Created on:2021-08-06 09:40

Hydraulic fault diagnosis, analysis and measures for AWC system of rolling mill

轧机AWC系统液压故障诊断、分析及措施
Hydraulic fault diagnosis, analysis and measures for AWC system of rolling mill

    在激烈的市场竞争中,各热带钢厂根据用户需要,必须小批量、多规格地组织生产。板坯不经过冷却而直接热装或直接轧制,可以大大简化工艺、降低能耗、提高产品的质量和生产效率,但这种连续化的作业要求具有能在线调整板坯宽度的设备;用户和后工序对热轧带钢的宽度控制精度的要求也越来越高。因此在立辊轧机装备AWC系统显得尤为重要。
In the fierce market competition, according to the needs of users, the tropical steel plants must organize production in small batch and multi specification. Direct hot charging or direct rolling of slabs without cooling can greatly simplify the process, reduce energy consumption, and improve product quality and production efficiency; The requirements of users and post process for width control accuracy of hot rolled strip are higher and higher. So it is very important to equip AWC system in vertical roller mill.

(1) AWC系统
(1) AWC system

AWC是自动宽度控制的英文缩写(Automatic Width Control),该系统安装于热轧机组粗轧区域立辊轧机中,是热轧带钢厂的重要设备之一,其主要功能是控制热轧带钢的宽度精度,包括自动位置控制APC (Automatic Position Control)、带钢头部和尾部的宽度控制、短行程控制、轧制滑移量补偿和锥度补偿等。伺服液压缸在立:辊轧机上的安装位置如图C所示。其主要作用是在轧钢过程中,对轧辊进行精确定位,控制板材的轧制宽度,提高板形质量。
AWC is the abbreviation of automatic width control, which is installed in the vertical mill of roughing area of hot strip mill. It is one of the important equipment in hot strip mill. Its main function is to control the width precision of hot strip, including automatic position control (APC), width control of strip head and tail, short stroke control, width control of strip head and tail, width control of strip head and tail, width control of strip head and tail, width control of strip head and tail, width control of strip head and tail, width control of strip head and tail, width control of strip head and tail, width control of strip head Rolling slip compensation and taper compensation. The installation position of servo hydraulic cylinder on vertical roller mill is shown in Fig. C. Its main function is to accurately position the roll, control the rolling width of the plate and improve the shape quality.

C1.jpg

AWC液压伺服控制系统主要由液压站、伺服控制阀架、液压管路、伺服液压缸等部分组成。液压站主要由四台(三用一备)A4VS01250DR型通轴斜盘式恒压变量柱塞泵、泵出口控制阀架和循环冷却过滤系统组成。压力油经泵出口控制阀架分别输向压力为31.5MPa的主油路和压力为18.0MPa的控制回路。其中伺服阀架是该系统的核心部分,阀架的控制原理如图D所示,其液压回路由两部分组成:一是伺服阀控制回路,在轧机正常工作时,伺服阀控制AWC伺服液压缸工作,其功能是达到轧机轧辊辊缝定位和在线控制带钢宽度的目的;二是旁通回路(检修回路),当轧机停机检修时,伺服阀控制回路截断,旁通液压回路投入工作,用于检查检修后的AWC伺服液压缸动作情况。
AWC hydraulic servo control system is mainly composed of hydraulic station, servo control valve frame, hydraulic pipeline, servo cylinder and other parts. The hydraulic station is mainly composed of four (three for use and one for standby) a4vs01250dr swash plate constant pressure variable piston pumps, pump outlet control valve frame and circulating cooling filtration system. The pressure oil is sent to the main oil circuit with pressure of 31.5Mpa and the control circuit with pressure of 18.0mpa respectively through the control valve frame at the pump outlet. The servo valve frame is the core part of the system. The control principle of the valve frame is shown in Figure D, and its hydraulic circuit consists of two parts: one is the servo valve control circuit. When the rolling mill works normally, the servo valve controls the AWC servo hydraulic cylinder to work, and its function is to achieve the purpose of positioning the roll gap of the rolling mill and online controlling the width of the strip steel; The second is the bypass circuit (maintenance circuit). When the rolling mill is shut down for maintenance, the servo valve control circuit is cut off and the bypass hydraulic circuit is put into operation to check the action of AWC servo hydraulic cylinder after maintenance.

