Pneumatics & Hydraulics


Hydraulic connectors with residual pressure

February 2024 Pneumatics & Hydraulics

Hydraulic connections are vital in both outdoor industrial machinery, for example in agriculture and earthmoving, and in indoor industrial machinery for presses and moulding. Examples include farm tractors attaching to various implements, or excavators using tools like hydraulic hammers or buckets. The goal is to enable quick, easy swaps to enhance machine flexibility and productivity.

In the past, connecting hydraulic lines involved manually unscrewing couplings on oil-filled hoses, leading to significant oil spillage and environmental pollution. With their occlusion valves, modern quick couplings have largely addressed this by retaining fluid post-disconnection on both the hose and machine side. However, challenges arise when machines or hoses heat up in the sun, causing oil expansion and creating high residual pressure in the lines, up to 100 bar. While certain machines have circuits to mitigate this, and hoses can act as accumulators, the residual pressure often makes connecting quick couplings difficult. Under pressure, the occlusion valves become like rigid hydraulic cylinders, which are hard to connect manually. For instance a common 1,3 cm hose coupling valve has a hydraulic pushing area of 1,5 cm2, translating to a theoretical hydraulic force of 150 kg at 100 bar pressure.

Operators use various methods to overcome this challenge. Some apply excessive force, risking damage to seals and valves. Others strike occlusion valves against hard surfaces to release oil and reduce pressure, leading to environmental pollution and equipment damage. Loosening pipe fittings to drain oil is another method, although it poses safety risks like high-speed oil spray.

The residual pressure problem incurs costs like wasted time, reduced lifespan of quick valves, machine downtime and potential damage to the brand image. Thanks to the 60 years of field experience of Stucchi Italy, Stucchi South Africa offers various technical solutions to these issues. Innovations include a double internal valve system in the APM series, and A-HD and FAP couplings for manual connection without fluid loss. The screw-to-connect system used in the VP, VEP and VEP-HD series allows easier connection against internal pressure. Stucchi’s latest technology also features a manual knob on the Saturn cast iron block, activating an internal valve to drain excess oil for safe, effortless connections.

For more information contact Stucchi South Africa, +27 11 458 1202, sales@stucchisouthafrica.com, www.stucchigroup.com





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