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调节阀安全运行的因素分析以及电动执行器出厂检测的注意事项

2018-09-14

调节阀安全运行的因素分析以及电动执行器出厂检测的注意事项
Analysis of factors affecting the safety operation of regulating valves and precautions for factory inspection of electric actuators

电站阀门、化工阀门、冶金阀门、高温高压阀门、电动执行器以及其他阀门在自动化程度较高的化工控制系统中,调节阀作为自动调节系统的终端执行装置,接受控制信号实现对化工流程的调节,要求各异,对电磁阀渗漏要求应按有关规定执行。它的动作灵敏度直接关系着调节系统的质量。据现场实际统计有70%左右的故障出自调节阀。因此在日常维护中总结分析影响调节阀安全运行的因素。
 Power station valves, chemical valves, metallurgical valves, high-temperature ,electric atuators and high-pressure valves and other valves are in the chemical control system with high automation, regulating valves are used as terminal actuators for automatic regulating systems to accept control signals to adjust chemical processes. Electromagnetic valve leakage requirements should be implemented in accordance with relevant regulations. Its motion sensitivity is directly related to the quality of the regulating system. According to the actual statistics on the site, about 70% of the faults come from the regulating valve. Therefore, the factors affecting the safe operation of the regulating valve should be summarized and analyzed during routine maintenance.

