原文：
1、返流 涡轮分子泵具有提供超清洁、无碳氢化合物的真空环境的能力，故常被用户选用。然而，用户也偶尔会发现涡轮分子泵提供不了不含碳氢化合物的真空环境。经调查发现碳氢化合物的来源，50%是操作失误所带来的问题，如涡轮分子泵的前级泵为油封式旋片泵时，没有控制返流的安全阀，不合理的放气程序都会引起油蒸汽的返流，不合要求的安全阀也会引起油污染。 为了在系统中实现无碳氢化合物这一要求，在前级泵不是干式泵的情况下，有必要了解涡轮分子泵的压缩比及如何给泵充气的一些基本知识。 2、压缩比 涡轮分子泵的压缩比是指前级管道（排气口处）的压力与进气口处的压力之比。由于被抽气体的分子量不同，泵对各种气体的压缩比也不同。气体分子量M的平方根与压缩比K的关系如图6所示，泵对氢的压缩比很小，一般为1000左右，这样一来如果前级管道中氢的压力为1×10-7Torr（13.33μPa），那么进气口处氢的压力则小1000倍，即为1×10-10Torr（13.33nPa）。由于氢是超高真空系统中主要的残余气体，所以氢的压缩比是决定涡轮分子泵的极限压力的关键因素。 涡轮分子泵对于大分子量的气体，如对那些碳氢化合物分子的压缩比是相当大的，一般高于1012。这个比值根据不同泵，以及不同分子量而不同，由于前级泵的不同和其它因素，涡轮分子泵的前级管道中的碳氢化合物的分压力在10-4Torr（13.33mPa）～10-6Torr（133.3μPa）之间，在这种条件下，在泵的入口处碳氢化合物的分压力将低了1012倍，即为10-16Torr（13.33fPa）或更低。这样几乎是无限小的压力，已超出了可测量的范围，即使最灵敏的质谱仪也难以测出。 3、充气措施 (1)为什么要充气 当涡轮分子泵关闭或运转极慢时，泵将不再有 足够大的压缩比（泵内压力梯度）来阻止前级侧存在的碳氢化合物通过涡轮叶片向真空室进行返流。这种现象称作反扩散或分子返流。在静态条件下，整个系统的压力均衡时，在前级管道侧，油的分压力通常为10-4～10-6Torr（或13.33mPa～133.3μPa）{zh1}也会波及到泵的入口处。当泵关闭时，适当地给泵内充气是控制油分子返流，保持真空室内无碳氢化合物的一种有效的措施。 当停泵后，碳氢化合物返流很快通过泵进入真空室内，如果系统仍保持在真空状态下，碳氢化合物将会粘在清洁的叶片和真空室的表面上。在随后再运转该系统时，将极难抽除粘着的碳氢化合物。另一方面，在涡轮分子泵停止运转时，如果给泵充入干燥氮气或干燥空气，则该干燥气体将给暴露的表面提供一层气体保护层，而且在系统充气后，返流的碳氢化合物由于与充入的气体混合起来，从而它的粘着能力很弱，在混合气体中碳氢化合物所占比例极小，在下一次抽空时也很快就能被抽走。 (2)延迟充气 虽然在泵断开电源后就应给泵充气已被大家所接受，且很平常，但是，涡轮分子泵在切断电源后，泵要渐渐地减速，若延迟几秒或几分钟再充气会更好一些。在泵减速到它平时速度的30%～50%期间，此时泵仍能起到抽气和压缩作用。能有效地使真空室处在真空状态下且能防止碳氢化合物的返流。延迟充气也能使阀门有足够的时间关闭，在经常停电的情况下，延迟充气是很有用的。为了延迟充气，前级真空必须维持在1～1000μmHg（1×10-3mmHg~1mmHg或133.3mPa～133.3Pa）范围之内，所以在涡轮分子泵与前级泵之间必须有一个真空阀，或者在前级泵内部装一个控制阀，该阀应在电源中断时，使涡轮分子泵与前级泵隔离开来。否则，通过前级泵、前级管道被充气，并导致了油的污染。 (3)在何处充气 在涡轮分子泵的前级侧充气，能强制使碳氢化合物立刻通过涡轮分子泵流入真空室。另一方面，若在涡轮分子泵吸入侧充气，能达到以清洁气体覆盖表面的目的。并使气流流向涡轮分子泵（自上而下），能暂时阻止、延迟碳氢化合物的返流，也有 些涡轮分子泵在压缩级之间进行中间充气，它和在吸入侧充气控制碳氢化合物返流几乎同样有效。在超高真空系统中，在压缩级充气尤其优越。因为中间充气不需要价格昂贵的金属密封的可烘烤的充气阀。 (4)怎样充气 如果涡轮分子泵置于一个清洁、干燥的周围环境中，就可以充室内的空气。然而充气入口的位置必须仔细选择。如果充气入口位置靠近油封式旋片泵的排气口位置之上，则充入的气体中会含有油蒸汽势必会对真空系统造成污染，而且如果空气是湿的，为了减少以后再抽气的时间，于是要充入干燥氮气或经过干燥器过滤的空气。另外也不一定总是充入大气压力下的气体，若充入气体的压力为几Torr（几hpa）的干燥气体就足以能控制碳氢化合物的返流。 4、前级管道设安全阀 如果不采用一个操作合理的前级管道安全阀，就有可能即污染涡轮分子泵又污染真空室。当前级泵断电停车时，前级泵就会给自己充气反向通到涡轮分子泵的排气口。这种前级泵充气会输送前级管道返流的泵油，之后通过涡轮分子泵进入真空室，这种现象称为油污染，被污染后涡轮分子泵的叶片就必须在厂家的指导下用氟利昂来清洗。 在涡轮分子泵与前级泵之间装上一个真空阀，可以防止反向充气，当停电时立刻关上此阀。理想的情况是，它即能对前级泵入口充气又不致于使泵油返流浸入安全阀。另外，只有当它的压力基本均衡时才能打开安全阀，否则 就有可能出现压力冲击前级管道的问题，例如，在断电瞬间前级泵压力将为大气压力，然而前级管道仍可能处于真空状态下。若阀门的两侧压力差很大，一旦通电阀门会立刻打开，含污染油的大气压下的气体将由前级泵冲向前级管道，从而会污染系统。所以安全阀需要一定的延迟开启的时间，以便让前级泵将阀门后的管道内抽成真空，阀前后的压差均衡时才可打开安全阀，总之采取办法来控制阀门的两侧的压力差，不使气流返冲。现在许多直联式旋片泵，在泵内装有安全阀，但阀门密封性能一定要保证，一旦阀门关不上后果相当严重，涡轮分子泵系统就会被油污染，这种问题是可能通过检测事先发现的。在运转的前级泵上安装一个前级真空规管，将泵关闭如果前级压力增加值在10～1000μmHg（1×10-2～1torr或1.333～

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译文：
1, reflux Turbo molecular pump has to provide ultra-clean hydrocarbon-free vacuum environments, it is often the user choose. However, users occasionally can not find turbo molecular pump to provide vacuum free of hydrocarbons. The survey found that the source of hydrocarbons, 50% of operational errors caused by problems such as turbo-molecular pump before the pump as oil seals rotary vane pump, no control valve regurgitation, unreasonable deflation program will lead to oil vapor reflux, non-conforming safety valve can also cause oil contamination. In order to achieve non-hydrocarbons in the system this requirement, the first stage pump is not the case of dry pumps, turbo molecular pump is necessary to understand the compression ratio and how to pump some basic knowledge of inflation. 