Marine gearbox daily maintenance and case sharing

By Ruby December 21st, 2022 1379 views

Gearbox---is one of the cores of the power transmission of the ship, and it is an indispensable equipment for every ship. The marine gearbox has the functions of inversion, clutching, deceleration and bearing the thrust of the propeller, and is matched with the main engine to form a marine power propulsion system. As shown below:

After the new gearbox runs for 50 hours for the first time, the filter element of the oil filter should be cleaned and replaced with a new clean oil. Refer to the following:

The maintenance of each working day is carried out according to item No. 1.

The maintenance of every 1000 hours is carried out according to item No. 2.

The maintenance every 5000 hours is carried out according to item No. 3.

Every 10,000 hours of maintenance is carried out according to item No. 4.

Number	Item	No.1	No.2	No.3	No.4
1	Check the gearbox oil level	√
2	Clean the outside of the gearbox	√
3	Check for oil and water leaks	√
4	Check for abnormal noise	√
5	Clean the filter		√
6	Cleaning hydraulic control components		√
7	Check the oil seal ring at the oil inlet		√
8	Check the installation accuracy of the input coupling		√
9	Check the output coupling installation accuracy and connecting screws		√
10	Remove top cover, crank check gear and clutch		√
11	Check and change oil			√
12	Check the oil pump			√
13	Check and clean cooler			√
14	Dismantling and checking the output skeleton rubber seal			√
15	Check friction plates and seals			√
16	Disassemble the case, check and replace the bearings everywhere				√
17	Clean all parts of the gearbox and oil pipes				√

Case 1
As shown in the figure, the handle of the hydraulic control part is not in place when the platoon is closed, and the front and rear gears are in a semi-clutch state when they are in the working stat.
The piston cannot be tightly pressed by oil pressure and the transmission capacity cannot be normal. In the half-clutch state, the gap between the friction plates is too large and the friction plates and the piston cannot be compressed, resulting in easy burnout of the friction plates.

Case 2
As shown in the picture is an essential tail shaft for every boat. The structure of the tail shaft in the above picture is a ball bearing. The user uses a crowbar to pry the tail shaft and find that there is an abnormal noise. The abnormal sound is not necessarily the sound of the gearbox itself, but is often caused by external factors. For example, the installation is not standardized, including the radial jump that does not reach the specification tolerance range of the gearbox installation, and the propeller is entangled with foreign objects and causes excessive resistance will make a strange noise.
The method to check the source of abnormal noise is: first remove the tail shaft screw, start the gearbox under no load, and check whether the abnormal noise comes from the gearbox. In the case of excluding the gearbox, it is suspected that the tail shaft is worn or the idle speed of the diesel engine is not enough.

Project

Reason

Method of exclusion

Gearbox Vibration

1. The installation accuracy is too low

2. The input high elastic coupling is damaged

3. Input and output coupling bolts or box bracket bolts are loose

4. Resonance

1. Correct the installation according to the requirements of the manual

2. Replace the coupling

3. Tighten the bolts

4. Avoid resonance speed

The oil pump is not on oil or the oil pressure is too low or the oil pressure is unstable

1. The oil pump or transition sleeve is damaged

2. The oil level is too low or the oil suction seal is not good

3. The oil seal ring at the oil inlet is damaged

4. Oil pressure gauge is damaged

1. Replace the oil pump or transition sleeve

2. Add oil or replace the sealing ring to tighten the joint

3. Replace the oil seal ring

4. Replace the oil pressure gauge

The working pressure cannot rise to the specified value after connecting and discharging

1. The time delay orifice in the hydraulic control part (Q06) is blocked

2. The piston is stuck in the hydraulic control part

1.Clear the orifice

2.Clean and repair the control valve

clutch slip

1. The working oil pressure does not rise after the oil pressure is too low

2. The friction plate wears excessively, and the flatness exceeds the range

3. The oil circuit is blocked or the oil seal ring is damaged

1. According to item 2 and item 3

2. Replace the friction plate

3. Check the oil circuit and replace the oil seal ring

Excessive belt torque

1. The friction disc is seriously warped

2. Improper use of oil

1.Replace the friction plate

2. Select oil according to technical specifications

Oil temperature is too high

1. The cooler is blocked or the cooling water flow is not enough

2. The friction plate sliding plate heats up

3. The rotating parts such as bearings and oil seal rings are damaged and heated

4. The lubricating oil pressure is too high

5. Oil aging

1. Clean the cooler and increase the flow of cold water

2. According to Article 4

3. Disassemble and inspect, replace the corresponding parts

4. Appropriately reduce

5. Change the oil

Oil and water leakage

1. Damaged seals

2. The sealing surface is damaged or contains debris

3. The bolts on the joint surface are loose

1. Replace the seal

2. Repair the seals

3. Tighten the screws

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