1、卡堵
1. Jamming
调节阀经常出现的问题是卡堵,常出现在新投运系统和大修投运初期,由于管道内焊渣、铁锈等在节流口、导向部位造成堵塞使介质流通不畅,或调节阀检修中填料过紧,造成摩擦力增大,导致小信号不动作大信号动作过头的现象。
 The regular problem of regulating valves is jamming, which often occurs in the new delivery system and the early stage of overhaul and transportation. Because the welding slag and rust in the pipeline cause blockage at the throttling orifice and guiding part, which makes the flow of the medium not smooth, or the filler is too tight in the repair of the regulating valve, which results in the increase of the friction force, and then causes the phenomenon that the small signal does not act and the big signal moves too far.
处理建议:可迅速开、关副线或调节阀,让脏物从副线或球阀处被介质冲跑。另一办法用管钳夹紧阀杆,在外加信号压力情况下,正反用力旋动阀杆,让阀芯闪过卡处。若不能则增加气源压力增加驱动功率反复上下移动几次,即可解决问题。如若仍不动作,则需解体处理。
 Handling advice: Quickly open or close the secondary line or regulating valve to make the dirt run from the secondary line or the ball valve by the medium. Another method is to clamp the valve stem with a pipe wrench. When the signal pressure is applied, the valve stem is forced to rotate forward and backward so that the spool flashes past the jamming part. If not, increase the air pressure and increase the drive power by moving it up and down several times, and through this, can solve the problem. If it still does not work, it needs to be dismantled.
2、泄漏
2. Leakage
2.1阀内漏:阀杆长短不适。阀杆太长,阀杆向上的(或向下)的距离不够,造成阀芯和蝶阀阀座之间有空隙,不能充分接触,导致关不严而内漏。阀杆太短,导致阀芯和阀座之间有空隙,不能充分接触,导致关不严而内漏。
2.1 Valve inner leakage: The length of the stem is not suitable. The valve stem is too long, and the upward (or downward) distance of the valve stem is not enough, resulting in a gap between the valve plug and the butterfly valve seat, which cannot be fully contacted, resulting in loose shut-off and internal leakage. The valve stem is too short, resulting in a gap between the valve plug and the valve seat that cannot be fully contacted, resulting in loose shut-off and internal leakage. 
处理建议:应缩短(或延长)调节阀阀杆使调节阀长度合适,使其不再内漏。
 Handling advice: The valve stem should be shortened (or lengthened), make the length of the regulating valve is appropriate so that it is no longer with inner leakage.
2.2填料泄漏:填料装入填料函以后,经压盖对其施加轴向压力。由于填料的塑性,使其产生径向力,并与阀杆紧密接触,但这种接触是并不是非常均匀的。有些部位接触的松,有些部位接触的紧,甚至有些部位没有接触上。闸阀在使用过程中,阀杆同填料之间存在着相对运动,这个运动叫轴向运动。在使用过程中,随着高温、高压和渗透性强的流体介质的影响,调节阀填料函也是发生泄漏现象较多的部位。造成填料泄漏的主要原因是界面泄漏,对于纺织填料还会出现渗漏(压力介质沿着填料纤维之间的微小缝隙向外泄漏)。阀杆与填料间的界面泄漏是由于填料接触压力的逐渐衰减,填料自身老化等原因引起的,这时压力介质就会沿着填料与阀杆之间的接触间隙向外泄漏。
2.2 Packing Leakage: After the packing is packed into the stuffing box, axial pressure is applied to the plug by the cover. Due to the plasticity of the packing, it generates a radial force and is in close contact with the valve stem, but this contact is not very uniform. Some parts of the loose contact, some parts of the contact tight, and even some parts of no contact. During the use of the gate valve, there is relative motion between the valve stem and the packing, this movement is called axial movement. In the process of use, with the influence of high temperature, high pressure and fluid medium with strong permeability, the valve packing box is also the site where more leakage occurs. The main reason of the leakage of the filler is the interface leakage, and leakage occurs to the textile filler (the pressure medium leaks outward along the tiny gap between the filler fibers). The interface leakage between the valve stem and the packing is caused by the gradual attenuation of the packing contact pressure and the aging of the packing itself. At this time, the pressure medium leaks outward along the contact gap between the packing and the valve stem. 
处理建议:为使填料装入方便,在填料函顶端倒角,在填料函底部放置耐冲蚀的间隙较小的金属保护环(截止阀与填料的接触面不能为斜面),以防止填料被介质压力推出。填料函各部与填料接触部分的金属表面要精加工,以提高表面光洁度,减少填料磨损。填料选用柔性石墨,因其具有气密性好,摩擦力小,长期使用后变化小,磨损的烧损小,维修容易,压盖螺栓重新拧紧后摩擦力不发生变化,耐压性和耐热性良好,不受内部介质的侵蚀,与阀杆和填料函内部接触的金属不发生点蚀或腐蚀。这样,有效地保护了减压阀阀杆填料函的密封,保证了填料的密封的可靠性和长期性。
 Handling advice: In order to make packing convenient, chamfering at the top of the stuffing box. Place a metal protection ring (the contact surface between the cut-off valve and the packing can’t be inclined) with less erosion resistance at the bottom of the stuffing box to prevent the packing from being pushed out by the medium pressure. The metal surface of each part of the stuffing box and the contact part of the packing should be fined to improve the surface finish and reduce the wear of the packing. Filler is made of flexible graphite, because of its good airtightness, low friction, small changes after long-term use, small wear loss, easy maintenance, no change in friction force after the retightening of the cap bolt, good pressure resistance and heat resistance, no erosion of the internal medium, no corrosive pitting or corrosion of the metal in contact with the stem and stuffing box. In this way, the seal of the pressure-relief valve stem packing box effectively protected, the reliability and long-term stability of the packing seal is ensured.
2.3阀芯、阀座变形泄漏:芯、阀座泄漏的主要原因是由于调节阀生产过程中的铸造或锻造缺陷可导致腐蚀的加强。而腐蚀介质的通过,流体介质的冲刷也可造成调节阀的泄漏。腐蚀主要以侵蚀或气蚀的形式存在。当腐蚀性介质在通过调节阀时,便会产生对阀芯、阀座材料的侵蚀和冲击使船用阀门阀芯、阀座成椭圆形或其他形状,随着时间的推移,导致阀芯、阀座不配套,存在间隙,关不严发生泄漏。
 2.3 The deformation leakage of spool and valve seat: spool, valve seat leakage is mainly due to the production of the valve in the process of casting or forging defects have resulted in the reinforcement of the corrosion. The passage of corrosive medium, the flushing of the fluid medium can also cause leakage of the regulating valve. Corrosion mainly occurs in the form of erosion or cavitation. When the corrosive medium passes through the regulating valve, it will produce the erosion and impact on the valve core and the seat material, so that the valve plug and the valve seat of the marine valve are formed into an elliptical shape or other shapes. Over time, the valve core and seat are not matched, with gap and resulting in loose shut-off and leakage
处理建议:关键把好阀芯、阀座的材质的选型关、质量关。选择耐腐蚀材料,对麻点、沙眼等缺陷的产品坚决剔除。若阀芯、阀座变形不太严重,可经过细砂纸研磨,消除痕迹,提高密封光洁度,以提高密封性能。若损坏严重,则应重新更换新阀。
 Handling suggestions: The key is to select suitable material and quality of the valve core and valve seat. Choose corrosion-resistant materials and strongly reject defective products such as pits and trachoma. If the valve core and the valve seat are not deformed seriously, they can be ground with fine sandpaper to eliminate the marks and improve the sealing finish to improve the sealing performance. If the damage is serious, the new valve should be replaced.
3、振荡
 3. Oscillations
调节阀的弹簧刚度不足,调节阀输出信号不稳定而急剧衬氟衬胶阀变动易引起调节阀振荡。还有说选阀的频率与系统频率相同或管道、基座剧烈振动,使调节阀随之振动。选型不当,调节阀工作在小开度存在着急剧的流阻、流速、压力的变化,当超过阀刚度,稳定性变差,严重时产生振荡。
 The spring stiffness of the regulating valve is insufficient, the output signal of the regulating valve is unstable, and the sudden change of the fluorine-lined rubber valve can easily cause oscillation of the regulating valve. It is also said that the frequency of the selection valve is the same as the frequency of the system or the severe vibration of the pipe and base makes the valve vibrate accordingly. Improper selection, there is a sharp flow resistance, flow velocity, and pressure changes in the valve operating at a small opening. When the valve stiffness is exceeded, the stability becomes worse, and the oscillation occurs when it is severe.
处理建议:由于产生振荡的原因是多方面的,因此具体问题具体分析。对振动轻微的振动,可增加刚度来消除。陶瓷阀如选用大刚度弹簧,改用活塞执行结构。管道、基座剧烈震动通过增加支撑消除振动干扰;选阀的频率与系统频率相同,则更换不同结构的阀;工作在小开度造成的振荡,则是选型不当流通能力C值选大,必须重新选型流通能力C值较小的或采用分程控制或子母阀以克服调节阀工作在小开度。
 Handling advice: due to the causes of the oscillations are various, specific problems should with specific analysis. For slight vibration, stiffness can be increased to eliminate it. Ceramic valves use large stiffness springs, and with piston actuating structure. The violent vibration of pipelines and bases eliminates the vibration interference by increasing the support; if the frequency of the valve selection is the same as the system frequency, the valves of different structures are replaced; if the oscillation caused by operating in the small opening, it is due to the improper selection of flow capacity of relatively large C value, flow capacity must be reselect the small C value or use split control or mother valve to overcome the operation of regulating valve in the small opening.

