一、振動原因分析:
1、 Vibration cause analysis:
調節(jié)閥的振動與噪聲根據其誘發(fā)因素不同,大致可分為機械振動、氣蝕振動和流體動力學振動等原因。
The vibration and noise of regulating valves can be roughly divided into mechanical vibration, cavitation vibration, and fluid dynamics vibration based on their triggering factors.
機械振動:
Mechanical vibration:
機械振動根據其表現形式可以分為兩種狀態(tài)。一種狀態(tài)是調節(jié)閥的整體振動,即整個調節(jié)閥在管道或基座上頻繁顫動,其原因是由于管道或基座劇烈振動,引起整個調節(jié)閥振動。此外還與頻率有關,即當外部的頻率與系統(tǒng)的固有頻率相等或接近時受迫振動的能量達到大值、產生共振。另一種狀態(tài)是調節(jié)閥閥瓣的振動,其原因主要是由于介質流速的急劇增加,使調節(jié)閥前后差壓急劇變化,引起整個調節(jié)閥產生嚴重振蕩。
Mechanical vibration can be divided into two states based on its manifestation. One state is the overall vibration of the regulating valve, that is, the entire regulating valve frequently vibrates on the pipeline or base, due to severe vibration of the pipeline or base, causing the entire regulating valve to vibrate. In addition, it is also related to frequency, that is, when the external frequency is equal to or close to the natural frequency of the system, the energy of forced vibration reaches a maximum value and resonance occurs. Another state is the vibration of the regulating valve disc, which is mainly caused by the sharp increase in medium flow rate, causing a sharp change in the differential pressure before and after the regulating valve, causing serious oscillation of the entire regulating valve.
氣蝕振動:
Cavitation vibration:
氣蝕振動大多發(fā)生在液態(tài)介質的調節(jié)閥內。氣蝕產生的根本原因在于調節(jié)閥內流體縮流加速和靜壓下降引起液體汽化。調節(jié)閥開度越小,其前后的壓差越大,流體加速并產生氣蝕的可能性就越大,與之對應的阻塞流壓降也就越小。
Cavitation vibration mostly occurs inside the regulating valve of liquid media. The fundamental cause of cavitation is the acceleration of fluid contraction and the decrease in static pressure inside the regulating valve, which causes liquid vaporization. The smaller the opening of the regulating valve, the greater the pressure difference before and after it, the greater the possibility of fluid acceleration and cavitation, and the corresponding blockage flow pressure drop.
流體動力學振動:
Fluid dynamics vibration:
介質在閥內的節(jié)流過程也是其受摩擦、受阻力和擾動的過程。湍流體通過不良繞流體的調節(jié)閥時形成旋渦,旋渦會隨著流體的繼續(xù)流動的尾流而脫落。這種旋渦脫落頻率的形成及影響因素十分復雜,并有很大的隨機性,定量計算十分困難,而客觀卻存在一個主導脫落頻率。當這一主導脫落頻率(亦包括高次諧波)在與調節(jié)閥及其附屬裝置的結構頻率接近或一致時,發(fā)生了共振,調節(jié)閥就產生了振動,并伴隨著噪聲。振動的強弱隨主導脫落頻率的強弱和高次諧波波動方向一致性的程度而定。
The throttling process of the medium inside the valve is also a process of friction, resistance, and disturbance. When turbulent fluid passes through a regulating valve with poor flow around the fluid, it forms a vortex, which will detach as the fluid continues to flow through the wake. The formation and influencing factors of this vortex shedding frequency are very complex and have great randomness, making quantitative calculation very difficult. However, objectively, there exists a dominant shedding frequency. When the dominant shedding frequency (including high-order harmonics) is close to or consistent with the structural frequency of the regulating valve and its accessories, resonance occurs, and the regulating valve produces vibration accompanied by noise. The strength of vibration depends on the strength of the dominant shedding frequency and the degree of consistency in the direction of high-order harmonic fluctuations.
二、方案:
2、 Solution:
從調節(jié)閥的使用和理論分析可以證明,誘發(fā)調節(jié)閥振動和噪聲的因素有很多,這些因素又相互影響,很多都是同時發(fā)生的,這就使調節(jié)閥的減震降噪更加困難,需要結合閥門材質、結構和流體動力學等方面綜合考慮。
From the use and theoretical analysis of regulating valves, it can be proven that there are many factors that induce vibration and noise in regulating valves, and these factors affect each other, many of which occur simultaneously. This makes it more difficult to reduce vibration and noise in regulating valves, and requires comprehensive consideration of valve material, structure, and fluid dynamics.
(1)增加剛度法 :
(1) Increasing stiffness method:
對振蕩和輕微振動,可增大剛度來或減弱,如選用大剛度的彈簧,改用活塞執(zhí)行機構等辦法都是可行的。
For oscillations and slight vibrations, increasing stiffness can be used to eliminate or weaken them. Methods such as using high stiffness springs or switching to piston actuators are feasible.
增加阻尼法 :
Increase damping method:
增加阻尼即增加對振動的摩擦,如套筒閥的閥塞可采用“O”形圈密封,采用具有較大摩擦力的石墨填料等,這對或減弱輕微的振動還是有一定作用的。
Increasing damping means increasing friction against vibration. For example, the valve plug of a sleeve valve can be sealed with an "O" ring, and graphite packing with high friction can be used. This can still have a certain effect on eliminating or weakening slight vibrations.
