Created on:2021-08-17 14:37

Maintenance of medium plate mill_ Improvement of hydraulic fine adjustment system

中板轧机的维修_液压微调系统的改进
Maintenance of medium plate mill_ Improvement of hydraulic fine adjustment system

    中板轧机的液压微调系统是提高板厚精度、控制板形、提高命中率的重要设施。某公司2500型中板轧机液压微调系统投入使用后,由于设计及使用方面的原因,不到1个月便出现伺服阀卡死,因而频繁更换。通过分析并作了相应改进,确保了该系统稳定、可控、高质量地运行,具体过程如下。
The hydraulic fine adjustment system of medium plate mill is an important facility to improve the accuracy of plate thickness, control the shape of plate and improve the hit rate. After the hydraulic fine-tuning system of 2500 medium plate mill was put into use, the servo valve was jammed in less than one month due to design and use reasons, so it was replaced frequently. Through the analysis and corresponding improvement, the stable, controllable and high-quality operation of the system is ensured. The specific process is as follows.

(1)存在的主要问题
(1) Main problems

    中板轧机液压微调系统存在的问题有以下几点:
There are several problems in the hydraulic fine adjustment system of medium plate mill

    ①过滤精度达不到目标精度要求,滤芯的过滤比偏小,滤芯更换频繁;
① The filtration accuracy can not meet the target accuracy requirements, the filtration ratio of the filter element is small, and the filter element is replaced frequently;

    ②安装及检修后没有足够的时间进行系统冲洗,使伺服阀、液压缸等受到污染;
② There is not enough time to flush the system after installation and maintenance, so that the servo valve and hydraulic cylinder are polluted;

    ③蓄能器的充气压力及安装位置欠妥,没有起到应有的作用,管路冲击振动大;
③ The charging pressure and installation position of the accumulator are not proper, which does not play its due role, and the impact and vibration of the pipeline are large;

    ④油温过高;
④ The oil temperature is too high;

    ⑤微调缸有杆腔液压油容易老化变质,缸体与活塞杆存在局部磨损;
⑤ The hydraulic oil in the rod cavity of the fine adjustment cylinder is easy to be aged and deteriorated, and the cylinder block and piston rod are locally worn;

    ⑥微调缸内的压下球面垫润滑不良、内外泄漏;
⑥ The spherical pad in the fine adjustment cylinder has poor lubrication and internal and external leakage;

    ⑦电气线路接地及插头接触不良。
⑦ Poor contact of electrical circuit and plug.

(2)改进措施
(2) Improvement measures

    ①保证系统目标清洁度 固体颗粒污染物是导致阀芯卡死、磨损、密封破坏的主要原因。中厚板轧机的液压微调系统是高压、大流量伺服控制系统,对固体颗粒污染物非常敏感。特别是大流量、高响应的MOOG伺服阀,阀芯径向间隙为2~5μm,其过滤精度必须优于NAS6级。采取的措施如下。
① To ensure the target cleanliness of the system, solid particle pollutants are the main causes of valve core sticking, wear and seal failure. The hydraulic fine-tuning system of plate mill is a high-pressure and large flow servo control system, which is very sensitive to solid particles. Especially for MOOG servo valve with large flow and high response, the radial clearance of valve core is 2 ~ 5 μ m. The filtration accuracy must be better than nas6. The measures taken are as follows.

    a.增设加油过滤辅助油箱,以便加油时过滤及存储备用油。
a. An auxiliary oil tank is added to filter and store spare oil during refueling.

    b.伺服阀前的压力过滤器滤芯精度由原来的10tlm增加到5pm。
b. The precision of the filter element in front of the servo valve is increased from 10tlm to 5pm.

    c.所有过滤器改用纳污能力高、过滤比大的滤芯,以延长滤芯的更换周期,减少因更换滤芯而可能带入的污染物。
c. All filters should be replaced by filter elements with high pollutant carrying capacity and high filtration ratio to prolong the replacement cycle of filter elements and reduce the pollutants that may be brought in due to the replacement of filter elements.

