Five-step test, the old driver teaches you to choose a second hand excavator
How to choose the right second hand excavator? When choosing a second hand excavator, it is necessary to test it on site. The question arises. How can we quickly identify the real situation of the second hand excavator? Many Jiayou actually don't know where to start the test. Today, let's take a look at the five-step test method summarized by the old driver.
Step 1: Idle Branch Combination (Heart Part - Engine Hydraulic)
Small digging idle bulldozer: Put the throttle to the lowest level, idle bulldozer, and small throttle holdup car to see the turntable and exhaust situation. For small excavations weighing less than 10 tons. If the shovel idles easily to lift the roof and the engine turns to 100-200 are normal, then the performance is basically good. On the contrary, if the equipment is easily suffocated or rotated beyond 200 rpm, the engine jitters badly, which indicates that the force is not very large, and the pressure of the engine and the pump does not match.
Idle-speed big-arm branch truck: put the upper and lower arms of the excavator at the lowest level, turn the bucket outward, touch the ground with the horse head, and support the truck at the top of the horse head to see if it can be lifted (Note: Xiaodug Xiaosong 56, Kubota series can not be supported because of the design of the truck itself). The same with bulldozer forklift truck, as a large excavation without bulldozer, can cooperate with this action, the force of the big arm forklift is very large, the forklift watches the engine turntable at the same time, the idle speed of the large excavation is usually 1000 revolutions, and the turning of the throttle truck is between 100 and 200. If idle speed cannot be supported, the engine speed exceeds a wide range or is choked out, which indicates that the engine power of the excavator does not match the pressure of the large pump, and there is serious wear and tear. Performance can be judged accordingly.
Idle limit action traffic jam: the upper and lower arms are lifted to the highest level, and the bucket receives the lowest level. Idle-speed traffic jam once and big throttle traffic jam once. Observe engine turn-around and exhaust smoke color at the same time.
Small digger: idle standard 900 rpm, turn 100-200 normal, maximum throttle turn no more than 300; big dig: idle 1000 rpm, turn 100-200 normal (200 rpm: any engine with good performance in high speed overflow, turn less than 200 rpm).
The above three points mainly determine whether the engine power matches the pressure of the hydraulic pump and whether the oil circuit is smooth. The three movements need to be combined and interpolated to operate. All of them refer to turning and holding up. In the actual excavator operation process, if these data and conditions are not up to the standard, the equipment will turn around when digging hard things, or even be suppressed, commonly known as holding up the car. If the performance is not good, it can not be competent for long-term excavation work. .
Step 2: Wear clearance of each part (joint part - working device clearance)
Gap wear of working device lifts the excavated arm to the horizontal position and rotates left and right. Three main positions are observed:
(1)The gap between the head of the horse and the arm;
(2) The gap between the forearm and the arm;
(3)The clearance between the upper arm and the main frame.
These two gaps are normal if they are not very large. Because we know that the normal excavator work, iron and iron friction must have wear, mainly depends on the gap between the arm and the main frame. If the gap is large, the wear and tear of the car will be serious and the maintenance will not be good. Or it can have a big impact if it's carried through the crushing hammer.
Cylinder clearance wear: the upper and lower arms of the bucket flat and gently lift the car, look at the upper arm, two arms, bucket several cylinder sleeve clearance. Small clearance makes wear lighter and lubrication better (butter beats more frequently). If the clearance is large, the wear is serious, the lubrication is poor (not diligent in maintenance), or the hammer is more.
Whether it is the arm or the cylinder, these are more important working devices. Through the combination of several actions, the maintenance status and specific working intensity of the excavator can be analyzed.
