TECHNICAL SUPPORT
Published 2026-04-29
If the hydraulic steering gear turns slowly when the ship is sailing, this is a common fault condition and will have a direct impact on the safety of the ship. This article will directly analyze the five most critical reasons for delayed rudder rotation, and also provide operable troubleshooting procedures and solutions to help the crew quickly identify the problem and restore the performance of the steering gear.
A large number of sailors have encountered this situation: the rudder blades react slowly after operating the tiller, and the time it takes to turn the rudder to the far left and then to the far right is much longer than normal. This generally means that the hydraulic system flow is not sufficient. According to actual ship repair operations, 90% of rudder blade rotation failures originate from the following five different aspects.
1. Insufficient oil supply from the oil pump
In the hydraulic system, the oil pump is the absolute core, and its output flow directly determines the steering speed. Common reasons for this situation include: the oil pump speed is too low, that is, the prime mover is faulty or the belt is slipping, the volumetric efficiency of the oil pump is reduced due to wear inside the oil pump, or the oil pump suction pipeline is clogged.
The method of troubleshooting is to measure the actual output flow rate of the oil pump, then compare it with the value set during the design, and also check whether the rotation speed of the oil pump driving device is in a normal state.
For worn oil pump components, two methods are adopted, either repair or replace, clean the oil suction filter, and adjust the prime mover to the rated speed as a solution.
2. Abnormal hydraulic oil viscosity or oil level
The filling efficiency of the oil pump and the internal leakage of the system will be directly affected by the viscosity of the hydraulic oil. If the viscosity is too high (just like using summer oil in winter), it will be difficult for the oil pump to absorb oil. If the viscosity is too low, the internal leakage will increase and the effective flow rate will be reduced. If the oil level is too low, the oil pump will suck in air, which will cause flow pulsation and decrease.
The troubleshooting method is as follows: check the position of the oil in the tank, and also observe the color and fluidity of the oil. Then take out the oil sample and test its viscosity. You must understand that ISO VG 32/46/68 is a common steering gear oil. The key point in writing this article is the impact of oil temperature on viscosity: if the cooler fails, causing the oil temperature to be too high, that is, the oil temperature is greater than 60°C, this will cause the viscosity to drop sharply.
Provide solutions: add oil to the standardized oil level, replace the hydraulic oil with a suitable brand, and repair the cooling system.
3. Serious internal leakage in the hydraulic system
Due to the wear of the control valve group inside the steering gear, such as the reversing valve, safety valve, or the cylinder seal, the high-pressure oil leaks back to the tank, reducing the actual flow involved in doing work; if the safety valve set pressure is too low or the valve core is stuck, it will also overflow before the rated pressure is reached.
The method for troubleshooting is to measure the pressure at the outlet of the oil pump and the pressure of the oil cylinder when performing full steering operation.. If the pressure difference is relatively large and the oil temperature rises rapidly, it indicates an internal leak.
The solution is to perform grinding operations or replace the valve core, replace the cylinder piston seal, and readjust the safety valve to the design pressure (usually 1.1 times the working pressure).
4. There is air in the oil circuit
The mixing of air into the hydraulic oil will cause the formation of air pockets, which will cause the output flow of the oil pump to be discontinuous and the pressure to fluctuate.Common reasons include: the oil level in the fuel tank is too low, the sealing conditions of the oil suction pipe are not tight, or the exhaust is not thorough enough after replacing the oil.。A common situation is as follows: the steering speed of the steering gear is slow after just undergoing maintenance. This is usually because the air in the system has not been completely discharged.。
The troubleshooting method is as follows: observe the oil level in the fuel tank to see if there are a lot of bubbles, and also see if there is any abnormal sound like a "gnawing" sound when steering.
The measures are as follows: To completely exhaust the system, generally set an exhaust screw at the highest point of the oil cylinder or valve group to exhaust, and then check the sealing condition of the oil suction pipeline.。
5. Mechanical jamming or overload
This is not a problem of the hydraulic system itself. However, the gap between the rudder blade and the bearing is too small, foreign objects are stuck, or the rudder stock is bent. These cause the mechanical resistance to become too large, which will cause the required oil pressure to rise abnormally, causing the safety valve to open frequently, or causing the oil pump to overload and slow down.
The method adopted during the investigation is to first disconnect the connection between the steering gear and the rudder stock, and then manually turn the rudder blades to check the flexibility of its rotation. Then, the steering time and working pressure before and after the disconnection are compared.
solution: Repair the mechanical part of the rudder system, remove foreign matter, and adjust the bearing clearance.
Q1: The rudder turns slowly but the pressure gauge shows normal. What’s going on?
A: The pressure is in normal state but the speed is relatively slow, which indicates that the flow rate is insufficient. Priority should be given to checking the speed of the oil pump, the oil level, and the oil suction filter.
Q2: Just after changing the hydraulic oil, the rudder turns slower. Why?
New oil, its viscosity is too high, or the air in the system is not exhausted. Check the oil brand number and perform the exhaust operation thoroughly.
Q3: The rudder turns slowly on one side, but normal on the other side. Where is the problem?
Checking the reversing valve, or checking the sealing condition of the cylinder on the corresponding side will reveal the problem and see if it is here. Check to see if the valve core is worn, or if there is internal leakage in the cylinder.
Q4: The rudder turns normally when the temperature is low, but slows down when the temperature is high. What is the reason?
The increase in oil temperature causes the viscosity to decrease, causing internal leakage to increase. The cooler and oil aging condition need to be checked. When encountering such problems, the prompts for article writing should focus on safety valve debugging.
Q5: How to quickly distinguish whether it is a hydraulic failure or a mechanical failure?
Disassemble the connection between the servo and the rudder stock, and test the servo without load. If the speed is normal under no load, then this is a mechanical jamming problem.
To summarize the core points: the fundamental reason for the slow rotation speed of the hydraulic steering gear is the lack of hydraulic flow in the system. The specific manifestations include problems with the fuel supply of the oil pump, abnormal oil viscosity and oil level, internal leakage, air mixed in, or excessive mechanical resistance. When carrying out troubleshooting operations, the order of "starting from the simple direction first, then moving from the outside to the inside" should be followed: first check the oil level and oil temperature, then check the oil suction filter and oil pump, and finally check the valve group and internal leakage of the cylinder.
Suggestions for immediate action:
1. Establish baseline data. When the steering gear is in normal condition, record the time it takes for the full rudder to turn from one side to the other. The industry reference standard for this time is 28 seconds. If this value is reached, maintenance is required. At the same time, the working pressure under each working condition is recorded.
2. Carry out periodic inspections, visually identify oil level, oil quality and pipeline leakage every week, clean the oil suction filter every month, and collect oil samples every quarter to test its viscosity, acid value and moisture.
3. Develop a fault plan and make the above five main causes and troubleshooting steps into a convenient and quick guide. This guide should be posted near the steering gear room to ensure that relevant personnel of the engine can quickly handle the fault according to the steps.
With the help of systematic inspection and maintenance, more than 90% of slow steering failures can be prevented or quickly repaired at the front, thereby ensuring the safety of ship navigation.
Update Time：2026-04-29
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