News Manhole Sight Glass with individual connection


Manhole Sight Glass Type 325 with individual connection

We received an enquiry for a Manhole Sight Glass. The term “manhole” describes a revision opening on mostly larger containers. Such revision openings are often used to reach the inner side of a container – e.g. for a cleaning process or for an inspection of the tank interior. The manholes often have individual connection flanges and hole patterns. The connection dimensions therefore deviate from the common and valid standards DIN EN 1092-1 & ASME B16.5.

The problem with the client’s existing sight glass was the repeated breakage of glass during the production process. Furthermore, we had no room for deviation in the outer geometry as well as for the hole pattern on the base flange. We had to ensure that the new manhole sight glass was adaptable to the existing connection flange with the nominal size DN 500. The remaining conditions were clear too: An operating overpressure of 1 bar(g) had to be taken into account in the design.

The sealing material in question was defined by the process medium “drinking water”. For the sealing, a material which has a drinking water approval KTW D1, D2 was used. The elastometer “EPDM” used by us is furthermore food-safe and thus FDA-conform after 21 §177.2600.

Due to the difficulties with the existing manhole sight glass, our construction department has examined the enquiry quite carefully. In order to prevent glass breakage, an important aspect is the force distribution on the sight glass plate. Moreover, the plane parallelism of the harmonising components plays an important role. 

As a basis for this special construction, we have chosen our Type 325 and adapted it to the underlying circumstances.

Nominal size: DN 500
Flange material: 1.4571
Connection type:

For screwing onto special borepattern

Glass material: Borosilicate glass
Gasket material:EPDM
Working pressure: max. 1 bar(g)
Medium: Drinking water

After a successful calculation, design and construction, we received the order for this interesting project and implemented it successfully. The manhole sight glass similar to type 325 with a nominal size of DN 500 is already in use with our client on-site.

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