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Common faults of testing machine

Date:2019/7/25 473 times Size:Large medium Small

Common faults: poor sensitivity of dial pointer, midway stop after unloading, or frequent change of zero position. There are many reasons for this phenomenon.




1. The pulley and its track on the gear bar are dusty and rusty. At this time need to remove clean, and then add a little watch oil.


2. The pointer shaft is dirty and should be cleaned.


3. There is contact between the toothed bar pressing plate and the toothed bar, which should be adjusted loose.


4. The oil return condition of buffer is poor, so it should be adjusted or cleaned. (of a bend blocked)


5. The belt on the force measuring piston falls off or is too loose (making the piston unable to run at a constant speed).


6. If the friction force of the force measuring piston increases or gets stuck in the oil cylinder, apply chrome oxide grinding paste to grind it until it is normal.


7. There are obstacles in the process of lifting the pendulum, or the pendulum shaft is too dirty or rusted, which makes the pointer return to zero and change greatly.


Common faults: when loading, sometimes the maximum load can not be loaded or unloaded during loading. This kind of fault often occurs, and there are many reasons.


1. The viscosity of oil used is too low (there is oil flowing out from the oil return pipe of oil delivery valve during loading). Generally, mineral oil with medium viscosity is used, without water, acid and other mixture, which does not decompose at room temperature and has constant consistency. If necessary, it can be measured with viscometer. If the oil is not used properly, the valve and oil circuit will be blocked, and vibration or pipeline leakage may be caused. It is better to use oil according to the instruction.


2. There is serious oil leakage in the oil pressure system. The oil leakage in the oil circuit system generally occurs at the connection of the buffer valve, oil return valve, oil delivery valve, oil pump and pipeline. After adding gasket, tighten the screw. If the sealing gasket is broken, it must be disassembled here and replaced with a new one. The gasket shall be made of red copper or aluminum alloy.


3. Insufficient oil in oil tank. When the load reaches a certain level, the oil return pipe of the oil delivery valve has "poof" and "poof" sound, and there is little oil output and bubbles. When the load can not rise again, there is no oil flowing out of the oil return pipe. Troubleshooting: add oil to the oil tank of the testing machine until the oil level reaches half of the sight glass.


4. The oil collector of the oil pump is not pressed on the pump body. In this way, each loading can only reach a certain load, and the load can not rise again, and there is no oil flowing out of the oil return pipe of the oil delivery valve. Troubleshooting: use a wrench to tighten the fixed screw at the rear end of the oil pump. If there is still a problem, remove the oil collector and add a gasket between the oil collector and the pump body.


5. The clearance between working piston and oil cylinder is too large, and there is too much oil spill in the clearance, which can be seen from the oil spill outlet. The method is to thicken the viscosity of the oil. If the problem can not be solved, the piston and oil cylinder should be replaced in the factory after precise measurement.


6. The clearance between the force measuring piston and the force measuring cylinder is large, which can be seen from the lower part of the force measuring cylinder when the tonnage is high. Normally, there is no oil drop or intermittent oil drop when the tonnage is high. If the oil flows out in a linear shape, it means that the force measuring piston should be replaced. When observing the oil leakage, pay attention to the difference between the joint oil leakage and the cylinder plug oil leakage, and do not make a wrong judgment due to wrong looking.


7. The piston and piston sleeve in the oil delivery valve are damaged or the spring becomes soft. In this way, the load that can be achieved by each loading is basically unchanged, and the noise of the oil delivery valve is large. When the load can no longer rise, the oil output of the oil return pipe of the oil delivery valve is large. Take out and grind the piston and piston sleeve. If the damage is serious, replace the spring.


8. The pressure stabilizing spring stiffness of oil delivery valve is low or the cavity of throttle needle is blocked. Main performance: each load can only reach a certain load, when the load can not rise again, the oil output of oil return pipe is large. Troubleshooting: replace the pressure spring with appropriate stiffness or clean the dirt.


9. The gap between the damping needle and the damping hole of the oil delivery valve is too small. Main performance: each load can only reach a certain load, when the load can no longer rise, the oil output of oil return pipe of oil delivery valve is large. Exclusion method: take out the damping needle, and file part of it with a file along the axial direction of the damping needle.


10. The belt that drives the oil pump is loose and has slipping phenomenon. After loading to a certain load, it can not rise again, no oil flows out of the oil return pipe of the oil delivery valve, and the oil pump has no working sound. Troubleshooting: loosen the motor fixing screw, adjust the position, make the belt taut, and then tighten the motor fixing screw. If the belt deformation is too large, it must be replaced with a new belt.


11. The plunger of oil pump is corroded. Main performance: in the loading process, the oil output of oil return pipe of oil delivery valve is discontinuous or fluctuates. When a certain load cannot be increased, no oil will flow out of the oil return pipe. Troubleshooting: take out the plunger and re polish it.


12. When the maximum load of the testing machine with safety valve exceeds 3% - 5%, it can be opened automatically to ensure that the testing machine will not be damaged due to overload. When the safety valve is not adjusted properly, or the valve tip and hole are not tightly closed, the pressure will not be high. The adjustment method is to dismantle the adjusting screw of the safety valve, check the damage of the parts, and replace it. If the overload is too much, screw the screw downward, and vice versa Spin up.


Common faults: when doing tensile test, the fracture of the sample is always broken on both sides. The reason for this phenomenon should first consider whether the main part of the testing machine is installed vertically or not. If this reason is eliminated, it can be eliminated from the following three aspects.


1. If the jaw is not in the right position during clamping, the specimen shall be clamped symmetrically according to the requirements.


2. The quality of the jaw is poor and the teeth are damaged, which not only affects the different center of the jaw, but also makes the sample slip during the test, making it difficult to identify the yield point. The jaw should be replaced at this time.


3. The lifting guide wheel is not adjusted properly, so that the upper and lower jaws are not concentric. A test rod shall be processed. After the upper and lower jaws are tightened, measure with a dial indicator based on two force columns until the adjustment is qualified.


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