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Circular Sight Glasses

Windows or portals that allow for direct visual access to operational systems, sight glasses are used in a wide range of industries to allow for easy monitoring of equipment and processes. Mounted directly into tanks, boilers, or pipelines, transparent sight glasses — which come in various forms, including tubes, discs, squares, and panels — provide engineers and operators with accurate, real-time information.

Sight glass windows can be made of tempered glass, toughened glass, or annealed glass, and can be constructed in a range of materials to suit specific needs; borosilicate, soda lime, and quartz are some of the most popular choices.

Along with sight flow indicators, sanitary flow indicators, specialty lighting, and other custom glass products, sight glasses are essential components of industrial process observation systems.

Types of Sight Glasses

Our sight glasses are installed directly in piping, reactors, tanks, and vessels, and are able to withstand high pressure, intense chemical corrosion, and elevated temperatures. Papailias' industrial sight glasses for tanks can now be constructed in a variety of shapes, out of many materials and styles of manufacture to choose. And to meet specific application needs, a range of optional accessories can be included in designs.

Sight ports or windows are typically constructed in circular disc form, sandwiched between two heavy-duty metal frames made of any number of alloys. The assembly can be held together with high-performance bolts and gaskets, or fused through manufacturing. Circular sight glass discs are commonly used in factories, water processing facilities, breweries, and dairies. Tanks and vats in various industrial operations also make frequent use of circular sight glasses. Typically, the highest-pressure sight glasses are almost universally circular.

Unique Sight Glass Variations

Papailias offers an array of unique sight glass variations for all applications and project requirements. Some of these include:

Borosilicate, or hard, glass discs — For exceptional thermal performance, clarity, and toughness

Hardened soda lime glass discs — For lower-pressure applications

Sanitary-grade sight glasses — For leak-tight, tool-less assembly to prevent contamination in food, dairy, and pharmaceutical applications

Industrial-grade sight glasses — Designed specifically for toughness in high-temperature, high-pressure, and highly corrosive environments

Weld-neck style sight glasses — For attachment to stub end pipes

Threaded-style sight glasses — For use with stub end pipes, ANSI flanged nozzles, or vessel studding outlets

Flanged sight glasses — Designed specifically to fit existing ANSI flanged nozzles or vessel studding outlets

Rectangular sight glasses — For particular vessel geometry

Quick-opening sight glasses — For easy sampling, cleaning, and maintenance access

Double-window sight glasses — For an extra layer of protection and reliability against stress concentration, thermal shock, corrosion, mechanical damage, and overall failure

Curved sight glasses — For a custom fit to curved or cylindrical vessels and pipes

Custom Sight Glass Solutions from Papailias

At Papailias Inc., we’ve been helping engineers accurately monitor operations since 1976. Working closely with your team, our expert engineers can design and manufacture round sight glasses to custom sizes and viewing dimensions, and we offer a wide range of material options to suit your specific system and requirements.

In addition to circular sight glasses and other sight glass shapes, we also provide flow indicators, level gauges, sanitary flow indicators, and a complete line of custom glass products and components for all types of process observation needs.

To learn more about our sanitary, industrial, and custom sight glass solutions, check out our circular sight glasses catalog or reach out to the team today to discuss how we can help with your process monitoring needs.


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NW

Weld Pad Style Circular Sight Glasses

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Series NW weld pad connection.

Series NW sight glasses are offered with nominal viewing diameters of 3", 4", 5", 6", 7", and 9". Custrom sizes and configurations are available upon request. Series NW sight glasses are manufactured from ASME Section VIII acceptable metals. Each sight glass is thoroughly inspected and will provide long and useful service under the most demanding processing conditions. Optional accessories include Type I wiper, Type II wiper and Type I spray washer, Type II spray washer assemblies and Type III Spray Rings. Series NW sight glasses are also available with Series PL, MSL, SLEX, REX, or FBX illuminators.

ASME code calculations and any resulting additional material needed to ...
PLF Series Circular Sight Glasses with Light

PLF Series Circular Sight Glasses with Light

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Series PLF - Combination light/sight glass for low pressure applications.

The Series PLF Light/Sight glasses are very economical and popular units for baghouses, electrostatic precipitators, ductwork, and many other low pressure applications. The unit utilizes a thin lower flange with the Series PL lighting fixtures supporting the lens and seal gasket.
NW-BW

Series NW-BW; Weld Neck Style Circular Sight Glasses

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This series of weld neck style sight glasses are designed for welding to a stub end pipe or may be suppied with a radius to saddle the pipe. Each is rated for 150 PSIG (10.3 Barg) at 300 ºF (149 ºC) with a tempered soda lime lens and 500 ºF (260 ºC) with a borosilicate lens. Sight glasses are constructed using code materials. Optional accessories include Series PL, MSL, SLEX, REX, FBX illuminators, and Type I wipers.
NW-RF Picture

Threaded Style Circular Sight Glasses

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This series of sight glasses are designed for attachment to stub end pipe, ANSI flanged nozzles or vessel studding outlets. Each is rated for 150 PSIG (10.3 Barg) at 300 ºF (149 ºC) with a tempered soda lime lens and 500 ºF (260 ºC) with a borosilicate lens. Sight glasses are constructed using code materials. Optional accessories include Series PL, MSL, SLEX, REX, FBX illuminators, and Type I wipers.
NW-RF Picture

Flanged Style Circular Sight Glasses, NW-RF

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This series of sight glasses are designed for attachment to an existing ANSI flanged nozzle or vessel studding outlet. Each is rated for 150 PSIG (10.3 Barg) at 300 ºF (149 ºC) with a tempered soda lime lens and 500 ºF (260 ºC) with a borosilicate lens and compatible gasket. Sight glasses are constructed using code materials. Optional accessories include Series PL, MSL, SLEX, REX, FBX illuminators, and Type I wipers.  High pressure ratings and ANSI Class connections are available upon request. Note: Series NW-RF sight glasses are not supplied with fasteners unless explicitly stated otherwise.