Biodegradable lubricants — Analysis of metalworking oils and hydraulic fluids by mass spectroscopy

Biodegradable metalworking oils and hydraulic fluids were screened for their base oil composition using a special mass spectrometric technique — direct exposure probe chemical ionisation mass spectrometry (CI(NH₃)-MS). All but one of the hydraulic fluid samples were rapeseed oil or trimethylolpropane trioleate based, the other sample being a neopentylglycol ester trimethylolpropane ester mixture. Ethylhexyl ester of rapeseed oil fatty acids (or similar) was present in some of the metalworking fluids in addition to rapeseed oil, whilst other samples were pure rapeseed oil. In several cases a trimethylolpropane/neopentylglycol ester base was found. Preliminary results for additive isolation/identification show the usefulness of preparative gel permeation chromatography.     

Lubricating properties of rapeseed‐based oils

Three commercially available hydraulic/transmission lubricants based on rapeseed oil have been investigated for their lubricating properties. The coefficient of friction, scuffing‐load capacity, and pitting resistance were evaluated, and the results compared with a corresponding commercial mineral‐based oil. The results showed in general a substantially lower coefficient of friction and better pitting resistance for rapeseed‐based oils than for the mineral oil. Scuffing load capacity was, with one exception, the same for all oils. As a result of lower shear stresses during contact, and a higher viscosity index, the temperatures in the gearbox were lower for the rapeseed oils tested than for the mineral oil. Insufficient antiwear behaviour at high loads was found to be a major drawback of these vegetable oils.     

Wear testing and specification of hydraulic fluid in industrial applications

The aim of this paper was to investigate the possibilities to use a model test to simulate the wear between cylinder bore and piston in a radial piston hydraulic motor. The tests were performed in a reciprocating test rig where the contact geometry is of the cylinder–plate type. The influence of different types of commercially available hydraulic fluids on wear protection and friction was studied. From the study, it was concluded that the use of water glycols can cause increased wear in hydraulic motors operating in low speed applications. It was also seen that the FZG test alone appears not to be enough as a hydraulic fluid wear test, at least not in the tribological conditions present in the performed wear test.     

Tribological properties of an environmentally adopted universal tractor transmission oil based on vegetable oil

Universal tractor transmission oil (UTTO) is multipurpose tractor oil formulated for use in transmissions, final drives, wet brakes and hydraulic systems of tractors employing a common oil reservoir. In the present work, the results of a series of tests performed to evaluate vegetable based oils are presented. Tribological properties of formulated rapeseed and high oleic sunflower based UTTO were investigated in the standard and non-standard test procedures and compared with the properties of commercially available synthetic and mineral UTTO. Performances of test oils were demonstrated by using SRV high frequency test device, four-ball test rig, and FZG spur gear test rig. For final tests a laboratory hydraulic system and a spur gear test rig were used.     

Performance of environment-friendly hydraulic fluids and material wear in cavitating conditions

The cavitation performance of various metals and hydraulic fluids used in a hydraulic system was evaluated using the vibratory test method. Mineral oil, vegetable oil and oil-in-water emulsions were used in the experiments. The materials were selected based on the general components employed in a hydraulic system—AA 5005 aluminium alloy, ASTM A536-84 ductile spheroidal graphite (SG) cast iron, ASTM A48-83 grey cast iron, AISI 303 stainless steel and BS 1400 LG2 bronze. It was observed that vegetable oil exhibits the best medium for erosion resistance for all metals due to its high viscosity index. Emulsions having higher oil concentration produced lesser erosion damage. It was seen that an increase in viscosity led to a decrease in the rate of growth and collapse of bubbles and hence reduced erosion on the surfaces of the specimens. The experiments also revealed that materials with high hardness had less cavitation damage for all lubricants. A comparison of cavitation performance revealed that materials and hydraulic fluids have a dependent relationship. Results indicate that AISI 303 stainless steel would be the best choice in the construction of a hydraulic system and this is especially the case when using a hydraulic fluid that has a high viscosity index.     

Testing,application, and future development of environmentally friendly ester base fluids

Biodegradation test methods have been compared with regard to test conditions and test parameters. It has been shown that three methods are, in principle, suitable for non-water soluble products. These are the Sturm test (OECD no. 301B), the MITI test (OECD 301 C), and the CEC L-33-T-82 test method. A comparison in an actual test showed that the CEC test gives the highest biodegradation values, while the Sturm test and the MITI test give lower values. It is noted that the CEC test measures the amount of material used for both energy production and growth of the biomass, while the other methods measure only the material used for energy production. A possible explanation for the difference between the Sturm and the MITI test results is given. The CEC test is shown to be more suitable for the lubricant industry. Applications of biodegradable lubricants are reviewed, particularly hydraulic fluids. It is shown that rape seed oil (natural ester) and synthetic polyol esters have similarities regarding structure but also significant differences. This results in much better thermal and oxidative stability for the synthetic esters. These also offer the possibility of making a range of products of different ISO grades with similar properties. Brief consideration is given to future potential, notably for biodegradable four-stroke lubricants. Finally, there is a timely reminder that, owing to the present limited availability of natural oils and fats and their cost, only 19% of the market for mineral oil base fluids could be replaced by natural oils and fats and their derivatives.     