2, compression ratio Turbo molecular pump before the compression ratio is the level pipe (exhaust orifice) pressure and the air inlet orifice pressure ratio. Because different molecular weight was pumping gas, pump gas compression ratio for various different. Gas molecular weight M and the square root of the relationship between compression ratio K as shown in Figure 6, the compression ratio of the hydrogen pump is small, generally around 1,000, so to pre-stage pipeline if hydrogen pressure 1 × 10-7Torr (13.33 μPa), then the inlet pressure of the hydrogen Office 1000 times smaller, namely 1 × 10-10Torr (13.33nPa). Because hydrogen is the major ultra-high vacuum system residual gas, hydrogen compression ratio is to determine the limit pressure for turbomolecular pumps a key factor. Turbo molecular pump for the large molecular weight gases, such as those hydrocarbon molecules in the compression ratio is quite large, generally higher than 1012. This ratio depending on the pump, and the different molecular weight and different, due to the different pre-pump and other factors, turbo molecular pump in the first stage pipeline partial pressure of hydrocarbons in the 10-4Torr (13.33mPa) ~ 10-6Torr ( 133.3μPa) between, in such conditions, the entrance of hydrocarbons in the sub-pump pressure will be 1012 times lower, ie 10-16Torr (13.33fPa) or less. This pressure is almost infinitely small, already beyond the measurable range, even the most sensitive mass spectrometer is also difficult to detect. 3, inflatable measures (1) Why should inflation When the turbo-molecular pump shut down or running very slow, the pump will no longer have enough compression ratio (pressure gradient pump) to prevent the presence of hydrocarbons before the class side of the vacuum chamber through the turbine blades to reflux. This phenomenon is called counter-proliferation or molecular reflux. Under static conditions, the pressure equilibrium of the system, first-class pipe side, the oil pressure is usually sub-10-4 ~ 10-6Torr (or 13.33mPa ~ 133.3μPa) eventually spread to the pump entrance. When the pump is off, due to inflation is to control the oil pump molecular reflux, hydrocarbon-free vacuum chamber to maintain an effective measure. When stopping the pump, the hydrocarbon reflux into the vacuum chamber through the pump soon, if the system remains in a vacuum, the hydrocarbons will be glued to clean leaves and the surface of the vacuum chamber. In the subsequent operation of the system will be extremely difficult extraction of hydrocarbons adhesion. On the other hand, the turbo molecular pump to stop running, if filled to the pump dry nitrogen or dry air, then the dry gas will provide a layer of the exposed surface of protective layer of gas and inflation in the system, the reflux of carbon As the hydrogen compounds and filled up the gas mixture to its weak adhesion ability, the percentage of hydrocarbon gas mixture is very small when the next will soon be taking the time to take away. (2) delay in inflatable Although the pump to pump off the power after the inflatable should have been accepted by all, and very common, but the turbo molecular pump to cut off the power, the pump should gradually slow down, if the delay in seconds or minutes will be re-inflated better. Reduction in the pump to its normal rate of 30% to 50% of the period, then the pump can still play the role of ventilation and compression. Can be effective in a vacuum chamber and can prevent the reflux of hydrocarbons. Delayed inflation valve can also have enough time off, in the case of frequent power outages, delayed inflation is very useful. In order to delay inflation, the former level of vacuum must be maintained at 1 ~ 1000μmHg (1 × 10-3mmHg ~ 1mmHg or 133.3mPa ~ 133.3Pa) range, so the turbo molecular pump with a pump must have a vacuum between the valves, or the first pump installed inside a control valve, the valve should be a power failure, so turbo molecular pumps with pumps to isolate. Otherwise, by the former-stage pump, the front pipes were inflated, and caused oil