    d.更换液压元件时,必须先用干净煤油清洗新元件、工具用具及连接处,伺服阀、压、力传感器等精密元件还须用精密电器清洗剂清洗,以防带人新的污染物。
d. When replacing hydraulic components, clean kerosene must be used to clean new components, tools and joints. Precision components such as servo valve, pressure sensor and force sensor must also be cleaned with precision electrical cleaning agent to prevent new pollutants.

    e.检修或安装管路、接头时,应采用机械切割下料,亚弧焊打底再普通堆焊,以防止焊渣、焊瘤进入管内,严禁随意割焊,并严格执行液压系统管路安装和冲洗的有关标准。
e. When repairing or installing pipelines and joints, mechanical cutting and blanking shall be used, sub arc welding shall be used for backing, and then common surfacing shall be used to prevent welding slag and weld bead from entering into the pipes. Cutting and welding at will is strictly prohibited, and relevant standards for installation and flushing of hydraulic system pipelines shall be strictly implemented.

    f.安装伺服阀前应先装上冲洗板对系统冲洗3~4h。
f. Before installing the servo valve, the flushing plate should be installed to flush the system for 3 ~ 4H.

    ②减小系统的冲击振动 中厚板轧机的液压微调系统是高压、大流量的伺服系统,伺服阀频繁响应,液压缸液柱快速调整,流量冲击很大。采取的措施如下。
② The hydraulic fine-tuning system of medium and heavy plate mill is a servo system with high pressure and large flow. The servo valve responds frequently, and the hydraulic cylinder adjusts quickly, resulting in great flow impact. The measures taken are as follows.

    a.定期检查蓄能器的冲气压力。在液压站内,作为辅助能源,蓄能器的流量应大于系统最大流量与泵工作流量之差,其充气压力约为系统工作压力的0. 80倍;在伺服阀前,设置吸收压力冲击的蓄能器,其充气压力约为系统工作压力的0.85倍;在主回油管上,设置吸收流量脉动的蓄能器,其充气压力约为系统回油管路压力的0.85倍。
a. Check the charging pressure of the accumulator regularly. In the hydraulic station, as an auxiliary energy, the flow of accumulator should be greater than the difference between the maximum flow of the system and the working flow of the pump, and its charging pressure is about 0.80 times of the working pressure of the system; In front of the servo valve, an accumulator is set to absorb the pressure impact, and its charging pressure is about 0.85 times of the working pressure of the system; The main oil return pipe is equipped with an accumulator to absorb the flow pulsation, and the charging pressure is about 0.85 times of the system oil return pipe pressure.

    b.管路设计时,到伺服阀的管路长度尽可能避免泵固有频率,即为1.14m的奇数倍,站内双筒压力过滤器后2条支管长度最好相差1.14m,这样可以实现H型滤波消振。
b. In the pipeline design, the pipeline length to the servo valve should avoid the natural frequency of the pump as much as possible, which is an odd multiple of 1.14M, and the length difference between the two branches behind the double cylinder pressure filter in the station should be 1.14M, so as to realize H-type filtering vibration elimination.

    c.系统不稳定是导致管路冲击振动的主要原因,合理调整APC调节系数和AGC调节参数,从而使系统既具有良好的稳定性,又具有快速的响应性。
c. The instability of the system is the main reason for the shock vibration of the pipeline. By adjusting APC adjustment coefficient and AGC adjustment parameters reasonably, the system has good stability and fast response.

    d.加密管夹,使管路连接牢固可靠。
d. Tighten the pipe clamp to make the pipe connection firm and reliable.

