Created on:2021-08-30 14:11

Fault diagnosis and maintenance of marine hydraulic equipment_ Hydraulic failure of fin stabilizer

Fault diagnosis and maintenance of marine hydraulic equipment_ Hydraulic failure of fin stabilizer

(1) Overview of fin stabilizer

Under the action of wind, current and wave, the ship produces six degrees of freedom motion: roll, pitch, head and tail roll, heave, roll and pitch. Among them, rolling is the most severe, which has the greatest impact on ship navigation safety and ship staff and equipment. Fin stabilizer is a special device for reducing the rolling of ship in navigation.

Fin stabilizer consists of actuator, hydraulic system and electric control equipment. Among them, the hydraulic system is the most important part of the whole device.

Although the fin stabilizer has undergone strict bench test, mooring test and navigation test before shipment, so as to ensure the effective and reliable operation of the device. However, in actual operation, there are still various faults, especially the hydraulic system. In the early stage of its operation and the later stage of long-term operation, the fault rate is often relatively high, and the faults are generally difficult to detect. The causes of faults are often intertwined by mechanical, electrical, hydraulic and other factors. Therefore, operators and users shall have considerable experience and ability in fault diagnosis and troubleshooting.

(2) Hydraulic fault diagnosis of fin stabilizer

Common faults during operation include oil leakage, high oil temperature, vibration, noise, etc. These kinds of faults sometimes appear alone, sometimes accompanied by other faults, sometimes accompanied by other faults, such as oil bubbles with the noise generated by hydraulic pumping air.

During the operation of the hydraulic system of fin stabilizer, most faults do not occur suddenly, but there are always some omens. In preventive inspection (manual monitoring), experienced maintenance personnel often use hearing, visual inspection, hand feeling and other methods to predict the occurrence of faults.

① See table 9-2 for common leakage faults and troubleshooting methods of oil leakage fin stabilizer.

② The phenomenon of heating is caused by small cooling water flow and low water pressure during the operation of the system. This is often because the inlet and outlet valves of the cooler are not opened in time or opened too small.

③ Vibration and noise vibration and noise come from mechanical transmission components or hydraulic system oil pulsation, etc. Although vibration and noise are two phenomena, they often go hand in hand and cause and effect each other. For example, the thread preload of the pipe joint of the oil suction pipeline is insufficient, which looses and leaks during the operation of the equipment, resulting in air suction noise and vibration caused by air suction. When reversing the directional valve, it will cause high-pressure pipeline vibration, loosen the pipeline joint and produce vibration. The causes of excessive noise in hydraulic system are: a. the fixing screws of motor base and pump frame are loose, and the pump and motor are not concentric; b. The stop valve of the oil suction pipeline is not opened or the opening is not large, it is blocked, the oil suction pipeline leaks, the oil temperature is low or the oil temperature is too high; c. The oil seal of the hydraulic pump journal without oil drain port is damaged, the flange seal ring at the oil inlet of the hydraulic pump is damaged, and the hydraulic pump is damaged; d. High pressure pipe clamp is loose; e. The overflow valve seat is dirty and there is air in the system; f. The electromagnet of the electro-hydraulic valve fails and the control pressure is unstable; g. Low oil level, oil contamination.

④ The main reasons for not working normally are: a. the working pressure can not be established, the working pressure is low (can not rise to the set value), and sometimes the pressure can not fall down after rising, so that the hydraulic system can not work normally, and even the moving parts are in the original position; b. Insufficient flow, no flow, or excessive flow, resulting in no action or unstable speed of hydraulic working mechanism (hydraulic cylinder and hydraulic motor); c. Hydraulic shock; d. Crawl.

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