From high-pressure hydraulic circuits in presses and machine tools to low-pressure, high-cycle cooling systems in injection moulding machines, fluid connectors form the invisible but vital network that keeps production safe, clean, and continuously operational, write Andreas Kock, Alexander Hertje, Richard Boulom, Andreas Akunick.
Yet, as production cycles accelerate and throughput rises, these systems face higher nominal and peak pressures along with greater flow demands through tubes and hoses – pushing them to their limits.
As a single connector failure can trigger safety risks and costly downtime that far outweigh the price of the component itself, connection systems must guarantee safe, continuous, and efficient operation even under the harshest loads.
Distinct industry demands
Both metal forming and injection moulding rely on secure, predictable fluid transmission – but their requirements differ significantly.
● Metal manufacturing: Hydraulic systems in presses and forming equipment often operate at pressures up to 800 bar, demanding exceptional resistance to pressure peaks, vibration, and fatigue.
● Injection moulding: Cooling circuits circulate water or glycol mixtures under much lower pressures (0–40 bar) but at elevated temperatures – often above 120 °C. Here, seal compatibility, flow optimisation, and ease of service take precedence over absolute pressure resistance.
Across both sectors, the same principles—secure sealing, fatigue resistance, ease of installation—are executed differently based on the specific stress conditions each industry presents.
High-pressure systems: engineering for extreme stress
In high pressure hydraulic systems, rapid pressure shifts combined with vibration can lead to metallic relaxation, gradually reducing the clamping force required for leak-free operation.
Traditional metal-to-metal seals, though robust, depend on precise assembly torque and flawless surface contact. New-generation fittings increasingly combine the strength of steel with elastomer-assisted sealing. By absorbing micro-movements and compensating for surface irregularities, soft seals prevent premature loosening while simplifying assembly in confined spaces.
For applications exceeding 120 °C, fluorocarbon (FKM) elastomers deliver essential heat resistance. And where soft seals cannot survive—such as turbine systems approaching 500 °C—engineers use fully metallic concepts like Parker’s Seal Lok Xtreme, which employs specialized metal-to-metal sealing geometries that maintain integrity purely through mechanical design.
Non-weld connection technologies, such as Parker’s EO-2 Form, are also replacing high-effort welded pipe systems. A robust alternative, the system utilises soft sealing technology alongside a formed tube end. This technology is mandatory in some applications with high tear-out safety requirements—such as parts of the press builder market—where cutting rings may be prohibited. Unlike welding, these threaded connections allow easy disconnection and reassembly, streamlining both retrofits and planned maintenance.
Material selection underpins system reliability, with high-performance steels balancing strength with machinability. Surface treatments such as anti-friction coatings on tube nuts further enhance assembly, reducing torque requirements – particularly valuable for large fittings in confined spaces.
Low-pressure systems: optimising flow and serviceability
In injection moulding, connection technology plays a crucial role in maintaining efficient cooling cycles. As moulds heat and cool during each production sequence, connectors must preserve flow efficiency and chemical compatibility with diverse fluids, including water-glycol mixtures and synthetic lubricants.
To meet these requirements, Parker’s low-pressure connection systems employ advanced polymers such as Polyamide PA 11 or PEEK (Polyether ether ketone). These materials combine lightweight construction with mechanical stability, enabling optimised flow path geometry that supports high throughput without additional pressure loss.
Pneumatic automation systems within moulding machines—controlling mould movements, ejection mechanisms, and auxiliary functions—operate in the same 0–40 bar range, conveying compressed air through repeatedly cycling lines. Here, quick-service connection designs are paramount, ensuring the product is easy for the customer to assemble and disassemble if needed. Interfaces like the push-on fitting and general threaded designs allow maintenance technicians to disconnect and reconnect lines without specialized tools – minimising downtime during mould changes, a key factor in maintaining production efficiency.
Safety and testing integrity
Ensuring safety in operation is as central to connector engineering as manufacturing efficiency – at 800 bar, a failed fitting becomes a projectile hazard or high-pressure injection risk. For this reason, high-pressure systems incorporate a fourfold safety margin: components must withstand four times their rated pressure without failure. This engineering principle ensures the tube or hose yields first if a system is overstressed, never the connection itself. Low-pressure compressed air systems follow ISO-defined threefold safety factors, ensuring predictable and controlled failure behaviour.
Components also undergo accelerated pressure cycling and temperature aging that simulate millions of operations. Dimensional camera inspection of every cutting ring or precision-machined part ensures consistency. When failures arise, Parker’s leading technology laboratories in Bielefeld and Rennes employ optical microscopy to determine root causes and refine designs for even longer lifetimes. When higher magnification is required, Parker works with specialised partner laboratories that provide electron microscopy capabilities.
Beyond physical testing, embedded sensor technology now extends this assurance into real-time operation. Integrated monitoring systems help prevent failures before they become catastrophic. Embedded sensor technology, from Parker SensoControl, offers a wide range of embedded sensors that track pressure, temperature, fluid level, and flow rates. Crucially, non-expensive, ISO-standardised test points can be easily integrated, allowing technicians to connect mobile measurement devices by hand. This capability permits high-resolution monitoring to detect “hidden” pressure peaks that are often invisible to conventional instrumentation, ensuring early detection and long system lifetime.
Evolving with industry demands
Connection technology continues to evolve alongside industry’s changing requirements. Production methods have advanced from purely machined components to hybrid processes – cutting rings, for instance, shifted from full machining to primarily forming with minor finishing, improving both speed and dimensional consistency.
As environmental regulations phase out leaded materials, Parker continues developing alternatives that match or exceed previous performance standards. Each material evolution requires substantial tooling investment and process revalidation, but these advances deliver tangible benefits: easier assembly for machine builders, longer service life in operation, and compliance with emerging safety and environmental standards.
Meeting needs through integrated expertise
By combining expertise in both high-pressure metallic hydraulics and advanced polymer fluid systems, Parker delivers solutions matched to each environment’s technical requirements. This integrated approach—supported by rigorous validation—enables manufacturers to achieve predictable assembly performance, easier maintenance, and safer operations.
Parker engineers also participate in ISO standardization committees, contributing field experience that shapes industry specifications for connection systems. Through proven expertise, a culture of continuous improvement, and decades of experience, Parker ensures its connection technologies don’t just meet current requirements – they deliver reliability for the production environments of tomorrow.
Author biographies:
Andreas Kock, Alexander Hertje, Richard Boulom and Andreas Akunick all work at Parker Hannifin in the Application and Product Management Business Unit. Parker Hannifin is a Fortune 250 company specialising in motion and control technologies.