    e.取消站内压力过滤器后的2个单向阀。液压微调的工作特点是在目标位置附近频繁调整,产生较大的流量及压力波动。如图4-25所示,当伺服阀换向时,伺服阀产生的流量及压力波动沿管路传播到单向阀3后,由于单向阀的隔离作用,蓄能器失去原有的减振作用,同时单向阀频繁关闭既产生较大的噪声,又缩短了使用寿命。改进后,增加一个单向阀,这样伺服阀产生的流量及压力波动就会沿单向阀6被蓄能器吸收,增大了系统的稳定性。
e. Cancel the two check valves behind the pressure filter in the station. The working characteristic of hydraulic fine-tuning is to adjust frequently near the target position, resulting in large flow and pressure fluctuations. As shown in Figure 4-25, when the servo valve reverses, the flow and pressure fluctuation generated by the servo valve propagates along the pipeline to check valve 3. Due to the isolation effect of the check valve, the accumulator loses its original damping effect. At the same time, the check valve is closed frequently, which not only produces larger noise, but also shortens its service life. After the improvement, a check valve is added, so that the flow and pressure fluctuation generated by the servo valve will be absorbed by the accumulator along the check valve 6, which increases the stability of the system.

    ③降低油箱温度 该系统工作压力高、流量大,且环境温度高,因此热平衡温度高。必须采取强有力的冷却设施强制冷却,同时应尽量减少因溢流阀或安全阀溢流而产生的能量损失。采取的措施如下。
③ The system has high working pressure, large flow and high ambient temperature, so the heat balance temperature is high. Strong cooling facilities must be adopted to force cooling, and the energy loss caused by overflow valve or safety valve should be minimized. The measures taken are as follows.

    a.中压系统压力较低(一般为3~5MPa),且流量较小,若和高压系统共用油源,需设置减压阀而造成能量损失,故中压系统最好单独设置供油系统。
a. The pressure of medium pressure system is low (generally 3-5mpa) and the flow is small. If it shares the oil source with high pressure system, it is necessary to set pressure reducing valve to cause energy loss. Therefore, it is better to set oil supply system separately for medium pressure system.

    b.管式直动式安全阀容易溢流,改用先导式溢流阀。
b. The pipe type direct acting safety valve is easy to overflow, so the pilot type relief valve is used instead.

    c.站内设置水冷式空调,降低环境温度。
c. The station is equipped with water-cooled air conditioning to reduce the ambient temperature.

    d.热交换器的维护是一个被容易忽视的问题。由于热交换前的油温较高,冷却水的品质是保证冷却效率的关键。而一般中板厂甩普通净循环水,水中杂质较多,长期在40~50℃温度下很容易结垢,使冷却效率大大降低。因此,热交换器每年至少应清洗一次,以确保冷却效率。最好设置散热系数较高的板式或列管式冷却器,根据热平衡条件选择合适散热面积的冷却器,确保油温不超过550C。
d. The maintenance of heat exchanger is a problem that is easily ignored. Due to the high temperature of oil before heat exchange, the quality of cooling water is the key to ensure the cooling efficiency. However, in general medium plate plants, there are many impurities in the common clean circulating water, and it is easy to scale at 40 ~ 50 ℃ for a long time, which greatly reduces the cooling efficiency. Therefore, the heat exchanger should be cleaned at least once a year to ensure cooling efficiency. It is better to set plate or tubular cooler with high heat dissipation coefficient, and select the cooler with appropriate heat dissipation area according to the heat balance conditions to ensure that the oil temperature does not exceed 550c.

    e.选用性能优良的,以减少泵内泄产生的能量损失。
e. Select the pump with excellent performance to reduce the energy loss caused by pump leakage.

    ④消除外泄漏 阀芯卡死、密封失效是引起系统内外泄漏的主要原因,特别是液压缸、伺服阀及压力传感器,其内外泄漏量直接影响到系统的稳定性及控制精度。采取的措施如下。
④ The main causes of internal and external leakage of the system are the stuck valve core and seal failure, especially the internal and external leakage of hydraulic cylinder, servo valve and pressure sensor, which directly affects the stability and control accuracy of the system. The measures taken are as follows.

    a.液压缸等关键密封采用耐高温高压、低摩擦的组合式密封。
a. Hydraulic cylinder and other key seals are combined seals with high temperature and high pressure resistance and low friction.

    b.尽可能减少法兰连接,多用焊接,同时法兰及阀台宜采用纯铜垫密封。
b. The flange connection should be reduced as much as possible and welding should be used. Meanwhile, the flange and valve seat should be sealed with pure copper gasket.

