Non-return valves by Parker Legris controlled and regulated

Check Valves from Parker Legris: Controllable, Adjustable, Industrial-Grade

Check valves from Parker Legris ensure flow in pneumatic and fluid circuits, prevent backflow, and enable targeted process control. In this category, you will find variants made of polymer, nickel-plated brass, and stainless steel, as well as versions for the food industry. The product range includes simple one-way check valves, industrially designed adjustable types, and piloted check valves (controlled check valves) for integration into complex control architectures.

Materials and Components: Why Selection is Crucial

The choice of material determines chemical resistance, pressure and temperature ranges, and cleanability. Polymer valves (e.g., POM, PTFE-coated elements) offer corrosion protection and are lightweight, suitable for neutral gases and liquids, and applications with lower mechanical stress. Nickel-plated brass combines good mechanical strength with increased corrosion resistance and is economical for general industrial applications. Stainless steel (CrNi materials such as 1.4404/316L) is mandatory for high hygienic requirements, chemically aggressive media, and elevated temperature/pressure demands; variants for the food industry meet specific surface and sealing specifications.

Design Principles: Valve Types and Functionality

Check valves operate on simple principles: a closing element (ball, flap, or diaphragm) opens when pressure is applied in the flow direction and closes upon pressure reversal to prevent backflow. Piloted check valves add an additional pilot line or a pilot valve that allows opening independently of local pressure. Adjustable check valves include adjustment mechanisms—e.g., pre-set springs, adjusting screws, or external actuators—to precisely control opening behavior, cracking pressure, and flow characteristics.

Connections, Seals, and Standards

Connection technology ranges from screw connections according to ISO/ANSI, threads (BSP, NPT), to quick connectors such as Parker Legris' Liquifit systems. For hygienic applications, clamp flanges and stainless steel screw connections with smooth transitions are common. Sealing materials must match the medium: NBR is suitable for oil and air applications, EPDM for water and steam applications, FKM/Viton for oil and chemical use, and PTFE/thermoset for high temperatures or aggressive media. In food-grade versions, FDA-compliant elastomers or completely metallic, aseptic designs are used. When selecting, pay attention to relevant standards such as ISO 9001, FDA compliance, 3A or EHEDG for food valves, and pressure equipment directives, if necessary.

Performance and Characteristics: What to Check

Key parameters include permissible operating pressure, cracking pressure, flow coefficient Kv/Cv, permissible temperature ranges, and response times. For piloted check valves, the pilot pressure requirement and the volume of the pilot line must also be considered. Adjustable variants should demonstrate documented adjustment accuracy and repeatability. When selecting for compressed air, vacuum, or liquid applications, check material compatibility and potential cavitation effects.

Fields of Application and Practical Scenarios

Check valves from Parker Legris are widely used: in pneumatic control circuits to prevent pressure losses, in hydraulic and fluid supplies for process safety, in dosing and filling systems as protection against contamination backflow, and in compressed air supply networks. In the food industry, aseptic check valves prevent cross-contamination between product and cleaning lines. In production lines with multiple parallel lines, piloted check valves enable targeted switching of individual lines without interrupting the main system. Practical example 1: Installation of a piloted check valve group in an assembly cell to reduce rejects. Here, piloted check valves replace mechanical shut-offs. A pilot line allows local pressure to be released while backflow is prevented by the valve. Result: faster changeover times and lower pneumatic energy loss. Practical example 2: Use of an adjustable check valve in a dosing line for liquids with different viscosities. By fine-tuning the cracking pressure, consistent dripping behavior and thus precise dosing quantities are achieved without expensive additional controls. Practical example 3: Use of stainless steel check valves with clamp connections in a CIP cleaning line of a dairy. The smooth internal surfaces and FDA-compliant seals enable complete cleaning and sterilization cycles without pressure losses due to leaks.

Integration and Installation Notes

During installation, observe: flow direction marking, prescribed upstream distances before sensitive valves, strain relief of connections, and correct sealing material selection. Piloted check valves may require separate filters for pilot and working lines to exclude contaminants in the pilot circuit. Adjustable variants should be adjusted in the final position and provided with a measurement report. Observe the maximum tightening torques for threaded connections to avoid deformation of the sealing surfaces.

Maintenance and Service Life

Maintenance intervals depend on the medium, purity, and operating parameters. Visual inspections for leaks, functional checks of the check valve action, and, for regulated types, verification of the adjustment position are minimally required. Spare part kits should include valve seats, seals, and spring components. For critical applications, a predictive maintenance plan based on operating hours and cycle counts is recommended.

Product Overview

* Polymer, nickel-plated brass, and stainless steel versions; standardized and hygienic variants; piloted and adjustable types. For technical details on connection dimensions, Kv values, material data sheets, and installation dimensions, you can find further information on our technical page: https://maku-industrie.de/technik. Application cases and examples of use are documented at https://maku-industrie.de/anwendungsbeispiele.

Selection Guide in Brief

Choose polymer for lightweight, corrosion-insensitive applications, nickel-plated brass for economical, mechanically robust solutions, and stainless steel for hygienic or aggressive media. Opt for adjustable variants when precise cracking pressures are needed, and for piloted check valves when central control or switching without local pressure build-up is required.

FAQs

1. Which check valve is suitable for food applications?

Use stainless steel versions (e.g., 316L) with smooth internal surfaces and FDA-compliant seals or completely metallic, aseptic designs. Pay attention to clamp connections and hygiene standards such as EHEDG or 3A, depending on the requirements.

2. How do I determine the correct cracking pressure?

The cracking pressure depends on the required tightness with low leakage and the system pressure. Adjustable valves allow fine-tuning; for simple prevention of backflow, choose a valve with a slightly higher cracking pressure than the usual pressure peaks in the system.

3. When is a piloted check valve the best choice?

Piloted check valves are useful when opening should occur independently of the local differential pressure, for example, for switching operations, selection processes in multi-line systems, or for remote release of sections without pressure build-up.