FEMA Ex-DNS / Ex-VNS pressure and vacuum switches are used for monitoring and controlling pressures in potentially explosive atmospheres. They are particularly suitable for chemical plants, process engineering applications and industrial systems where aggressive liquids or gases must be monitored safely.

The Ex-DNS and Ex-VNS series feature a robust stainless steel sensor made of 1.4571. All wetted parts of the sensor system are made of high-quality stainless steel and welded without filler materials. The pressure sensor is hermetically sealed and contains no gasket materials. This makes the devices especially suitable for demanding media where chemical resistance, tightness and operational safety are essential.

Ex-DNS versions are typically used for pressure applications, while Ex-VNS versions are intended for vacuum or negative pressure applications. The series is factory-calibrated for falling pressure. This means that the switching pressure set on the scale corresponds to the switching point when the pressure is falling.

The devices are designed for potentially explosive atmospheres and are equipped with an M16x1.5 terminal connection. Depending on the device version, different pressure and vacuum ranges are available. Selecting the correct switch depends on the medium, pressure range, temperature, Ex zone, process connection, electrical switching capacity and system requirements.

Pressure detection is mechanical. The applied pressure or vacuum acts on the measuring element and actuates a microswitch when the set limit value is reached. The switching signal can be used for control, limit monitoring, alarm or shutdown functions.

Typical Applications

Pressure monitoring in potentially explosive atmospheres
Vacuum monitoring in Ex applications
Chemical plants and process engineering applications
Monitoring of aggressive liquids and gases
Limit monitoring in pipelines, vessels and apparatus
Process control in systems with increased safety requirements
Applications with wetted parts made of stainless steel 1.4571

Advantages of FEMA Ex-DNS / Ex-VNS Pressure and Vacuum Switches

For Ex areas: suitable for applications in potentially explosive system areas
For aggressive media: suitable for aggressive liquids and gases
Stainless steel sensor 1.4571: wetted sensor components made of high-quality stainless steel
Hermetically sealed pressure sensor: high tightness and no gasket materials in the sensor area
For pressure and vacuum: DNS for pressure applications, VNS for vacuum and negative pressure applications
Mechanical switching principle: no auxiliary power required for pressure detection
M16x1.5 terminal connection: suitable for industrial electrical connection in Ex applications

Ex-DNS / Ex-VNS at ICS Schneider

ICS Schneider offers FEMA Ex-DNS / Ex-VNS pressure and vacuum switches for demanding applications with aggressive media and potentially explosive atmospheres. The devices are suitable for operators, plant manufacturers and service companies requiring a robust mechanical solution for pressure or vacuum monitoring in chemical and process engineering plants.

When selecting the correct Ex-DNS or Ex-VNS switch, the medium, pressure or vacuum range, required switching point, maximum permissible pressure, temperature, process connection, electrical switching capacity, Ex zone, protection rating, material compatibility and installation situation should be considered. For aggressive media and Ex applications, suitability should always be checked based on the specific process data and applicable explosion protection requirements.

FAQ – Frequently Asked Questions about FEMA Ex-DNS / Ex-VNS Pressure and Vacuum Switches

1. What are FEMA Ex-DNS / Ex-VNS pressure and vacuum switches?

FEMA Ex-DNS / Ex-VNS are mechanical pressure and vacuum switches for potentially explosive atmospheres. They monitor pressure or negative pressure limits and actuate an electrical contact when the set switching point is reached.

2. Which media are Ex-DNS / Ex-VNS suitable for?

The devices are suitable for aggressive liquids and gases. Exact suitability depends on the medium, concentration, temperature, pressure range and compatibility of stainless steel 1.4571.

3. What is the difference between Ex-DNS and Ex-VNS?

Ex-DNS is used for pressure applications. Ex-VNS is intended for vacuum or negative pressure applications. Both series use a chemically resistant stainless steel sensor.

4. Which material is in contact with the medium?

The wetted sensor components are made of stainless steel 1.4571. The pressure sensor is hermetically sealed and designed without gasket materials in the sensor area.

5. What does Ex version mean?

Ex version means that the switch is intended for use in potentially explosive atmospheres. Exact suitability depends on the respective Ex marking, zone and system classification.

6. What does calibration for falling pressure mean?

Calibration for falling pressure means that the switching pressure set on the scale corresponds to the switching point when the pressure is falling. The reset point is higher by the amount of the switching differential.

7. Can Ex-VNS switches be used for vacuum?

Yes. Ex-VNS versions are intended for vacuum and negative pressure applications in potentially explosive atmospheres.

8. Do Ex-DNS / Ex-VNS require a supply voltage?

No supply voltage is required for mechanical pressure detection itself. An electrical connection is only required for the switching contact or switching signal.

9. What electrical connection do Ex-DNS / Ex-VNS have?

The Ex-DNS / Ex-VNS versions have an M16x1.5 terminal connection. Electrical integration must be carried out according to the Ex requirements of the system.

10. Are Ex-DNS / Ex-VNS suitable for chemical plants?

Yes. The devices are particularly suitable for chemical plants and process engineering applications where aggressive liquids or gases must be monitored.

11. What information is important for selecting the correct switch?

Important information includes the medium, pressure or vacuum range, switching point, maximum pressure, temperature, process connection, electrical switching capacity, Ex zone, protection rating, material compatibility and installation situation.

12. Why is material compatibility important for aggressive media?

Even high-quality stainless steel materials are not suitable for every aggressive medium. The medium, concentration, temperature and operating conditions must therefore be checked before using an Ex-DNS or Ex-VNS switch.

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