Underground tunnel projects keep advancing toward greater burial depths, longer tunneling distances and complex geological formations. As core equipment, shield machines and hard rock Tunnel Boring Machines (TBMs) run continuously under harsh working conditions characterized by intense vibration, alternating high pressure, dust and humidity. The hydraulic system acts as the "lifeline" of tunneling machinery, and the stability of pipe connectors directly governs equipment operational safety and construction efficiency. To tackle the pain points of tunneling equipment, our company has developed dedicated SAE flange solutions for hydraulic piping of shield machines and TBMs. With heavy load capacity, excellent shock resistance and leak-proof performance, the products provide stable and reliable pipe connection solutions for hydraulic systems of tunnel engineering machinery.

During tunneling operations of shield machines and TBMs, cutterhead cutting, reciprocating motion of thrust cylinders and cyclic loading of grippers generate persistent high-frequency vibration and pressure shocks. Subjected to alternating loads, conventional threaded joints tend to suffer from thread loosening, seal failure and hydraulic oil leakage. The confined working space inside tunnels means any leakage will not only contaminate equipment and construction environments, but also cause unplanned downtime, bringing huge schedule losses and maintenance costs.

SAE flanges adopt a face-sealing structure uniformly compressed by multiple bolts, presenting remarkable advantages in vibration and shock resistance over traditional threaded connections. To fully verify product reliability under heavy shock loads in tunnel working conditions, a series of bench durability tests have been completed: at a rated working pressure of 35MPa, the product withstands peak pressure shocks up to 42MPa and successfully passes 1,000,000 cycles of alternating pressure fatigue testing. After testing, the sealing surface remains intact with no external leakage, and the bolt preload attenuation is controlled within 5%. In the composite vibration durability test under 10–500Hz frequency and 15g acceleration for 200 consecutive hours, no loosening occurs on flange connections and sealing performance stays stable. For Code62 flanges, the hydrostatic burst pressure reaches ≥140MPa with a safety factor above 4, reserving sufficient safety margin.

Our SAE flanges specially designed for shield tunneling are manufactured in strict accordance with the SAE J518 standard, covering a full range of specifications including Code61 and Code62 high-pressure split flanges, solid weld flanges and flange adapters. The flange bodies are produced by precision forging with stress relief treatment, and the sealing surfaces are CNC machined to guarantee sealing accuracy. Material options include carbon steel, 304/316 stainless steel and duplex stainless steel, suitable for ordinary strata and tunnel environments with high corrosion from saline groundwater. EN10204 3.1 material certificates are available for all products to achieve full traceability of quality.

The products are widely applied to core positions such as thrust systems, cutterhead drive hydraulic circuits, segment erector cylinders, tail grouting systems, screw conveyor hydraulic pump stations of shield machines, as well as gripper systems and main engine hydraulic pipelines of hard rock TBMs. Custom non-standard flanges and special adapters can be supplied to meet restricted piping layout of host machines and inconsistent interfaces in renovation projects. The flange assemblies are easy to assemble and disassemble, simplifying on-site maintenance inside tunnels and effectively cutting maintenance costs.

With years of experience in R&D and manufacturing of hydraulic fluid fittings, we provide one-stop supporting services covering SAE flanges, hydraulic fittings and pipe assemblies. Our products are widely used in shield machines, TBMs, mining machinery, large hydraulic stations, offshore engineering equipment and other fields. We continue to deepen our expertise in fluid connection technology for tunnel engineering machinery, continuously optimize forging and machining processes, and develop pipe connectors adapted to extreme working conditions. We deliver high-quality and highly reliable hydraulic piping supporting solutions for tunneling equipment manufacturers and facilitate the high-quality development of underground engineering equipment in China.