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Valves – Selection, Design, and Industrial Application

Valves control, isolate, and throttle media in industrial plants. Material, design, connections, sealing system, and actuation type are crucial for their function and service life. On this category page, you will find technical valves for compressed air, gases, water, oils, and aggressive chemicals, as well as specially designed solutions for high temperatures and abrasive media. The following sections provide specific selection criteria, descriptions of typical designs, details on materials and seals, and practical application examples to help you identify the right valve and operate it safely. Further technical information and application examples can be found under Technology and Application Examples.

Functional Categories and Typical Designs

Valves can be functionally divided into shut-off, control, check, safety, and proportional valves. Shut-off valves (ball valves, gate valves, needle valves) allow fully open or closed operation. Control valves (diaphragm valves, globe control valves) enable controlled flow and pressure adjustment. Check valves prevent backflow without external energy. Safety valves protect systems by pressure-controlled opening. Proportional valves are electrically or pneumatically actuated for fine control loops in automation systems.

Mechanical designs primarily include ball, needle, globe, gate, and diaphragm valves. Ball valves offer low flow resistance and long service life with fast switching times. Needle valves enable precise fine control of small flows. Diaphragm valves combine shut-off function with high media separation, making them preferred for corrosive or high-purity media. Gate valves are suitable for aggressive solid-laden media or significant pressure differences.

Materials and Surfaces – Selection by Medium

Material selection depends on the chemical resistance, temperature, pressure, and abrasive properties of the medium. Common materials include stainless steels (1.4404/316L, 1.4571/316Ti) for chemical resistance and food applications, brass and bronze for cost-effective water and air systems, cast iron and cast steel for large nominal diameter water and steam installations, and special alloys (Hastelloy, Duplex, Superduplex) for aggressive chlorine or acid environments. Plastic materials such as PVDF, PTFE, and PFA are used for highly corrosive media or where metallic contamination must be excluded.

Surface treatments enhance corrosion protection and tightness: electropolished internal surfaces (up to Ra < 0.4 µm) are standard for hygienic applications; ceramic coatings reduce wear from abrasive solids; galvanic coatings (nickel, chrome) improve wear and corrosion behavior in less critical cases. For food and pharmaceutical applications, documentation of surface roughness and passivation is mandatory.

Seals, Seat Geometries, and Leakage Rates

Seal selection influences chemical resistance, temperature range, and wear resistance. Elastomers such as NBR, EPDM, and FKM cover standard media: NBR for oils and air, EPDM for hot water/steam, and FKM (Viton) for high temperatures and aggressive organic media. For highest chemical resistance, use PTFE- or PFA-filled seals; PTFE offers extremely low friction and broad chemical compatibility but is less elastic and requires constructive compensation for tightness. Metal seals are used at high temperatures and pressures where elastic materials fail. Seat geometries (soft seat vs. metal seat) determine continuous operation and leakage rates: soft seats achieve < ANSI Class VI, while metal seats tolerate higher temperatures and abrasive media but may exhibit higher leakage rates.

Connections, Standards, and Testing Requirements

Connection types must match the system: threaded connections according to BSP/ISO 7, NPT for international thread standards, flanges according to DIN/EN, ANSI/ASME for large systems, and hygienic clamp and Tri-Clamp connections for food/pharma. Weld ends (socket or butt weld) ensure smooth internal surfaces and reduced dead volume. Pay attention to standard conformity: Pressure Equipment Directive (PED/AD2000), EN 12516/ISO 5208 for tightness tests, ATEX certification for potentially explosive atmospheres, and FDA/EC 1935/2004 for food contact. Manufacturer specifications for test pressures, leakage rates, and cyclic fatigue strength are crucial for operational safety.

Actuation Types and Automation

Manual handwheels and levers are suitable for low switching frequency. Pneumatic linear and quarter-turn actuators offer fast, powerful movements and are preferred in processes with compressed air supply. Electric actuators enable precise positioning, integrated position feedback, and easy PLC integration. Hydraulic actuators are used for very high forces. For automation, the integration of limit switches, position feedback (0–10 V, 4–20 mA, or digital bus protocols), and safety functions (fail-safe, energy-free positions) must be considered.

