Hazard of reverse flow of hydraulic oil

Because of the wind turbines in the brake system (spindle brake and yaw brake) drive is low viscosity hydraulic oil that is used by the media and the execution of the braking system parts (piston) constant motion in working process, thus inevitably has the problem of oil leakage. On the one hand, the oil leakage can cause the pressure drop of the hydraulic system, which can not meet the technical requirements of the wind turbine. On the other hand, the leakage of grease will cause pollution to the unit and bring safety hazards to the operation of the operation and maintenance personnel. In order to solve the problem of piston movement lead to leakage of hydraulic oil, brake and hydraulic system manufacturers usually inside the brake and hydraulic system of hydraulic circuit set in the drainage of the hydraulic oil circuit, directs the leakage of hydraulic oil tank of hydraulic system, so can avoid the pressure drop caused by the leakage of hydraulic oil, and leakage of hydraulic oil can be recycled, environmentally efficient. The connection structure of the drain circuit of hydraulic system is shown in figure 1.

 

The leakage circuit structure of the brake is designed according to the sealing structure inside the brake. The internal sealing structure of the brake usually consists of two rubber sealing rings around the piston, which can be divided into the sealing ring and the dustproof ring according to the function. On one side of the sealing ring located close to the bottom of the cylinder (i.e., away from the side of the lining), can bear high pressure, reach tens of mpa, to ensure that the brake in the braking state under the pressure of the hydraulic oil from leaking; The side of the shield is located in the far away from the bottom of the cylinder, can withstand pressure is relatively small, generally within 5 bar - 10 bar, main function is to prevent all kinds of impurity penetration into the brake, brake external pollution of hydraulic oil. Brake piston in the process of up and down there will be a leakage of hydraulic oil from the bottom of the cylinder to seal and shield, and leakage of hydraulic oil into the brake oil circuit, then be directed back to the fuel tank, back in the hydraulic system pressure loop. General wind turbine hydraulic system of the fuel tank position is higher than the yaw brake 2 m to 3 m, the leakage of hydraulic oil is to accumulate the oil circuit after the return pipe, can enter the tank, so the shield should be able to withstand back pressure caused by the hydraulic oil in the tubing. The drain circuit of yaw brake is shown in figure 2.

 

However, the actual operation and maintenance work found that the leaking hydraulic oil that should have been led to the oil tank was accidentally overflowed in the piston of the yaw brake. Hydraulic oil since the yaw brake piston upper overflow, dripping on the brake disc, the yaw friction pair (friction plate and brake disc) the friction of the environment pollution, lead to drift the friction coefficient of friction pair is no longer uniform, stable friction performance is no longer a big vibration and noise; Friction plate of friction material with resin matrix composites, vulnerable to oil intrusion and degeneration, wear rate rise sharply, the working life of the friction plate falling fast, beyond the missile d etection maintenance cycle of wind turbines, if not timely discovery will lead to brake discs are lining back wear serious accidents. The friction film of yaw brake is contaminated with grease as shown in FIG.3.

The above:Hydraulic gear pump is worn and repaired.