The DFK switches are mounted on top of vessel. The inside level of liquid is checked by the float integral with a vertical rod; when level rises up to the preset height, the float makes the output device trip (trip on rise); when level comes down again and exceeds the preset height, the float makes the output device come back to the initial position (reset on fall); between the set and reset heights there is always a gap, named differential : see below. The inverse function is available too : Trip on fall and Reset on rise. The
output device can be electric or pneumatic, is snap action and is placed in the housing.

APPLICATIONS. They are fit for small and large dimensions vessels and for industrial fluids/liquids such as chemical, petrochemical, solvents, etc. For liquids with specific gravity from 500kg/m³ up.

The Level Switches meet the ATEX standard .

Connection to vessel. Top mounting by flange, rating ANSI 150, 300, 600psi.
Flange is per ANSI or UNI/DIN standards, in carbon steel ASTM 105N,
stainless steel AISI 304, or stainless steel AISI 316 :

Housing . Material : Aluminium cast, in electric or pneumatic version :
• 1 or 2 microswitches SPDT, simultaneous action ; size : Ø155×200mm, flame-proof EEx dc IIC T6; 1 hole for electric connection : ¾ ” NPT-F threaded (or ½” NPT-F) housing-holder height : 80mm for temperatures of –20/+180°C 145mm for higher or lower temperatures.
• 1 pneumatic valve On-Off-Vent; Ø125×180mm, water-proof; 3 holes for air connection ¼” NPT-F : inlet, outlet and vent; housing-holder height : 70mm for temperatures of –20/+180°C
130mm for higher or lower temperatures.

Rod. It defines the height at which the Switch trips; its length L changes on the basis of customer’s needs, with a maximum of 50-60cm. The rod, float, and other inner parts are in stainless steel AISI 316.

Differential. The Switch trips when level rises up to X point and resets when gos down to Y point, as per the side sketch; usually between X and Y there is a differential of 30÷65mm about : it changes on basis of the specific gravity of liquid. Also the inverse function is available : Trip on fall and Reset on rise.

Upon request, special versions can be produced too.