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Engine Valve Seat Disassembly and Reaming Method

Aug 1, 2023 | Technical Literature | 0 comments

The engine valve seat is one of the important parts in the diesel generator accessories mechanism. Its function is to connect the valve and the valve guide, so that the valve can be opened and closed smoothly. Because the valve seat is in a high temperature and high pressure environment for a long time, it is prone to wear and aging, resulting in valve failure and affecting the normal operation of the diesel generator set. Therefore, the maintenance method of the engine valve seat is very important.

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Disassembly and inspection of valve seat

1. Check the valve seat wear

Check the wear of the valve seat Before repairing the valve seat, it is first necessary to check the wear of the valve seat. Generally speaking, the degree of wear of the valve seat can be measured by visual inspection or using measuring tools, such as drawing several evenly distributed plain lines on the valve working surface with an aluminum pen, and then inserting the valve into the valve In the seat, lightly or turn it, take out the valve and observe whether the returned plain lines are cut evenly, if there are lines that are not cut, it indicates that the seal is not tight and needs to be ground. If the valve seat is severely worn, it needs to be replaced with a new one.

2. Remove the valve seat

Before removing the valve seat, the valve and valve guide need to be removed first. Then, use a special tool to remove the valve seat from the valve seat hole. When removing the valve seat, care should be taken not to damage the valve seat hole and the valve seat.

3. Clean the valve seat

After the valve seat is disassembled, the valve seat needs to be cleaned. First, soak the valve seat in the cleaning solution for a period of time, and then use a brush to clean the dirt on the surface of the valve seat. After cleaning, dry the valve seat with a clean cloth.

4. Install a new valve seat

After cleaning, you need to install a new valve seat. First, put the new valve seat into the valve seat hole, and then use a special tool to press the valve seat into the valve seat hole. When installing the valve seat, you need to pay attention to the direction and position of the valve seat to ensure that the valve seat is installed correctly.

5. Install the valve and valve guide

After installing the new valve seat, the valve and valve guide need to be reinstalled. First, put the valve into the valve hole, and then use a special tool to install the valve guide to the valve seat. When installing the valve and valve guide, it is necessary to pay attention to the direction and position of the valve and valve guide to ensure correct installation.

6. Check after installation

After installing the valve and valve guide, you need to check whether the valve gap is correct. If the valve gap is not correct, you need to adjust it. When adjusting the valve gap, you need to use special tools to make adjustments to ensure that the valve gap meets the requirements.

Valve trimming steps

If it is found that the valve seat wear is not very serious after the valve train is disassembled, it should be repaired. The reason for this is that the valve seat has burnt out after working for a long time, which leads to the leakage of the valve seal. After the valve seat is trimmed, the sealing performance of the valve can be improved. For the operation of the engine, it is better to achieve the goal of no leakage in the work process of the group gas, so as to promote the maximum output of the power of the diesel generator.

1. Select the dumpling knife guide rod

According to the inner diameter of the HuaChai valve guide, select a suitable guide rod with a larger knife, and insert it into the valve guide, so that the guide rod fits the surface of the inner hole of the valve guide.

2. Sanding hardened layer

Because there is a hardened layer on the valve seat of the diesel generator, the knife often slips when it is cut. In this case, you can use a coarse emery cloth pad under the knife for sanding, and then cut it.

3. First dumpling

Firstly put the 45″ sharp knife (use rent, thin knife depending on the situation) on the guide rod, make the key letter of the sharp knife align with the flange of the lower end surface of the sharp knife handle, and then sharpen. When sharpening, the sharp knife It should be upright, and the force of both hands should be even and stable, and it should be cut clockwise. If you return the knife counterclockwise, do not use force to prevent the blade from becoming blunt until the ablation, spots and depressions on the valve seat of the diesel generator are removed. Defects so far.

4. Rial fitting and trimming of contact surfaces

After the preliminary comparison, the matching valves that have been polished should be used for trial matching.

