Diaphragm valve

The diaphragm valve is a special type of valve that is often used in industrial applications where sterility, resistance to aggressive media, or precise control of liquids and gases are of central importance. It is characterized by its hygienic design, high tightness, and ability to operate reliably under difficult conditions.

Design of a diaphragm valve

The central component of a diaphragm valve is the diaphragm, a flexible, elastic component that controls the flow of the medium through the valve. The main components of a diaphragm valve include:

Housing: The valve housing, which accommodates the diaphragm and the medium, is usually made of corrosion-resistant materials such as stainless steel, plastic, or high-alloy steels to handle aggressive or reactive media.
Diaphragm: This is made of elastic materials such as PTFE (polytetrafluoroethylene), EPDM (ethylene propylene diene rubber) or other special elastomers. It separates the valve actuator from the medium and prevents direct contact, making it ideal for sterile or high-purity applications.
Upper part/actuator: The actuator can be manual (with a handwheel) or automated (pneumatic or electric). The actuator pushes the diaphragm down and closes the flow.
Valve seat: The valve seat is the surface against which the diaphragm presses to completely seal the flow.

How the diaphragm valve works

The diaphragm valve works by using a flexible diaphragm that is pressed onto the valve seat by the actuator to interrupt the flow of the medium. When the valve is opened, the diaphragm is pulled upward, creating a channel for the medium.

There are two main types of diaphragm valves:

Direct-acting diaphragm valves: In this design, the actuator presses the diaphragm directly onto the valve seat to interrupt the flow. These valves are simple in design and particularly suitable for low-pressure processes and smaller flow rates.
Controllable diaphragm valves (e.g., pneumatic): In this version, the actuator is operated by pneumatic or electric controls to enable more precise control of flow and pressure. These valves are suitable for applications where flow must be controlled automatically or remotely.

Advantages of diaphragm valves

High tightness: The diaphragm completely seals the interior of the valve, making diaphragm valves extremely tight and suitable for use in systems where leaks cannot be tolerated.
Sterile conditions: Since the medium never comes into contact with the valve actuator and the diaphragm is the only component that touches the medium, diaphragm valves are ideal for hygienic and sterile applications. This makes them indispensable in the pharmaceutical industry, food production, and biotechnological processes.
Corrosion and chemical resistance: Diaphragm valves can be used in environments where aggressive chemicals, corrosive liquids, or abrasive media are present. The diaphragms and housing materials are selected accordingly to ensure that the valve remains functional even under extreme conditions.
No dead space: Unlike many other valve types, which have dead spaces (areas where media can collect and stagnate), diaphragm valves are designed so that the flow path is completely flushed. This prevents the accumulation of contaminants and bacteria and is particularly important in sensitive processes such as water treatment and pharmaceuticals.
Low maintenance: Diaphragm valves have relatively few moving parts and require minimal maintenance, especially when used in sterile or chemically aggressive environments.

Areas of application for diaphragm valves

Diaphragm valves are indispensable in many industrial sectors, especially where sterile or high-purity conditions are required or aggressive media are used. Typical areas of application include:

Pharmaceutical industry: Diaphragm valves are often used in the manufacture of pharmaceuticals and biotechnological products because they can ensure sterile conditions. They are also easy to clean (CIP – Clean-in-Place) and support sterile production processes.
Food and beverage industry: In this industry, diaphragm valves are used because of their hygienic properties and ease of cleaning to ensure high standards in the processing and production of food and beverages.
Chemical industry: Diaphragm valves are used in chemical processes where aggressive or corrosive media must be controlled safely and reliably. Thanks to the resistance of the diaphragm and the choice of materials, they can also be used under extreme conditions.
Water and wastewater treatment: In drinking water treatment or wastewater treatment plants, diaphragm valves enable precise control of fluid flows. Their resistance to chemical cleaning agents and their ability to prevent contamination make them an ideal choice.

Limitations and disadvantages

Despite their advantages, diaphragm valves have some limitations:

Limited pressure range: Diaphragm valves are not suitable for extremely high-pressure applications. The flexibility of the diaphragm sets a limit on the maximum pressure that the valve can handle.
Limitations at extreme temperatures: Although diaphragms are made of resistant materials, they can lose elasticity or even be damaged at extremely high temperatures. Therefore, they are only suitable for use in high-temperature environments to a limited extent.
Limited control accuracy: Diaphragm valves are ideal for on/off applications (open or closed), but less suitable for precise flow control compared to other valve types such as ball segment valves or throttle bodies.

Summary

The diaphragm valve is an extremely versatile and robust valve that is used in industry, especially in sensitive and sterile environments. It offers excellent tightness, corrosion resistance, and durability, making it particularly suitable for applications in the pharmaceutical industry, chemical industry, food production, and water treatment. Thanks to its simple design and high efficiency, the diaphragm valve remains a reliable choice for controlling media in industrial processes, even under demanding conditions.