News Tank Sight Glass Type 390 DN 350

Tank Sight Glass Type 390 DN 350

Once again, we had the pleasure of working on an interesting project in which maximum viewing aperture was prioritized from the outset. The requirement formulated in the inquiry was to enable a simple adaptation of a tank sight glass to an existing tank. In the case of extensions to existing tanks, a simple retrofit is usually the decisive factor.

Our technical sales department worked out a possible concept in close cooperation with our customer. Finally, our tank sight glass type 390 with welding spigot according to DIN EN 1092-1 came into question.

After checking the existing vessel's space conditions, our customer was interested in the nominal size DN 350. Our tank sight glass of type 390, has a sight opening of Ø 340 mm for the nominal size DN 350.

After our customer had checked and calculated the cut-out reinforcement in accordance with AD2000 leaflet B9, the foundation stone for this project was laid.


Our further task was to design the valve for the respective operating parameters. For this purpose, our design department designed the tank sight glass for a maximum possible operating overpressure of 6 bar(g). In order to ensure safe and trouble-free operation with a sight opening of Ø 340 mm, a borosilicate glass was selected, which was manufactured in accordance with the existing DIN 7080.


The flange material in contact with the product was chosen to be equivalent to the existing vessel material, so the stainless austenitic steel 1.4404 (316L) was considered. This stainless steel has a very high corrosion resistance due to its molybdenum additive and is mostly used in the food industry, in the pharmaceutical industry and for pressure vessels.

The sealing material in contact with the product was specified to us by the customer, an elastomer seal made of FKM (fluorocarbon rubber). This sealing material can be used at an operating temperature of up to +200°C and also has almost the best chemical resistance of all elastomers.

Our tank sight glass type 390 is generally a cost-efficient solution when it comes to the possibility or the need of process observation. Due to the welding ends according to DIN EN 1092-1, our type 390 can also be welded onto pipe ends or branches. We offer our Type 390 in a wide range of nominal pressure ratings. Our standard product range includes the nominal pressure stages PN 16, PN 40, PN 63, PN 100 and PN 160.

Higher nominal pressure ratings can also be tested and designed on request. Therefore, please do not hesitate to contact us. We can cover the nominal diameter range DN 25 to DN 350 as standard, deviating nominal diameters can also be requested here if required. If the performance of already high-grade stainless steel alloys is not sufficient to safely monitor a critical process medium, high-alloy special materials can also be offered.

For further information please do not hesitate to contact us.

+49 (0) 2461 91634 00