Application of the SOLDO SW Series NAMUR Feedback Device in Explosion-Proof Systems of Pneumatic Control Valves

Application of the SOLDO SW Series NAMUR Feedback Device in Explosion-Proof Systems of Pneumatic Control Valves

—— Taking a Lubrizol feeding system as an example

Introduction

In the field of chemical engineering and process control (such as in Lubrizol\\\'s feeding systems), precise control of gases, liquids, and steam is key to ensuring process stability, and the sites often require very high explosion-proof standards.

The core actuator of this project uses the SEVICON pneumatic diaphragm double-seat control valve from Zhuhai Shengwei Technology. This valve features a double-guided structure and is equipped with a multi-spring actuator, offering advantages such as compact structure, sensitive action, and large valve capacity, making it especially suitable for non-clean media applications where high pressure differentials and higher leakage rates are allowed.

The main technical parameters are as follows:

I. Configuration Plan for the Signal Reception Device

This project employs:

SOLDO SW Series Inductive NAMUR Relay + Safety Barrier + Pneumatic Regulating Valve; the NAMUR signal output is a low-current intrinsically safe signal, which is connected to the PLC/DCS system via the safety barrier to provide feedback on valve position status.

Typical parameters for NAMUR signals (reference values):

Operating voltage: 8VDC (supplied by the safety barrier).

Output current:

Detected object close (positioned):

Current ≤ 1.2 mAetected object has moved away (not in position):

Current ≥ 2.1 mAOutput type: Two-wire NAMUR (compliant with EN 60947-5-6 standard).

II. Selection and Parameter Requirements for Safety Guards

The NAMURtransmitter must be used in conjunction with a safety enclosureto form a complete intrinsically safe circuit.

TypicalForward voltage (Uo):

≤ 28VShort-circuit current (Io):

≤ 93mAMaximum output power (Po):

≤ 660mWSafety rating: Ex ia IIC or Ex ib IIC.

It is recommended to use a separate safety enclosure to enhance the system’s resistance to interference.

III. SOLDO SW Series NAMUR Signal Wiring Specifications

1. Instructions for connecting the NAMUR signal circuit.

Circuit configuratSafety barrierion:

Safety Zone PLC/DCS

Safety barrier

NAMUR transmitter (hazardous area).

It employs a two-wire connection method, with the safety enclosure providing the working power supply and completing signal isolation.

2. Selection of the diameter for NAMUR signal grounding wires.

It is recommended to use intrinsically safe, blue, shielded twisted-pair cables.Recommended specifications:

1.0 mm² to 1.5 mm².Available models:

IA-KVVP or equivalent intrinsically safe signal cables.

3. Grounding requirements.

If a Zener-type safety barrier is used, it must be reliably grounded.

The grounding resistance is recommended to be ≤ 4Ω.

The grounding systems for hazardous areas and safe areas should be designed separately.

When using a separate safety barrier, the grounding requirements can be simplified, making the implementation of the project more convenient.

IV. System wiring instructions (SW series + safety enclosures)

The typical wiring logic is as follows:

The NAMUR transmitter connects to the input port of the safety enclosure using two wires.

The output of the safety barrier is connected to the DI module of the PLC.

The PLC detects changes in current and uses this information to determine the current state (on/off).

The NAMUR signal uses changes in current to identify its state, with the typical determination being as follows:

≤1.2 mA: Valve position in place (ON state).

≥2.1 mA: Valve position not in place (OFF state)

V. Application features and advantages

1. Satisfy this security explosion requirement

The NAMUR + Safety Gate combination enables safe signal transmission in hazardous areas to meet the requirements of Zone 1 / Zone 2 applications.2. Improving system reliability

The inductive non-contact detection method is used to avoid the problem of mis-operation caused by mechanical wear.

3.Strengthen the resistance to interference

Current-type signal design is suitable for long distance and complex electromagnetic environments.

4. Compatibility with mainstream control systems

Can be directly connected to the PLC / DCS system digital inputmodule.

VI. SUMMARY OF THE APPLICATION

In the LUBRIZOL feeding system, the combination of SOLDOSW series NAMUR feedback device and safety gate is used to realize the safe and reliable signal feedback of pneumatic throttle valve under explosion-proof conditions.

This solution not only meets the requirements for local explosion protection but also effectively enhances the stability of system operation and the reliability of the engineering design. It has been widely applied in the fields of chemical processing and process control.