1、 Causes of leakage in hydraulic system of hydraulic press
(1) Caused by design and manufacturing defects;
(2) The pipe joint is loose due to impact and vibration;
(3) Dynamic seals and mating parts wear each other (especially hydraulic cylinder);
(4) The oil temperature is too high and the rubber seal is incompatible with the hydraulic oil. The following is the combination of the above several aspects on the control of leakage measures.
2、 Control method of hydraulic system leakage control of hydraulic press
Solution 1: solutions to design and manufacturing defects
1. The selection of external matching of hydraulic components often plays a decisive role in the leakage of hydraulic system of hydraulic press. This determines that in the design of new products and the improvement of old products, the selection of cylinders, pumps, valves, seals, hydraulic accessories, etc. should be based on the principle of selecting the best from the good and selecting the low from the excellent carefully and comparatively.
2. Reasonable design of the installation surface and sealing surface: when the valve group or pipeline is fixed on the installation surface, in order to obtain a satisfactory initial seal and prevent the seal from being squeezed out of the groove and being worn, the installation surface shall be straight, the sealing surface shall be finished, the surface roughness shall be 0.8 μ m, and the flatness shall be 0.01/100 mm. There should be no radial scratches on the surface, and the pre tightening force of the connecting screw should be large enough to prevent surface separation.
3. In the process of manufacturing and transportation, the key surface should be prevented from bumping and scratching. At the same time, the assembly and debugging process should be strictly monitored to ensure the assembly quality.
4. The hidden danger of leakage of some hydraulic press hydraulic system must be eliminated.
Method 2: reduce impact and vibration
In order to reduce the leakage of the hydraulic system of hydraulic press caused by the loosening of pipe joints under impact and vibration, the following measures can be taken:
① All pipes shall be fixed with damping supports to absorb shock and vibration;
② Use low impact valve or accumulator to reduce impact;
③ Proper arrangement of pressure control valves to protect all components of the system;
④ The number of pipe joints shall be reduced as far as possible, and the pipe joints shall be welded as far as possible;
⑤ Use straight thread joint, tee joint and elbow instead of taper pipe thread joint;
⑥ Try to use oil return block instead of each piping;
⑦ According to the maximum pressure used, the torque of bolt and plug should be specified to prevent the joint surface and seal from being eroded;
⑧ Install the coupling correctly.
Three ways to reduce hydraulic seal wear
Most of the seals of the hydraulic system of the dynamic hydraulic press are designed accurately. If the seals are processed properly, installed correctly and used reasonably, they can ensure that there is no leakage for a long time. From the design point of view, designers can adopt the following measures to extend the life of dynamic seals:
1. Eliminate side load on piston rod and drive shaft seal;
2. Protect piston rod with dust ring, protective cover and rubber sleeve to prevent impurities such as abrasives and dust from entering;
3. In order to prevent the dust from accumulating in the oil, proper filter device and easy to clean oil tank are designed and selected;
4. Keep the rod and shaft speed as low as possible.
Method 4: requirements for static seals
Static seals prevent oil leakage between rigid fixed surfaces. The size and tolerance of sealing groove in hydraulic system of hydraulic press should be designed reasonably, so that the installed seal will deform to a certain extent, so as to fill the micro depression on the mating surface, and increase the internal stress of the seal to higher than the sealed pressure. When the part stiffness or bolt pre tightening force is not large enough, the mating surface will separate under the action of oil pressure, resulting in the gap or increasing the gap that may exist from the beginning due to the uneven sealing surface. With the movement of the mating surface, the static seal becomes the dynamic seal. The rough mating surface will wear the seal and the variable clearance will nibble at the seal edge.
Scheme 5: control oil temperature to prevent seal deterioration
Premature deterioration of hydraulic seal may be caused by many factors, one of which is high oil temperature. If the temperature increases by 10 ℃, the service life of the seal will be reduced by half. Therefore, it is necessary to reasonably design an efficient hydraulic system or set up a forced cooling device to keep the optimal oil temperature below 65 ℃; the construction machinery shall not exceed 80 ℃; another factor may be the compatibility between the oil used and the sealing material. The type and type of the hydraulic oil and seal shall be selected according to the operation manual or relevant manual Material to solve the compatibility problem and prolong the service life of the seal.