In DEH commissioning of thermal power steam turbine, the problem of high-pressure regulating valve jitter will be encountered. In this case, we need to calmly analyze, find problems from phenomena and find methods from problems. The following are the methods of diagnosis and treatment of this problem from the perspective of design and commissioning, hoping to give some reference to power plants and commissioning units.

超高壓針閥一般采用角形單座結(jié)構(gòu),加工簡(jiǎn)單,閥座容易配換,閥芯為單導(dǎo)向結(jié)構(gòu)。閥門角形單座結(jié)構(gòu)流路簡(jiǎn)單,阻力小,適用于高壓差、高粘度、含懸浮物和顆粒狀物質(zhì)流體,可以避免結(jié)焦和堵塞,也便于自凈和清洗。閥芯和閥座是超高壓針閥進(jìn)行開關(guān)控制的兩個(gè)核心零件,組成超高壓針閥開關(guān)的動(dòng)密封副。通過控制閥芯與閥座之間錐形密封面的接觸與分離,實(shí)現(xiàn)閥通道的關(guān)閉和開啟。閥芯與密封圈之間的圓周密封面構(gòu)成閥的滑動(dòng)密封副,用于保證閥室與外界的密封。閥芯采用針形,靠錐面密封,一般閥芯錐角為59°,閥座錐角為60°。實(shí)驗(yàn)證明在開錐孔時(shí),錐角選取45°～60°時(shí),孔邊緣的應(yīng)力集中系數(shù)小,且使應(yīng)力出現(xiàn)在錐孔的小端。閥座錐角大,閥芯錐角小時(shí),靠上表面密封,有利于提高閥的使用壽命.

Ultra high pressure needle valve generally adopts angular single seat structure, with simple processing, easy replacement of valve seat, and single guide structure of valve core. The angular single seat structure of the valve has simple flow path and low resistance. It is suitable for fluids with high pressure difference, high viscosity and containing suspended and granular substances. It can avoid coking and blockage, and is also convenient for self purification and cleaning. The valve core and valve seat are the two core parts of the ultra-high pressure needle valve for switching control, which form the dynamic sealing pair of the ultra-high pressure needle valve switch. By controlling the contact and separation of the conical sealing surface between the valve core and the valve seat, the valve channel can be closed and opened. The circumferential sealing surface between the valve core and the sealing ring constitutes the sliding sealing pair of the valve, which is used to ensure the sealing between the valve chamber and the outside world. The valve core is needle shaped and sealed by conical surface. Generally, the cone angle of the valve core is 59 ° and the cone angle of the valve seat is 60 °. Experiments show that when the cone angle is 45 ° ~ 60 °, the stress concentration factor at the edge of the hole is small, and the stress appears at the small end of the cone hole. Large cone angle of valve seat, small cone angle of valve core and sealing against the upper surface are conducive to improving the service life of the valve

在出現(xiàn)高壓調(diào)閥抖動(dòng)的情況時(shí)，我們可以首先查看閥門指令是否發(fā)生數(shù)據(jù)上的變化，來(lái)進(jìn)行分別的處理。

In case of jitter of high-pressure regulating valve, we can first check whether the valve command changes in data for separate processing.

一、閥門指令未發(fā)生變化，那么問題就可能出現(xiàn)在伺服卡以及伺服閥之上。若是閥門指令未發(fā)生變化并且伺服卡輸出穩(wěn)定，則問題可能是伺服閥卡澀或者油動(dòng)機(jī)與閥門連接有卡澀。若是此時(shí)伺服卡輸出晃動(dòng)，則可能的問題有：伺服卡PI參數(shù)不合理、閥位反饋波動(dòng)（LVDT故障、LVDT屏蔽不良等問題引起）、伺服卡故障。

1、 If the valve command does not change, the problem may appear on the servo card and servo valve. If the valve command does not change and the servo card output is stable, the problem may be that the servo valve is jammed or the connection between the hydraulic servo motor and the valve is jammed. If the output of the servo card shakes at this time, the possible problems are: unreasonable PI parameters of the servo card, valve position feedback fluctuation (caused by LVDT fault, poor LVDT shielding and other problems), and servo card fault.

二、閥門指令自身發(fā)生變化，則我們需要查詢?yōu)槭裁磿?huì)出現(xiàn)指令的抖動(dòng)。若是在并網(wǎng)之前就發(fā)生指令波動(dòng)的問題，則原因可能有：轉(zhuǎn)速PI參數(shù)不合理，引起過調(diào)；轉(zhuǎn)速通道故障，引起轉(zhuǎn)速信號(hào)的非正常波動(dòng)，進(jìn)而導(dǎo)致轉(zhuǎn)速回路的輸出波動(dòng)。而轉(zhuǎn)速通道故障的可能原因有：磁阻探頭故障、轉(zhuǎn)速屏蔽不良等。而若是在并網(wǎng)之后發(fā)生閥位指令波動(dòng)，則原因可能有：功率、壓力回路PI參數(shù)不合理，導(dǎo)致出現(xiàn)過調(diào)；閥門運(yùn)行在流量曲線拐點(diǎn)處；一次調(diào)頻轉(zhuǎn)速波動(dòng)；遙控指令波動(dòng)等。

2、 If the valve command itself changes, we need to query why the command jitter occurs. If the command fluctuation occurs before grid connection, the reasons may be: the speed PI parameter is unreasonable, resulting in overshoot; Speed channel failure causes abnormal fluctuation of speed signal, which leads to output fluctuation of speed circuit. The possible causes of speed channel failure are: magnetoresistive probe failure, poor speed shielding, etc. If the valve position command fluctuates after grid connection, the reasons may be: unreasonable PI parameters of power and pressure circuit, resulting in over regulation; The valve operates at the inflection point of the flow curve; Primary frequency modulation speed fluctuation; Remote control command fluctuation, etc.

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