321A Sight glasses similar to DIN 28121 | ACI Industriearmaturen GmbH

Sight glass fitting type 321A - similar to DIN 28121 for flange mounting on ASME flanges B16.5

Short description - Round tank sight glasses Type 321A similar to DIN 28121

The ACI sight glass fitting type 321A for mounting on flanges according to ASME B16.5 has been cosntruiled similar to DIN 28121. It is sealed on the media side by a PTFE-enveloped corrugated ring seal. Since this seal is located in the force shunt, the flange parts of the sight glass lie directly on each other and thus protect the glass plate in the best possible way.

The sight glass type 321A is delivered pre-assembled and ready to use without additional effort. Mounting on a support flange according to ASME B16.5 is possible. Should the unlikely event occur that the glass is damaged during operation, the entire fitting can be replaced with little effort.

The sealing in the force shunt prevents the gaskets from being loosened, which means that it is no longer necessary to tighten the clamping screws on site.

The PTFE-enveloped corrugated ring seal makes the tank sight glass type 321A suitable for foodstuffs, acids, alkalis and most aggressive chemicals. As with all our sightglasses, the glass pane itself can be additionally protected against damaging influences by a mica pane or a FEP protective screen.

You can also order accessories such as wipers type SWI, spraying devices SVI or lights directly from us, adapted exactly to your application.

As a flange material you have the choice between high-quality stainless steel grades such as 1.4541 (321), 1.4571 (316Ti), 1.4404 (316L) or according to customer specifications as well as the lower alloyed steel grades such as P265GH or S235JRG2 for less corrosion-prone locations. As glass, we rely on MAXOS ® borosilicate glass, proven in industry, in accordance with the current DIN 7080 standard.

Technical data


Base flange:

carbon steel / 1.4541 (321) / 1.4571 (316Ti) / 1.4404 (316L) / 1.4306 (304L) / 1.4539 and many more

Cover flange:

carbon steel / 1.4541 (321) / 1.4571 (316Ti) / 1.4404 (316L) / 1.4306 (304L) / 1.4539 and many more

Sight glass:

Borosilicate glass DIN 7080 (up to 200°C)


PTFE enveloped gasket (up to 200°C)


similar to DIN 28121

Nominal size:

DN40 to DN200

Operating pressure: max. 20 bar

-for higher pressures see Type 322


Tmax. 200°C

- For higher temperatures see Type 323

Gasket selection:

PTFE enveloped gasket acc. to DIN 28121

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321A Sight glasses similar to DIN 28121