The DLBF Switches are mounted on a side of vessels by means of flange. The liquid level is checked by a float integral with a small metallic tube; this tube has a flattened part like in Bourdon tube, so that it can be bent only in the vertical sense. A thin rigid plate is placed within the tube and transmits the movement up to the output device placed within the housing.

When liquid level rises up to the preset point, the float makes the output device trip (trip on rise); then, when level comes down again and exceeds the preset point, the float makes the output device come back to the initial position (reset on fall). Between the set and reset points there is always a gap, named differential; it is only 20 ±5mm in the standard case, but can be up to 300mm in special versions like in Fig. 10 prepared upon request. The inverse function is available too : Trip on fall and Reset on rise.

The output is placed in the housing and can be electric (type DLBF7) or pneumatic (type DLBF5); the trip is snap action in the case of electric microswitch, whilst takes a few instants in the case of pneumatic switch.

These Switches assure very high reliability : the hydrostatic lift on the float is transmitted to the output device in a quite direct way, i.e. without any sliding mechanical parts, and so without any risk of friction or jamming.

 

These Level Switches meet the ATEX standard .

In addition to the basic version (Fig. 2) with flange FL in Ø 3-4”, also other special versions are available, as for example :

• closed in cylindrical chamber with threaded sleeves connections (ANSI 150, 300 psi, Ø1”÷1½” NPT-F) : 

• closed in cylindrical chamber with flange connections, in I, L shape (ANSI 150, 300 psi, Ø1”÷2”) : 

• closed in cylindrical chamber in T shape, with 3 flanged branches (ANSI 150, 300 psi, Ø3”÷4”) : 

• other versions, to be defined together with user ..