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1通过在线监测液压油污染提高液压挖掘机性能摘要 高价值产品的原始设备制造商（OEM）通常为客户提供维护或服务包，以确保其产品在整个生命周期内保持最高的效率。为了快速高效地规划维护要求，OEM 厂商需要有关其产品的使用和磨损的准确信息。近几十年来，航空航天工业尤其成为使用实时数据进行产品监控和维护调度的专家。通常产生大量来自产品监控的实时使用数据，并将其传回 OEM，进行诊断和预测分析。最近，其他行业，如建筑业和汽车业，也开始发展这些领域的能力，基于条件的维修（CBM）越来越受欢迎，作为满足客户需求的手段。煤层气需要由 OEM 对实时产品数据进行连续的监控，但是对于这些行业尤其是建筑业来说，最大的挑战在于缺乏准确和实时的了解产品如何被使用可能是因为复杂的供应链存在于建设项目中。本研究重点关注移动液压系统的当前动态数据采集技术，在这种情况下使用移动在线粒子污染传感器;目的是评估适应性以达到条件维护的诊断和预后要求。它得出结论，液压油污染分析，即检测金属颗粒，为测量液压元件的实时磨损提供了可靠的方法。关键字：液压油，污染，粒子传感器，建筑项目，诊断，预后1.移动产品维护策略1.1 介绍传统上，产品的设计和制造符合客户的要求，但这些都可能发生巨大变化,随着时间的推移。 但是，建筑设备，卡车，公共汽车和飞机等高价值产品预计会有长寿命。 这些产品通常作为舰队数量购买，可能在服役 10 至 30 年或更长时间.产品销售协议通常包括一个维护包，这可能是最常见和最有效的方式确保产品保持高可靠性水平1。 出售维修或其他服务产品服务被称为产品服务系统（PSS） 。 PSS 已被定义为可销售的一组产品服务能够2共同满足用户的需求2。 这种制造方法已经被开发为可持续发展替代制造商和消费者的生产和消费的传统概念3。 PSS 旨在通过延长现有的寿命来减少制造新产品的原材料消耗4产品5然而，很难预测复杂产如建筑设备需要多年的维护，特别是当产品工作条件和工作类型未知时。 因此，维护已经成为 OEM 厂商运营预算的重要组成部分6，并且企业通过降低维护计划中目前存在的复杂性和不确定性来寻求解决这一负担。更大的实时数据采集和处理应使他们能够对现场的产品状况进行更准确的评估（即在退回工厂进行维护和修理之前） 。 Madenas 表示，对服务和维护系统开发的研究对研究人员的兴趣不大，而且这种有限的研究往往侧重于航空航天领域7。然而，其他具有高数据交易的行业，以及汽车和建筑行业等重大保修和维护成本也应受到实时数据采集和处理驱动的预防性维护方案的好处。本文报告的研究集中在通常用于移动液压系统（即建筑和采矿机械）上的动态数据采集技术。 它利用 22 吨液压挖掘机进行 1900 小时油污监测研究，以确定改善液压系统维护方式的方法，即通过有效的金属污染检测。1.2 维护方法维护经常被认为是关于固定不再能够实现其设计功能的产品; 这也称为运行失败（RTF） 。 英国标准将维护定义为：“所有技术和行政行为，包括监督行动，旨在保留项目或恢复其能够执行所需功能的状态的组合” ，8。澳大利亚维护工程学会（MESA）指出，“维护是工程决策和相关行动，必须和足够的优化指定的能力” ，9。 在这个定义中，“指定功能的优化”意味着产品的功能应该是以高水平的性能和可靠性进行交付。曾俊华表示，维护的主要目标是以成本有效的方式维护系统功能10，但维护已被描述为在任何给定系统的整个产品生命周期中所需的昂贵和令人生畏的支持元素11。 凯利进一步表示，维护应以最低资源成本达到约定的产出水平和运行模式，并在系统的状况和安全性的限制之内12。 总之，维护必须确保所需的可靠性，可用性，效率和物理能力产品13。 基于条件的维护（CBM）是基于对其状况和维护物流的非侵入性测量来维护工程资产的理念14。西南研究所（SRI）的研发经理苏珊祖比克说，航空航天工业认为，煤层气是一种维护理念，主动管理资产的健康状况，以便在需要时进行维护，而对设备的影响最小（Zubik 2010） 。 CBM 旨在防止故障发生 10，因此设备状况通过检查和诊断进行评估，维护操作只在必要时进行15。美国空军（USAF）将 CBM 定义为从嵌入式传感器获得的武器系统状况的实时评估和/或使用便携式设备的外部测试和测量得到的一组维护过程和功能16。诊断和预后是 CBM 计划中的两个重要组成部分，其诊断涉及故障检测和预测，在发生故障和退化预防之前处理17。以前的研究证实，机器组件，传感器数据采集，数据提取，转换和分析都是预后维护的关键方面18。Rausch（2008）指出了几种常用的监测方法，如振动分析，工艺参数建模，摩擦学，热成像和目视检查。 传感器通常嵌入到系统的关键部分，以获得与系统健康有关的数据1。例如，劳斯莱斯公司使用引擎健康管理（EHM）提供其“由电力供应”监控服务。 Rolls 3Royce Trent 发动机永久安装约 25 个传感器，它们提供数据（即发动机各个位置的压力，涡轮机气体温度和冷却空气温度）19。 有了这样的真实时间数据，OEM 可以诊断产品的状况，同时仍然在现场运行。 分析技术包括网络和基于概率的自主系统，用于实时失败预测预测20。煤层气是基于降级系统的状态启动的，因此，只有在出现降级已经达到临界水平时，组件才被更换。 因此，可以将设备的非计划停机时间最小化。 此外，预测组件故障时间的能力意味着可以大大降低生命周期成本（LCC） ，因为组件和设备的寿命可以充分利用。 因此，原始设备制造商或服务提供商也可以通过更准确地了解维护所需的内容来更准确地制定服务计划表20。1.3 维护中的挑战关于现场运行的产品的现状的不确定性使得 OEM 厂商难以有效和成本有效地计划维护计划。 这导致维护不足的产品的风险更大，这可能导致故障和更长的计划外停机时间，这两者都是客户不能接受的。 为了减少这种不确定性，需要获取和处理与产品使用特别相关的准确产品数据，以确定所需的维护/服务的频率和类型。 Scheidt 将数据分类为静态和动态生命周期数据21。静态数据包括在产品设计阶段创建的产品信息，如产品规格，物料清单（BOM）和维修手册。 动态数据在产品操作阶段收集，通常在客户使用（而不是由OEM）使用时，包括使用模式，维修操作，环境工作条件和组件磨损率等数据。 数据通常存储在板载数据记录器和处理器中。 OEM 也使用问卷调查来获取产品性能，使用模式和客户满意度。一些较大的 OEM 厂商邀请其经销商和客户进行为期一周的会议，分享他们的产品体验22。虽然可以以这种方式收集大量关于产品性能的第一手反馈信息，但这种信息变得过早迅速，可能会出现错误，歧义和主观性。原始设备制造商从产品中收集准确和实用的实时（动态）数据是很困难的。 当设计产品时，假设在特定条件和方法中使用，如设计规范中所述，但是某些客户（用户）可能会滥用产品，从而降低运营寿命。 在施工设备行业，产品经常受到非正统的恶劣使用和日常维护保养的不足，这可能导致零件加速磨损，缩短寿命。 为了解决这个问题，OEM 可以考虑根据航空航天工业来监测产品的实时使用情况。 监控系统使服务提供商能够立即安排必要的维护，检测到异常事件。 还可以提取和分析任何相关的实时数据，以确定所需的工作和部件23。然而，涉及产品使用数据的生成，处理和管理的数据监控系统是复杂和昂贵的，并且可能超过被监视的组件的成本。 沃尔沃建筑设备北美远程技术经理比尔索伯（Bill Sauber）表示，OEM 厂商倾向认为，如果收集更多动态的实时操作数据，将会获得更多的信息。 然而，这个数据大多只是噪音。 Caterpillar 的技术应用专家 Johnathan Metz 还表示，客户很可能被数量庞大的数据所淹没，与客户的需求无关24。 因此，如果没有系统及时分析收集的数据，只能获得有限的价值25。