Technical article - level indicators | ACI Industriearmaturen GmbH
Technical article Level indicators

Technical articles and interesting facts about - level indicators

Technical contribution: Level indicator

In this technical contribution you will get an overview of level indicators, their typical designs and application possibilities.

Figure 1: Typical rectangular sight glasses as level indicators

Figure 1: Typical rectangular sight glasses as level indicators

Level indicators can be considered a special type of tank sight glass. The viewport is, as shown in Figure 1, narrow and long. Such a sight glass, installed into a tank, offers an easy way to observe the tank liquid level from outside without requiring floaters or other additional parts. Clear and colourless liquids can be more easily visualised by using a “reflex” glass. This type of glass is serrated on the inside, improving visibility of the liquid’s meniscus as shown in Figure 2.

Figure 2: The difference between reflex and transparent sight glasses according to DIN 7081

Figure 2: The difference between reflex and transparent sight glasses according to DIN 7081

For some applications it may be desirable to design the level indicator as a bypass valve. In such cases, the superficially welded base flange is replaced by a housing closed at the rear, which can be fitted with either welded spigots, threaded connections or flanges, as shown in Figure 3 as an example.


Figure 3: Different types of bypass level indicators

Figure 3: Different types of bypass level indicators

If observation from multiple angles or a backlit view is desired, a sight glass of type 422 as shown in Figure 4 can be used.



This type of sight glass can be equipped with threaded connections, welding connections, flanges, or any other desired process connection, and is uitable for high pressures above 35 bar and temperatures up to 243 °C.



Type 422 level indicators are suitable for comparatively high pressures of 35 bar and more as well as temperatures up to 243°C.




Our level indicators and further information can be found here.

Figure 4: ACI Type 422, a completely closed level indicator with inspection openings on both sides

Figure 4: ACI Type 422, a completely closed level indicator with inspection openings on both sides

+49 (0) 2461 91634 00
info@aci24.com