Hydraulic fittings and couplings are often overlooked in mobile machinery design, yet they play a critical role in any fluid power system. In extremely high-pressure hydraulic applications, a leak or accidental disconnection can cause serious personal injury or damage to machinery. Therefore, machine builders must select fittings of the correct size, material, pressure and temperature rating, and application to ensure safety, functionality, and cost optimization.
Hydraulic hose safety can be ensured by using quick-connect fittings or quick couplings that make a repeated connection and disconnection between fluid lines and the equipment they are attached to. One of the most common designs is the flat face, which is available as push-to-connect, threaded, or screw-in. Flat face couplings eliminate cavities where fluid or air can rest, thus removing the chance for trapped pressure and leakage. These couplings provide high flow and low pressure drop, and their sleeve-locking feature reduces the chance of accidental connection, removing leakage and spillage risks.
As mobile machinery requirements evolve, manufacturers are expanding their range of flat face couplings to meet demand. For example, Stauff recently released the new QRC-FG series of threaded flat-face couplings that can be coupled under residual pressure on both sides. While the predecessor series could only be coupled on the plug side at up to 250 bar, the new series has a second valve so that the sleeve can now be easily coupled by hand under residual pressure. With these couplings, the flow rate is higher, and the coupling forces are lower.
Though flat face couplings are mainly used in large demolition excavators, Stauff makes a case for use in other heavy-duty construction and agricultural machinery — basically any equipment exposed to high contamination levels. Solids and air cause hydraulic oil to age more quickly and be replaced more frequently, while humidity condenses and corrodes oil consistency. Dirt particles also promote abrasion on system components. As such, flat face screw couplings minimize drip quantities and prevent the entry of dirt particles and air into the hydraulic system.
In addition to safety concerns, electrification continues to influence mobile machinery with an emphasis on electro-hydraulic hybrid systems. However, hydraulic fitting manufacturers aren’t feeling the impact of electrification nearly as much as other component manufacturers.
From the fitting manufacturer position and their markets served, electrification has been used as a primary mover to drive hydraulic systems — think electric forklifts, scissor lifts, and material handling equipment. Those machines, in simplest form, use a battery or electric source to power an electric motor that drives the pumps and other system components. Moving away from fossil fuels and electrification of other vehicles, such as heavy haul semi-trucks, has changed little for many fittings companies, as customers continue to use traditional hydraulic adapters. However, this has opened some new doors for traditional hydraulics.
Aside from design, some hydraulic fitting and coupling manufacturers are expanding their product offerings due to acquisitions and companies exiting the market. For example, Dayco North America is leaving the hydraulics category, and Kurt Hydraulics will take over the manufacture and supply directly to all Dayco distributors.
“As a long-time partner to Dayco’s hydraulic coupling business, our hose and couplings are interchangeable with Dayco’s product line and have a part match in the Kurt catalog and website,” said Scott Czupryna, national sales manager for Kurt Hydraulics, in a recent article. “Kurt Hydraulics has been manufacturing hydraulic fittings for Dayco for over 20 years, and has its own distribution network, so the transition is a natural one for us.”
Kurt Hydraulics is in the process of creating individual accounts for Dayco customers and providing notice to those customers. Additionally, Kurt is setting up a warehouse in Canada to better serve Canadian distributors.
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