Today, I will show you how to test the hydraulic system to identify the quality of the second-hand excavator.


1.Try This Action

There are all kinds of single movements here. Start from the bottom, first push the shovel, do the top and bottom of the bulldozer, don't touch the structure when you look at it, or you can't reach the end, then try to push the shovel, you can jack up the whole machine. Stay for a few minutes to see if there is an automatic drop if there is a leak. In the cylinder or leak into the short tube; try again, before entering about 10 meters, then back about 10 meters, at the same time see if there is obvious deviation, if there is obvious deviation, the oil path is uneven, need to be repaired, then one side, before and after Walk and see if you can succeed. In general, when the engine is at medium speed, it should be able to walk on one side. (The idling speed cannot be unidirectional walking is common and is generally not included in the fault range). Try the rotation again. The trial transfer operation should be divided into fast forward and slow turn. When the operation is slow, the rotation reaction is too slow or too fast, too slow means that the pilot handle is not rotated by one-third of the stroke. Excessive movement means that the pilot handle starts to move slightly, the swinging motion starts immediately, the reaction is too fast, and the braking performance is also tested. After the handle stops working, the rotary motion should be rotated again. Some brake performance is poor, may have to turn 180 degrees to stop, this is the problem, to deal with, personally think that the second-hand excavator's brake range is less than 45 degrees, are qualified; try the bucket, stick, boom movement, The speed is not strict, it is generally felt by hand, but can be provided for reference here: Take Yuchai's YC230-8 as an example, the stick sticks out and takes the entire journey for about 3 seconds, the stick sticks out and takes Take the entire journey for about 4.5 seconds, the boom rises or falls from the lowest to the last, about 5 seconds. If the action is too fast or too fast, the general machine will directly feel it. low. Too fast and too slow are problems. Too slow to affect efficiency, too fast to damage the machine, should be repaired, the value will drop;

2.Try To Seal

All the actions of the bulldozer can be tried, but the place where the walking is difficult can only be tested on the ramp. The parking lot stopped for half an hour on a slope of about 20-30 degrees. If the running motor has an internal leak or other problem, it will automatically slide. Down, turn the test brake angle, try to seal other working devices: turn the work device to the other direction of the dozer blade, the top of the dozer blade, the working device jack up, pay attention to the force of each cylinder, and then fill the air, If there is no machine with a dozer blade, dig a bu. A bucket of mud (or something like a weight), the bucket is finished, the stick will reach the end, the boom will reach the highest point (or higher), set it aside, then go indoors to drink tea, wait for half Hours, then see which cylinder's stroke varies greatly. I personally think that an excavator with thousands of hours of work usually has a change of 10 cm or less after half an hour. If there are multiple internal leaks, they need to be processed. If there is an internal leak, the value will drop again;

3.Measuring Pressure

This is the key, and it is difficult to do because the non-professional second-hand excavator evaluation host does not necessarily have a pressure gauge and pressure measuring connector when looking at the machine. Can only use the method of point 2 above to jack up, feeling no power. To estimate that the hydraulic system is not enough, if each action is to measure the professional two excavator evaluation, the pump pressure, pilot pressure and return pressure, the pump pressure is not enough, the strength is not enough, the pilot hydraulic pressure may cause slow movement. If the return pressure is too high, the temperature measurement is likely to rise. If the pressure is too small, insufficient oil supply will affect the work of the oil-filled parts. For example, the pumping pressure of a rotary motor may vary depending on the model size, which is typically 13.5 tons. The above models need about 31.5Mpa, and the following models are 16-27MPa. According to the model size, the pilot pressure is generally 3.5Mpa-4Mpa, and the return pressure is generally 0.3Mpa-0.5Mpa. Need to be repaired.