Type 317 - PN 0 | Circular sight glass | ACI Industriearmaturen GmbH

Circular Sight Glass Fittings Type 317 - for pressurless use

Tank Sight Glasses Type 317 for unpressurised vessels

Round tank sight glasses for welding are used to observe and illuminate the interior of closed vessels like tanks, silos and other similar installations. ACI Tank sight glasses of Type 317 are designed based on the established standard DIN 28120 and adapted for unpressurised vessels. The devices consist of two stainless steel flanges fixing the sight glass disc and the gaskets in place. 

Installation involves cutting an opening into the vessel wall and welding the base flange either onto or into the hull of the vessel. Once the weldment is finished, the glass and gaskets are fixed to the base flange using the cover flange and included fasteners. Type 317 is, unlike Type 318, 319 or 320, not intended as a pressure retaining part! These devices provide a simple viewport. 

For this reason, Type 317 is built significantly lighter and thinner than other common sight glass fittings.

Type 317’s fasteners are sunk into the cover flange to avoid protruding parts. This greatly reduces the risk of injuries or damage even in confined spaces. Despite the low expected stresses, we manufacture our type 317 from the same high quality stainless steel 1.4571 (316Ti) that our clients have successfully used in their installations for many years. The sight glass window itself is made from reliable borosilicate glass 3.3 according to DIN 7080 and sealed with high quality gasket material specifically chosen for your operation conditions. Our gasket material range includes commonly used materials like graphite with and without sheet metal inlays, KlingerSIL C4400 aramid fibre gaskets, pure PTFE, or rubber materials like NBR.

Just like our other types of tank sight glasses, Type 317 is available with optional accessories like wipers, spray nozzles or light fixtures.

Detailed technical information about our tank sight glass type 317 can be found further down on this page.

Technical details


Base flange:
1.4571 (factory standard)

Cover flange:
1.4571 (factory standard)

Steel on request

Sight glass:
borosilicate glass to DIN 7080
Soda-lime glass according to DIN 8902

Klingersil® or as desired



similar to DIN 28120 but for pressureless application

Nominal size:

DN50 up to DN200

Nominal pressure:

PN 0 - for unpressurised operation


With borosilicate glass up to max. 280 °C
With soda lime glass to max. 150 °C


Optional versions are possible.

Sectional view_Type_317
DN 50 80 100 125 150 200 300 400
Da [mm] 140 165 190 215 240 190 370 450
Di [mm] 80 100 125 150 175 225 300 370
h1 [mm] 10 10 10 10 10 10 15 20
h2 [mm] 15 15 15 15 15 15 20 25
kg 2 2,8 3,2 4,3 5,1 6,8 12,2 23
Nm* 6 4 5 5 6 8 9 11

'KlingerSil® C4400

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Type 317 - PN 0 | Circular sight glass