High-pressure flow sight glasses PN63 | PN100 | PN160 | PN250 | PN320 or PN400

High-pressure flow sight glass fitting

The ACI high pressure sight flow indicators type 520 - PN63 | PN100 | PN160 | PN250 or PN320 have a solid body made of various materials ranging from heat resistant structural steel P250GH (1.0460) to stainless steels such as 1.4541, 1.4571 or acid resistant special steels such as 1.4539. Depending on the pressure rating, flanges are welded on in accordance with DIN EN 1092-1 and tested within the scope of the AD2000 directive. On request, other materials such as nickel-based alloys or Hastelloy for the highest stresses are also available. The fittings are usually manufactured with two viewing windows, which allows observation of the processes from two sides or fluoroscopy of the process medium.

In the standard version, a sight glass made of thermally hardened borosilicate glass 3.3 or highly temperature-resistant quartz or sapphire glass, specially manufactured for your application, serves as the viewing window. Depending on the temperature and chemical stress, sealing is done with flat gaskets selected exactly for your application, for example made of graphite (novaphit MST XP) or mica-based gaskets.

Due to the solid housing, our flow sight glass type 520 can be equipped with test connections for measuring instruments or additional process connections (e.g. internal thread) on request.
In the standard version, type 520 is designed for up to 160 bar within the scope of DIN EN 1092-1. If your process requires a higher operating pressure, simply contact us. The sight glass housing and the glass plates can (depending on the size) be designed for up to 320 bar operating pressure.

Type 520 is pre-assembled at the factory and subjected to a pressure test at 1.5 times the nominal pressure. See also the animation video further down this page.

Watch the animation video or look at the tecnical data.

Technical data


1.0460 / 1.4301 / 1.4306 (F304L) / 1.4404 (F316L) / 1.4410 (Super Duplex) / 1.4435 (F316L) / 1.4462 (F 51) / 1.4529 (Alloy 926) / 1.4539 (Alloy 904L) / 1.4541 (F321) / 1.4547 (F44) / 1.4550 (F347) / 1.4571 (316Ti) / 1.4828 / 1.4841 / 1.4876 ( Alloy 800H) / 1.4878 / 1.7335 / 2.4068 (Alloy 201) / 2.4360 (Alloy 400) / 2.4375 (Alloy K500) / 2.4602 (Alloy C-22) / 2.4605 (Alloy 59) / 2.4610 (Alloy C-4) / 2.4816 (Alloy 600) / 2.4819 (Alloy C-276) / 2.4856 (Alloy 625) / 2.4858 (Alloy 825) / 3.7035 (Titan)

Nominal size:

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

Nominal pressure:

PN63, PN100, PN160, PN250, PN320, PN400


The design is order-related.


With borosilicate glass up to max. 280 ° C

(Higher temperatures on request)


Straight through flow sight glasses
Optionally available in three-way or four-way shape.


Optional versions are possible.

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High pressure sight glass PN63 | PN100 | PN160 | PN250 | PN320 | PN400