    c.取消站内蓄能器用管式直动安全阀及先导调压阀后的单向阀,同时将调压阀台上的其中一个先导式调压阀改作系统安全阀。
c. The pipe type direct acting safety valve and the check valve behind the pilot pressure regulating valve for the accumulator in the station are canceled, and one of the pilot pressure regulating valves on the pressure regulating valve station is changed into the system safety valve.

d.压力传感器原为锥面内孔密封,而该系统在设计时却没有考虑设置锥面密封的内外接头,安装时直接采用端面组合垫密封,由于端面密封面不平且接触面太少,又不够扳手位,因而经常漏油。要求厂家对压力传感器的外形尺寸作改进,并改组合垫密封为紫铜垫密封(见图Z),效果非常好。
d. The pressure sensor used to be sealed with cone surface inner hole, but the inner and outer joints of cone surface seal were not considered in the design of the system, and the end face combined gasket seal was directly used in the installation. Because the end face sealing surface is uneven, the contact surface is too few, and the wrench position is not enough, oil leakage often occurs. The manufacturer is required to improve the overall dimension of the pressure sensor, and change the combined gasket seal to red copper gasket seal (see Fig. z), the effect is very good.

Z.jpg

    ⑤微调缸有杆腔液压油老化变质及缸体与活塞杆局部磨损的改进 系统只作液压微调,不作液压压下,故其液柱基本不变。活塞杆与缸体的接触位置长期在一处,从而使活塞杆与缸体产生局部磨损,引起液压缸泄漏,影响系统的稳定性及控制精度,严重时使液压缸报废。同时有杆腔的液压油因得不到及时更换,导致油液老化变质,影响密封件的使用寿命,使活塞杆与缸体表面产生点蚀破坏。采取的措施如下。
⑤ The hydraulic oil in the rod cavity of the fine adjustment cylinder is aged and deteriorated, and the cylinder block and piston rod are worn locally. The system only makes hydraulic fine adjustment, not hydraulic reduction, so the liquid column is basically unchanged. The contact position between the piston rod and the cylinder block is in the same place for a long time, which causes local wear between the piston rod and the cylinder block, causes the leakage of the hydraulic cylinder, affects the stability and control accuracy of the system, and even makes the hydraulic cylinder scrapped. At the same time, the hydraulic oil with rod cavity can not be replaced in time, which leads to oil aging and deterioration, affects the service life of seals, and causes pitting damage on the surface of piston rod and cylinder block. The measures taken are as follows.

    a.每月定期改变一次液压缸的液柱高度。
a. Change the height of hydraulic cylinder once a month.

b.在有杆腔进油管路上设置2个高压截止阀(见图A),以实现有杆腔液压油的更换操作。方法如下:液压微调系统打停车位一设定液压缸液柱值为最大一关闭进油截止阀,打开放油截止阀一系统打工作位,排尽有杆腔的液压油至油箱一打开进油截止阀,关闭放油截止阀一液压微调系统打停车位一完成换油操作。
b. Two high-pressure stop valves (see Fig. a) are set on the oil inlet pipe of the rod cavity to realize the replacement of the hydraulic oil in the rod cavity. The method is as follows: the hydraulic fine-tuning system opens the parking space, sets the hydraulic cylinder liquid column value to the maximum, closes the oil inlet stop valve, opens the oil discharge stop valve system working position, exhausts the hydraulic oil with the rod cavity to the oil tank, opens the oil inlet stop valve, closes the oil discharge stop valve, opens the hydraulic fine-tuning system parking space, completes the oil change operation.

