Емкостекло.Sight glasses for industrial vessels
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Engineering catalog · process vessels

Sight glasses for industrial vessels

Selection by construction, pressure, temperature and medium — from the fitting class to a vendor-ready inquiry.

Select a constructionOpen the catalog
Circular sight window diagram: body, seal, glass element and a light sliceDd
Conventional diagram, not to scale. Actual dimensions and versions follow the manufacturer documentation.

Choose by mounting method

Not sure how the fitting mounts? The selector determines classes from operating conditions.

Weld-inThe fitting is welded into the vessel wall — DIN 28120-type constructions.Onto an existing flangeMounting on a prepared flange — DIN 28121-type constructions.Not sureDetermine the classes from pressure, temperature and medium.

Catalog categories

Meaningful groups: how mounting works, which limits are considered, where each construction is used.

Engineering services

All calculations run locally in the browser; nothing you enter is sent anywhere.

Fitting class selectorStep-by-step input, explainable classes, list of open clarifications.Vendor RFQ sheetStructured inquiry: copy, download as .txt, print. No server submission.View areaA = π(d/2)² from the free view diameter.Disc massm = ρ·π(d/2000)²·(t/1000), idealized cylinder geometry.Pressure converterbar, kPa, MPa, Pa, psi, atm via a single Pa base.Temperature converter°C, °F, K with a correct scale offset.PCD hole spacingChord between adjacent holes: s = D·sin(π/n).

The tools never send your inputs to a server or to analytics.

DIN 28120 and DIN 28121 — what is the difference

Two fundamentally different load paths — and different mounting requirements.

DIN 28120 — weld-in fittingCircular sight glass fitting welded into the vessel wall; the load passes through the glass element (force-fit).DIN 28121 — load bypasses the glassThe construction carries the effort around the glass disc (force shunt), often onto a prepared flange. Not an automatic replacement for DIN 28120.Detailed construction comparisonCompatibility of a specific assembly is confirmed by the fitting manufacturer or the vessel designer.

How a typical fitting is built

Cutaway of a conventional circular fitting: body, medium-side seal, glass disc, compensating gasket, cover and fasteners. The diagram explains the parts; it is not a factory drawing.

How a typical fitting is builtd
Conventional diagram, not to scale. Actual dimensions and versions follow the manufacturer documentation.

Applications

Typical vessels and processes that require visual observation of the medium.

Sight window for a chemical reactorObserving the reaction, foam and medium colour in a jacketed vessel under pressure.Sight window for a mixing vesselObserving mixing homogeneity and level: oblong windows and lighting.Sight window for a food-grade tankHygienic requirements, CIP washing and materials that contact the product.Sight window for a silo and bulk-material vesselLevel and bridging observation without excess pressure; dusting and cleaning.Process washing and hygienic requirementsHow CIP/SIP modes affect the glass, gaskets and fitting construction.

Engineering reference

Reviewed material on selection, installation and limits of sight glasses.

DIN 28120 and DIN 28121: construction and connection differencesHow weld-in fittings differ from constructions with a load path bypassing the glass, and why replacing one type with the other requires verification.How to choose a sight glass for a vessel: 10 input parametersA checklist of input data: task, mounting, geometry, pressure, temperature, medium, materials, lighting, documents, maintenance.DN, PN, glass dimensions and the view diameter: what they meanFour different characteristics that are often confused: DN, PN, the free diameter and the glass outer diameter.DIN 7080 borosilicate glass: scope and limitsWhat DIN 7080 describes, why 280 °C is a characteristic of the element and not of the assembly, and what to verify at replacement.PTFE, EPDM, FKM, graphite gaskets: what must be clarifiedThe roles of medium-contact and compensating gaskets and four questions to ask about any seal material.How to replace a glass disc: what to measure and which documents are neededA step-by-step replacement procedure: measurements, material selection, documents, safety.

A transparent methodology

Every technical value on the site carries a link to its primary source — a standard overview or manufacturer documentation. Values without a confirmed source are not published.

The tools perform only honest computations: geometry and unit conversion. No “suitable” verdicts without manufacturer confirmation.

Contacts and commercial terms are not published until verified. The RFQ sheet is generated locally and handed to the vendor directly.

Values without a confirmed source are not published on this site.Technical review: 2026-11-04