The pressure limiters of the FD series are built in accordance with the special guidelines for liquefied gas technology. All parts in contact with the medium are made of stainless steel 1.4104 and 1.4571. The pressure sensor is self-monitoring. This means that if the measuring bellows ruptures, the pressure limiter switches to the safe side.

The pressure sensor therefore complies with the special design requirements within the meaning of the VdTÜV bulletin “Pressure 100”. The pressure limiters are operated in intrinsically safe control circuits. By using an isolating switching amplifier, the control circuit is also monitored for interruption and short circuit.

Type FD16-327 covers a set point range of 3-16 bar. The switching differential is 1.5 … 3.0 bar. This version uses an internal lockout.

Technical Data

• Pressure connection: External thread G 1/2 pressure gauge connection, G 1/4 female thread according to DIN 16 288.
• Switch housing 300: Aluminium die casting GD Al Si 12.
• Mounting position: Vertical, with switching device facing upwards.
• Protection class: IP65.
• Explosion protection: Ex-i, only in combination with an isolating switching amplifier.
• Materials of wetted pressure sensing element: Housing 1.4104, pressure bellows 1.4571. All parts fully welded. Safety diaphragm made of Perbunan and not in contact with the medium.
• Ambient temperature: −25 °C to +60 °C. At ambient temperatures below 0 °C, suitable measures must be taken to prevent condensation from forming in the sensor and in the switching device.
• Max. medium temperature: +60 °C.
• Outdoor installations: Protect the device against direct weather influences. Provide a suitable protective cover.
• Max. permissible operating pressure: 40 bar.
• Switching pressure: 3 to 16 bar. Adjustable at the spindle after removing the terminal connection box.
• Adjustment: Series FD16-316 and FD16-327 are factory-adjusted for rising pressure. The adjustable switching pressure shown on the scale corresponds to the switch point at rising pressure; the reset point is lower by the amount of the switching differential.
• Lockout after shut-off: Internal lockout. To release the lockout: after reducing the pressure by approximately 2.5 bar, press the red button on the scale side of the pressure switch with a tool.
• Line break and short-circuit monitoring: For types FD16-326 and FD16-327, the control circuit is monitored for short circuit and line break in conjunction with the isolating switching amplifier. A resistor combination built into the pressure switch ensures that a defined current always flows during normal operation. In the event of a short circuit or interruption, the current changes and the relay switches to the safe side.