D1.jpg

    AWC液压系统选用的伺服阀为MOOG公司的D792-S99JOQA6VSX2-O(用于E1立辊轧机上)和D792-S80JOQA6VSX2-O(用于E2立辊轧机上)两种型号的高响应伺服阀,两者的流量分别为1000L/min和800L/min。
The servo valves of AWC hydraulic system are d792-s99joqa6vsx2-o (used on E1 vertical roll mill) and d792-s80joqa6vsx2-o (used on E2 vertical roll mill) of MOOG company with high response, and their flow rates are 1000L / min and 800L / min respectively.

AWC液压系统的主要性能参数如下表所示。
The main performance parameters of AWC hydraulic system are shown in the table below.

 

AWC液压系统的主要性能参数
Main performance parameters of AWC hydraulic system

序 号
Serial number

名 称

性 能 参 数

1

系统工作压力/MPa

31.5

2

系统额定工作流量/(L/min)

1050

3

系统使用介质

难燃液 N822-300

4

介质正常工作温度范围/℃

45~55

5

油脂清洁度

NAS1638 5级/ISO440616/14/11

6

邮箱总容积/L

8000

 

(2)故障现象
(2) Fault phenomenon

在一次设备检修过程中,对AWC系统的伺服油缸进行了更换,检修完成后,通过旁通回路控制伺服油缸动作,并对其进行排气操作,油缸动作平稳,无异常。但在对伺服油缸进行标定测试时,发现其中一只伺服油缸动作异常,该缸活塞杆伸出至最大行程位置便不再动作,而且失去控制,无论伺服阀的输入信号给定为多少,伺服油缸还是停留在原位置上。在控制阀架上手动控制旁通回路的电磁换向阀,该伺服油缸动作平稳,工作正常。电气人员对系统的电气元件和线路进行了检测,均无异常。图E、图F是采样获得的上下伺服油缸的伺服阀给定基准和伺服阀主阀芯的位置反馈信号曲线。
In the process of an equipment overhaul, the servo cylinder of AWC system was replaced. After the overhaul, the servo cylinder was controlled by the bypass circuit, and the exhaust operation was carried out. The action of the servo cylinder was stable and there was no abnormality. However, during the calibration test of the servo cylinder, it is found that one of the servo cylinders acts abnormally. When the piston rod of the cylinder extends to the maximum stroke position, it will no longer act and lose control. No matter how much the input signal of the servo valve is given, the servo cylinder still stays in the original position. The electromagnetic directional valve of bypass circuit is manually controlled on the control valve frame, and the servo cylinder operates smoothly and normally. The electrical personnel tested the electrical components and circuits of the system, and there was no abnormality. Figure E and figure f are the given reference of servo valve of upper and lower servo cylinder and the position feedback signal curve of main spool of servo valve.

E1F1.jpg

(3)故障诊断、分析及措施
(3) Fault diagnosis, analysis and measures

①故障诊断通 过旁通回路控制伺服液压缸动作正常可以判断伺服液压缸没有故障,工作正常;通过伺服阀的检测曲线,在图E中,伺服阀的主阀芯位置反馈信号E1_SvoFbOSTop由20%跃升至80%附近,并发生振荡,反映到控制上伺服液压缸的伺服阀上,其主阀芯由“零点”位置偏移至最大位移处并发生振荡。在图F中,伺服阅的主阀芯位置反馈信号E1_SvoFbOSBot在20%附近振荡,反映到控制下伺服液压缸的伺服阀上,其主阀芯在“零点”位置处发生振荡。这恰好与故障现象中“伺服液压缸活塞杆伸出至最大行程位置便不再动作”相符。结合同一侧上下伺服液压缸的伺服阀的给定基准和主阀芯位置反馈曲线,可以得到以下结论:由于AWC控制系统是闭环控制系统,输入信号和反馈信号不断比较进行调节,故上伺服阀主阀芯在最大位移处受到输入基准信号调节的影响,有始终使主阀芯回到零位的趋势而出现振荡。下伺服阀主阀芯在零位出现振荡,是因为两个伺服阀控制的伺服液压缸处在同一侧,并且互相影响,下伺服阀主阀芯的振荡是因上伺服阀主阀芯的振荡而引起的。故障出在控制上伺服液压缸的伺服阀上。
① Fault diagnosis through the bypass circuit control servo hydraulic cylinder action is normal, can judge the servo hydraulic cylinder has no fault, work normally; Through the detection curve of the servo valve, in Figure e, the main spool position feedback signal E1 of the servo valve_ Svofbostop jumps from 20% to 80% and oscillates, which is reflected on the servo valve of the upper servo hydraulic cylinder. The main valve core shifts from the "zero" position to the maximum displacement and oscillates. In Figure F, the main spool position feedback signal E1 of the servo valve is displayed_ Svofbosbot oscillates around 20%, which is reflected on the servo valve of the servo hydraulic cylinder under control, and the main valve core oscillates at the "zero" position. This is just in line with the phenomenon that "the piston rod of servo hydraulic cylinder will no longer move when it reaches the maximum stroke position". According to the given reference of the servo valve and the feedback curve of the main spool position of the upper and lower servo hydraulic cylinders on the same side, the following conclusions can be drawn: as the AWC control system is a closed-loop control system, the input signal and feedback signal are constantly compared for adjustment, so the main spool of the upper servo valve is affected by the adjustment of the input reference signal at the maximum displacement, There is always a tendency to make the main spool return to zero position and oscillation occurs. The main spool of the lower servo valve oscillates at the zero position because the servo hydraulic cylinders controlled by the two servo valves are on the same side and interact with each other. The oscillation of the main spool of the lower servo valve is caused by the oscillation of the main spool of the upper servo valve. The fault is in the servo valve of the servo hydraulic cylinder.

