The level of liquid present in a vessel is checked by the float being inside the main body, the chamber, of the Level Switch. 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.

Differently from DA, the type DB is provided with inspection flanges, allowing to open the instrument and to clean it from possible residues of the liquid under control.

 

The Level Switches meet the PED and ATEX standards
 

APPLICATIONS. Alarm for Max and Min level, control of pumps on vessels including simple water or chemical corrosive or toxic liquids, under pressures and temperatures also very high or very low; for liquids with specific gravity from 500kg/m³ up.
 

Body.

Materials : Carbon steel ASTM A106B, stainless AISI 304, or AISI 316.
Size : Øouter 4” (114,3mm), different thickness as per ASME standards.

Rating : ANSI 150, 300, 600, 1500, 2500 psi.

Bottom : The Side-Side Switches have drain hole ¾” NPT-F threaded (upon request, ½” NPT-F or 1” NPT-F), with or without accessories (plugs, valves, etc).

Inspection flanges : Øouter 3” in the ratings ANSI 150÷600 psi (face RF)

                                Øout. 2½” in the ratings ANSI 1500÷2500 psi (face RJ).
 

Connections to vessel.

Materials : Carbon steel ASTM A105N, stainless AISI 304, or AISI 316.

• Flanges as per ANSI standards : 150÷2500 psi, and Ø 1÷2” (page 32).

• Flanges as per UNI/DIN stds : PN 10÷100, e DN 25÷100 (page 33).

• Sleeves, both threaded and socket welding.

Mounting : Side-Side or Side-Bottom.

Center-to-center distance M : As per Tab. 3; other distances, upon request.
 

Housing .

Aluminium cast, in electric or pneumatic version :

• With 1 or 2 microswitches SPDT with simultaneous action (page 9); 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.

• With 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.
 

Differential.

The Switch trips when level reaches the X height and resets when comes back to Y height (or on the contrary), as per the side sketch. Usually the X point is fixed at 70mm below the top connection, and between X and Y there is a differential of about 30÷65mm (it changes on basis of the specific gravity of liquids); but, upon request, such heights and differentials can be made different too.

 

Outer finish.

Switches in carbon steel have the standard painting so realized : first coat in epoxy resin, and outer coat in green polyurethane resin; suitable for corrosive marine environments and tropical climates. Switches in stainless steel are polished and left bare.

 

Upon request, special versions can be produced too.