Economy, Service Life, and Maintenance

Life cycle costs arise from acquisition, installation, maintenance, and failure risks. Soft-seated valves offer low acquisition costs and good tightness but require more frequent seal replacement with abrasive media. Metal-seated valves show longer service lives under abrasive loads but require more precise adjustment and occasional re-machining. Replaceable seal kits and modular designs reduce downtime. The correct lubrication concept or media separation prevents seizing and extends intervals. Based on the planned switching frequency, create a maintenance plan with defined inspection cycles for tightness, actuation force, and operating times.

Practical Examples

Example 1 – Compressed Air Supply in Assembly Plants: In pneumatic conveying lines, ball valves with PTFE seats ensure fast shut-off with low leakage rates. Pneumatic quarter-turn actuators with spring return guarantee a defined safe position in case of power failure. To minimize pressure losses, short pipelines, correctly dimensioned nominal sizes, and internal electropolished connections are crucial.

Example 2 – Chemical Dosing Station: In a dosing station for acids and alkalis, diaphragm valves with PTFE diaphragms and PVDF housings are used. The diaphragm separates the medium from drive and structural components, reduces dead volume, and enables gas-free media separation. Electrical position feedback and flow measurement in the control loop guarantee precise dosing and traceability.

Example 3 – Steam System in Process Industry: Steel safety relief valves with spring mechanisms protect steam boilers from overpressure. Metal seat designs ensure functionality even at high temperatures and abrasion. Control valves in the steam supply work with heat-resistant seals (graphite or metal-to-metal sealing systems) and are regulated by pneumatic actuators to enable fast response times during load changes.

Example 4 – Food Production: For CIP and SIP-compliant processes, hygienic diaphragm and seat valves made of 1.4404 with electropolished internal surfaces are used. Clamp connections allow quick disassembly for cleaning. Sealing materials are FDA-compliant (e.g., EPDM or FDA-PTFE), and the design avoids dead spaces.

• Key selection criteria: medium, temperature/pressure, switching frequency, desired leakage rate, connection type, material compatibility, and standard requirements

Specific Selection Recommendation

For abrasive solids, choose valves with hardened seat surfaces or ceramic lining and metal or PTFE-mounted seating systems. For hygienic applications, electropolished stainless steel versions with clamp connections and FDA-compliant seals are mandatory. For systems in Ex-zones, only use approved and certified actuators. Document certificates, material certificates (EN 10204/3.1), and test reports already in the quotation phase to accelerate later approvals.

Further Information

Technical datasheets, circuit diagrams, and installation instructions help with final design. Detailed technical resources on materials, standards, and testing procedures are available under Technology. Practical reports and realized projects with specific specifications and lessons learned can be found under Application Examples.

FAQs

1. Which material is suitable for my valve with corrosive media?

For chloride-containing or highly corrosive media, highly alloyed stainless steels (Duplex, Superduplex) or nickel-based alloys (Hastelloy) are recommended. For very aggressive chemical media, PTFE- or PVDF-lined housings are the better choice; documentation of chemical resistance to the specific medium and temperature is required.

2. How do I choose between soft-seated and metal-seated valves?

Soft-seated valves offer better tightness and lower acquisition costs but are less resistant to abrasive particles and high temperatures. Metal seats are more durable under abrasive loads and high temperatures but are associated with higher leakage rates and higher maintenance. Medium properties, temperature, pressure, and switching frequency are decisive.

3. What tests should valves pass before commissioning?

Essential tests include tightness testing (according to EN ISO 5208/ISO 5208 or ANSI standards), pressure testing (hydraulic or pneumatic according to PED requirements), functional testing of the actuation, position verification, and for hygienic applications, passivation and surface roughness certificates. Additional tests may include material certificates (EN 10204) and ATEX or Ex-protection certificates.