Daily inspection of hydraulic system of hydraulic press

Update:15 Dec 2021

Before the hydraulic transmission system of a hydraulic […]

Before the hydraulic transmission system of a hydraulic press fails, there will often be some small abnormal phenomena. Through sufficient daily maintenance, maintenance and inspection in use, some possible faults can be found and eliminated as early as possible based on these abnormal phenomena, so as to achieve the greatest possible The purpose of reducing failures.

The main content of the daily inspection is to check the status of the hydraulic pump before and after it is started and before it stops running. Daily inspections are usually carried out by relatively simple methods such as visual, auditory, and hand touch.

(1) Visual inspection before work

A large number of leaks are easy to detect, but a small amount of leaks at the tubing joints are often difficult to find. However, such a small amount of leakage is often a precursor to system failure. Therefore, the seal must be checked and cleaned frequently. The looseness of the upper hose joint is often a pre-exception symptom of mechanical failure. If you find that the hose and pipe joints are loose and cause a small amount of leakage, you should immediately tighten the joints. For example, the tightness of the thread at the connection between the piston rod of the hydraulic cylinder and the mechanical part.

(2) Inspection before starting the pump

Before starting the hydraulic pump, pay attention to whether the fuel tank is refueled according to the regulations, and the refueling amount is based on the upper limit of the level gauge. Use a thermometer to measure the oil temperature. If the oil temperature is lower than 10°C, the system should be operated in a no-load state (with the overflow valve in an unloading state) for more than 20 minutes.

(3) Pump startup and inspection after startup

When the hydraulic pump is started, use the start-stop-stop method to start, repeat several times to increase the oil temperature, and then enter normal operation after the various actuators operate flexibly. If the pump has no output during the start-up process, stop and start immediately, check the reason, and do the following checks after the pump is started.

① Cavitation inspection When the hydraulic system of the hydraulic press is working, it is necessary to observe whether the piston rod of the hydraulic cylinder is jumping during movement, whether there is leakage when the hydraulic cylinder is fully extended, and whether the hydraulic pump and overflow valve are present under heavy load Abnormal noise, if the noise is very loud, this is the most ideal time to check for cavitation.

The main cause of cavitation in the hydraulic system of a hydraulic machine is due to air suction in the suction part of the hydraulic pump. In order to prevent cavitation, all joints at the suction pipe of the hydraulic pump must be tightened to ensure the sealing of the suction pipe , If the noise cannot be removed even when these heads are tightened, the machine needs to be shut down immediately for further inspection.

②Check for overheating Another symptom of hydraulic pump failure is overheating. Cavitation will produce overheating, because when the hydraulic pressure reaches a certain temperature, it will compress the gas in the oil cavity and produce overheating. If overheating is found due to cavitation, stop immediately for inspection.

③Bubble inspection If air leaks from the suction side of the hydraulic pump, the air will enter the system and form bubbles in the oil tank. The presence of air bubbles in the hydraulic system of a hydraulic press will cause three problems: one is to cause the actuator to move unevenly, which affects the volume elastic modulus of the hydraulic oil; the other is to accelerate the oxidation of the hydraulic oil; the third is to produce cavitation, so we must especially prevent air Enter the hydraulic system of the hydraulic press. Sometimes air may seep into the hydraulic system of the hydraulic press from the fuel tank, so always check whether the oil height of the hydraulic oil in the fuel tank meets the specified requirements, whether the nozzle of the oil suction pipe is immersed below the oil surface, and maintain a sufficient immersion depth. Practical experience has proved that the oil port of the oil return pipe should be guaranteed to be less than 10cm below the lowest oil level in the oil tank.

When the system is working stably, in addition to paying attention to the oil volume, oil temperature, pressure and other issues at any time, check the working conditions of the executive components 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 defect or an abnormal phenomenon that cannot be eliminated by external adjustment, it can be disassembled for repair or replacement of parts.