High pressure flow sight glasses Type 522 with threaded connection | PN 160 | PN 250 | PN 320

High pressure flow sight glass with threaded connection | PN 160 | PN 250 | PN 320 

The ACI high-pressure sight glass type 522 is designed for the observation and illumination of processes at an operating pressure of up to 320 bar. The basic version of the solid stainless steel or steel housing has two female threaded connections to Whitworth, NPT or a standard you specify, which are machined directly into the solid housing wall. This eliminates the need for welding seams and other extensive processing and allows us to keep delivery times short.

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

Depending on your process data, a glass pane made of borosilicate glass 3.3 in accordance with DIN 7080. For special requirements, we additionally use mica protection discs.

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

Our sight glass type 522 is subjected to a 100% pressure test with 1.5 times the nominal pressure in accordance with applicable guidelines and is delivered to you fully assembled. Should parts of the fitting, for example the sight glass, wear out or become damaged through continued use, simply inform us of the order number affixed to the housing and we will arrange for a replacement as quickly as possible.

Technical data


C.22.8, 1.4541, 1.4571, etc.


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

Nominal size:

1/4" - 2"

Nominal pressure:

up to max. 320 bar


With borosilicate glass up to max. 280 ° C

(Higher temperatures on request)

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High pressure flow sight glass Type 522