High pressure sight glasses | ACI Industriearmaturen GmbH

High pressure flow sight glasses Type 522 with threaded connection

SHORT DESCRIPTION - FLOW SIGHT GLASS with threaded connection

The ACI high-pressure sight glass type 522 is designed for the observation and illumination of processes at an operating pressure of up to 400 bar. The basic version of the solid stainless steel or steel body has two BSP G or NPT or internal thread connections which are integrated directly into the solid housing wall. This enables us to dispense with welding seams and other extensive processing and to keep delivery times short.

As body materials, we use the same range of high-quality steel and stainless steel grades as for our other sight glasses, such as the proven austenite 1.4571, highly acid-resistant 1.4539, the internationally highly recognised 1.4404 and many other materials, including duplex steel and high-performance alloys such as Hastelloy.

Depending on your process data, a borosilicate glass pane 3.3 based on DIN 7080 or, for higher temperatures, quartz glass or sapphire is used as a special window.

For sealing, we use high-quality graphite or mica composite gaskets in the main force connection, for example novaphit MST or Klinger Milam.

Our Type 522 sight glass is subject 100% to a pressure test with 1.5-fold nominal pressure according to the applicable directives and is supplied to you fully assembled. If parts of the fitting, such as the viewing windows, are subject to wear due to continuous use or are damaged, it is sufficient to notify us of the order number on the casing and we will provide a replacement as soon as possible.

Read on for detailed technical information.

Technical data


C.22.8, 1.4541, 1.4571, etc.


Straight through flow sight glasses with female thread connection BSP G or NPT.
Optionally available in three-way or four-way shape.

Nominal size:

1/8" - 4" (The design is order-related. Not every nominal pressure is possible at any size)

Nominal pressure:

up to max. 400 bar


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

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High pressure sight glasses