YGM Hydraulically Tightened Nuts

I. Main Applications

YGM Hydraulic Nuts (hereinafter referred to as hydraulic nuts) are primarily used in threaded connections for their connecting and securing functions. Common nuts are typically tightened using wrenches or electric tools. However, in large machinery like coal mining machines, which experience high intensity work and severe vibration, using standard nuts can lead to gradual loosening due to insufficient preload, eventually losing their securing effect. To achieve greater preload, hydraulic nuts are applied in large machinery such as coal mining machines, offering high connection strength and excellent anti-loosening properties. The use of hydraulic nuts for securing ensures safer and more reliable operation of machinery like coal mining machines, as well as easier and faster disassembly, enhancing work efficiency. In certain applications, replacing traditional nuts with hydraulic nuts allows for the simultaneous tightening of multiple hydraulic nuts, achieving uniform preload and making assembly more precise, improving equipment performance. Hydraulic nuts can also be used on large equipment in the metallurgy, copper, and aluminum industries, such as for installing and removing propellers, rudder blocks, bearings, train wheels, couplings, flywheels, and gears.

II. Work Pressure

The YGM series hydraulic nuts are primarily used for keyless connections of connecting components. Their working principle involves utilizing ultra-high-pressure oil to generate a thrust on the shaft, thereby evenly connecting the piston body face to the equipment.

a. The ultra-high-pressure oil pump has a low flow rate, with working pressure reaching up to 220MPa. For instance, the oil cavity area of the M42 hydraulic nut is approximately 3155mm². At a working pressure of 180MPa, it can apply an approximately 568kN pretension force to the matched high-strength bolts, which is 72% of the bolt guaranteed load.

b. Available in both axial and radial lubrication methods.

c. Standard working pressure: 63～153 MPa.

Section 3: Model Meanings

Section 4: Mechanical Structure Diagram of Hydraulic Nuts

The structure of the hydraulic nut assembly is shown in Figure 1.
Mainly composed of: 1. Retaining Nut; 2. Piston Body; 3. Combined Sealing Ring; 4. Nut Cylinder.
5. Steel balls; 6. Oil plugs; 7. Comprising transition joints and quick connectors.

Five: Hydraulic Nut Tightening Principle

a. By utilizing the power of a super-high-pressure hydraulic pump, the hydraulic nut extends the fastening bolt axially, nearing the yield point of the material. It then locks the threads using the material's inherent elasticity. The working principle of the hydraulic nut is illustrated in Figure 2.

b. Select the lubrication direction for the hydraulic nut (which includes axial and radial lubrication methods).

c. Remove the dust cap from the hydraulic nut (Refer to Figure 2 for radial oil injection. Please unscrew the plug (thread size M10X1) from the radial oil injection hole, being careful to remove the steel ball and install it in the radial oil injection hole.), then install the copper washer, transition fitting, and quick connection and tighten them to prevent oil leakage. See Figure 1 for details.

d. After screwing the screw into the hydraulic nut thread hole, install it onto the equipment and tighten the nut (when installing, the nut should be tightened towards the equipment), apply force to press the nut against the equipment, ensuring that there is minimal gap between the face of the hydraulic nut and the equipment face. See Figure 2 for illustration.
e. Connect the quick couplings, use the power source to increase pressure. The pressure oil produced by the high-pressure oil pump enters the oil cavity of the hydraulic nut through the high-pressure flexible hose step by step. The bolt is elongated within its elastic deformation range, causing the cylinder body and piston of the hydraulic nut to gradually separate. By stretching the threaded high-tension bolt, a certain gap is formed between the cylinder body of the hydraulic nut and the clamp nut, as shown in Figure 2. Rotate the clamp nut to tighten it against the cylinder body, ensuring that the high-tension bolt remains elongated after the high-pressure pump is depressurized. At this point, it is crucial not to extend the hydraulic nut piston beyond the ********* stroke to prevent the piston from detaching from the cylinder. Once the hydraulic nut reaches the pre-tension force, maintain the power source in a stable state and stop increasing pressure.

Section 6: Hydraulic Nut Specifications

Section 7: Important Notes

a. After operating for a period, the hydraulic nuts should be checked for loose joints to ensure proper functioning.

b. Strictly avoid using damaged, worn, or aged seals, hydraulic hoses, and quick couplings.