Gear Lubrication in Inert Gas Atmospheres

An investigation was made of the effect of inert gas atmospheres on the gear load-carrying capacity of lubricants. The experiments were performed in two types of gear test machines, using case-hardened AMS-6260 steel test gears. It was found that two mineral oils (a solvent-extracted turbine oil base stock and a USP grade white mineral oil), as well as the same oils fortified with different extreme-pressure additives, all exhibited a decided increase in load-carrying capacity when the gears were operated in an atmosphere of nitrogen or argon instead of air. On the other hand, the response of synthetic lubricants was not found to be necessarily similar. In fact, only one of the six synthetic fluids tested showed any significant increase in load-carrying capacity when the gears were operated in a nitrogen atmosphere.     

滚齿机复合材料滑动导轨磨损性能

为了掌握滚齿机复合材料滑动导轨磨损性能,在振动爬行原理、Reynolds理论及复合材料滑动导轨工况参数的基础上,建立了复合材料滑动导轨稳定磨损阶段的磨损深度随磨损时间变化关系模型,提出了磨损深度测试方案,成功研制出复合材料滑动导轨磨损测试试验机。运用滚齿机复合材料滑动导轨样件进行了磨损试验,分析了复合材料滑动导轨磨损深度的试验与理论数据,揭示了复合材料滑动导轨磨损规律。理论数据与试验数据相比较,两者相对误差低于5%,验证了理论研究的正确性,表明该研究可为滚齿机复合材料滑动导轨的油槽结构、油槽几何参数及油膜承载能力的优化设计与导轨选型提供有益参考。     

Mechanical testing of hydraulic fluids

The antiwear properties of hydraulic fluids are important because hydraulic pump and motor wear is costly. While international hydraulic fluid performance standards continue to be developed, e. g., the ISO/TC28/SC4 committee's draft ISO DIS 11158 ‘Specifications for mineral oil hydraulic fluids’, the normal hydraulic fluid performance specifications represent minimum requirements. Performance specifications for nonmineral oil hydraulic fluids are also being developed. Typically, both the user and the fluid manufacturer possess insufficient objective information about the antiwear properties of special fluids, e. g., environmentally acceptable hydraulic fluids (EAHF) or fire‐resistant hydraulic fluids (FRHF) for use in hydraulic equipment such as axial‐piston pumps, vane pumps or radial‐piston motors. Manufacturer's specifications must therefore be determined. The required lubrication properties can be determined by either laboratory pump tests or a field trial, often at the customer's expense. The lubrication properties of a hydraulic fluid should ideally be determined under conditions that are equivalent to field practice. This paper will discuss the use of the vane pump test and the FZG gear test to gauge ‘recommended’ hydraulic fluid performance; many non‐mineral hydraulic fluids, such as environmentally acceptable hydraulic fluids, fire‐resistant fluids or synthetic hydraulic fluids, cannot be used in axial‐piston systems based only on results obtained with these tests, and additional testing is always required. Proposals are made for testing of such fluids on a variable‐load test rig. These tests are done with axial‐piston pumps, or other similar displacement systems, and are intended to determine the industrial suitability of non‐mineral hydraulic fluids.     

Minimizing the hydraulic side effects of weirs construction by using labyrinth weirs

It is no doubt that weirs are one of the most important hydraulic structures that play a vital role in irrigation project. So, it is necessary to minimize the hydraulic side effects of weirs. Throughout this paper, experiments were conducted to investigate the suitable dimensions and shape of weir's crest to increase head loss, decrease upstream bank level upstream weir and get the most economic structure. Various crest angles of labyrinth weir were tested under different flow conditions. Also back water curve upstream weir was studied according to different weir crest angles. A case of linear weir crest was also included in the test program. The experimental results indicated that labyrinth weirs have lower operating heads and longer crest length compared with a linear weir having the same lateral space and the same discharge. Results showed that the crest weir angle of 60° is the best angle of weir crest. It reduces water level above crested level and the relative jump depth by 18% and 20%, respectively. In addition, it increase the average values of the dissipated energy and the discharge coefficient by 15% and 14%, respectively. It also gave maximum reduction in backwater curve profile by about 17%. Furthermore, the model was verified using CFD numerical model. The numerical results agreed with the experimental results.     