pollution. (3) where the inflation Turbo molecular pump in the first grade side of the inflatable, can force the hydrocarbons into the immediate adoption of turbo-molecular pump chamber. On the other hand, if the suction side of the turbo molecular pump inflatable, can achieve the purpose of cleaning gas covered surface. And to air flow turbo molecular pump (top down), can temporarily stop, delay hydrocarbon reflux, also some turbo molecular pump in the middle between the compression level inflatable, inflatable side of it and control in the inhalation of carbon hydrogen compounds almost equally effective reflux. In the ultra-high vacuum systems, pneumatic compression level, particularly advantageous. Inflatable in between the metal does not require expensive sealing inflation valve can be baked. (4) how inflation If the turbo-molecular pump placed in a clean, dry environment, it can be filling the indoor air. However, inflation must carefully choose the location of the entrance. If the inflatable entrance located near the oil seals rotary vane pump outlet location above, then the gas will be filled with oil vapor will inevitably pollute the vacuum system, and if the air is wet, in order to reduce the exhaust later time, so be filled dry nitrogen or air through the dryer filter. Another is not always sufficient pressure gas into the atmosphere, if the filled gas pressure of several Torr (a few hpa) the dry gas is enough to control the hydrocarbon reflux. 4, the front channels set safety valve If you do not use a first-level pipeline operation of reasonable safety valve, it is possible that pollution has contaminated turbo molecular pump chamber. Stopping the current pump power, the former-stage pump will reverse himself inflated to the turbo molecular pump through the exhaust port. This pre-pump inflation level before transmission pipeline will pump oil reflux, followed by turbo-molecular pump into the vacuum chamber, a phenomenon known as oil pollution, contaminated leaves after the turbo molecular pump in the factory must be under the guidance of Freon to clean. In the turbo molecular pump with a pump fitted with a vacuum between the valve, can prevent reverse inflation, when the power failure immediately shut the valve. Ideally, it is before the pumps can import inflation it will not come to pump oil immersion safety valve regurgitation. In addition, only when its basic equilibrium pressure relief valve to open, or there may be pressure from the impact of the pipeline before the class, for example, in electricity before the pump pressure will be instantaneous atmospheric pressure, however, may still be at the front stage pipelines vacuum. If the large pressure difference on both sides of the valve, the valve will immediately open once the power, oil pollution, atmospheric pressure with gas pumps will be rushed to the former level before the pipeline, which will pollute the system. So open the safety valve requires a certain time delay to allow the valve before the pump after the pumping into the vacuum pipe, valves before and after the equilibrium pressure required to open the safety valve, short take measures to control the valves on both sides The pressure difference, not to flow back red. Now a lot of direct-coupled rotary vane pumps, the pump that has the safety valve, the valve sealing performance but must ensure that, once the valve is not the serious consequences to turbo molecular pump system will be oil pollution, the problem is possible found by testing in advance. Pumps in operation prior to Install a pre-level vacuum gauge will shut down if the first stage pressure pump to increase the value of the 10 ~ 1000μmHg (1 × 10-2 ~ 1torr or 1.333 ~