Série MF20Chave de microfluxo

Warning: Electrical Safety

The MF20 Series flow switch is a mains voltage device. Death or serious injury may result if this switch is not correctly installed and operated. All electrical work on this switch must be performed by a fully qualified and licensed electrician.

Vertical Mounting Required

The MF20 must be mounted vertically with flow upward through the body. Gravity returns the piston to the off position when flow stops. There is a direction of flow arrow on the switch body — the switch will not operate against a reversed flow. The switch can be mounted directly on the suction or discharge valve of a metering pump.

Three Switch Points (Pistons A/B/C)

Three pistons ship with every MF20, each with an accurate and predictable switch point. The ‘A’ piston is fitted as standard (most sensitive); the ‘B’ and ‘C’ pistons are packed in the box. Switch points span 0.32 L/h to 12.8 L/h (MF20-B and MF20-R; the MF20-C needs twice the flow). The piston is changed by unscrewing the inlet adaptor (part No. 2) and inserting the new piston. The spanner octagon on the inlet adaptor accepts a standard gas cylinder spanner (28 mm across the flats).

Pulsed-Flow Behaviour

In pulsed-flow applications without a pulse dampener, if the pulse frequency is less than the electrical response time the MF20 may respond with a train of on/off pulses rather than a continuous on signal. Add a small in-line dampener if a steady output is needed.

Chemical Compatibility — DO NOT USE WITH

The MF20 wetted parts are glass-reinforced polypropylene with Viton O-ring seals (and PVC spigots). NEVER use this switch with: (1) sodium hypochlorite > 10% concentration; (2) ferrous or ferric solutions (e.g. ferric chloride); (3) solvents, hydrocarbons or alcohol solutions of any kind; (4) sulphuric acid > 50% concentration; (5) nitric acid > 20% concentration. For other media, use our Chemical Compatibility tool, widely available chemical compatibility charts for polypropylene and Viton, or ask Kelco.

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Pressure De-rating at Elevated Temperatures

The 1800 kPa max operating pressure applies at 15 °C. Maximum operating pressure must be de-rated linearly in direct proportion to temperature increase, to a maximum of 1 bar absolute at 80 °C. In other words, only use this switch at elevated temperatures in non-pressurised systems that are totally open to atmosphere in all circumstances and under all conditions.

Clean Fluid & Line Filtration

The MF20 contains a close fitting piston and should only be used where the process fluid is reasonably clean and free of entrained or suspended material. Fluids containing large particulate matter, ferrous materials or fibrous matter should not be used in this switch. If the degree of contamination of the process fluid can’t be guaranteed, fit suitable line filtration upstream of the MF20.

Pipe & Tube Connections

The MF20 is terminated with ¾" BSPP male threads, which can be screwed directly into pipe sockets and used in ¾" piping. It is also supplied with ¾" unions and ½" (15 NB) PVC spigots — thick walled, designed to be tapped ¼" BSP for compression fittings if required, and suitable for solvent gluing directly into 15 NB PVC or ABS pipe fittings — plus 3 sets of tube flare fittings to suit 6 by 4, 8 by 4 and 12 by 9 flexible tube.

Reed Switch Protection

The MF20 uses reed switches as the primary switching element. They offer an operating life in excess of 100 million cycles but must not be electrically overloaded. Where the reed switch is the main switch, use interposing relays and avoid inductive loads, and fit suitable protection such as diodes or rate effect suppression circuits. Avoid capacitive coupling effects on long cable runs by using shielded cable, and fit diode protection to the reed switches in DC applications.

Typical Applications

Control for backup dosing pumps, chemical metering pump control, chemical injection point status, laboratory applications, loss of prime detection and batch control.

Hazardous Areas

The MF20-B and MF20-C are simple apparatus under AS/NZS 60079.11 and may be used in a hazardous area only as part of an intrinsically safe circuit, connected through suitably certified associated apparatus. They are not Ex certified in their own right. The full conditions of use are given in the installation sheet. The MF20-R is not certified for use in hazardous areas and must not be installed in any area classified as hazardous under AS/NZS 60079.10 (Zone 0, 1, 2, 20, 21 or 22).