Tribological properties and action mechanism of N,N-dialkyl dithiocarbamate-derived S-hydroxyethyl borate esters as additives in rapeseed oil

Four N,N-dialkyl dithiocarbamate-derived S-hydroxyethyl borates with different carbon chains were synthesized and characterized. Their tribological performances as additives in rapeseed oil (RO) were investigated using two four-ball test machines. It was found that they can greatly improve the extreme pressure and antiwear properties of RO when they are used as additives in RO. The elemental composition and chemical nature of the antiwear film generated on the surfaces of the steel balls were studied with X-ray photoelectron spectroscopy (XPS) and their antiwear mechanism was put forward.     

Metalworking emulsions from industrial vegetable oils

In the present work, an attempt has been made to develop the indigenous formulation for metalworking lubricants by replacing mineral oils partially with non‐edible industrial oils like rapeseed and karanja oil. Metalworking formulations consist of vegetable oil, mineral oil, an emulsifier and commercial additives for better performance. Non‐edible vegetable oils such as karanja and rapeseeds are renewable, biodegradable and cheaper than synthetic fluids. The constituent vegetable oils and mineral oils were evaluated for physico‐chemical characteristics and blended as per the saponification value and viscosity requirements of the reference oils. The so formulated oils are taken as 5% oil‐in‐water emulsion and tested for lubricity, load bearing capacity, particle size distribution, wear test, weld load test and plate‐out test. Performance of all formulated oils was compared with that of the reference oils, and optimized to meet the market requirements. Copyright © 2008 John Wiley & Sons, Ltd.     

电液步进油缸特性的理论分析及试验研究

针对在高炉和连铸机等重工业恶劣工况下,采用传统液压伺服系统,抗油液污染能力低、可靠性差等问题,依据直接位移反馈闭环控制原理,结合数字化控制方式,开发了步进式电液控制液压缸。阐述了电液步进缸的工作机理,并对其进行数学建模和理论分析,建立了系统传递函数方框图。在试验台上对电液步进缸的内泄漏流量、十脉冲精度、一步精度、重复位置精度和频率响应等静动态性能进行测试,结果表明,电液步进缸在开环状态下也具有较高的控制精度和响应速度,可靠性高、抗油液污染能力强。     

A study of the tribological behaviour of perfluoro-polyethers

The tribological behaviour of perfluoropolyethers (PFPEs) was investigated by performing four-ball extreme-pressure (EP), Falex, four-ball wear, Reichert, SRV (both point-plane and plane-plane contacts), Amsler and TE 77 determinations on four commercially available Fomblin Y fluids, which cover the entire viscosity range. For comparison a petroleum-based hydraulic oil was subjected to the same tests.In load-carrying capacity measurements (four-ball EP and Falex tests) the PFPEs also surpassed the hydraulic oil as an EP gear lubricant.The performances of the PFPEs in determinations of their wearpreventing characteristics were variable. They were better than the hydraulic oil in Reichert tests but behaved in a roughly identical way in four-ball wear determinations and were inferior to it in the SRV (point-plane contact) method.The irregular behaviour is due to the different severity of operating conditions. The harsh strains exerted in four-ball EP, Falex and Reichert tests led to elevated contact temperatures, thus causing the decomposition of fluorinated macromolecules. The subsequent reactions of decomposition products originated the fluoride films to which the relevant performances of PFPEs are ultimately due. As the stresses to be endured in the SRV (point-plane contacts) tests had not been so extreme, the temperature at which the thermal decomposition of PFPEs would have begun was not attained.The more fluid the grade, the better was its performance in four-ball wear tests, since a lower viscosity led to a more abundant supply of lubricant at the rubbing spots and thus to a smaller wear rate.Lubrication was hydrodynamic in SRV (plane-plane contact), Amsler and TE 77 tests, and hence no damage took place in them. Friction coefficients, which depended on both testing machine and test conditions, were slightly higher for PFPEs than for the hydraulic oil.     

Oxidation Stability and Tribological Behavior of Vegetable Oil Hydraulic Fluids

The new generation of vegetable oil hydraulic fluids has a price advantage and provides field longevity comparable to synthetic esters at moderate temperature.

This article investigates the oxidation stability and tribological behavior of fully formulated vegetable oil hydraulic fluids. Differences in origin (canola, soybean, and sunflower oil) and the degree of unsaturation are studied. Modified ASTM D943 (Dry TOST) was found reliable to evaluate the impact on oxidative stability of various additive packages in vegetable oils. Tribological testing utilized laboratory hydraulic pumps such as the Vickers V 104C, Vickers 20VQ, and Vickers PFB-5 under a variety of temperatures, pressures, pump outputs, and speeds. The conditions of aging fluids were monitored by evaluation of TAN, viscosity, wear rate, and depletion of antioxidants. Voltammetric technique was applied to determine the concentration of antioxidant in systems. Based on analysis of antioxidant consumption, the main degenerative process in vegetable oils under demanding pump operations is similar to pyrolytic degradation, rather than oxidation.

