Quick-connect couplings – plug-in quick connections for hydraulic systems

Hydraulic quick-connect couplings are quick-release connection elements that allow hydraulic hoses or pipes to be connected or disconnected quickly and safely – often without the use of tools. They are used wherever attachments or tools are frequently changed, such as in agriculture and forestry, construction, industrial equipment as well as in mobile and stationary hydraulic systems. Self-sealing mechanisms minimize leakage during disconnection and save time during maintenance or changeover operations.

The size of a quick-connect coupling is primarily determined by the inside diameter (nominal diameter) or the outside diameter of the hydraulic line. Common nominal diameters are DN6, DN10, DN13, DN20 and DN25, corresponding approximately to 3/8", 1/2", 5/8" and 3/4". The dimensions of the socket and plug (A/B dimensions) must also match the mating coupling. Correct sizing ensures optimal flow and safe pressure resistance within the system.

• ISO A: Commonly used in agricultural equipment
• ISO B: Typical for industrial applications
• Ball-type and poppet-type couplings: Different sealing and locking mechanisms
• Flat Face (ISO 16028): Particularly robust and dirt-resistant, ideal for construction sites and heavy-duty applications; in some cases connectable under pressure

The selection depends on the operating environment, contamination level, required leak-tightness and ease of use.

• Maximum operating pressure and possible pressure spikes
• Material selection (steel, stainless steel, brass) suitable for the fluid and environment
• Appropriate thread type (metric, BSP, NPT)
• Temperature range and suitable sealing materials (e.g. NBR, PTFE)
• Capability to connect under pressure (CDP/UDP versions)

The material must be chemically compatible with the hydraulic medium and the environmental conditions. Steel provides high strength, stainless steel excellent corrosion resistance, and brass is suitable for specific applications. Equally important are the seals – materials such as NBR or PTFE must withstand the medium and temperature to prevent leakage and system failures.

Dust caps protect sensitive sealing and valve surfaces from dirt, moisture and mechanical damage. They are usually made of durable plastic or rubber and significantly contribute to the longevity and functional reliability of the couplings. Cleaning and periodic replacement are part of good maintenance practice.

• Determine size and thread type accurately
• Check operating pressure and flow requirements
• Ensure material and seal compatibility with the medium and environment
• Verify connectability (whether connection under pressure is required)
• Confirm compliance with relevant standards (e.g. ISO 7241, ISO 16028)

These standards define dimensions, performance characteristics and test procedures, ensuring interchangeability of quick-connect couplings from different manufacturers. ISO 7241 applies to common coupling types (A/B), while ISO 16028 specifically covers flat-face versions. They guarantee compatibility, safety and reliable operation in hydraulic systems.