LUMIGLAS® Straight-Through Sight Glass — Inline Flow Sight Glass for Pipelines (1/2″–8″)

Description

The LUMIGLAS® Straight-Through Sight Glass — also known as an inline sight glass or flow sight glass — is a flanged pipeline assembly that provides direct visual inspection of liquid flow, fluid colour, and process condition along the pipeline axis. Because the body installs, in line with the pipe, flow passes straight through the fitting with minimal pressure drop and no flow diversion.

The body is precision-machined from stainless steel and fitted with a borosilicate or tempered soda-lime safety glass plate for clear, undistorted viewing under process conditions. In addition to the standard stainless steel body, carbon steel, rubber-lined, and fluorine-lined variants are available for corrosive or chemically aggressive service conditions.

The series covers nominal bore sizes from 1/2″ (15 mm) to 8″ (200 mm), with a standard pressure rating of Pg = 10 kg/cm² (≈ 10 bar) and a maximum working temperature of 300°C (glass-type dependent). Consequently, it is widely specified for reflux lines, cooling water circuits, drain inspection, food & beverage production, chemical process, and petrochemical pipeline applications.

Technical Specifications

Why Specify a Straight-Through Inline Sight Glass?

Unlike tee-mounted or angled viewports, a straight-through sight glass installs directly along the pipe centreline. As a result, flow passes through the body without diversion, which means pressure drop is kept to a minimum and no additional pipe fittings are required. This makes the inline design particularly well suited to space-constrained installations and high-velocity flow lines.

In addition, the replaceable glass plate design allows field servicing without removing the body from the pipeline. Furthermore, the wide range of body materials — from standard stainless steel through to rubber and PTFE/fluorine linings — means a single product family covers general industrial service as well as chemically aggressive applications.

Main Connection Dimensions

All dimensions in mm. Confirm final values against the official datasheet before ordering.

L = external length · H = external height · Glass Ø = glass plate diameter · t = plate thickness. Weights are approximate. Confirm against the official datasheet before ordering.

Typical Applications

The LUMIGLAS® inline sight glass is well suited to any process line where operators need to confirm flow presence, detect phase changes, or monitor fluid colour. However, the specific body material and glass type must be matched to the operating fluid.

• ▸Reflux and return lines — visual confirmation of flow return in distillation, reactor, and heat exchanger circuits
• ▸Cooling water systems — flow rate and fluid clarity monitoring in closed-loop cooling circuits
• ▸Drain and receiving lines — inline inspection of effluent colour and flow presence before tank entry
• ▸Food & beverage processing — hygienic flow observation on CIP-compatible stainless steel lines
• ▸Chemical & petrochemical pipelines — PTFE/rubber-lined variants for corrosive media
• ▸Water treatment plants — dosing line confirmation, filter backwash observation, and effluent inspection

Installation & Maintenance

• !Use rated gaskets and apply even bolt torque in a cross-pattern sequence to avoid point loading on the glass plate.
• !Inspect the glass for chips or cracks before pressurising the line. Do not use a damaged glass plate.
• !Keep spare glass plates and gaskets on site for critical lines. Replacement is field-serviceable without removing the body.
• !Do not exceed rated pressure (Pg = 10 kg/cm²) or temperature (300°C) without consulting Lumistar technical sales.

Frequently Asked Questions