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FEMA DNS / VNS Pressure and Vacuum Switches with Stainless Steel Sensor 1.4571

FEMA DNS / VNS pressure and vacuum switches are used for monitoring and controlling pressures in chemical plants, process engineering and industrial applications. They are particularly suitable for aggressive liquids and gases where media-resistant materials and a robust sensor design are required.

The DNS and VNS series feature a stainless steel sensor made of 1.4571. The pressure sensor is hermetically sealed and designed without gasket materials. This makes the devices especially suitable for applications involving aggressive media, high tightness requirements or reliable pressure monitoring under demanding process conditions.

The chemical version has a switching housing with surface protection. Depending on the device version, variants with IP65, gold-plated contacts or Ex-i operation in combination with a suitable isolating switching amplifier are available. The DNS/VNS series is calibrated for falling pressure. This means that the switching pressure set on the scale corresponds to the switching point at falling pressure.

The devices operate mechanically and require no additional auxiliary power for pressure detection. The applied pressure or vacuum acts on the measuring element and actuates a microswitch. This creates an electrical switching signal that can be used for control, limit monitoring or alarm functions.

Typical Applications

• Pressure monitoring in chemical plants
• Monitoring of aggressive liquids and gases
• Vacuum monitoring in process engineering applications
• Limit monitoring in pipelines, vessels and apparatus
• Process control in industrial plants
• Applications with high requirements for wetted materials
• Monitoring tasks in systems with stainless steel media contact parts

Advantages of FEMA DNS / VNS Pressure and Vacuum Switches

• For aggressive media: suitable for aggressive liquids and gases
• Stainless steel sensor 1.4571: wetted sensor components made of high-quality stainless steel
• Gasket-free pressure sensor: hermetically sealed and plasma-welded sensor design
• Chemical version: switching housing with surface protection for demanding environments
• For pressure and vacuum: suitable for monitoring positive and negative pressure ranges
• Mechanical switching principle: no auxiliary power required for pressure detection
• Safety-related design possible: depending on the version, available with SIL2 according to IEC 61508-2

FEMA DNS / VNS at ICS Schneider

ICS Schneider offers FEMA DNS / VNS pressure and vacuum switches for demanding applications with aggressive liquids and gases. The devices are particularly suitable when standard pressure switches are not sufficient due to media compatibility, gasket materials or environmental conditions.

When selecting the correct DNS or VNS switch, the medium, pressure or vacuum range, required switching point, maximum pressure load, temperature, process connection, electrical switching capacity, protection rating, contact material and requirements for Ex-i or SIL should be considered. For aggressive media, the chemical compatibility of the wetted materials should always be checked based on the specific process data.

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

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

FEMA DNS / VNS are mechanical pressure and vacuum switches for monitoring pressure limits. They are mainly used in chemical plants and process applications with aggressive liquids or gases.

2. Which media are DNS / VNS suitable for?

The devices are designed for aggressive liquids and gases. Exact suitability depends on the medium, temperature, concentration and operating conditions and should be checked based on material compatibility.

3. What is the difference between DNS and VNS?

DNS is typically used for pressure ranges, while VNS is intended for vacuum or negative pressure applications. Both series use a chemically resistant sensor design with a stainless steel sensor.

4. Which materials are in contact with the medium?

The wetted sensor components are made of stainless steel 1.4571. The pressure sensor is hermetically sealed and does not use gasket materials in the sensor area.

5. What does chemical version mean?

The chemical version is designed for demanding chemical applications. It has a switching housing with surface protection and wetted sensor components made of stainless steel.

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 DNS / VNS be used for vacuum?

Yes. The VNS versions are intended for vacuum or negative pressure applications. They are suitable for monitoring negative pressure ranges relative to atmospheric pressure.

8. Do DNS / VNS require a supply voltage?

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

9. Are versions with gold-plated contacts available?

Yes. Depending on the variant, DNS/VNS versions with gold-plated contacts are available. These are particularly suitable for low switching capacities and signal circuits.

10. Are DNS / VNS suitable for intrinsically safe circuits?

Depending on the version, DNS/VNS switches can be used in intrinsically safe circuits. A suitable isolating switching amplifier must be provided and the corresponding Ex-i version must be considered.

11. What protection rating is available?

The chemical version is available with protection rating IP65 depending on the variant. Actual protection depends on correct installation, connection and ambient conditions.

12. What information is important for selecting the right switch?

Important information includes the medium, pressure or vacuum range, switching point, maximum pressure load, temperature, process connection, electrical data, contact material, protection rating and possible requirements for Ex-i or SIL.