Type 318 - PN 2,5 | Circular sight glass | ACI Industriearmaturen GmbH

Circular Sight Glass Fittings Type 318 - PN 2,5

Short description - round Tank Sight Glasses Type 318 PN2,5

Our tank sight glass fittings Type 318 (PN2.5) are intended for welding installation into or onto a pressure vessel wall and provide a way to observe and illuminate the interior of the tank. ACI tank sight glass fittings of Type 318 have been designed based on DIN 28120 for an operating pressure of up to 2.5 bar. Two flanges of high quality stainless steel 1.4571 (316Ti) surround a glass disc made up chemically highly resistant borosilicate glass 3.3 according to DIN 7080, creating a nearly maintenance-free inspection port.

Contrary to the sight glass fittings described in DIN 28120, our Type 318 is significantly thinner and the hexagon head screws barely protrude out of the cover flange, thus reducing the space required for installation. Type 318 closes the gap between our non pressure retaining Type 317 and the stronger types 319 and 320.

The sight glass fitting is sealed using flat gaskets specifically selected for your application from our vast range of gasket materials. Apart from commonly used aramid fibre gaskets, we can offer Type 318 with sophisticated materials like PTFE, NBR, graphite composites and many other gasket types.

If the glass disc’s maximum operating temperature of 280°C does not suffice for your application, or your process fluids are challenging even for highly resilient borosilicate glass, a mica disc specifically fitting your sight glass provides additional protection of the glass surface against steam or aggressive chemicals like highly alkaline solutions. Like the rest of our tank sight glass fittings, Type 318 is available equipped with wipers type SWI, spray nozzles or lights. Read on to learn more technical details of our Type 318!

Technical details


Base flange:
RSt 37-2, H II, 1.4571 (factory standard)

Cover flange:
RSt 37-2, H II, 1.4541 (factory standard)

Special materials on request

Sight glass:
Borosilicate glass to DIN 7080
Soda-lime glass according to DIN 8902

Klingersil® or as desired

5.6 galvanized, A4-70


similar to DIN 28120 but PN 2,5

Nominal size:

DN 50 - DN 200 (larger nominal diameters on request)

Nominal pressure:

up to 2,5 bar


With soda-lime glass up to max. 150°C

With borosilicate glass up to max. 280°C

With borosilicate glass & mica shield up to max. 320°C

For higher temperatures please ask us.


Special designs/options

a) With wiper SWI

b) With LED or halogen lights, also ATEX-certified

c) With O-ring seal (suitable for vacuum)

d) High-temperature version with quartz glass

e) Other special designs on request


Optional versions are possible.

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Type 318 - PN 2,5 | Circular sight glass