Kingplas - Plastic blow molding machine manfacturer
Maintenance and troubleshooting of hydraulic servo system of hollow blow molding machine
Hollow blow molding machine hydraulic servo system is a hydraulic system with high-precision technical requirements, mainly composed of electro-hydraulic servo valves, relief valves, check valves, inlet and return filters, accumulators, hydraulic manifolds, high-pressure hydraulics Pump and motor, oil cooler, fuel tank and other components.
The maintenance and maintenance of the hydraulic servo system requires more professional technical knowledge and skills. The repair of some parts, such as electro-hydraulic servo valves, requires professional knowledge and skills, and requires the use of professional testing equipment and machinery. high. Therefore, large hollow blow molding machine equipment manufacturers need to have sufficient knowledge and sufficient technical preparations to maintain the hydraulic servo system in order to ensure the long-term stable operation of the hydraulic servo system.
In the long-term operation of a large-scale hollow blow molding machine, in addition to the design and manufacturing factors, the stable operation of the hydraulic servo system requires attention to the following aspects:
1.Ensure the operating quality of hydraulic oil in the hydraulic servo system
The operating quality of hydraulic servo system hydraulic oil is much higher than that of other hydraulic systems. The hydraulic servo system of a large-scale hollow blow molding machine runs continuously for a long period of time, and can generally run continuously for 3-6 months. Therefore, it is of great practical and economic significance to ensure the operating quality of the hydraulic servo system oil.
(1) Control of hydraulic oil temperature During the continuous operation of the hydraulic servo system, the temperature of the hydraulic oil will be affected by various factors such as climate, operating conditions, and the temperature of the cooling water. According to the introduction of the relevant sections of some hydraulic design manuals, the operating temperature of the hydraulic oil is preferably between 25 ~ 80 ° C. However, from the long-term use of large hollow blow molding machines, it is found that the temperature control interval of hydraulic oil in the hydraulic servo system is smaller, and the operating temperature of the hydraulic oil is preferably controlled between 25 ~ 40 ° C. When the temperature of the hydraulic oil is in this range, the servo valve, hydraulic pump, accumulator, filter and other components will operate in a relatively good state, which can ensure the stable operation of the hydraulic servo system. If the hydraulic servo system is operated at oil temperature above 55 ℃ for a long time, the following problems may occur:
1) Accelerate the aging of hydraulic oil. Hydraulic oil will accelerate the oxidative deterioration process due to the rise in oil temperature.
2) After the hydraulic deterioration, it is easy to combine with some small particles and fine fibers washed out in the hydraulic servo system, resulting in strong adhesion dirt. These dirt may be deposited on the spool, control orifice, filter element, etc. of the servo valve, which will hinder the operation of the spool, block the control orifice, and reduce the oil passing area of the filter element, which will cause the malfunction or failure of the servo valve.
3) The temperature rise of the hydraulic oil will directly cause the viscosity of the oil to drop, and the self-lubricating balance inside the servo hydraulic pump will be broken, which will aggravate the wear of the hydraulic pump and cause it to fail in advance, and it will also cause the internal wear of other parts. Exacerbation causes premature damage.
4) Accelerate the aging rate of various types of seals of parts and components, especially the seals of PU materials may be faster. Due to the decline of various sealing properties, hydraulic oil leakage will be caused, which will easily cause environmental pollution of the oil and increase the cost of maintenance and oil replacement.
In order to ensure the stable operating temperature of hydraulic oil in the hydraulic servo system, more work can be done on the cooling efficiency of the oil cooler of the hydraulic servo system. Appropriately reducing the temperature of the cooling water and installing an automatic control valve for the cooling water inlet water, and appropriately increasing the heat exchange area of the oil cooler are all methods that can control the operating temperature of the servo hydraulic oil. In the case of high temperature at the production site, it is particularly necessary to pay attention to the fluctuation and rise of the temperature of the hydraulic oil in the hydraulic servo system. When the oil temperature is too high, effective and effective measures need to be taken to improve it.
(2) Control of hydraulic oil moisture Because most hydraulic servo systems are designed as open systems, the moisture in the surrounding air can be exchanged into the hydraulic oil through an air filter installed in the oil tank. In addition, if the oil cooler is not well sealed, the cooling water may penetrate into the hydraulic oil; if the oil tank of the hydraulic servo system is not well designed, the water during normal cleaning may leak into the oil tank. After the hydraulic oil is added to the water, the quality of the oil will drop quickly, and a foamy liquid will be formed, which will directly affect the operation of the servo valve, cause the quality of the plastic parison to be reduced, and affect the smooth production of the product.
If the oil cooler leaks or seeps in other places during the normal inspection, it needs to be treated in time. If the humidity at the production site is too high, you can take measures to prevent the operating temperature of the hydraulic oil from being too low, that is, to control the oil temperature at 30-40 ° C. In this way, it is possible to evaporate and remove moisture mixed from the air by the temperature of the oil itself.