因此，为了具有成本效益和竞争力，建筑设备 OEM 厂商将设计监控系统作为整体产品设计的一部分非常重要。 要做到这一点，有必要了解在不同运行模式下产品的状况如何受到影响，以及如何检测出这种情况的变化。 这是至关重要的，因此监控系统，包括传感器的位置和数量可以被设计为通过实时数据分析来最大化他们可以提供的有用知识，同时最大限度地降低传感器安装和操作4所带来的成本。 本文的其余部分介绍了通过 1900 h 油污染监测研究进行的 CBM 移动在线颗粒污染传感器的适用性评估。2.监测液压系统预测故障建筑行业 OEM 如 Caterpillar Inc.（CAT） ，Komatsu 有限公司和 J C Bamford 挖掘机有限公司为各行业生产重型设备，如反铲装载机，轮式装载机和液压挖掘机，用于处理各种行业的大型和重型材料。 世界上超过 45的建筑机械是液压挖掘机26，因为与其他建筑机械相比，其生产率高，操作简便27。大多数挖掘机由内燃机提供动力。 与传统的汽车不同，传动发动机的动力来驱动在液压系统内提供流动的液压泵（图 1） 。 液压是通过限制液体的介质传递力和/或运动的科学，并且通过推动该限制液体来传递动力。 泵被安装以推动电路周围的油，有时会对其加压。阀块通常用于控制油的流动和方向。 这些是金属铸件，其中油路机构与阀芯相交，其数量取决于要控制的服务数量。 控制阀的故障可能导致生产损失，比预防成本贵多倍28。挖掘机，如吊臂，铲斗，铲斗和回转马达的主要结构部件通过液压柱塞移动。 液压马达将流体动力转换为线性力和运动。 由液压油缸产生的线性力是系统压力和有效面积的乘积，减去系统效率低下。非公路挖掘机液压回路的复杂性以及他们必须忍受的艰难的工作条件，意味着这种系统的可靠性始终是认真考虑的29。 液压系统运行分析表明，系统及其部件的可靠性取决于压力，流量，温度，粘度和颗粒污染物等多种因素30。 Muncie Inc. Muncie Power Products 的培训和教育主管戴夫道格拉斯（Dave Douglass）声称 70-90的液压系统故障可归因于污染的油32。加拿大国家研究委员会还发现，82的磨损问题是由于磨损，侵蚀和疲劳造成的颗粒引起的故障33。 国家流体动力中心（NFPC）也认为，他们的石油污染之一管理课程，无法解决和有效管理污染将导致昂贵的停机时间和部件寿命短34。 CAT Ltd 认为，油中磨损颗粒的浓度是潜在组分问题的关键指标。 因此，条件监测的油分析技术为运营商带来了巨大的潜在收益35。 为了澄清，对于 DesCase，TBR 策略总裁兼可靠性服务副总裁 Ingalls 和 Barnes 将油污染物定义为污垢，水，空气，磨损碎片和泄漏的冷却液36。液压回路污染物影响液压设备的性能和使用寿命，导致三种系统故障之一：退化：间隙尺寸的颗粒与两面相互作用，经常引起磨损，腐蚀和曝气问题37。间歇性：污染会导致阀芯上的暂时阻力或防止提升阀移动。尽管微粒很可能被阀芯重复移动而被冲走，但只有完全拆卸才能确保不会再次发生故障38。灾难性的：当几个大颗粒或大量的小颗粒导致运动部件完全缉获时，突然发生这种情况39。有许多不同类型的污染物可能导致系统故障，其中水分可能是最常见的40。 一般来5说，液压系统中有三种主要的污染源：内置污染物，也称为主要污染物，来自液压元件的制造，组装和测试41。由于系统的密封不足，例如柱塞42或油层的通气盖过滤不足39，经常会发生压痕污染。 在采矿业中使用的机器在液压系统中倾向于具有高水平的硅，污垢和水。 在维护过程中也可能引起污染，特别是在重新注入液压油时，如果不考虑环境污染38。产生的污染，也称为磨损，是由于液压部件在使用过程中的接触而引起的，并不总是可以避免的44。Improving hydraulic excavator performance through in line hydraulic oil contamination monitoringAbstractIt is common for original equipment manufacturers (OEMs) of high value products to 6provide maintenance or service packages to customers to ensure their products are maintained at peak efficiency throughout their life. To quickly and efficiently plan for maintenance requirements, OEMs require accurate information about the use and wear of their products. In recent decades, the aerospace industry in particular has become expert in using real time data for the purpose of product monitoring and maintenance scheduling. Significant quantities of real time usage data from product monitoring are commonly generated and transmitted back to the OEMs, where diagnostic and prognostic analysis will be carried out. More recently, other industries such as construction and automotive, are also starting to develop capabilities in these areas and condition based maintenance (CBM) is increasing in popularity as a means of satisfying customers demands. CBM requires constant monitoring of real time product data by the OEMs, however the biggest challenge for these industries, in particular construction, is the lack of accurate and real time understanding of how their products are being used possibly because of the complex supply chains which exist in construction projects. This research focuses on current dynamic data acquisition techniques for mobile hydraulic systems, in this case the use of a mobile inline particle contamination sensor; the aim was to assess suitability to achieve both diagnostic and prognostic requirements of Condition Based Maintenance. It concludes that hydraulic oil contamination analysis, namely detection of metallic particulates, offers