, and 111. Selection is based on the service medium, operating pressure and temperature, visibility at the installation point, viewing direction, the need to distinguish liquid from gas flow, and maintainability. In steam service, attention should be given to thermal stress on the sight glass, gasket tightness, and possible fouling of the viewing area from oxides or condensate deposits.

DIN and ANSI versions are available, with pressure ratings including PN10, PN16, PN25, PN40, Class 150, 150 lbs, and 300 lbs, depending on type. End connections include BSP, NPT, flanged, socket weld, and butt weld, with references to DIN EN 1092, DIN EN 10226-1, ANSI B1.20.1, and EN ISO 9692 for selected designs. Body materials include grey cast iron EN-JL 1040 / EN-GJL-250, carbon steels 1.0425, 1.0460, 1.0619 / 1.0619+N, and stainless steels 1.4404, 1.4408, and 1.4571, selected according to pressure class, temperature range, corrosion allowance, and media compatibility.