Sight Glasses & Inspection Windows

A sight glass lets operators monitor fill levels, flow rates, and process conditions without opening hatches or climbing structures. In mining and heavy industry, the sight glass panel cops impact from falling material, vibration from adjacent equipment, and chemical exposure from process fluids. Polycarbonate sheet handles all three. It absorbs impacts that would shatter glass, resists vibration fatigue, and stands up to most mineral acids and process chemicals found on mine sites.

For applications where optical clarity is critical and impact risk is low (laboratory vessels, water treatment monitoring panels, or clean-side process windows) acrylic sheet provides a glass-like finish with better scratch resistance than polycarbonate. Acrylic is also the better choice where the sight glass is exposed to certain solvents that can stress-crack polycarbonate.

Hopper and bin level windows are the most common order: a rectangular or circular polycarbonate panel bolted into a flange on the side of a storage hopper so the operator can check fill level from ground level. We supply these with bolt holes drilled to your PCD (pitch circle diameter) so they bolt straight onto the existing flange without on-site machining.

Pipeline inspection windows let operators visually confirm flow in gravity lines, slurry pipes, and water circuits. Pump housing windows are common on dewatering and process pump stations where the operator needs to see cavitation or blockages without pulling the casing apart. Screen deck inspection panels sit above vibrating screens so the operator can see the screen mesh condition and discharge pattern from the walkway above.

Every sight glass is CNC routed to your drawing: circles, ovals, rectangles with radius corners, or any custom profile. Bolt holes are positioned to match the existing flange pattern, and edges are finished smooth to sit flat against the gasket face. For flanged sight glasses we can also supply a matching HDPE backing ring if needed.

Replacement sight glasses for existing equipment are straightforward. Send us a photo or sketch of the existing panel with dimensions and bolt centres, and we will cut a drop-in replacement. For new equipment builds, send us the GA drawing and we will pick off the sight glass details and quote the full set.

For most mining sight glasses, 6-10mm UV-stabilised polycarbonate is the standard. It handles temperatures up to 120°C, resists most mineral acids, and survives impacts that would destroy glass or acrylic panels. Where the aperture exceeds 500mm unsupported span, step up to 12mm or add an intermediate support bar to limit deflection under wind or pressure loads.

Acrylic is the better pick for laboratory, water treatment, and clean-process sight glasses where scratch resistance and optical clarity matter more than impact strength. Cast acrylic gives a near-glass finish and is easier to polish if it does pick up surface marks during service.

Mine-site shutdowns often need a full set of replacement sight glasses across multiple equipment items. We supply batch orders with each panel labelled by equipment tag number so the crew can install them in sequence. Volume pricing applies to batch orders. The more panels in the set, the lower the unit cost.

Get a quote for sight glasses and inspection windows. Send us your flange drawing or existing panel dimensions and we will price a drop-in replacement or full shutdown set.