Created on:2021-08-28 09:59

Fault diagnosis and maintenance of marine hydraulic equipment_ Steering gear paralysis

Fault diagnosis and maintenance of marine hydraulic equipment_ Steering gear paralysis

(1) Steering gear paralysis

Engine room valve group is one of the main components of a ship's servo hydraulic steering gear. It is an integrated structure of hydraulic parts. Its internal schematic diagram is shown in Figure D. The ship is equipped with steering gear in the cab and steering gear compartment, which can carry out follow-up steering control respectively, and the engine room valve group is used for steering without follow-up solenoid valve.

During the steering test of the solenoid valve, there was a fault that the rudder could not return when turning to the left full rudder position. The steering gear in the cab and steering engine room could not operate, and the system was paralyzed. Carefully observe the indication of the instrument. When the steering gear in the cab is operated to the left, the reading of the oil inlet pressure gauge is the set pressure of the overflow valve. When it is operated to the right, there is no pressure indication, and it is switched to the steering gear operation in the steering engine room. The phenomenon is the same as above. Operated by solenoid valve, the oil inlet pressure gauge always takes the set pressure of overflow valve as the indicated value no matter whether the control switch is operated to the left or right rudder.

(2) Fault analysis and measures

According to the above analysis, the fault is caused by the fact that the valve core of the steering solenoid directional valve is not reset and is always in the "left rudder" position. Return the valve core to its original position and confirm that there is no jamming. Operate the steering gear and work normally.

It can be seen that although the system is equipped with multiple sets of control devices to improve reliability, the electromagnetic directional valve of the engine room valve group failed and the steering gear was paralyzed. Obviously, the design of engine room valve group is not perfect. If the internal cleanliness of the system is improved, such faults may be avoided. However, under the conditions of long ship construction period, many people and miscellaneous types of work, it is difficult to ensure the "absolute" cleanliness of the system. In addition, during electromagnetic steering, the steering electromagnetic directional valve works frequently, which makes the hidden danger of failure always exist.

How to ensure that the steering gear can still work normally when the engine room valve group fails will be the key to improve the reliability of the system. If a hydraulic lock is added at both a and B as shown in Figure D, and the steering oil circuit is isolated from the control oil circuit, the failure of any control device will not affect the normal operation of the steering gear, and the reliability of the system will be guaranteed.

 

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