• The hydraulic system experiences pulsating pressure due to dynamic loads caused by external forces acting on the rudder. These fluctuations can place stress on the connecting flanges.
• Sudden manoeuvres can create pressure pulsations as the hydraulic system responds quickly to changes in direction or speed. These rapid demands may exceed the design limits of the flanges.
• Harsh sea conditions can generate vibrations and stresses in the piping system, leading to severe damage or failure of connecting flanges over time.
• Failing to conduct regular inspections and measurements of clearances can lead to unnoticed wear and damage in the system, potentially compromising the integrity of the flanges.
• Ensuring the proper tightness of holding-down bolts and other fastening arrangements. If these bolts are loose, it can lead to failure in the piping and flanges due to vibrations.
• Cracks in welded joints and wear in flexible hoses can develop over time if not regularly inspected, eventually leading to a failure of the connecting flanges.

• The main steering capability due to a single failure in any part of one of the power actuating systems shall be regained in not more than 45 seconds.
• The main steering shall comprise at least two identical power actuating systems, each capable of meeting the requirements. Loss of fluid from one system shall be capable of being detected, and the defective system shall automatically get isolated so that the other system shall remain fully operational

Shown in the diagram is a “Fail safe steering gear” having two independent power actuating systems that can

• Work simultaneously in normal operation, meeting the requirement OR
• Work independently and meet the requirement
• In the event of loss of fluid from any one system, it can be detected and isolated automatically so that the other system can remain fully operational.

Sequence of events during hydraulic oil leak:

Case 1: Consider an oil leak from any pipe for cylinders 1 and 2 with the No. 1 pump running:

1. No. 1 tank level will come down to L1, and it will sound an alarm on the bridge and in ECR
2. When the tank level further drops to L2, i.e. low-low level, the no. 1 pump stops.
3. Stopping the No. 1 pump also stops the attached auxiliary pump. So the line pressure drops, due to which the normally closed by-pass valves ‘X’ and ‘Y’ open.
4. Simultaneously, the auto isolation valves ‘A’, ‘B’ and ‘C’ will be operated by an electric signal. A, B and C are normally open valves. The electric signal will close them. So, systems 1 and 2 will be completely separated. Thus, the defective system, I.e. system 1, is isolated.
5. Along with the operation of the auto isolation valves, the No. 2 pump will start automatically. The attached auxiliary pump will act on the by-pass valve ‘Y’ and close it. This enables cylinders 3 and 4 to be in normal operation.
6. It should also be noted that since system 1 is completely isolated, there is no oil pressure to operate the bypass valve. So the by-pass valves remain open, thereby removing the hydraulic lock for the ram movement in cylinders 1 and 2

Case 2: Consider an oil leakage from any pipe of cylinders 3 and 4 with the No. 1 pump running:

Points 1, 2 and 3 are the same as case 1

1. Simultaneously, the auto isolation valves ‘A’, ‘B’ and ‘C’ will be operated by an electric signal. This will shut the normally open valves A, B and C. Thus, systems 1 and 2 will be completely separated
2. Along with the operation of auto isolation valves, the No. 2 pump will start automatically. The attached auxiliary pump will act on the by-pass valve ‘Y’ and close. So, cylinders 3 and 4 will come into normal operation.
3. Now, since the leak is between the pipe of cylinders 3 and 4, the level of the no. 2 tank will drop to L1 and give an alarm.
4. The level will further drop to L2, but the pump will not stop and changeover to ensure that the leak is from the pipe of cylinders 3 and 4
5. When the no. 2 tank level drops to L3, the no. 2 pump stops and the no. 1 pump starts to operate the steering using cylinders 1 and 2
6. Starting the no. 1 pump will ensure that the by-pass valve ‘X’ is shut, and stopping the no. 2 pump will ensure that the by-pass valve ‘Y’ is open

This ensures the operation of the steering Gear with the defective system fully isolated.