液压油外文翻译.docx

外文资料 hydraulic fluidsfor long service life, safety reasons, and reliable operation of hydraulic circuits, it is very important to use the correct fluid for the application. the most common fluid is based on mineral oil, but some systems require fire resistance because of their proximity to a heat source or other fire hazard. （water is also making its return to some hydraulic systems because it is inexpensive, fireproof, and does not harm the environment.）transmit energy.the main purpose of the fluid in any system is to transmit energy. electric, internal combustion, steam powered, or other prime movers drive a pump that sends oil through lines to valves that control actuators. the fluid in these lines must transmit the prime movers energy to the actuator so it can perform work. the fluid must flow easily to reduce power losses and make the circuit respond quickly.lubricate.in most hydraulic systems, the fluid must have good lubrication qualities. pumps, motors, and cylinders need ample lubrication to make them efficient and extend their service life.mineral oils with anti-wear additives work well and are available from most suppliers. some fluids may need special considerations in component design to overcome their lack of lubricity.seal.fluid thickness can be important also because one of its requirements is for sealing. almost all pumps and many valves have metal to metal sealing fits that have minimal clearance but can leak at elevated pressures. thin watery fluid can flow through these clearances, reducing efficiency and eroding the mating surfaces. thicker fluids keep leakage to a minimum and efficiency high.there are several areas that apply to specifying fluids for a hydraulic circuit. viscosity is the measure of the fluids thickness. hydraulic oils thickness is specified by a sus or ssu designation, similar to the sae designation used for automotive fluids. sus stands for saybolt universal seconds (or as some put it, saybolt seconds universal). it is a measuring system set up by a man named saybolt. simply stated, the system takes a sample of fluid, heats it to 100 f, and them measures how much fluid passes through a specific orifice in a certain number of seconds.viscosity is most important as it applies to pumps. most manufacturers specify viscosity limits for their pumps and it is best to stay within the limits they suggest. the prime reason for specifying a maximum viscosity is that pressure drop in the pump suction line typically is lowand if the oil is too thick, the pump will be damaged due to cavitation. a pump can move fluid of any viscosity if the inlet is amply supplied. on the other end, if fluids are too thin,pump bypass wastes energy and generates extra heat. all other components in the circuit could operate on any viscosity fluid because they only use what is fed to them. however,thicker fluids waste energy because they are hard to move. thin fluids waste energy because they allow too much bypass.viscosity index (or vi) is a measure of viscosity change from one temperature to another. it is common knowledge that heating any oil makes it thinner. a normal industrial hydraulic circuit runs at temperatures between 100 and 130 f. cold starts could be as low as 40to 50 f. using an oil with a low vi number might start well but wind up with excessive leakage and wear or cause cavitation damage at startup and run well at temperature. mostindustrial hydraulic oils run in the 90- to 105-vi range and are satisfactory for most applications.pour point is the lowest temperature at which a fluid still flows. it should be at least lower than the lowest temperature to which the system will be exposed so the pump can always have some lubrication. consider installing a reservoir heater and a circulation loop on circuits that start or operate below 60 f.refined mineral oil does not