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Pneumatic actuators

eDART Pneumatic actuators are an effective, reliable and cost effective actuator. The unique design eliminates the use of tiebars which reduce the size and weight of the actuator. The biased spring options – which allow for fail action but are piped Double Acting for superior control – are specifically designed to be used on modulating control applications. On actuator mounting the feedback system is modelled to give linear response to the valve position.

General Information

Features

  • Double piston seal and continuous PTFE wear strip for reliably long service and reduced wear.
  • Variety of stroke lengths available.
  • Compact and robust design.
  • Self-contained bias spring pack – welded pre-compressed safe design.

Material of Construction

  • Plates – Mild Steel Painted.
  • Cover plate – 304 Stainless Steel.
  • Cylinder tube – Glass Reinforced Fibre.
  • Shaft – 304 Stainless Steel.
  • Guide Bush – Vesconite.
  • O-rings – Buna N.
  • Wear strip – PTFE.

Standard Sizes

 
Size Stroke [mm] Notes
160 105; 165 Spring Pack is only available in 105mm stroke
200 175; 250 Spring Pack is only available in 175mm stroke
250 280 Spring Pack is only available in 280mm stroke
300 350; 450 There are two standard strokes on this model, no spring pack option, please consider air-spring or volume tank.
400 450 No spring pack option, please consider air-spring or volume tank.
550 550 No spring pack option, please consider air-spring or volume tank.

Options

  • Double Acting (DA).
  • Fail Retracted (FR).
  • Fail Extended (FE).
  • Stroke may be limited either with an internal hard stop or by shortening the barrel as required.
  • Full Stainless-Steel construction for corrosion resistance.
  • Internal (Linear Pot) Feedback.

Applications

  • Dart Valves.
  • Pinch Valves.
  • Diaphragm Valves.
  • Knife Gate Valves.
  • yDart Valves.
  • eDART Valves.
  • Dosing Valves.
  • Sluice Gate Control.
  • Third party valves.

Product Variations

The double acting actuator is designed to be accurate (in that the piston stem is guided with a vesconite bush and high tolerance endplates ensure that the piston remains concentric to the cylinder bore) and robust (double piston seals, continuous PTFE wear strip and radial oring sealing on the endplates) so that the positioner can control the valve precisely and effectively over long periods of time.
The bias springpacks are fitted to a modified double acting eDART actuator which allows a coupling between the spring pack and the piston. When the air fails, the spring assists the process to fail to the desired position – that is, a plug and seat will want to fail closed in the flow-over the plug case by the natural fluid action. The bias springpack gives the valve system enough force to overcome any friction that might otherwise prevent this from occurring.
The heavy-duty fail-action is similar to the bias fail-action in that the standard double acting actuator is modified to put a springpack on the top to either extend or retract the piston when there is air failure. The actuator is still piped double acting so that the position of the piston may be controlled more easily by a positioner than if only one side of the cylinder was pressurised so that it acted against the spring. In this configuration, the springpack generates more force because there are two counteracting springs working in parallel. Because springpack sizing is dependent on application specific factors like flow direction, fail-direction, pressure drop across the valve and valve type, it is recommended that an eDART engineer assists with this calculation
To achieve good control on a slurry valve, a high quality positioner is required with a responsive means of actuation and a reliable feedback mechanism. For the most part the eDART mechanical feedback mechanism utilising a linkage arm rather than a sliding joint is suitable, but when the strokes are long – greater than 300 mm – the linkages get large and unwieldy. It is better to utilise the internal feedback version in this case which has a magnetic transducer that extends inside a modified actuator stem to report on the position electronically. This is also a necessary solution when the application is particularly dirty and/or the positioner needs to be mounted remotely.
The pedestal offers a complete modulating (or on-off) control package where the actuator is coupled to the positioner with linear feedback. There also is an anti-rotation device and stroke indication. The pedestal may be mounted on a flotation tank to control customer supplied seat, plug and shaft or may be mounted on inline valves like globe valves for air control or slurry knife gate valves for isolation. These pedestals may also be branded with customer specific logos, colours and tag plates. Options include mounting for proximity switches, volume boosters, solenoid valves, air-filters, lock up valves and the eDART DVC controller.