②分析 打开伺服阀主阀芯端盖检查,发现伺服阀端盖上定位销脱离了主阀芯的定位孔,直接抵挡在伺服阀的主阀芯端面上,如图G所示。伺服阀正常工作时,主阀芯定位销孔与端盖定位销的位置应如图H所示。
② After analyzing and opening the end cover of the main valve core of the servo valve for inspection, it is found that the locating pin on the end cover of the servo valve is separated from the locating hole of the main valve core and directly resists the end face of the main valve core of the servo valve, as shown in Fig. G. When the servo valve works normally, the location of the locating pin hole of the main valve core and the locating pin of the end cover shall be as shown in Fig. H.

G1H1.jpg

出现定位销脱离定位销孔的故障现象,主要原因是:伺服液压缸在做测试时,液压缸的活塞快速运动,若无杆腔进油,则需要供应大流量的油液,此时,伺服阀主阀芯开口度达到最大位置,如果还达不到此时伺服液压缸的流量要求,伺服阀主阀芯则可能超过其最大行程来满足流量的需求。伺服液压缸不断快速运动的同时,伺服阀的主阀芯也在不断地超越其最大行程做往返运动,在此间,伺服阀的主阀芯就会沿着其中心线发生偏转,随着偏转角度的不断增大,最后就会出现图G所示的现象。
The main reason for the failure of the locating pin breaking away from the locating pin hole is: when the servo hydraulic cylinder is testing, the piston of the hydraulic cylinder moves rapidly. If there is no rod cavity to feed oil, it needs to supply a large flow of oil. At this time, the opening degree of the main valve core of the servo valve reaches the maximum position. If it can not meet the flow requirement of the servo hydraulic cylinder at this time, The main spool of servo valve may exceed its maximum stroke to meet the flow demand. While the servo hydraulic cylinder is constantly moving rapidly, the main spool of the servo valve is constantly moving back and forth beyond its maximum stroke. During this period, the main spool of the servo valve will deflect along its center line. With the increasing deflection angle, the phenomenon shown in Fig. g will finally appear.

③措施 伺服阀端盖定位销的原长度为8mm,重新制作定位销,长度增加2mm。将新制作的10mm长的定位销装在伺服阀上,AWC系统自此以后没再出现类似故障现象。
③ Measures: the original length of the locating pin of the servo valve end cover is 8mm, and the length is increased by 2mm by remaking the locating pin. After the newly made 10 mm long locating pin was installed on the servo valve, the AWC system did not have similar failure phenomenon since then.

AWC系统的这种故障完全出自伺服阀的选型上,所选用伺服阀的额定流量与现场实际所需的流量相比偏小,设计时考虑的余量过小。
The fault of AWC system is caused by the selection of servo valve. The rated flow of the servo valve is smaller than the actual flow, and the allowance is too small.
The fault of AWC system is caused by the selection of servo valve. The rated flow of the servo valve is smaller than the actual flow, and the allowance is too small.

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