DIN Check Valves and Non-Return Valve Connections

DIN fitting connections can be used with check valves and non-return valves when the valve body and tube connection match the system design. These valves are installed where flow should move in one direction and backflow must be blocked.

A check valve may look similar to a large inline fitting, but it contains internal components that respond to flow and pressure. The connection style still has to match the tube, thread, seal, and application.

How Check Valves Work

A check valve is a spring-loaded valve used in liquid or gas systems where reverse flow must be prevented. In normal flow, pressure opens the valve and lets fluid pass in one direction.

If flow decreases or tries to reverse, the internal spring moves the disc toward the seat and stops backflow. Common valve parts include the body, seat, disc, and spring. Some designs may also use a hinge pin, stem, ball, disc arm, or elastomer seal.

The valve body should show the flow direction. Installing the valve backwards can block the intended flow path or leave the system unprotected from reverse flow.

Seal Choice and Leakage

Metal sealing surfaces may allow some leakage. Where leak-tight shutoff is required, especially with gas or hazardous chemicals, an elastomer such as Buna-N or FKM may be used to improve sealing.

Seal selection should match the fluid, temperature, pressure, and chemical exposure of the system.

Common DIN and BSPP Valve Connections

Metric and BSPP threaded check valve tube connections can include 24 degree flareless to 24 degree flareless, 24 degree flareless to BSPP or metric parallel with an elastomer seal, and female BSPP to female BSPP connections.

Before replacing one, identify the tube series, metric thread, BSPP thread, sealing method, and flow direction. A valve with the right thread but the wrong internal connection style can still be the wrong part.

Alternating Valves

European-style alternating valves are T-shaped valve bodies that allow flow from one of two inlet ports to pass through a single outlet. An internal floating ball closes the inlet port that is not being used.

When pressure comes from the opposite inlet, the ball shifts and closes the other port. This lets the valve choose between two sources while directing flow to one outlet.

Alternating valves commonly use a steel body and steel ball. The ball provides metal-to-metal contact with a resilient seal seat for leak-tight shutoff, but the connection should allow proper shoulder-stop contact inside the cone. Typical end connections are 24 degree flareless shuttle valve tube styles.