a reliable way to measure real time wear of hydraulic components.Keywords:Hydraulic oil，contamination，Particle sensors，Construction equipment，Diagnostic， Prognostic1. Maintenance strategy for mobile products1.1. IntroductionTraditionally, products are designed and manufactured to meet customers demands, but these can change dramatically over time. However, high value products such as construction equipment, trucks, buses and aeroplanes are expected to have long lifespans. These products are often bought in quantity as a fleet and are likely to be in service for 10 to 30 years or moreProduct sales agreements often include a maintenance package and this is perhaps the most common and effective way to ensure that the products maintain a high reliability level 1. Selling maintenance or other services together with the product in a bundle is known as a Product Service System (PSS). A PSS has been defined as a marketable set of products and services capable of jointly fulfilling a users needs 2. This manufacturing approach has been developed as a sustainable 7alternative to the conventional concepts of production and consumption for both manufacturers and consumers 3. PSS aims to reduce the consumption of raw materials for manufacturing new products 4 by prolonging the life span of existing products 5.However, it is very difficult to predict the maintenance that complex products such as construction equipment will require over many years, particularly when the conditions within which the product is working and the types of work being done are unknown. As a result maintenance has become an important part of operational budgets for OEMs 6, and companies seek to address this burden by reducing the complexity and uncertainty which currently exist in maintenance planning. Greater real time data acquisition and processing should enable them to conduct more accurate assessments of a products condition in the field (i.e. before it is returned to the factory for maintenance and repair). Madenas stated that research into service and maintenance system development attracts little interest from researchers, and furthermore, this limited research tends to focus on the aerospace sector 7. However, other industries with high data transactions, and significant warranty and maintenance costs, such as the automotive and construction industries, should also benefit from preventative maintenance schemes driven by real time data acquisition and processing. The research reported in this paper focused on a dynamic data acquisition technique that is typically used on mobile hydraulic systems (i.e. construction and mining machines). It draws on a 1900-h oil contamination monitoring study of a 22-tonne hydraulic excavator, to identify ways to improve maintenance regimes in hydraulic systems, namely through effective wear metal contamination detection.1.2. Maintenance approachesMaintenance is often perceived as being about fixing products that are no longer able to fulfil their designed functionality; this is also known as run to failure (RTF). British Standards define maintenance as: “The combination of all technical and administrative actions, including supervision actions, intended to retain an item in, or restore it to, a state in which it can perform a required function”, 8. The