have enough lubricating qualities to meet the needs of modern day hydraulic systems. several lubricity additives to enhance that property are added to mineral oil as a specific manufacturers package. these additives are formulated to work together and should not be mixed with others additives because some components may be incompatible.refined mineral oil also is very much affected by temperature change. in its raw state it not only has low lubricity but also would thin out noticeably with only a small increase in temperature. viscosity modifiers enhance the oils ability to remain at a workable viscosity through a broad temperature range.there are several causes of hydraulic oil oxidation. these include contamination, air, and heat. the interaction of these outside influences cause sludge and acids to form. oxidation inhibitors slow or stop the fluids degradation and allow it to perform as intended.wear inhibitors are additives that bond with metal parts inside a hydraulic system and leave a thin film that reduces metal-to-metal contact. when these additives are working, they extend part life by reducing wear.in most hydraulic systems, fast and turbulent fluid flow can lead to foaming. anti-foaming agents make the fluid less likely to form bubbles and allow those that do form to dissipate more rapidly.moisture in the air can condense in a hydraulic reservoir and mix with the fluid. rust inhibitors negate the effect of this unwanted water and protect the surfaces of the systems metal components. all of these additives are necessary to extend system life and improve reliability.overheating the fluid can counteract the additives and decrease system efficiency.overheating also thins the oil and reduces efficiency because of internal bypassing. clearances in pump and valve spools let fluid pass as pressure increases, causing more heating until thefluid breaks down. external leaks through fittings and seals also increase as fluid temperatures rise. another problem caused by overheating is a breakdown of some seal materials. most rubber compounds are cured by controlled heat over a specific period of time. continued heating inside the hydraulic system over long periods keeps the curing process going until the seals lose their resiliency and their ability to seal. it is best if hydraulic oil never exceeds 130f for any extended period. installing heat exchangers is the most common cure for overheating but designing heat out of a circuit is the better way.cold oil is not a problem as far as the oil is concerned but cooling does increase viscosity.when viscosity gets too high, it can cause a pump to cavitate and damage itself internally.thermostatically controlled reservoir heaters easily eliminate this problem in most cases.fire-resistant fluidscertain applications must operate near a heat source with elevated temperatures or even open flames or electrical heating units. mineral oil is very flammable. it not only catches fire easily but will continue to burn even after removing the heat source. this fire hazard situation can be eliminated by several different choices of fluids. these fluids are not fireproof, only fireresistant,which means they will burn if heated past a certain temperature but they will not continue to burn after removing them from the heat source.generally, the fire-resistant fluids do not have the same specifications as mineral oil-based fluids. pumps often must be down rated because the fluids lubricity or specific gravity is different and would shorten the pumps service life drastically at elevated pressures or high rotary speeds. some fire-resistant fluids are not compatible with standard seal materials so seals must be changed. always check with the pump manufacturer and fluid supplier before using or changing to a fire-resistant fluid.wateroriginally, hydraulic circuits used water