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Flow sight glasses type 521 - highpressure


The ACI high-pressure sight glass type 521 has a solid steel or stainless steel body and two sight glass discs especially manufactured for the high operating pressure in accordance with DIN 7080. As with most of our high-pressure sight glasses in the standard version with high-quality graphite gaskets, the sealing is usually done with TA-Luft approval.

The opposing sight openings allow the process to be observed from both sides or the medium to be X-rayed as required.

The Type 521 is equipped with two welding ends and can be installed directly into your plant as delivered. We orient ourselves on the pipe dimensions of DIN EN 1092-1, but other connection dimensions are also possible on request. In small nominal diameters, the connection pieces are formed directly from the sight glass housing so that no additional welding seams occur on the sight glass fitting. In this way we keep the delivery times short and avoid mechanical weak points and uneven surfaces inside the body.

For very high operating temperatures, the Type 521 Flow Sight Glass can be equipped with high-quality special glass based on quartz or sapphire glass as well as flat gaskets based on mica.

The flow sight glass type 521 is also suitable for chemically demanding applications such as acids or alkaline solutions. Simply talk to our experts about your individual requirements!

The sight glass type 521 is delivered completely assembled and tested for pressure resistance. Further down on this page you will find detailed technical information!



  • Body made of: C.22.8, 1.4541, 1.4571, (all weldable materials)


  • Straight through with butt weld ends
  • Optionally available in three-way or four-way shape.

Nominal size:

  • DN 15 to DN 200 (The design is order-related. Not every nominal pressure is possible at any size)

Nominal pressure:

  • up to max. 1000 bar (The design is order-related. Not every nominal pressure is possible at any size)


  • With borosilicate glass up to max. 280 °C
  • With quartz glass up to max. 500 °C
  • (Higher temperatures on request)


  • The design is order related.


  • Optional versions are possible.
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