Maintenance Engineering Society of Australia (MESA) states that“Maintenance is the engineering decisions and associated actions necessary and sufficient for the optimisation of specified capabilities”, 9. In this definition, “the optimisation of specified capabilities” implies that the products functionality should be delivered at a high level of performance and reliability.Tsang stated that the primary objective of maintenance is to preserve system functionality in a cost-effective manner10, yet maintenance has been described as an expensive and daunting element of support required throughout the product lifecycle of any given system 11. Kelly went even further by suggesting that maintenance should achieve the agreed output level and operating pattern at a minimum resource cost, and within the constraints of the systems condition and safety12. In summary, maintenance must ensure the required reliability, availability, efficiency, 8and capability of a physical product 13.Condition-based maintenance (CBM) is a philosophy for maintaining engineering assets based on non-intrusive measurement of their condition and maintenance logistics 14. The R & D manager of Southwest Research Institute (SRI), Susan Zubik, stated that the aerospace industry considers CBM to be a maintenance philosophy to actively manage the health condition of assets in order to perform maintenance only when it is needed, and with the least disruption to the equipments uptime (Zubik 2010). CBM is designed to prevent the onset of a failure 10, hence equipment condition is assessed by inspection and diagnosis, and maintenance actions are performed only when necessary 15. The United States Air Force(USAF) defines CBM as a set of maintenance processes and capabilities derived from real-time assessment of weapon system conditions obtained from embedded sensors and/or external test and measurement using portable equipment 16. Diagnostic and prognostic are two important components in a CBM programme, where diagnostic deals with fault detection and prognostic deals with fault and degradation prevention before they occur 17. Previous studies confirm that machine components, data acquisition from sensors, data extraction, transformation and analysis are all key aspects of prognostic maintenance 18.Rausch (2008) noted several common monitoring methods, such as vibration analysis, process parameter modelling,tribology, thermography and visual inspection. Sensors are often embedded into critical parts of the system to obtain data relevant to system health 1. For example, Rolls Royce uses Engine Health Management (EHM) to offer its “Power by the Hour” monitoring service. There are about 25 sensors fitted permanently on a Rolls Royce Trent engine, which provide data(i.e. pressure at various locations of the engine, turbine gas temperature and cooling air temperature) 19. With such real time data, OEMs can diagnose the condition of products whilst still operational in the field. Analysis techniques include neural networks and probabilistic-based autonomous systems for real time failure prognostic predictions 20.CBM is initiated based on the state of the degrading system, and therefore components are only replaced when the level of degradation has reached a critical level. As a result, unscheduled down time of the