Marine hydraulic motor The equipment has simple structure, excellent low-speed performance, impact resistance, reliable operation and other characteristics, and is widely used on the corrugated cable (anchor) machine of ships. However, the hydraulic winch (anchor) system adopted by the ship barge manufacturer of Ningbo Port on 3088kW tugboat has been produced five times since 1996 Five star hydraulic motor The failure of shell fragmentation is rare. In order to prevent this kind of accident from happening, this paper introduces Hydraulic motor The case and reason of shell damage are simply analyzed, and the preventive measures are pointed out.
1、 Basic condition of fault
The hydraulic winch (windlass) system of 3088kW high horsepower tugboat manufactured by Ningbo Port barge manufacturer adopts two types of daily production, Beichuan and Guangyang. The specific situation is as follows:;
In the process of tugboat berthing aid operation, the hull of the hydraulic motor of the winch is broken, and there are two specific cases.
1. The speed of is too fast. In the process of cable laying, the high horsepower tug adopts the cooperative operation of pushing and launching in the process of berthing operation, and the main cable is always tied to the big ship being berthed. During jacking, the main cable is recovered; When towing away, the tug reverses, and the winch is gradually towed away when it reaches the required length (generally between 50~70m). In this way, the winch needs about ten times of cable retraction and release in each mooring operation. If the emergency is changed from pushing to pulling, the tug will reverse quickly and the winch will release the cable quickly. When the tug reverses and the speed of the tug reaches the speed of the winch, the hydraulic motor of the winch will break,
2、 Reason description
According to the analysis of the hydraulic motor shell fragmentation, there is an external force to reach the motor output force, so that the motor is in the working condition when the pump is running. The specific reasons are:
1. In the process of cable laying, the tug reverses the speed of the ship to reach the speed of cable laying of the winch, and the external force of the winch reaches the output force of the motor, so that the motor is in the running state of the pump. From the case of five times of shell fragmentation, the speed of cable laying is relatively low. In specific application, the high gear is between 20~50m/min, while when the tug is in normal operation, the main engine reverses with the main cable at a low flat speed ratio (40Or/min), and the ship speed can reach 3~4 knots (93~120m/nin) from 0~50n. In general, the length of cable laying is 50~100m during operation. Therefore, during the berthing aid operation, the reverse speed of the tugboat is not adjusted well when the emergency is transferred from the jacking to the towing. The towing winch is released at the speed of 90~120m/min, the hydraulic motor is in the pump condition, and the corresponding required absorption capacity is 110~140l/m. The large output of the hydraulic pump in the surface hydraulic system can only meet the displacement of the motor when the cable is laid at the speed of 50 m/min. When the reverse ship speed reaches 50 n/min (1.62 knots/h), the hydraulic oil pump is not enough to deliver oil to the equipment, resulting in a vacuum condition. According to the basic theory of gas-liquid two-phase flow, when the vacuum condition reaches the required value, the equipment hydraulic oil will release gas, because when the cable is laid, usually pipe B enters oil and pipe A discharges oil,
The working sequence of each cylinder of the motor is 1~- 2 - 3 - 4 - 5 repeatedly, which will lead to gas-liquid two-phase flow of the fourth cylinder at a higher position in the system earlier. When the piston rod of the fourth cylinder drops, the inlet of the cylinder block oil passage will lead to air mass. When the piston rod goes up repeatedly, the air mass will quickly crack and explode, resulting in high pressure and cracking of the motor cylinder block with the inlet of the oil passage as the core. If pipes A and B are connected relatively, the cracks lead to the same inducement on the first cylinder of the motor. However, it can eliminate the possibility of motor overspeed. Because the speed range of the hydraulic motor is 1~400 r/min, when the motor is 400 r/min, the cable laying speed is 150 m/min, and the sailing speed is more than 6
Section. However, it is difficult for the tug to reach this speed when reversing with cable (the main engine speed is 400~450 r/min), so the probability of overspeed damage can be eliminated.
2. The hydraulic motor shell cracks when the car runs away, which is mainly caused by the hydraulic system without fluid replacement. When the winch brakes, the control valve is interlocked and closed, and the system does not supply oil to the motor. When the brake deviates, the main cable slides, and the motor is pushed to rotate in the direction of cable laying. In addition, the cable laying pipe A discharges oil, and pipe B feeds liquid through the safety valve. Generally, the volumetric efficiency of the hydraulic motor is 90%~95%. In the repeated process, nearly 10% of the hydraulic oil enters the low-pressure oil chamber of the motor and returns to the oil tank through the low-pressure pipeline system, so that the oil volume of the system continues to decrease, resulting in vacuum. Similarly, the fourth cylinder, which is relatively high in the relative position, causes gas-liquid two-phase flow earlier, leading to the cracking of the motor housing. If A and B are connected relatively, the cracking results in the first cylinder.
4、 Preventive measures
The key methods to avoid cracking of the hydraulic motor housing and the system vacuum are as follows:
1. During operation, avoid the tug reversing at high speed, and make the reversing speed consistent with the laying speed of the winch. In case of heavy wind and rainstorm, release the relatively long buffer cable on the springboard according to the wave height, so as to prevent the tugboat's hull gravity from acting on the main cable in the wave trough, leading to brake deviation. When pulling away, the length of the streamer shall be more than 70m to avoid the interference of heavy rain and wind. The impact force on the main cable exceeds the braking force, resulting in brake deviation. If necessary, the main cable shall pull one or release the clutch on the bollard.
2. In the construction and selection of the hydraulic system of the winch: ① The demand for fast cable laying in specific work shall be comprehensively considered. From the characteristics of the motor and the loading specification of the winch, the standard of emergency cable laying can be reached when the cable laying speed reaches 100m/min. The key is the output of the hydraulic pump.
