Where is the safety valve of Komatsu excavator 200-8?

We may not know much about excavators when it comes to safety valves, but we may have some impressions when it comes to overload (overflow) valves, oil drain valves or auxiliary guns. Some common problems of excavators are caused by the failure of safety valves, such as slow speed, weakness, bursting of oil pipes or hydraulic oil pipes, bending of cylinder levers, etc. Today we will solve these problems.

Not much to say, let's introduce the safety valve and its fault solution in detail. I believe everyone will gain a lot.

Understand the safety valve

The safety valve is installed on the main control valve (distributor) on one side of the drive valve stem. From the appearance, the safety valve is cylindrical, which is very similar to the main pressure relief valve. The difference lies in the adjusting thread at the top. The safety valve has one thread and the main safety valve has two threads. At the pressure set point, the pressure set point of the safety valve is higher than that of the main relief valve.

Under normal circumstances, the safety valve is not involved in the work, so the pressure measurement of the safety valve is special and cannot be measured directly with instruments. The pressure of the main safety valve needs to be raised in advance, and can only be measured after it is higher than the pressure value of the safety valve.

Working principle of safety valve

Every hydraulic circuit on the excavator has a safety valve, and every action is related to the safety valve. The safety valve is a pressure relief valve, which consists of a spring, a spring seat, a valve needle and an oil inlet at the bottom.

When high-pressure oil enters the working device and passes through the bottom oil inlet, the pressure will gradually increase and gradually overcome the compression force of the spring. When the safety valve reaches the set pressure, the spring opens completely, and the hydraulic oil enters the oil return through the valve needle, giving full play to the role of protecting the working device.

Function of safety valve

The safety valve is installed in the working oil circuit of the main control valve in order to limit the maximum pressure of the oil circuit. For example, manually adjust the pressure of the main relief valve. When the overflow pressure of the excavator exceeds the set pressure of the safety valve, the safety valve opens to release the pressure, so that the working oil circuit does not exceed the set pressure of the safety valve, and the oil circuit is safe and smooth.

Another function is that in the process of excavator construction, if heavy objects fall from the sky and hit the oil cylinder, bucket and boom, if there is no safety valve to protect the hydraulic circuit, huge hydraulic impact will burst the oil pipe, damage the valve core and seal of each control valve, and even damage the main pump, so the protection function of the safety valve is very important.

Failure caused by safety valve

The hydraulic oil pipe burst and the cylinder rod bent.

The main reason is that the safety valve has been artificially adjusted. In order to improve the overall working force of excavators, some excavators have increased the pressure settings of main safety valves and safety valves to increase the strength of excavators. However, if this is done, under the long-term high-pressure operation of the excavation, the probability of the hydraulic oil pipe bursting will increase, and even the cylinder lever will bend because it can't bear the huge pressure.

Lack of strength and slow speed

Due to the failure of the safety valve, the valve core is stuck, or the overflow port is blocked by oil, which will lead to low pressure, affect some actions, lack of power and slow action. At this point, some customers will adjust the pressure of the main relief valve, but no matter how to adjust the pressure, it will not rise. The cause of the failure is probably the safety valve, so the safety valve should be checked immediately.

Key summary

Because the performance of excavator in normal operation is not directly affected by safety valve, safety valve is often ignored in excavator. Therefore, the driver of the hunting car reminds everyone that the safety valve should also be checked during the maintenance of the excavator. Once the safety valve is found to have internal wear and other faults, it must be replaced with a new safety valve in time.

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