equipment can be minimised. Furthermore, the ability to predict the time to a components failure, means that Life Cycle Cost (LCC) may be greatly reduced because the life of the components and equipment can be utilised fully. OEMs or service providers can therefore also plan their service schedules more accurately, by knowing exactly what is required for the maintenance 20.1.3. Challenges within maintenanceUncertainties about the current condition of products operating in the field make it extremely difficult for OEMs to plan maintenance schedules efficiently and cost effectively. This results in greater risks of under-maintaining products, which can lead to failure and longer, unscheduled 9down-times, both of which are unacceptable to customers. To reduce such uncertainties, accurate product data, particularly related to product use, needs to be acquired and processed to determine the frequency and types of maintenance/service required. Scheidt categorizes data as static and dynamic life cycle data 21.Static data includes product information created during the product design phase, such as the product specification, Bill of Materials (BOM) and service manuals. Dynamic data is collected during the products operational phase, commonly whilst it is being used by customers (rather than by the OEM), and consists of data such as usage patterns, servicing actions, environmental working conditions and components wear rates. The data is typically stored in an on-board data logger and processor. OEMs also use questionnaires to capture product performance, patterns of use and customer satisfaction levels.Some larger OEMs invite their dealers and customers to a week-long conference to share their product experiences 22.Although a large amount of first-hand feedback on the products performance can be gathered in this way, this type of information becomes out-of-date rapidly, and is can be subject to error, ambiguity and subjectivity.It is challenging for OEMs to collect accurate and useful real time (dynamic) data from a product. When products are designed, assumptions are made that they will be used in particular conditions and methods, as stated within the design specification, however, some customers (users) may misuse the products, thereby reducing operational lifespan. In the construction equipment industry, products are often subjected to unorthodox harsh usage and inadequate daily maintenance care, which can lead to accelerated wear on components, shortening life expectancy. To address this, OEMs may consider monitoring real time usage of the product, as per the aerospace industry. Monitoring systems enable service providers to schedule necessary maintenance immediately an abnormal event is detected. Any relevant real time data can also be extracted and analysed to determine the work and parts that are required 23. However, data monitoring systems which involve the generation, processing and management of the product usage data are complex and expensive, and may even exceed the cost of the components that are being monitored. Bill Sauber, Volvo Construction Equipment North Americas manager of remote technologies, stated that OEMs have a tendency to assume that if more dynamic, real time operational data are collected, more information will be captured. However, this