Comparison of wear between intake and exhaust valves of diesel engines

Due to the high-temperature and high-pressure exhaust gas discharged from the exhaust valve, the working conditions of the exhaust valve and seat are quite harsh. Generally, it is believed that their wear rate is faster than that of the intake valve and seat. In fact, the opposite is true. In our work, we have found that on many models, the wear of the intake valve and seat is faster than that of the exhaust valve and seat.

The degree of wear varies with different working environments

Most large-scale construction machinery powered by diesel engines operates outdoors. Although they are equipped with air filters, due to the presence of a considerable amount of dust and sand in the air, some of it is always sucked into the cylinder, causing the intake valves and seats to be frequently eroded by hard sand and constantly worn. Especially when the filter element of the air filter is damaged or the intake pipe is not tightly sealed, the wear rate will accelerate. However, the air inhaled by the diesel engine is compressed in the cylinder and its temperature rises (500-700℃), causing the diesel mist sprayed at the right time to ignite spontaneously. The expansion of the gas pushes the piston through two strokes to complete one working cycle. Some of the sand grains soften at high temperatures, while others sink into the cylinder. As a result, the wear on the exhaust valve and seat is relatively much less. As for Marine diesel engines or indoor fixed operation diesel generator sets, due to the clean environment and low dust content in the air, the wear rate of their intake valves and seats is slower.

2. The degree of wear varies depending on the materials used in the production

Most exhaust valves and seats are made of heat-resistant alloys or alloy cast iron (for some imported diesel engines, such as those produced by Caterpillar in the United States, the working surface of the exhaust valve is also inlaid with high-performance wear-resistant materials). Therefore, in terms of material and hardness, they are better than intake valves and seats, and their wear rate is slower than that of intake valves and seats.

To prevent premature wear of the intake valve and seat, it is necessary to strictly follow the provisions of the user manual to regularly inspect the air filter, and replace the damaged filter element and the failed rubber gasket in a timely manner. It is essential to keep the intake pipe sealed and clean to prevent dust and sand from directly entering the cylinder without filtration, which will accelerate the wear of the intake valve and seat. This will also aggravate the cylinder liner piston assembly and significantly shorten the service life of the diesel engine