  • Apply red lead oil on the push-shaped working surface of the valve seat of the diesel generator, put it into the conduit and turn it for 2~3 circles (do not shoot it), then take out the valve to observe its connection. The normal requirement is that the contact surface should be in the middle and lower part of the valve working slope. The width of the intake valve is about 1.0~2.0mm, and the width of the exhaust valve is about 1.5~2.5mm. Tight fit.The contact position is correct.
  • The correct contact position between the valve and the valve seat is in the middle and lower part of the valve push-shaped working surface, and the width is 1.5-2mm. Make the contact surface move downwards. If the contact surface is lower, use a 75″ knife to cut the lower opening to move the contact surface. In the initial comparison, try to make the valve contact surface in the middle and lower part. You should try while comparing. match. In order to prolong the service life of the diesel engine valve seat and the valve, when the contact surface is 1mm away from the lower edge of the valve, the matching can be stopped.

5. Fine dumplings

Finally, use a 45° (or 30° fine-edged knife or place a fine emery cloth on the knife to finely grind) the working surface of the valve seat of the diesel generator to improve the smoothness of the contact surface, and finally check with red lead oil , valve with
The contact surface of the valve seat of the diesel generator should be an uninterrupted annular belt. It should be pointed out that the above methods and requirements are only basic, and should be handled flexibly according to the specific conditions of the valve seat of the diesel generator during the comparison. During maintenance, it is sometimes encountered that the width and height of the valve seat of the diesel generator is larger than the contact surface of the working day, and if 15 is used at this time. When the knife is more catchy, there will be a new contradiction of the variable volume of the contact surface. If in order to solve this new contradiction, when using 45° (or 30°) for comparison, the diameter of the valve seat of the diesel generator will be enlarged, which will cause the contact surface to move upward. Therefore, in this case, Although the contact surface is too high, as long as the contact surface is still far from the working surface of the valve
If it is more than 1mm, it is allowed to be used, otherwise the valve must be replaced or the valve seat of the diesel generator must be re-fitted. According to the requirements, it is better to have the contact surface lower in the middle range, but in the repair, sometimes due to the technical limitations of the seat and the valve, it is not necessarily necessary to consider future repairs, and it is generally higher than 100 and lower. It is also possible to work within 05m”. It should also be explained here that the angle of the push-shaped working surface of the valve, although the intake and exhaust valves of most models are 45, but some are 30, so when cutting You must not make a mistake when laughing at the valve seat of the oil generator.

Precautions

1. Slight ablation

When it is found that it is a slight burnt situation, it can be handled by grinding. Use finer abrasive sand to wipe the working surface of the valve, and grind it with a grinder or by hand. The working principle is to use the valve to rotate on the seat circumference The abrasive sand removes the ablated part and restores it to the original smooth contact surface to achieve a tight fit and achieve the purpose of sealing.

2. Large ablation area

When the ablation area is found to be large, it is necessary to use a valve reamer to repair the valve seat ring. The purpose is to remove the burnt area. , Grinding after finishing.

3. The ablation area is too large

When it is found that the ablation area is too large, the grinding and cutting can no longer be repaired, then the valve seat ring must be replaced to complete the repair (this situation depends on the engine, some cars do not have valve seat rings) , the valve directly acts on the cylinder head, in this case the cylinder head must be replaced,) that is, after replacing the new seat ring (cylinder head) and valve, sometimes simple grinding is required to check the airtightness.

Summary : In summary, the maintenance methods of the engine valve seat include checking the wear of the valve seat, dismantling the valve seat, cleaning the valve seat, installing a new valve seat, installing the valve and guide, and repairing the valve. When repairing the valve seat, you need to use special tools and cleaning fluid to ensure correct and safe operation. At the same time, you need to pay attention to the direction and position of the valve seat to ensure correct installation. Correct maintenance methods can effectively prolong the service life of the valve seat , to ensure the normal operation of the engine.

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