NAMUR Pneumatic Valves VDI/VDE 3845 Series: Complete Guide

Introduction to NAMUR Valves

NAMUR pneumatic valves represent one of the most standardized and versatile components in the pneumatic automation industry. The term "NAMUR" refers to a German association of users of automation technology in the process industry (Normenarbeitsgemeinschaft für Mess- und Regeltechnik), which established this standard to ensure interchangeability and compatibility between different manufacturers.

The main advantage of these valves lies in their standardized interface according to the VDI/VDE 3845 standard (compatible with ISO 5599), which defines mounting dimensions and connection patterns. This standardization allows any NAMUR valve to be mounted directly on rotary pneumatic actuators such as quarter-turn actuators or pneumatically operated ball valves, regardless of the manufacturer.

In the U.S. industrial context, these valves have gained significant relevance in sectors such as:

• Petrochemical industry and refineries (especially in Texas and Louisiana)
• Water treatment plants (distributed throughout the United States)
• Food industry (particularly in California, Illinois, and Wisconsin)
• Pharmaceutical industry (concentrated in New Jersey, Pennsylvania, and North Carolina)
• Process automation in general

The adoption of the NAMUR standard has greatly simplified the design, installation, and maintenance of pneumatic systems in the United States, reducing downtime and facilitating component replacement without requiring modifications to the installation. This translates into lower operating costs and greater efficiency in industrial processes.

Technical Specifications

NAMUR Interface and Mounting Dimensions

The NAMUR interface, defined by the VDI/VDE 3845 standard, establishes precise dimensions for direct mounting on rotary actuators:

• Mounting pattern: rectangular with 2 fixing holes at a distance of 80 mm (standard) or 130 mm (for larger actuators)
• Connection holes: specific configuration to allow direct control of the actuator
• Air slots: predefined arrangement for inlet and outlet ports
• Shaft height: 20 mm or 30 mm depending on actuator size

Construction Materials

NAMUR pneumatic valves are manufactured with various materials according to the demands of the working environment:

• Valve body: Primarily anodized aluminum for standard applications, AISI 316 stainless steel for corrosive environments or food applications, and brass for some specific applications.
• Seals and gaskets: NBR (nitrile) for standard applications (-10°C to +70°C), FKM (Viton) for high temperatures (up to +150°C) or exposure to chemicals, and EPDM for food applications or with ozone.
• Internal components: Stainless steel for springs and mechanical components, ensuring durability and corrosion resistance.

Performance Characteristics

Typical technical specifications include:

• Working pressure: 2 to 10 bar (standard), with variants available for low pressure (0.5-6 bar)
• Nominal flow rate: From 350 Nl/min to 1200 Nl/min, depending on size and design
• Response time: Generally between 15 and 50 ms for activation, and 20-60 ms for deactivation
• Life cycle: Greater than 10 million cycles under normal operating conditions
• Operating temperature: Standard -10°C to +60°C, with variants available for extended ranges

Electrical Specifications

For NAMUR solenoid valves, the most common electrical specifications are:

• Supply voltages: 24V DC, 110V AC, 230V AC (50/60 Hz)
• Power consumption: From 0.5W to 8W, depending on model and manufacturer
• Protection class: IP65 as standard, with options up to IP67 and IP69K for extreme environments
• Connection options: DIN 43650 connectors (ISO 4400), M12 connectors, or integrated cables
• ATEX classification: Versions available for zones 1, 2, 21 and 22 according to specific requirements

Types and Applications

NAMUR 3/2-Way Valves

3/2-way valves (three connections, two positions) are widely used to control single-acting actuators. In NAMUR configuration, these valves:

• Function: Control the flow of air to a single chamber of the actuator, allowing the return to be performed by an internal spring
• Main applications:
  • Quarter-turn actuators with spring return
  • Single-acting ball and butterfly valves
  • Systems where a predefined safety position is required in case of power failure

In the U.S. industrial context, these valves are particularly common in:

• Water treatment plants in municipalities such as Chicago, New York, and Los Angeles, where they control safety valves
• Fire protection systems in industrial facilities across the United States
• Dosing processes in the food industry in California and the Midwest

NAMUR 5/2-Way Valves

5/2-way valves (five connections, two positions) are mainly used to control double-acting actuators:

• Function: Direct pressurized air alternately to each of the actuator chambers, allowing precise bidirectional control
• Main applications:
  • Double-acting rotary pneumatic actuators
  • Control of ball valves with pneumatic actuator
  • Systems requiring controlled positioning in both directions

In the U.S. industrial context:

• Automotive plants in Michigan, Tennessee, and Kentucky employ these valves in their production lines to control actuators in assembly tools
• Chemical industries in Texas and Louisiana use NAMUR 5/2 valves in processes that require precise flow control
• The pharmaceutical sector in New Jersey and North Carolina implements these valves in sterile manufacturing processes

Specialized Variants

The market offers specialized versions for specific applications:

• NAMUR ATEX valves: Certified for use in potentially explosive atmospheres, they are widely used in refineries in Texas and Louisiana, as well as in chemical plants along the Gulf Coast
• Food industry versions: With FDA-compliant materials and IP69K certification, they are common in food processors in California, Wisconsin, and Illinois
• High-temperature variants: Designed to operate in environments up to +150°C, they are found in foundries in Pennsylvania and Ohio
• Low-consumption models: With coils of just 0.5W, ideal for remote installations or solar-powered installations, such as pumping stations in rural areas of the United States

Selection Guide

Choosing the right NAMUR valve requires considering multiple technical and operational factors:

Fundamental Technical Criteria

1. System pressure requirements:
   • Determine minimum and maximum working pressure
   • Consider pressure fluctuations in the pneumatic network
   • Evaluate acceptable pressure drop across the valve
2. Required flow capacity:
   • Calculate the required flow rate according to actuator size and desired response time
   • Consider the Cv or Kv factor of the valve (flow coefficient)
   • For large actuators, select valves with greater flow capacity
3. Environmental conditions:
   • Temperature: select suitable sealing materials according to the temperature range
   • Exposure to chemicals: opt for resistant materials (FKM, EPDM, etc.)
   • Corrosive environments: consider stainless steel valves
   • Explosive atmospheres: select versions with appropriate ATEX certification
4. Compatibility with the actuator:
   • Verify the NAMUR mounting pattern (80mm or 130mm)
   • Check the type of actuator (single or double acting)
   • Consider the size and torque of the actuator to properly dimension the valve

Sizing Methodology

For correct sizing, follow these steps:

1. Calculate the volume of the actuator chambers (V = πr²h for cylinders)
2. Determine the required response time (T) for the application
3. Calculate the necessary flow rate: Q = V/T
4. Add a safety factor of 1.5 to 2
5. Select a valve with a nominal flow rate higher than calculated

Practical example: For a rotary actuator with a chamber volume of 0.5 liters that must complete its travel in 2 seconds, the required flow rate would be Q = 0.5L/2s = 0.25 L/s = 15 L/min. Applying a safety factor of 1.5, we would look for a valve with a minimum flow rate of 22.5 L/min.

Additional Considerations

• Safety function: Determine the safety position in case of power failure (normally open or normally closed)
• Pilot type: Electric (solenoid), pneumatic, or manual according to control needs
• Energy consumption: Especially relevant in installations with multiple valves or with energy limitations
• Certification requirements: ATEX, SIL, FDA, or others according to the industrial sector

Installation and Maintenance

Mounting Procedures

Proper installation of NAMUR valves ensures their optimal performance:

1. Preparation:
   • Clean the mounting surfaces of the actuator and valve
   • Verify compatibility of NAMUR dimensions
   • Check that gaskets are in good condition
2. Physical mounting:
   • Correctly align the valve holes with those of the actuator
   • Use fixing screws of suitable material (stainless steel for corrosive environments)
   • Apply the recommended tightening torque (generally 4-6 Nm for M5 screws)
3. Pneumatic connection:
   • Use push-in fittings or threaded connections appropriate to the size of the ports
   • Use pneumatic tubes of sufficient diameter to avoid restrictions
   • Ensure tightness with PTFE tape or liquid sealant on threaded connections

Electrical Integration

For NAMUR solenoid valves, it is essential to:

• Verify that the supply voltage corresponds to that specified on the coil
• Use cables with adequate cross-section (minimum 0.75 mm² for distances up to 50m)
• Install surge protection when necessary
• Ensure proper sealing of electrical connections (appropriate tightening torque on cable glands)
• In ATEX environments, strictly comply with electrical installation requirements according to the zone

Preventive Maintenance

An adequate maintenance program includes:

• Monthly visual inspection: Verify absence of leaks, physical damage or corrosion
• Quarterly check: Verify response times and correct operation
• Annual maintenance:
  • Cleaning filters in the supply line
  • Checking gaskets and seals
  • Checking electrical connections
  • Measuring electrical consumption in solenoid valves
• Preventive replacement: Every 5-7 years or according to manufacturer's recommendations, even if they don't show obvious failures

Troubleshooting Common Problems

Problem	Possible Causes	Solutions
Valve doesn't switch	- Lack of electrical signal - Defective coil - Insufficient pressure	- Verify electrical supply - Check coil continuity - Measure inlet pressure
Air leaks	- Deteriorated seals - Loose connections - Damage to the body	- Replace gaskets - Retighten connections - Replace the valve
Slow response	- Restrictions in the line - Insufficient lubrication - Internal wear	- Clean lines and mufflers - Check lubrication system - Inspect internal components

Market and Suppliers

Overview of American and European Manufacturers

The U.S. market for NAMUR valves is dominated by both domestic and European manufacturers of recognized prestige:

• American manufacturers: Offer products with excellent quality-to-price ratio, extensive distribution networks, and quick availability across the country
• German manufacturers: Known for their high quality and precision, they offer products with excellent durability and technical support
• Italian manufacturers: Present a good quality-price relationship and wide availability in the American market

Supply Chain Considerations

When selecting a supplier, it's important to evaluate:

• Stock availability and delivery times to minimize downtime
• Distribution network in the United States, especially near industrial hubs such as Houston, Chicago, Los Angeles, Detroit, and the Northeast
• Long-term spare parts supply capability
• Compatibility with existing systems and standardization possibilities

Technical Support

A differentiating factor among suppliers is the level of technical support:

• Availability of technical documentation in English
• Technical assistance service in the United States
• Training programs for maintenance personnel
• Online selection and configuration tools

Total Cost of Ownership

Beyond the acquisition price, it is essential to consider:

• Durability and expected life cycle (significant differences between manufacturers)
• Energy consumption (especially relevant in installations with many valves)
• Maintenance and spare parts costs
• Standardization and reduction of spare parts inventory

Conclusion

NAMUR pneumatic valves represent a consolidated industrial standard that provides numerous advantages in terms of standardization, ease of installation, and maintenance. Their widespread adoption in American industry has contributed significantly to the efficiency and reliability of pneumatic systems in key sectors such as petrochemicals, food, pharmaceuticals, and water treatment.

The proper selection of these valves, considering factors such as working pressure, flow rate, environmental conditions, and specific application requirements, is fundamental to ensuring optimal performance and a long service life. Likewise, correct installation and regular preventive maintenance are crucial aspects to maximize performance and minimize downtime.

In a market with multiple options from manufacturers and distributors, it is essential to evaluate not only the initial cost but also factors such as spare parts availability, technical support, and total cost of ownership. Choosing a trusted supplier like Pneumatig, specialized in quality pneumatic components, can make a significant difference in the reliability and efficiency of your pneumatic systems.