Created on:2021-08-27 15:30

Fault diagnosis and maintenance of marine hydraulic equipment_ Fault analysis of hydraulic system of ship windlass

Fault diagnosis and maintenance of marine hydraulic equipment_ Fault analysis of hydraulic system of ship windlass

(1) Failure cause analysis

There are three main reasons for this serious accident.

① Due to human negligence, the cooling seawater of hydraulic oil is not opened, the hydraulic oil cooler is not cleaned regularly, the hydraulic oil is not inspected and replaced regularly, the filter is not cleaned regularly, and the daily inspection of equipment is not accurate.

② The quality of hydraulic oil in the system is deteriorated, which causes excessive wear of and hydraulic motor, scratch of hydraulic cylinder, power reduction and abnormal sound.

③ Improper operation of crew members and users, but the typhoon has been determined to attack, but they leave the port to catch the ship schedule; When anchoring in strong wind and waves, its output exceeds the rated output; The operator and commander did not pay extra attention when the ship rose and fell.

(2) Precautions for marine engineers to use hydraulic oil system

① Generally speaking, the manual does not specify the replacement time limit of hydraulic oil, but long-term use is easy to cause deterioration and moisture (water vapor seeps into the expansion gravity tank and leakage of cooling system, etc.). If there is no leakage or supplement under special circumstances, all hydraulic oil must be renewed after 4 ~ 5a of use.

② Regular cleaning of hydraulic oil filter. The hydraulic oil must be cleaned every month or every other month. Regular cleaning can not only understand the wear of internal parts of the hydraulic oil system, but also judge whether the quality of the hydraulic oil is degraded by its color and taste.

③ After long-term use, hydraulic oil has considerable degradation in power transmission, lubrication performance, cooling performance and rust prevention performance. It originally showed neutral reaction or weak alkaline reaction, but it showed acidic reaction after aging. It not only has no protective effect on metal, but is corrosive. At this time, the liquid oil must be replaced or treated.

Hydraulic oil is a very expensive consumable oil, so the deterioration speed of hydraulic oil should be slowed down as much as possible to prolong its service life. There is no certain standard for the service life of hydraulic oil, which varies greatly due to the proper design, maintenance and use of the machine. In case of the following circumstances, the deterioration speed of hydraulic oil will inevitably accelerate: a. the machine often operates under full (overload) or overload, and the hydraulic oil temperature is high; b. The effect of hydraulic oil cooler is poor (dirty), and the hydraulic oil temperature exceeds 65 ℃; c. There is water infiltration in the hydraulic oil, or there are unclean impurities in the hydraulic oil; d. The hydraulic oil is used for too long, the function is degraded, and the lubrication effect becomes worse.

After the deterioration of hydraulic oil, its properties and chemical reaction have considerable changes. The main changes are as follows.

a. Viscosity increases. After the deterioration of hydraulic oil, its viscosity increases significantly, the flow is difficult, the liquid friction resistance increases, and the lubrication performance decreases.

b. Reduced cooling performance. Due to the reduced fluidity, the lubrication circulation between the bearing and the relative moving friction surface is reduced, and the bearing is prone to heating or peeling.

C. is easy to frother. After the deterioration of hydraulic oil, due to the increase of viscosity, it is more difficult to remove moisture and impurities. After strong stirring, there will be froth, accelerated oxidation and acidification.

d. Produce sludge. After a long time of high temperature and stirring, the hydraulic oil is easy to produce sludge sedimentation due to its oxidation in contact with air.

④ Identification and maintenance of hydraulic oil deterioration.

Whether the hydraulic oil is deteriorated or not, the common identification methods are: A. sampling and sending it to the oil dealer for analysis and identification; b. Viscosity comparison method; c. Simple acid value determination method; d. Diffusion test method.

Attention to hydraulic oil maintenance: A. hydraulic oil shall be used according to the specified specifications and shall not be replaced arbitrarily; b. The hydraulic oil shall be kept clean as far as possible to avoid the possibility of invasion of moisture and impurities; c. All equipment equipped with fine filter shall be used as far as possible; d. The hydraulic oil shall absolutely avoid high temperature for a long time, and the oil temperature of the running machine shall not exceed 65 ℃; e. When replacing the hydraulic oil, the residual lubricating oil in all pipeline systems shall be removed as far as possible to prolong the service life of the new oil; f. Prevent grease from entering the hydraulic oil.

⑤ Treatment of deterioration of hydraulic oil. Put it into a special sedimentation tank to heat, precipitate and purify the oil. If it is found that the hydraulic oil of the machine has shown slight acid reaction, it can be treated by alkali washing method. At present, a small movable oil separator has been developed, which is specially used in the hydraulic oil system, and can completely purify the water and other impurities in the hydraulic oil. In order to prevent and reduce accidents, the most important and effective link is oil purification. Therefore, the engineer must carefully and carefully give full play to the function of the oil separator.

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