to transmit energy (hence the word hydraulics). the main problem with water-filled circuits was either low-pressure operation or very expensive pumps and valves to operate with this low viscosity fluid above 500 to 600 psi. when huge oil deposits were discovered, mineral oil replaced water because of its additional benefits. water made a brief comeback during an oil shortage crisis but quickly succumbed when oil flowed freely again.in the late 90s, water again made inroads into oil-hydraulic systems. several companies have developed reliable pumps and valves for water that operate at 1500 to 2000 psi. there are still limitations (such as freezing) to using water, but in certain applications it has many benefits.one big advantage is that there are fewer environmental problems during operation or in disposing of the fluid. price also is a factor because water costs so little and is readily available almost anywhere.some suppliers are making equipment that operates on seawater to eliminate possible contamination of the earths potable water sources. these systems operate at elevated pressures without performance loss.high water-content fluidssome types of manufacturing still use water as a base and add some soluble oil for lubrication.this type of fluid is known as high water-content fluid (or hwcf). the common mixture is 95% water and 5% soluble oil. this mixture takes care of most of the lubricity problems but does not address low viscosity concerns. therefore, systems using hwcf still need expensive pumps and valves to make them efficient and extend their life.rolling mills and other applications with molten metals are one area where hwcf is prevalent. often the soluble oil is the same compound used for coolant in the metal-rolling process. this eliminates concerns about cross-contamination of fluids and the problems it can cause.water-in-oil emulsionssome systems use around 40% water for fire resistance and 60% oil for lubrication and viscosity considerations. again, these are not common fluids because they require special oil and continuous maintenance to keep them mixed well and their ratio within limits. most manufacturers do not want the problems associated with water-in-oil emulsions so their use isvery limited.外文资料翻译液压油考虑到使用寿命长短，安全性的原因，以及液压回路可靠运行性，液压系统中使用正确的液压油这是非常重要的。最常见的液压油是基质矿物油，但有些系统因为靠近热源或其它火灾隐患要求防火性能较高。（水也可以循环应用于液压系统，因为它便宜，防火，不污染环境。）传输能量液压油在液压系统中的主要作用是传输能量。电力、内燃机、蒸汽动力或其他原动机驱动泵，通过液压油传递到控制阀门，控制执行元件传送能量。在这些回路传输能量时液压油必然为执行机构的主要推动者，因此可以执行工作。流动的流体必须要尽量降低功率损失，使回路迅速作出反应。润滑 在大多数液压系统中，润滑液是必须得到质量保证的。泵、马达、液压缸等都需要充足的润滑液，来提高效率和延长其使用寿命。具有抗磨损添加剂的矿物油工作良好，而且销路很好。一些液压油可能需要特殊考虑组件设计，以克服他们的润滑不足。密封 液压油密度也同样十分重要，因为它的一个重要性能要求是密封。几乎所有的泵和液压阀都是由许多金属件组装而成，金属密封配合间隙很小，但有可能泄漏升高液压系统的压力损失。薄水状液压油可能流过这些间隙，降低效率，损坏了配合的表面。较稠的液体可将泄漏不断的降到最低限度，提高效率。有几种液压油适用于指定的液压回路流体的领域。粘度是用于测量流体的粘稠度的，液压油的密度是由ssu指定的，类似于sae指定为汽车使用流体。 sus代表（或如一些说法，赛波特秒通用）的赛波特通用秒，这是一个由一名为赛波特的人建立的测量系统。简单地说，该系统采用的液体样品是加热到100时，测量在特定时间内有多少液体通过节流孔。在液压泵的运用中液压油粘度是最为重要的，大多数制造商指定的液压油粘度极限，他们建议最好限定在这个范围内。指定最大粘度的主要原因是，在泵的吸入管路压降通常很低，如果液压油太浓，泵会由于气蚀而被损坏。如果进入油箱的气体被充足提供，一个泵则可以带动任何粘度的流体。另一方面，如果液体密度太小，液压泵则会泄漏能量从而产生多余的热量。回路中的所有其他组件可以在任何粘度流体运作，因为他们只用于供给传动。然而，密度较大的流体会由于难带动而相对浪费能源；密度较小的流体浪费能源，是因为他们损失太多。粘度指数（或vi）是用于测量在不同温度下黏度的变化的参数。任何油液加热后密度都会变小这是常识。一个正常的工业液压线路的运行温度在100至130华氏度和冷启动则是40至50华氏度。使用低粘度指数的液压油运行会很好，但是，在启动和运行高速中，过多的气体的进入会造成气蚀和磨损或损伤。大多数工业液压油在90105 vi的范围内运行，并且对于大多数应用系统是比较令人满意的。倾点是液体仍可以流动的最低的温度。只有在比最低温度还要低的温度下该系统将暴露，因此泵就需要一些润滑。考虑安装一个冷却回路和一个加热器回路，就可以在低于60华氏度的情况下仍可以启动该系统。 精制矿物油并不具备足够的润滑油的质量，以满足现代液压系统的需要。但几种润滑添加剂，为了提高液压油的品质被添加到矿物油中，这作为具体的生产厂家的一揽子计划，这些添加剂配比在一起工作，不应与其他添加剂混合，因为某些组成成分可能是不相容的。精制矿物油也经常受温度变化的影响。在其原始状态下，它不仅具有较低的润滑性，而且随着稍微的温度加热也可将密度变小。粘度调节剂提高液体的性能并保持在一个可行的粘度范围内。 液压油的氧化有以下几个原因。这些原因包括杂质污染，空气侵入和热量。这些外来因素的影响是污泥和酸相互作用形成。氧化抑制剂可以阻止液体的氧化，并允许它取得预期效果。抑制剂是一种添加剂，与液压系统内的金属部件紧密连接在一起，并留一个润滑薄膜，减少金属与金属的接触磨损。当这些添加剂工作时，他们将减少磨损延长零件寿命。在大多数液压系统中，液压油的快速流动和湍流会导致气泡。防泡沫剂使流体不太可能形成泡沫，并允许那些确实形式消散更为迅速。 空气中的水