Step 3: Test the clearance and deceleration of slewing disk (waist and limb part - X frame of slewing deceleration disk)
Test the upper and lower clearance of the plate: lift the bulldozer shovel and place the excavator in a horizontal position. Lift up your arms and magnify them. Increase frequency and speed, make the upper and lower parts of the excavator shake, people crouch in the middle of the plate to observe the gap between the upper and lower parts of the plate: if the gap is too large, it means that the wear of the car's plate is relatively serious, the excavator that breaks the hammer for a long time is the most obvious, because the pressure transmission of the hammer on the pump and the violent vibration of the hammer will lead to. The gap between the top and bottom of the market is too large. The serious situation will affect the normal work of the excavator and need to be repaired. (Examples: For example, for some municipal greening projects, land leveling requirements are very high. When working, the steering cab will be shaken by the violent shaking of the whole plate. When the driver sits in the cab and operates the pilot handle, it will shake slightly. It is difficult to find the leveling. It is suggested that the dial bearing should be measured by a dial indicator.
Test the clearance between the left and right of the large plate: idle, gently click on the rotation, if the excavator immediately rotates, it proves that the clearance is very small. On the contrary, there will be a few seconds of bluntness after the point goes down, indicating that the gear wear is serious, the gear between the decelerating gears can not hold or the clearance between the gears is too large to bite; the digger arm can also be raised, the two arms are vertical to the ground, and the clearance can be looked back slightly.
Testing whether the rotary brake is out of range: idle speed, maximum throttle and minimum throttle are tested separately. In the process of left and right rotation, stop suddenly to see if the excavator rotation can stop. Usually the excavator has a certain brake protection when the rotation stops, with a small buffer. But if the deceleration is beyond control, it will affect the work. For example, if the excavator is engaged in loading or throwing earth, excessive deceleration and overrun will throw the material out of the prescribed range. Increase the difficulty of the driver's operation of the excavator.
Three action combinations listen to motor and speed reduction whether there is abnormal noise: do the above actions, but also listen to motor and rotary deceleration whether there is abnormal noise, there is stuck.
Rotary deceleration and back-loading motor are very important as the waist part of excavator, and the cost of maintenance is very high. The performance tests of the above four actions are embodied in the detection process. For example, the measurement of the upper and lower clearance of the large plate will be measured by a percentile meter, and the accuracy will be several millimeters to zero.
Step 4: Chassis test (lower limb foot part - four wheels)
Whether idle unilateral walking is strong or not: idle moving the left walking control handle, see if the original position can be turned, and test the right side. This action can not only test whether the walking motor is strong, but also test whether the power matches between the engine and the walking motor. If in situ immobilization or throttling indicates power mismatch, or motor problems.
Whether walking is deviated: The excavator is placed in a horizontal position, pushing the walking rod to see if it is walking in a straight line. If you just walk, the deviation indicates that the wear degree of the motor on both sides is not the same or the flow rate of the pump valve to the two motors is not the same. Serious conditions require maintenance.
Walking speed: commonly known as the tortoise and rabbit gear, adjusting by holding the switch during walking. For example, under special working conditions, the excavator needs to move in fast gear. There is no fast or slow gear that can affect the speed and efficiency of work.
Inspection of chassis vulnerable parts: After the above three actions, support the car with the arm and bulldozer, and watch the chassis parts wear and tear of chain plate, chain rib, chain bone (chain joint), supporting wheel, drag chain wheel, driving gear, etc. Close the key door and keep the branch car in good condition. At the same time, you can check whether several cylinders are relieved.
Step 5: Motion Matching Degree: (Brain Part - Main Control Valve)
The degree of motion matching is commonly known as work action. We try to make the following several action combinations.
Can demonstrate a set of loading action (digging bucket, arms, rotation combination to see whether the work is smooth);
Act while walking (do basic movements in walking mode to see if the stuck is serious);
Rotary overhead tray (rotary combination of arms and arms).
Through this series of action combination, we can judge whether the car action matches and whether the main valve is stuck. At the same time, the sensitivity of each action can be considered side by side. Engine power, flow rate of hydraulic pump, walking motor, deceleration and rotary motor deceleration can be connected, and the performance of excavator can be judged comprehensively.