为了更好的避免电动调节阀或电动执行器门在现场管线上出现故障,出厂前,应该尽可能的在检测线上全面检测,一般检测的遵循事例如下:
 In order to better avoid failure of the electric regulating valve or electric actuators in the field pipeline, before leaving the factory, it should be fully tested as far as possible on the test line. The following are examples of general inspections:
(1)一般情况下,阀门不作强度试验,但修补过后阀体和阀盖或腐蚀损伤的阀体和阀盖应作强度试验。对于安全阀,其定压和回座压力及其他试验应符合视镜视盅阀其说明书和有关规程的规定。
 (1) Under normal circumstances, the valve shall not be subjected to strength tests. However, after the repair, the valve body and valve cover or corroded valve body and valve cover shall have a strength test. For safety valves, their constant pressure, return pressure and other tests shall comply with the specifications and regulations of the visual mirror cup valve.
(2)阀门安装之彰应作强度和密封性试验。低压阀门抽查20%,如不合格应100%的检查;中、高压阀门应100%的检查。
 (2) Strength and tightness tests shall be made prior to valve installation. Low-pressure valve checks 20%, if unqualified, all should be in inspection; medium and high pressure valves should be 100% inspection.
(3)试验时,阀门安装位置应在容易进行检查的方向。
 (3) During the test, the valve installation position should be in a place where it is easy to check.
(4)焊接连接形式的阀门,用肓板试压不行时可采用锥形密封或O型圈密封进行试压。
 (4) Valves in the form of welded joints may be tested by taper seals or O-shaped sealing ring when the pressure test is not suitable with a sampan plate.
(5)液压试验时就将阀门空气尽量排除。
 (5) The valve air should be eliminated as much as possible during the hydraulic test.
(6)试验时压卫生级阀门力要逐渐增高,不允许急剧、突然地增压。
 (6) The pressure of the sanitary valve in the test should be gradually increased, and it is not allowed to pressurize abruptly and suddenly.
(7)强度试验和密封性式验持续时间一般为2-3min,重要的和特殊的阀门应持续5min。小口径阀门试验时间可相应短一些,大口径阀门试验时间可相应长一些。在试验过程中,如有疑问可延长试验时间。强度试验时,不允许阀体和阀盖出现冒汗或渗漏现象。密封性试验,转子泵一般阀门只进行一次,安全阀、高压阀等生要阀门需进行两次。试验时,对低压、大口径的不重要阀门以及有规定允许渗漏的阀门,允许有微量的渗漏现象;由于电站用阀、化工阀门、冶金阀门、高温高压阀门以及其他阀门要求各异,对电磁阀渗漏要求应按有关规定执行。
(7) The duration of strength test and sealability test is generally 2-3 minutes, and important and special valves should be tested last 5 minutes. Small-diameter valve test time can be correspondingly shorter, large-diameter valve test time can be longer. During the test, the test time can be extended if in doubt. In the strength test, the valve body and valve cover are not allowed to sweat or leak. In the sealing test, the general valve of the rotor pump only be tested once, safety valve, high pressure valve and other important valves need to be tested twice. During the test, for the low-pressure, large-diameter, non-essential valves and the valves that are allowed to leak, a slight leakage is allowed; due to the requirements of power station valves, chemical valves, metallurgical valves, high-temperature and high-pressure valves and other valves are various. Solenoid valve leakage requirements should be implemented in accordance with relevant regulations.