(3)增大導向尺寸,減小配合間隙法 :
(3) Increase the guiding dimension and reduce the fit clearance method:
軸塞形閥一般導向尺寸都較小,所有閥配合間隙一般都較大,有0.4~lmm,這對產生機械振動是有幫助。因此,在發(fā)生輕微的機械振動時,可通過增大導向尺寸,減小配合間隙來削弱振動。
Axial plug valves generally have smaller guiding dimensions, and all valve clearances are generally larger, ranging from 0.4 to 1mm, which is helpful for generating mechanical vibration. Therefore, when slight mechanical vibration occurs, the vibration can be weakened by increasing the guide size and reducing the fit clearance.
(4)改變節(jié)流件形狀,共振法 :
(4) Change the shape of the throttle element and eliminate resonance method:
因調節(jié)閥的所謂振源發(fā)生在高速流動、壓力急劇變化的節(jié)流口,改變節(jié)流件的形狀即可改變振源頻率,在共振不強烈時比較容易。具體辦法是將在振動開度范圍內閥芯曲面車削0.5~1.0mm。如某廠家屬區(qū)附近安裝了一臺自力式壓力調節(jié)閥,因共振產生嘯叫影響職工休息,我們將閥芯曲面車掉0.5mm后,共振嘯叫聲消失。
The so-called vibration source of the regulating valve occurs at the throttling port with high-speed flow and rapid pressure changes. Changing the shape of the throttling component can change the frequency of the vibration source, which is relatively easy to solve when the resonance is not strong. The specific method is to turn the curved surface of the valve core within the range of vibration opening by 0.5-1.0mm. A self operated pressure regulating valve was installed near the residential area of a certain factory, and due to resonance, it caused a whistling sound that affected the rest of employees. After we lowered the curved surface of the valve core by 0.5mm, the resonance whistling sound disappeared.
(5)更換節(jié)流件共振法 :
(5) Replacing throttle components to eliminate resonance method:
①更換流量特性,對數改線性,線性改對數
① Change flow characteristics, logarithmic to linear, linear to logarithmic
②更換閥芯形式。
② Replace the valve core form.
如將軸塞形改為“V”形槽閥芯,將雙座閥軸塞型改成套筒型;將開窗口的套筒改為打小孔的套筒等。
If the plug type is changed to a "V" groove valve core, and the double seat valve plug type is changed to a sleeve type; Change the sleeve for opening windows to a sleeve for punching small holes, etc.
(6)更換調節(jié)閥類型以共振:
(6) Change the type of regulating valve to eliminate resonance:
不同結構形式的調節(jié)閥,其固有頻率自然不同,更換調節(jié)閥類型是從根本上共振的有效的方法。一臺閥在使用中共振十分厲害———強烈地振動(嚴重時可將閥破壞),強烈地旋轉(甚閥桿被振斷、扭斷),而且產生強烈的噪音(高達100多分貝)的閥,只要把它更換成一臺結構差異較大的閥,立刻見效,強烈共振奇跡般地消失。如某維尼綸廠新擴建工程選用一臺DN200套筒閥,上述三種現象都存在,DN300的管道隨之跳動,閥塞旋轉,噪音100多分貝,共振開度20~70%,考慮共振開度大,改用一臺雙座閥后,共振消失,投運正常。
Different structural forms of regulating valves naturally have different natural frequencies. Changing the type of regulating valve is an effective method to fundamentally eliminate resonance. A valve resonates severely during use - it vibrates strongly (can be damaged in severe cases), rotates strongly (even the valve stem is broken or twisted), and produces strong noise (up to over 100 decibels). As long as it is replaced with a valve with a significant structural difference, it immediately takes effect, and the strong resonance miraculously disappears. If a new expansion project of a certain Vinylon factory uses a DN200 sleeve valve, all three phenomena mentioned above exist. The DN300 pipeline jumps, the valve plug rotates, the noise is over 100 decibels, and the resonance opening is 20-70%. Considering the large resonance opening, after switching to a double seat valve, the resonance disappears and is put into normal operation.
減小汽蝕振動法 :
Reducing cavitation vibration method:
對因空化汽泡破裂而產生的汽蝕振動,自然應在減小空化上想辦法。①讓氣泡破裂產生的沖擊能量不作用在固體表面上,特別是閥芯上,而是讓液體吸收。套筒閥就具有這個特點,因此可以將軸塞型閥芯改成套筒型。②采取減小空化的一切辦法,如增加節(jié)流阻力,增大縮流口壓力,分級或串聯(lián)減壓等。
For the cavitation vibration caused by the rupture of cavitation bubbles, it is natural to find ways to reduce cavitation The impact energy generated by bursting bubbles does not act on the solid surface, especially on the valve core, but is absorbed by the liquid. The sleeve valve has this characteristic, so the plug type valve core can be changed to a sleeve type Take all measures to reduce cavitation, such as increasing throttling resistance, increasing the pressure at the constriction port, grading or series pressure reduction, etc.
避開振源波擊法 :
Avoiding source wave impact method:
外來振源波擊引起閥振動,這顯然是調節(jié)閥正常工作時所應避開的,如果產生這種振動,應當采取相應的措施。
External vibration sources can cause valve vibration, which should be avoided during normal operation of the regulating valve. If such vibration occurs, corresponding measures should be taken.
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