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    • Main Office
      Burkert South Africa (PTY) Ltd
      Visitors address:

      233 Albert Amon Road
      Millennium Business Park
      Meadowdale / Germiston

      Mailing address:

      P.O. Box 26260
      East Rand
      1462
      Phone +27 11 574 6000
      Fax +27 11 454 1477
      E-Mail fnyrf.mn@ohexreg.pbz
    • Office
      Durban Branch
      32 Grays-Inn Crescent
      Westville

      Phone +27 31 266 1600
      Fax +27 31 266 1495
      E-Mail fnyrf.mn@ohexreg.pbz
    • Office
      Cape Town Branch
      Unit 26, Northgate Business Park
      Northgate Estate

      Phone +27 21 510 7137
      Fax +27 21 510 7135
      E-Mail fnyrf.mn@ohexreg.pbz
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Proportional valves

Switching solenoid valves, which are normally closed, form the basis for Bürkert proportional valves. Making constructive modifications to switching solenoid valves can achieve a balance of the spring and magnetic force for any coil current. The level of the coil current and magnetic force determines the stroke of the plunger or the valve opening, whereby the valve opening and the current are ideally linked by a linear dependence.

Servo-assisted proportional valve
The Figure shows the operating principle of such a valve. When it is closed, the medium at the input side has a pressure of p1, the core or plunger (3) has dropped out and therefore presses on the pilot seat (4). As a result of this and the force of the piston spring, which acts on the piston (2), the main seat (5) is closed. A restrictor port (6) allows the medium to enter the control chamber (1) and press on the diaphragm or gasket from above with a pressure px.
If the restrictor port, pilot seat and area ratios on the main stage are rated accordingly, the compression forces on the piston reach equilibrium when the seat is opened by a certain position. With proportional pilot control, ideally, the piston follows the continuous axial movement of the plunger precisely at the distance that creates this equilibrium.

Diagram of a servo-assisted proportional valve

Direct acting proportional valve

1 Valve body, brass or stainless steel
2 Plunger, FKM (standard)
3 O-ring, FKM (standard)
4 Glide ring, PTFE compound
5 Return spring, stainless steel
6 Stopper with integrated adjusting screw, stainless steel
7 Plunger, stainless steel
8 Coil, Epoxy-encapsulated

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