Openingsdruk

Openingsdruk is a technical term used in hydraulics, pneumatics and safety engineering to describe the pressure at which a valve, diaphragm or other pressure-relief device begins to open or leak, allowing fluid to pass. This opening point is also referred to as cracking pressure in some contexts and is distinct from the pressure at which the device fully lifts or reseats.

In spring‑loaded devices, opening pressure depends on the balance between the spring force, valve geometry and friction, and can be affected by temperature, fluid viscosity, back pressure, and wear. It is common for opening pressure to shift over time due to aging or contamination, which is why regular testing and calibration are important for critical applications.

Measurement and specification usually appear on product datasheets as a set or opening pressure, expressed in units such as bars, MPa, or psi. For safety and reliability, the opening pressure is typically chosen to be above normal operating pressure but well below the device’s maximum allowable pressure. Some systems distinguish between opening pressure (cracking pressure) and full lift pressure, the latter being the pressure at which the valve is fully open.

Applications include pressure‑relief valves, safety valves, check valves and other devices designed to protect equipment and personnel. Proper setting of openingsdruk is essential to prevent nuisance opening during normal operation while ensuring rapid response in overpressure conditions.

See also: pressure-relief valve, cracking pressure, set pressure, valve design.