Fault diagnosis and localization maintenance strategy of marine hydraulic motor

Ship deck machinery uses hydraulic transmission for nearly one hundred years. According to incomplete statistics, nearly 30% of the hydraulic system failure is due to hydraulic motor failure. Therefore, it is important to understand the fault type and the law of the fault of the hydraulic motor, and to diagnose and maintain the hydraulic transmission system of the ship.

Common faults and maintenance strategies of 1. marine hydraulic motors

Different conditions require hydraulic transmission equipment using different hydraulic motors. Table 22-2 shows some commonly used marine low speed large torque hydraulic motors and their main performance parameters. The single action radial piston hydraulic motor has simple structure and is suitable for low speed stability. Double swashplate axial piston hydraulic motor has wide speed range and good low speed stability. When the hydraulic motor is required to output large torque and has good low speed stability, the internal curve multiple action radial piston hydraulic motor is usually adopted.

The hydraulic motor hydraulic drive system in normal use should be smooth, no abnormal sound, otherwise indicate equipment installation conditions, or change within the motor stator blade or spring components such as the occurrence of adverse defects. Because of bad working conditions and large load, marine hydraulic motors are prone to various faults after a period of use. Many of these forms the miasma of diversity, low speed stability deterioration (wear) is the most common fault of marine hydraulic motor, the reasons are mostly due to pollution caused by hydraulic oil. The working conditions of the ship hydraulic system is very bad, all kinds of impurities easily mix hydraulic oil in the hydraulic motor parts of the premature wear and the amount of irregular oil leakage increased, resulting in a sharp decline in the stability of low speed hydraulic motor. The hydraulic oil pollution is a great evil to the whole hydraulic system. It damages the hydraulic pump, makes the oil supply and the oil supply pressure disorderly fluctuation, and will also cause the deterioration of the low speed stability of the hydraulic motor. The prevention of pollution and cleaning of hydraulic oil is a task that must be paid special attention to by the hydraulic system of ships. In addition, the hydraulic motor used for a period of time, the original setting back pressure becomes small, may also change the hydraulic motor with low speed stability, in this regard, the return oil pressure adjustment, reasonable selection of oil return back pressure.

Marine hydraulic motor used for a period of time, the noise increases obviously, which is mainly due to the motor in the condition of operation of high load, lubrication condition and not a good guarantee, lead to bearing components, mechanical parts of the relative motion coupling and other moving parts wear, the parts with errors. In addition, the hydraulic shock and the hydraulic oil hole phenomenon also cause the noise of hydraulic motor to increase. In fact, a variety of faults occur in hydraulic systems for a variety of reasons.

Hydraulic system of various components and auxiliary parts of the work conditions of the interaction and influence, and even the length of the pipeline, the thickness, direction, distribution are closely related to this. As an example, the output torque of the hydraulic motor is reduced as a result of insufficient oil supply. In addition to the statement in table 22-2, it may also be related to the malfunction of the electronic control circuit of the components, such as the solenoid valve, etc.. Therefore, the common faults of hydraulic motors described in table 22-3 only include some reasons for higher frequency.

2. selection principle of replacing domestic components

The working parameters of the hydraulic system include pressure, flow rate, temperature, etc.. The main parameters that represent the performance of the hydraulic system are pressure and flow. When the load was determined according to the maximum resistance torque of hydraulic motor, hydraulic motor and hydraulic cylinder and know the requirements of the working speed range, can work pressure and flow estimation system for the hydraulic motor, the hydraulic system to determine the required maintenance components (hydraulic motor) to provide the exact basis. Therefore, the correct choice of hydraulic motor pairs is an important factor in the formulation. The common faults of marine hydraulic motors and their cause analysis and general elimination methods are shown in table 22-3.

Reasonable maintenance of the hydraulic system is a crucial task.

The choice of hydraulic motor is usually based on motor torque, speed, installation size and hydraulic system is a large working pressure and other parameters.

Since the hydraulic motor belongs to the actuating element in the system, it is often started with load, that is, under the maximum load torque condition. Most of the ship machinery is large power load, if the hydraulic motor does not have enough starting torque, it can not work properly. In order to reduce the volume of the system, improve the system reliability, directly connected with the hydraulic motor with low speed often working mechanism, so the marine hydraulic motor with large starting torque, wide speed range and good stability at low speed.

The output torque of the hydraulic motor is:

From the upper model, the output torque of the hydraulic motor is proportional to its displacement and pressure. Therefore, increasing working pressure or increasing displacement is the simplest method for hydraulic motor to obtain large output torque. However, to improve the work pressure, the hydraulic motor and even the entire hydraulic system seal more stringent requirements. Otherwise, as the leakage increases, the volume efficiency of the motor will be reduced, the torque will be reduced, and the heating of the whole hydraulic system will be affected, the life of the accessory will be affected, and the reliability of the system will eventually decline. Therefore. For the maintenance of a ship's hydraulic transmission equipment, the domestic hydraulic components are selected. First of all, the working pressure of the selected hydraulic motor should be determined according to the maximum working pressure of the original hydraulic system. Secondly, according to the speed of the demand, choose to be able to match the original hydraulic pump with each turn of the displacement to determine the flow of motor work. Finally, according to the installation environment, choose the hydraulic motor geometry size, so as to facilitate installation.

Considering the ship hydraulic system to meet the harsh working environment, ship machinery load characteristics and work requirements, and ensure the reliability of the system is high, the marine hydraulic system generally choose method to increase motor displacement to achieve high torque hydraulic motor.

When the hydraulic motor increases the displacement, the output torque is proportional to the increase, while the speed is inversely proportional to the decline. The speed of the hydraulic motor is:

Obviously, to increase the output torque of the hydraulic motor by increasing the displacement, the speed of this kind of motor must be lower, that is to say, the marine hydraulic motors are mostly low speed and large torque hydraulic motors.

Compared with the high speed motor, the low speed hydraulic motor has higher volume and weight, but higher reliability and longer service life. Therefore, it does not require high sensitivity to commutation and speed regulation, but has higher requirement for the torque of transmission, so it is difficult for ship machinery with poor working conditions

It is more suitable. In addition, because the motor speed is low, the low speed working mechanism can be directly connected with the hydraulic motor, so that the whole transmission mechanism is reduced in size and the weight is reduced.

Therefore, in the hydraulic system of the ship, the high speed hydraulic motor is no better than the low speed hydraulic motor in weight and performance. The weight and volume of a speed reduction device completely eliminates the advantages of a high speed hydraulic motor with small size and light weight.

Hydraulic components of ship hydraulic drive system is damaged after the selection of hydraulic components for domestic maintenance, not only reduces the maintenance cost of the ship hydraulic equipment, and make the domestic hydraulic components has been applied in actual production, accumulate experience for the development of national industry. Hydraulic motor is an important component of the overall level of hydraulic industry. Its wide application has opened a new way for domestic hydraulic components to hit the international market.