Before the failure of the hydraulic transmission system of the hydraulic press, there are often some small abnormal phenomena, and through sufficient daily maintenance, maintenance and inspection in use, some possible faults can be found and eliminated early according to these abnormal phenomena, in order to minimize the purpose of failure.
The main content of daily inspection is to check the state of the hydraulic pump before starting, after and before stopping operation. Daily examination is usually carried out by visual, auditory and hand touch and other relatively simple methods.
(1) Appearance inspection before work
A large number of leaks are easy to detect, but a small amount of leakage at the tubing joint is often not easy to be found, but this small amount of leakage phenomenon is often a precursor of system failure, so for the seal must be regularly checked and cleaned, hydraulic machinery on the hose joint loosening is often a precursor of mechanical failure. If the joints of hoses and pipes are found to be loose and produce a small amount of leakage, the joints should be tightened immediately. For example, the tightness of the thread at the connection between the piston rod of the hydraulic cylinder and the mechanical part.
(2) Check the pump before starting
Before starting the hydraulic pump, pay attention to whether the tank is refueled according to the regulations, and the amount of refueling is based on the upper limit of the liquid level gauge. Use a thermometer to measure the oil temperature. If the oil temperature is 10 ° C, the system should be operated for more than 20 minutes without being lower than the load (so that the relief valve is in the unloading state).
(3) Check the pump starting and starting
The hydraulic pump starts with the start-stop method when starting, repeat several times to make the oil temperature rise, and then enter normal operation after the operation of each actuator is flexible. During the start process, if the pump has no output, stop the start immediately and check the cause. After the pump starts, the following checks need to be done:
When the hydraulic system of the hydraulic press is working, it is necessary to observe whether the piston rod of the hydraulic cylinder is pulsating during movement, there is no leakage when the hydraulic cylinder is all stretched out, and there is no abnormal noise in the hydraulic pump and relief valve when the heavy load is heavy, if the noise is very large, this is the ideal time to check the cavitation.
The main reason for the cavitation of the hydraulic system is that there is air suction in the oil suction part of the hydraulic pump. In order to eliminate the cavitation phenomenon, it is necessary to tighten the joints of the hydraulic pump suction pipe to ensure the sealing of the suction pipe. If the heads are tightened, the noise still cannot be removed, it is necessary to stop the machine immediately for further inspection.
The other symptom of the failure of the hydraulic pump is overheating, cavitation will produce overheating, because when the hydraulic press is hot to a certain temperature, it will compress the gas in the oil hole and produce overheating. If it is found that the overheating caused by cavitation should be stopped immediately for inspection.
③ Check of bubbles If the suction side of the hydraulic pump leaks air, the air will enter the system and form bubbles in the tank. The existence of bubbles in hydraulic system of hydraulic press will cause three problems: first, it will cause the movement of actuator elements to be unstable and affect the bulk elastic modulus of hydraulic oil; The second is to accelerate the oxidation of hydraulic oil; Third, cavitation is produced, so it is necessary to prevent air from entering the hydraulic system of the hydraulic press. Sometimes air may also penetrate from the tank into the hydraulic system of the hydraulic press, so it is necessary to often check whether the oil temperature height of the hydraulic oil in the tank meets the specified requirements, whether the nozzle of the suction pipe is submerged below the oil level, and to maintain a sufficient depth of immersion. Practical experience has proved that the oil port of the return pipe should be guaranteed to be less than 10cm below the height of the low oil level in the tank.
When the system is working stably, in addition to paying attention to the oil amount, oil temperature, pressure and other problems at any time, it is also necessary to check the working condition of the actuator and control components, and pay attention to the oil leakage and vibration of the entire system. After the system has been used for a period of time, if there is a bad or abnormal phenomenon, the external adjustment method cannot be excluded, it can be dismantled for repair or replacement of parts.
