The maintenance of hydraulic device is the hydraulic system overhaul,the hydraulic components as a basic component of blow molding machine.Hydraulic system is mainly composed of: power components, executive components, control and adjustment components, auxiliary components and working medium five parts.The main points of maintenance and repair of hydraulic components are summarized as follows.
1.Hydraulic Components-Hydraulic pump maintenance points
(1) After the hydraulic pump is disassembled, check the wear of the internal friction pair of the pump.
(2) Remove rust and burr, and study and repair damaged parts to make the fit clearance meet the requirements.Clean all parts, then oil them for assembly.
(3) Replace seals and other parts that cannot be repaired.
(4) Performance test items:
①Air tightness test: fill the tested pump with clean gas with pressure of 0.16mpa, then immerge the pump in anti-rust solution for 3 minutes, and slightly shake it. No air leakage is allowed in the test.
②Displacement inspection test: the displacement is measured under rated speed and no-load pressure, and the value is within 95% ~ 110% of the nominal displacement.
③Volumetric efficiency test: the volumetric efficiency is measured under rated working conditions, and its value conforms to quality and other provisions.
④Overload test: there is no abnormal phenomenon when running for more than 1 minute at rated speed, 125% of rated pressure or the highest pressure.
2.Hydraulic Components-Oil filter overhaul points
(1) Disassemble the oil filter, clean the shell, cover and other parts with gasoline or kerosene, and clean the metal filter element in the following order:
Clean with gasoline or kerosene, blow with compressed air, clean with gasoline or cleaning agent, fine wash with gasoline or detergent, static.
(2) Carefully check the rust and scar conditions, and deal with them.Replace the metal core if it is damaged.
(3) If the paper filter element is to be replaced.
(4) Replacement of seals.
(5) Check the action of products with indicator needle and bypass valve.
(6) Pay attention not to scratch the filter element during assembly, and the seal should be coated with oil or lubricating oil.
3.Hydraulic Components-Pressure control valve maintenance points
(1) After disassembling the pressure control valve, check the rust, scar, wear, single-side contact, surface roughness, burr and hole dirt of the valve core and pilot valve.
(2) Check the internal body, seat surface condition.
(3) Remove rust spots and burrs of all parts, study and repair some scars of the matching parts, so that the matching gap can meet the requirements, and then carefully clean all parts, and apply lubricating oil for assembly.
(4) Replace seals and damaged parts of spring machine.
(5) Performance test items:
①Adjusting pressure characteristics: it can be adjusted from the lowest pressure to the rated pressure, and the pressure value is stable. The adjusting screw is sensitive and reliable.
②Pressure loss: the pressure loss shall not exceed the specified value or meet the service requirements at the rated flow rate.
③Pressure shimmy: the internal leakage shall not exceed the standard value under the rated pressure, and the valve cover and other places shall not have leakage phenomenon.
④Leakage: the internal leakage shall not exceed the standard value under the rated pressure, and the valve cover and other places shall not have leakage phenomenon.
4.Hydraulic Components-Direction control valve maintenance points
(1) Disassemble the directional control valve to check the wear and tear, scar and unilateral contact of the valve core.
(2) Check the valve body, valve hole sliding part of the wear, scars and skew.
(3) Check the loosening, deformation and wear of the electromagnet parts of the solenoid valve.
(4) Replace seals, springs and other damaged parts.
(5) Go out for burrs and rust marks of various parts, study and repair the scars on the matching parts, and make the matching clearance meet the requirements.Clean all parts carefully, then apply lubricating oil for assembly, and confirm the normal operation after assembly.
(6) Performance test items:
①Reversing stationarity: the reversing valve should be stable when reversing, and the reversing impact should not exceed the specified value or meet the use requirements.
②Reversing time and reset time: the reversing time of the main spool of the reversing valve should be flexible, reset quickly, and the adjusting performance of the reversing pressure and time must be good.
③Pressure loss: when passing the rated flow rate, the pressure loss shall not exceed the specified value.
④Leakage: under rated pressure, the leakage shall not exceed the specified value, and there shall be no leakage at the valve cover and other places.
⑤One-way valve to do open pressure test, the value shall not exceed the specified value.
5.Hydraulic Components-Flow control valve maintenance points
(1) Disassemble the flow control valve to check the scarring and wear of the throttle port.
(2) Check the corresponding positions of throttle and scale.
(3) Check the status of pressure compensation valve spool.
(4) Replace seals, springs and damaged parts that should not be repaired.
(5) Remove rust spots and burrs of each part to make it meet the specified requirements, then carefully clean all parts and apply oil for assembly, strictly prevent dirt from mixing into the throttle port, pay attention to the installation position of the throttle part, and confirm the normal operation after installation.
(6) Performance test items:
①Regulating flow characteristics: flexible, reliable and stable flow value can be adjusted within the range of minimum flow to maximum flow.
②Stability: for the speed regulating valve throttle to the minimum opening, measure the flow stability through the speed regulating valve, the change value should not exceed the requirements.
③Leakage: measure the internal leakage under rated pressure.The value shall not exceed the specified value and no external leakage shall be allowed at the valve cover, etc.
6.Hydraulic Components-Hydraulic cylinder maintenance points
(1) Disassemble the hydraulic cylinder to check the internal and piston rod surface scars and wear.
(2) Check the installation status of piston seals, the fastening degree of mounting screws, and the damage and causes of seals.
(3) Check the rust and pollutant adhesion status of all parts inside the cylinder.
(4) Replace seals, dust proof parts and other parts not suitable for repair.
(5) Performance test items:
①Movement stability: the hydraulic cylinder shall be subjected to full stroke reciprocating movement test under no load. The reciprocating action shall be more than 5 times, and the movement shall be normal and smooth.
②Minimum starting pressure: under no-load condition, pressure oil is injected into the rodless cavity of the tested cylinder, and the minimum starting pressure at the start of the piston rod is gradually pressurized and recorded. The minimum starting pressure is required to comply with relevant quality regulations.
③Minimum stable speed: it is required that there is no abnormal phenomenon such as “crawling” when the hydraulic cylinder moves at the minimum speed.
④Internal leakage: under the rated pressure, the leakage from the high-pressure cavity through the sealing place to the low-pressure cavity conforms to the relevant quality grading regulations.
⑤Leakage: under the condition of full load, the full stroke shall be reversed more than 20 times, and there shall be no leakage of piston rod and joint surface.
⑥Pressure test: when the rated pressure of the tested hydraulic cylinder is less than or equal to 16Mpa, the test pressure shall be 1.5 times of the rated pressure and the pressure shall be maintained for 1-5min;When the rated pressure of the tested hydraulic cylinder is greater than or equal to 16Mpa, the test pressure shall be 1.25 times of the rated pressure and the pressure shall be maintained for 2-5min.All parts must not be damaged plastic deformation and other abnormal phenomena.
⑦Buffering performance: the buffering performance test should be carried out for the hydraulic cylinder with buffering device.During the test, reciprocate according to the maximum speed required by the design, observe the buffering effect, and meet the design or use requirements.
⑧Full stroke inspection: make the piston of the tested hydraulic cylinder stay at both ends of the stroke, measure the full stroke length, and its value meets the design requirements.
The maintenance of hydraulic components is to improve efficiency, extend service life, no or less failure, and reduce maintenance costs for the purpose of the operation process.
Only correct maintenance of hydraulic components can ensure its reliable operation, good performance and maximize the benefits.
For more blow molding knowledge, please pay attention to Yankang blow molding machine blog:https://www.yankangmachine.com/category/blog/.