data will mostly be just noise. Johnathan Metz, technology application specialist from Caterpillar also suggested that customers are likely to be overwhelmed by the sheer quantity of data, and its irrelevance to customers needs 24. Hence, if there is no system in place to analyse collected data in a timely manner, only limited value will be gained 25. Therefore, to be cost effective and competitive, it is very important for construction equipment OEMs to design the monitoring systems as part of the overall product design. To do so, it is necessary to understand how the products condition will be affected under different modes of operation, and how such changes in condition may be detected. This is critical such that monitoring systems, including the location and number of sensors can be designed to maximise the useful knowledge they can provide through real time data 10analysis, yet minimize costs incurred by sensor installation and operation. The remainder of this paper presents an assessment of the suitability of mobile inline particle contamination sensors for CBM, which was undertaken through a 1900 h oil contamination monitoring study.2. Monitoring hydraulic systems to predict faultsConstruction industry OEMs such as Caterpillar Inc. (CAT), Komatsu Ltd. and J C Bamford Excavators Ltd. Manufacture heavy equipment for various industries, such as backhoe loaders, wheeled loaders and hydraulic excavators for handling bulky and heavy materials for various industries. More than 45% of the worlds construction machines are hydraulic excavators 26, because of their high productivity and ease of operation compared to other construction machines 27. Most excavators are powered by a combustion engine. Unlike a conventional automobile, the generated power of the engine is transmitted to drive the hydraulic pumps which provide the flow within the hydraulic system (Fig. 1). Hydraulics is the science of transmitting force and/or motion through the medium of a confined liquid, and power is transmitted by pushing on this confined liquid. Pumps are installed to propel the oil around the circuit and, at times, pressurise it.Valve blocks are often used to control the flow and direction of the oil. These are metal castings in which oil-ways orgalleries are intersected by valve spools, the number of which depends on the number of services to be controlled. Failure of control valves can cause a loss of production which is many times more expensive than the cost of prevention 28. The primary structural components of an excavator, such as the boom, dipper arm, bucket and slew motor are moved by hydraulic rams. Hydraulic rams convert fluid power into linear force and motion. The linear force generated by a hydraulic ram is a product of system pressure and effective area, minus system inefficiencies. The complexity of off-highway excavators hydraulic circuits and the tough working conditions they must endure, means that the reliability of such systems is always a serious consideration 29. Analysis of hydraulic system operations indicates that the reliability of the system and its components will depend on a large number of factors 30, including pressure, flow,temperature, viscosity and particulate contaminants 31. Dave Douglass
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