A non-return valve is an important component in many industrial systems because it ensures that liquids and gases only move in one direction. It prevents the flow from travelling backwards, protecting equipment such as pumps, tanks and valves from backflow that can cause damage or contamination. Check valves are also known as non-return valves and are common in food, pharma, chemical and water treatment process plants.

How does a non-return valve work?

A non-return valve works by opening automatically when the liquid or gas flows in the right direction - and closes immediately if the flow reverses. This is done either by a spring, a ball or a flap that is pressed against the seat by the reversed pressure. The valve reacts without the need for external control or manual operation.

The beauty of a non-return valve is that it protects your system from unwanted backflow. Imagine, for example, a pump emptying a tank. When the pump stops, the liquid could in principle flow back - but the non-return valve automatically closes and prevents it. This way, the integrity and efficiency of the system is preserved.

What types of check valves are there?

There are several different types of check valves - each with their own benefits and typical applications:

• Ball check valve: A ball moves freely and closes against the seat when the flow reverses. A robust and simple solution, often used in systems with particles or high viscosity.
• Flap check valve: A flap or disc tilts up and down depending on the flow direction. Suitable for systems with high flow and low pressure drop.
• Spring-loaded check valve: A spring keeps the valve closed and opens only at a certain differential pressure. Provides precise control and is used in systems with varying pressure conditions.

The choice depends on the media being transported, pressure level, temperature and hygiene requirements. Some non-return valves are also available in sanitary design for use in food and pharmaceutical production.

Where are check valves used?

Check valves are used in many types of industrial processes - especially where it is critical to avoid backflow:

• Food industry: Prevents contamination between batch processes and protects pumps and tanks.
• Pharma and biotech: Ensures sterile operation and unidirectional flow in processes with high hygiene requirements.
• Water treatment: Protects against backflow that can introduce impurities into clean systems.
• Chemical industry: Prevents aggressive or reactive liquids from flowing backwards and damaging equipment.

Wherever precise dosing, mixing ratios or system protection is required, the check valve is a key part of overall safety and functionality.

Find the right non-return valve at Alflow

At Alflow, we offer a wide range of check valves to match both hygienic and industrial needs. Whether you need a spring-loaded stainless steel check valve or a flap valve for high flow in a CIP-compliant facility, we will help you find the right solution.

We offer counselling around:

• Sizing and flow conditions
• Material selection for aggressive or sterile media
• Compatibility with pumps and valves
• Documentation and hygiene standards

With our experience and specialisation in process equipment, we make it easy for you to select and integrate the right check valve into your system - safely, efficiently and documentably.

FAQ

Where should a non-return valve be placed?
It should be installed where you want to prevent backflow - typically right after a pump or at the inlet of a tank. It must be positioned correctly in relation to the direction of flow.

How should a non-return valve be reversed?
The arrow on the valve body indicates the flow direction. The valve must be mounted so that the flow goes in the direction of the arrow - otherwise it will not work properly.

What is a non-return valve?
It is another term for a non-return valve. Both terms cover a valve that prevents liquid or gas from flowing backwards.

How do you check a non-return valve?
This can be done by pressure testing, visual inspection or by listening for abnormal sounds in the system. In some cases, the valve must be disassembled for a thorough check.