Type 335 - PN3 | Tank sight glass | ACI Industriearmaturen GmbH

Oval Sight Glass Level Indicator Type 335 - PN3

Vessel sight glass LEVEL INDICATOR

The ACI tank sight glass Type 335 is a lightweight construction that offers a significantly enlarged viewing opening than our Type 330, for lower operating pressure up to 3 bar. Due to this structure, Type 335 combines the functions of our round container sight glasses such as Type 318 and our filling level indicators for container wall installation Type 330.

Like our other sight glass fittings, Type 335 can be fitted not only with the highly resistant borosilicate glass proven in industry, but for your most demanding uses also with quartz glass or the especially robust and scratch-free sapphire glass.

For sealing, we use flat gasket materials from well-known manufacturers, which we select based on your individual requirements. For many areas, we use the proven aramid fibre seal C4400 by KlingerSIL. For high temperatures, we trust in novaphit MST by Frenzelit, and for chemically challenging uses such as strong acids, the sight glass is sealed with pure or expanded PTFE.

Type 335 is supplied preassembled. After welding the basic flange, the supplied seals are fixed together with the sight glass by the cover flange, whereby even very low torque is sufficient to achieve sufficient sealing force.

If there is unexpected damage to the sight glass during operation, our competent team of technicians and salespeople are available to provide a replacement.

Read on for technical details or watch the product video above in the slider !

Technical details


Base flange:
1.4571, 1.4404, 1.4435, 1.4462, 1.4539, 1.4541, 2.4602, 2.4610, P265GH, Alloy , Super Duplex

Cover flange:
1.4571, 1.4404, 1.4435, 1.4462, 1.4539, 1.4541, 2.4602, 2.4610, P265GH, Alloy , Super Duplex

DIN 912, A4-70 or special materials

Glass plates:
Borosilicate glass acc DIN 7081

Universal Quality (aramid fiber)
(Other materials available)


oval longitudinal sightglass
for insertion or welding

Nominal size:

von 270 bis 760 mm

Nominal pressure:

Operating pressures up to 3 bar

(Vacuum version available on request)


100°C or 243°C

depending on glass and gasket selection.

Gasket selection:

PTFE (200°C)

FKM (200°C)

NBR (100°C)

C4400 (150°C)

Silicone (200°C)

EPDM (140°C)

Graphite (280°C)


Optional versions are possible.

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Type 335 - PN3 | Tank sight glass