(3) Control of hydraulic oil pollution For the hydraulic servo system with better sealing, the pollution of hydraulic oil mainly comes from two aspects. The first aspect is the metal wear particles of various parts and some fine particles attached to the parts in the system, which are mixed into the oil under the long-term flushing of the hydraulic oil. Within the first 1-2 years of the new equipment's use This type of pollution accounts for a large proportion; the second aspect is the aging and deterioration of the oil, which is easy to generate carbides. They are combined with the fine particles in the oil, which easily block the small pores in the servo valve and directly affect the servo valve. Works fine.
In order to reduce the impact of oil pollution on the hydraulic servo system, the filter elements of the oil inlet and outlet filters of the hydraulic servo system should be regularly replaced, the filter elements of the precision filters of the servo valve should be regularly flushed or replaced, and the oil of the hydraulic servo system should be regularly checked. Whether the liquid meets the quality requirements (generally checked regularly every year). The oil that does not meet the requirements of the hydraulic servo system needs to be replaced in time. The oil must be changed in accordance with the relevant operating procedures.
(4) Selection of hydraulic oil For the hydraulic servo system, the quality of the hydraulic oil is a key factor that affects whether the servo hydraulic system can be used normally. In the use, it is absolutely not allowed to choose the secondary refined oil as the servo. As the hydraulic oil, anti-wear hydraulic oil with a better brand must be selected, so as to effectively ensure the long-term stable operation of the servo hydraulic system.
2. Keep the hydraulic servo system clean
Although the hydraulic servo system is generally designed as a relatively closed system, pollutants outside the system still easily enter the oil through the pores of the filter element, causing hydraulic oil pollution. Therefore, in the usual maintenance and maintenance, long-term attention needs to be kept to keep the hydraulic servo system clean.
3. Precautions for maintenance of hydraulic servo system
1) Because the operation of the hydraulic servo system requires a highly clean hydraulic environment, special attention must be paid to the cleanliness of the surrounding environment when disassembling various components of the hydraulic servo system. All components must be placed in a clean environment after removal. .
2) The joint surfaces of various valve bodies cannot be cleaned with items that are easy to lose fiber such as cotton yarn, to prevent the fibers from mixing into the flow channel of the valve body and affecting the movement accuracy of parts.
3) When using a solvent such as gasoline to flush the filter element of the servo valve, pay special attention to ventilate the surrounding environment and pay attention to fire prevention.
4) During the installation of some hydraulic servo systems, the connection screws and joint surfaces use adhesives to enhance the connection effect. It may not be easy to disassemble. It needs to be cleaned with acetone and pretreated. When using acetone, it is necessary to pay attention to the surrounding environment. Pay attention to fire prevention. Volatile gases generated by ketones are harmful to the human body, and care must be taken to protect the maintenance personnel.
5) Before removing the components of the hydraulic servo system, be sure to stop the operation of the system and unload the pressure in the system to determine that the system pressure is 0 before proceeding to the next operation.
4. Judgment and elimination of common faults of hydraulic servo system
The hydraulic servo system of a large hollow blow molding machine generally has a low failure rate under normal operating conditions. Under normal circumstances, in the first year of equipment commissioning, there will be relatively many types of failures. A more accurate judgment of various faults is one of the important contents of doing good maintenance and repair work of the hydraulic servo system.
Generally speaking, if a large-scale hollow blow molding machine is continuously produced, the hydraulic servo system will rarely fail during the long-term operation of the equipment. However, if the equipment usage rate is not high, and the equipment is in the south of China, the hydraulic servo system may fail continuously every time it is turned on, and sometimes it may take 3 to 5 days to deal with various types of equipment failure. This will cause too much inconvenience to production. Recognizing and mastering these characteristics, and then formulating effective technical measures, can reduce the occurrence of various faults in the hydraulic servo system of the equipment.
(1) Maintenance of control circuit during equipment shutdown If the equipment shutdown time is not too long, the control circuit of the hydraulic servo system can be energized to reduce the occurrence of wire oxidation in the control circuit. Servo valve wires are thinner, especially solder joints, and are more likely to lose reliability due to moisture and oxidation. If the downtime is longer, regular power maintenance can be performed weekly. The power maintenance time should not be shorter than 8h.
(2) Maintenance and operation of the hydraulic servo system before the equipment is turned on. If the equipment is stopped for a long time, the hydraulic servo system needs to be maintained and operated before the equipment officially resumes production. The servo valve can be removed, the small precision filter of the servo valve can be cleaned, and the flushing plate can be installed on the position of the servo valve. The hydraulic servo system can be started for flushing and maintenance operation for more than 8 hours. In general, when the downtime is more than one month, flushing and maintenance must be performed before starting.