By selecting the appropriate synergistic additive packages, a remarkable pump longevity can be obtained for each vegetable base stock studied.     

基于滤膜淤积法的油液污染在线监测系统

针对油液污染是导致液压系统故障的主要原因以及目前国内外油液污染大多不能实现在线监测的现状,提出基于滤膜淤积法的恒功率测量法,在保证功率恒定的情况下测量通过某一固定体积时的压差来间接测量油液的污染度。采用阀用直流电磁铁作为主推动力元件来推动特制液压缸内活塞杆来获得压降,自制金属滤膜作为传感元件,并设计了监控软件操作平台,完成了油液污染在线监测系统的设计、调试和试验工作。试验结果表明,该系统能给出相应的ISO、NAS及SAE油液污染等级,并有良好的人机交互能力。与离线测试装置相比,具有可信的精确度和实时性,可满足生产现场的使用要求,具有一定的推广应用价值。     

Vegetable and synthetic hydraulic fluids to improve the overall efficiency of a hydrostatic transmission

The purpose of the investigation reported here was to determine whether or not a hydrostatic transmission can act as an alternative to a conventional one, and, if so, to ascertain to what extent the fluid type contributes to an improvement in the efficiency of the hydrostatic transmission. The results presented in this paper are derived from an experimental field test of the hydrostatic transmission of a belt conveyor. This belt conveyor is one part in an ore‐transport line at LKAB mining company in Kiruna. The hydrostatic transmission replaced a conventional transmission consisting of an electric motor, a belt drive and a gearbox. The hydrostatic transmission was operated using three different hydraulic fluids: Shell Tellus TX 68, a conventional mineral oil; Mobil SHC 526, a synthetic fluid; and Binol Hydrap II, a vegetable fluid. All fluids have the same ISO viscosity grade, VG 68. The measurements on the transmission show a 3% overall efficiency improvement when using vegetable and synthetic hydraulic fluids compared with the mineral oil. The current at the start of the transmission was reduced by a factor of 6, compared to that of the conventional transmission. The installed 110 kW electric motor was replaced with one of 55 kW. The test also showed that a closer study of all operating conditions, and a selection of components suited to the size of the load, can improve the overall efficiency of the hydrostatic transmission.     

A2F-10泵试验对工程机械液压油寿命评价

面对液压技术发展和复杂的工况,为了选择和开发工程机械适用的液压油,需要可靠、有效的评价手段。根据日本工程机械协会标准方法(JCMAS P045)要求,设计建立了A2F柱塞泵台架,利用试验过程中液压油的黏度、酸值、泡沫特性、油泥和金属含量变化,对工程机械上应用的各种液压油进行综合性能评价。研究表明选择II类及以上基础油和无锌添加剂技术的液压油具有更长的使用寿命。     

Tribological properties of non‐ferrous coating lubricated with rapeseed oil containing lubricant additives

With the increasing requirements of environmental protection, using lead, hexavalent chromium and other heavy metals will be prohibited in different surface coatings. In this paper, the non‐ferrous CrN coatings and the rapeseed oil were chosen as friction pair and biodegradable lubricant. The tribology properties were investigated using SRV‐IV reciprocating friction wear test. The worn surface of CrN coatings was observed and analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The results indicate that the rapeseed oil containing 1 wt.% MoZn (MoDTC (molybdenum dithiocarbamate) + ZnDTP (zinc dithiophosphate) (1 : 3)) exhibits better friction‐reducing properties than the rapeseed oil containing 1 wt.% PN (an amine salt of an alkoxylphosphate) additives, whereas the rapeseed oil containing 1 wt.% PN additive exhibits better wear resistance properties than the rapeseed oil containing 1 wt.% MoZn additives. This is partly attributed to the tribophysical and tribochemical reactions between the lubricant and the CrN coating sliding surfaces. Copyright © 2012 John Wiley & Sons, Ltd.     

低温环境中热冲击载荷对电液伺服比例阀动态性能影响测试

低温环境中液压元件动态特性对系统整体性能与功能的影响至关重要。为研究电液伺服比例阀在低温环境中受到高温油液热冲击载荷时动态性能的变化,在设计的低温液压综合试验系统中对某型电液伺服比例阀进行了不同温度下的冷启动与热冲击阶跃响应特性和频率响应特性试验。对比分析测试结果表明,无论是冷启动还是热冲击工况下,随着环境温度降低,油液黏度增加,被试阀的响应时间都会逐渐变长。热冲击工况下的响应时间比冷启动工况下短,但相较于常温启动要长。当环境温度越接近于油液工作的极限低温,其对阀动态性能的影响越显著。