⑥缸内压下球面垫润滑球面垫的作用是止推及自位。液压缸与压下丝杆在过平衡力作用下,通过球面垫的自动对中可靠接触。由于安装位置的限制,球面垫只能放在微调缸活塞杆内。该处因低于排油口,润滑油无法循环,同时由于压下丝杆与压下螺母以及压下丝杆与球面垫的磨损产生大量的铜屑,均积沉在该处,导致压下丝杆与球面垫咬死、粘合,球面垫失去原有的作用。严重时,导致微调缸活塞杆转动,密封及位移传感器破坏,机械压下装置过早磨损,如图B所示。为此,必须定期人工清除老化变质的润滑油及铜屑、油泥等污染物。这是一件非常烦琐,但又不得不做的工作,因为它很重要。另外,由于该区域环境非常恶劣,虽然设置了伸缩式防尘罩,但灰尘、烟气、水汽等杂物仍很容易进入微调缸的有杆腔,加速了有杆腔的磨损及密封件的损坏。通过向防尘罩内注入干净的压缩空气可以有效防止灰尘、烟气、水汽等杂物的进入。
⑥ The function of spherical pad is thrust and self-aligning. Under the action of over balance force, the hydraulic cylinder and the screw down screw are in reliable contact through the automatic centering of spherical pad. Due to the limitation of installation position, the spherical pad can only be placed in the piston rod of fine-tuning cylinder. At the same time, due to the wear of the screw down screw rod and screw down nut, and the screw down screw rod and spherical pad, a large number of copper filings are accumulated at this place, resulting in the screw down screw rod and spherical pad biting and bonding, and the spherical pad losing its original function. If it is serious, the piston rod of fine adjustment cylinder will rotate, the seal and displacement sensor will be damaged, and the mechanical screwdown device will be worn prematurely, as shown in Figure B. Therefore, it is necessary to remove the aged lubricating oil, copper scraps, oil sludge and other pollutants regularly. This is a very trivial work, but it has to be done, because it is very important. In addition, due to the very bad environment in this area, although the telescopic dust cover is set up, the dust, smoke, water vapor and other debris are still easy to enter the rod cavity of the fine-tuning cylinder, which accelerates the wear of the rod cavity and the damage of the seal. By injecting clean compressed air into the dust cover, it can effectively prevent the entry of dust, smoke, water vapor and other debris.

B1.jpg

    ⑦电气线路接地及插头接触不良的改进 电气线路接地及插头接触不良,将严重影响系统的稳定性及控制精度,出现辊缝漂移,液压系统管路异常振动现象。应定期检查电气线路是否接地,插头是否接触不良。另外,系统应设置失压保护电源,以防止突然停电而使整个计算机系统程序丢失。
⑦ Improvement of poor electrical circuit grounding and plug contact poor electrical circuit grounding and plug contact will seriously affect the stability and control accuracy of the system, resulting in roll gap drift and abnormal vibration of hydraulic system pipeline. Regularly check whether the electrical circuit is grounded and whether the plug is in poor contact. In addition, the system should be equipped with voltage loss protection power supply to prevent the loss of the whole computer system program due to sudden power failure.

(3)改进后的效果
(3) Effect of improvement

    改进后,油液的清洁度长期控制在NAS6级以上,未出现因油液污染导致伺服阀卡死、液压泵及密封件过早破坏等故障。管路冲击振动明显减小,因冲击振动而引起的崩管、泄漏现象很少发生。油温控制在40~50℃之间,液压泵、伺服阀、微调缸的使用寿命达到2年以上,10mm钢板同板差控制在+0.10mm以内的命中率达到95%以上,系统的可开动率达到99%以上,实现了系统的可控、可靠、低耗、稳定运行。
After the improvement, the cleanliness of the oil is controlled above nas6 level for a long time, and there is no fault such as servo valve stuck, hydraulic pump and seal premature damage caused by oil pollution. The impact vibration of the pipeline is obviously reduced, and the pipe collapse and leakage caused by the impact vibration are rare. When the oil temperature is controlled between 40 ℃ and 50 ℃, the service life of the hydraulic pump, servo valve and fine-tuning cylinder can reach more than 2 years, the hit rate of the same plate difference of 10 mm steel plate controlled within + 0.10 mm can reach more than 95%, and the start-up rate of the system can reach more than 99%, which realizes the controllable, reliable, low consumption and stable operation of the system.

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