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18
桥式起重机
设计
机械
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18吨桥式起重机的设计—机械部分,18,桥式起重机,设计,机械,部分
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附录1 Crane Work Needs More TechniqueCrane work needs more technology. Construction of tower cranes are the main vertical transportation equipment and also a measure of construction companies and equipment strength of the important logo, in todays increasingly competitive construction market, to meet the construction needs of many construction companies have bought the tower crane. With the tower crane at the construction site of the widely used by the tower crane accident also caused more and more to peoples lives and property brought about great losses. According to national statistics, the departments concerned, the tower crane accident rate reached 2.77 percent. Its security problem is still the urgency of the construction Loose training, testing and oversight requirements for the people who work around construction cranes have fostered a false sense of security in our industry. The recent deadly tower-crane collapse at a congested New YorkCity building site should be a wake-up call for us to question and step up our current safety practices.Training and testing is king when it comes to safety. But the construction industry is putting unqualified personnel in the seats of construction cranes, even with todays testing. In many places, no experience is necessary after passing a standardized test. One week of study will give some people enough knowledge to pass a certification examination, and then they can jump into the cab of a crane.Imagine that a commercial airline pilot had the same training as a certified crane operator. How would you feel the next time you decided to fly? In California, it takes more hours of training to wield a pair of scissors in a hair salon than to operate potentially dangerous lifting machinery. How does this make sense?Riggers and signal persons also need standard training and testing to ensure safety under the hook. Employers usually allow any craft to signal a crane on a jobsite, despite best practices that require only qualified people do so. How is it then that uncertified and untrained people are allowed to signal and rig under the hook of a licensed or certified operator?Tower cranes are particularly risky as urban sites become more congested, and the risk of a catastrophic event is very high during climbing operations. Yet most tower-crane climbing crews are trained in a non-traditional manner, via secondhand knowledge that has been passed down over time. The problem with this type of hand-me-down knowledge is that it changes over the years, leaving out small-but-important details along the way. This osmosis of knowledge leads crews to develop their own tricks for climbing cranes, often forsaking basic safety in an attempt to save time and energy.In many cases, there are no safety devices or alarms to warn of a serious problem. Climbing crews are subjected to pressures that affect safety-critical decision-making. It is not uncommon for climbs to continue with damaged or leaking hydraulic systems, out-of-adjustment or jammed guide rollers, often working in the dark and for extended hours. This MacGyver method of climbing, where every jump becomes a new adventure, should not be the norm.Climbing-frame designs vary among manufacturers, but the operational steps are similar in principle. The climbing process is relatively straightforward, with a mixture of physical work and technical procedure. It is not complex; it is more about knowing the proper sequence of what needs to be done and then following the steps, one by one, making sure each step has been successfully completed before moving onto the next. It is essential that everyone know exactly what is going on and what the dangers are at every stage.Thats why the industry needs standardized training, testing and oversight for this work, including a practical assessment of competence. Technicians should have model-specific training directly from the manufacturer, along with a level of practical experience. Inspectors, too, should be required to have specific technical training. They should be independent from all aspects of installation and maintenance to allow for objective decisions. Key personnel on erection crews should have standard training and testing.When these needs are satisfied, crane operations should be carried out in strict accordance with the manufacturers instructions, engineering principals and governmental laws. But industry stakeholders and lawmakers need to step up their lax standards to protect the public. New York City residents, who have seen their homes turned into dust and debris, would be shocked at the way the industry deals with these issues.The birth worldwide industry early post-war years, the crane industry came to an aImost complete standstill. By the end of the decade, however, crane construction had diversified and spread around the world and the industry seemed infused with newfound energy that left it flourishing as never before. Lightweight cranes that arrived on site ready for use came to dominate construction sites as people realised the advantages of not having to dismantle them between jobs. These new designs did away with the need to have other lifting equipment assisting during rigging - a big contrast to the cumbersome rigging of previous designs. But, before all this could happen came the horrors of the Second World War. By 1940 afl of Europe was completely caught up in the conflict. By the time the war ended, Europe and other parts of the world had been subjected to extraordinary political, economic and social changes that would affect the entire fabric of society, including the construction and crane industries, for many decades to come. In the US, steam locomotives were starting to be replaced by diesel - by 1953 more than 50 per cent of all locomotives would be diesel. During the war the mass production of excavators, scrapers and cranes continued. 1940, for example, saw Thew launch the new Lorain Motocrane series. This consisted of three cranes which, for the first time in history, were mounted on chassis built by the crane manufacturer itselfi The smallest crane, the MC-2, could lift 7.6 tonnes, the MC-2 9.9 tonnes and the MC-3 13.5 tonnes. These cranes were delivered to the army by the thousand, and were also mounted on portals for use as harbour cranes (the MC-4 model). The war had, of course, taken its toll on the number of able-bodied men available to work in the crane industry and there was a serious shortage of good crane drivers. At Thew, newcomers were taught crane operations over a two-day course presented by A C Burch, an experienced mechanic and graduate of the Naval Academy, and L K Jenkins. These two gentlemen were probably the originators of operator training as we know it today. As they had actually designed the Motocrane, both knew it inside out and were pleased to pass on this knowledge.In response to the long-standing problems,in which the swinging angle of the hoisted load and the velocity of swinging angle is difficult to measure in engineering practice,a state observer is designed by the use of information about the crane trolleys position,and as a result,the trolley load-hoisting system combines with the state observer so conceived to form an online soft measurement system.By introducing the difference between the observers output and that of the trolley load-hoisting system,and transmitting it to the output end of the observer upon gain vector adjusting by the observer,the pole points of the observer are configured on the same point at the negative real axle,thereby realizing a stable,fast soft measurement for the system variables.Simulation experiments show that:the online soft measurement system possesses a fairly high level of robustness;as the pole points grow,however,the soft measurement system grows in the scope of adaptability to changes in the hoisted .更多load and in the length of the hoisting wire rope.But as the pole points overly grow,a sudden increase in measurement errors may occur either way;when the pole points are set,the result of a soft measurement is more sensitive to the length change of the hoisting rope than to the change of the hoisted load.起重机的工作需要更多的科学技术 塔式起重机是建筑施工垂直运输的主要设备，也是衡量一个建筑施工企业装备实力的重要标识，在当今竞争日益激烈的建筑市场，为满足施工需要，很多施工企业都购置了塔式起重机。随着塔式起重机在施工现场的广泛使用，由塔式起重机引发的伤亡事故也越来越多，给人民的生命财产带来重大损失。据国内有关部门统计资料表明，塔式起重机的事故率已达2.77%。其安全问题仍然是建筑施工中的忧患起重机的工作需要更多的科学技术，松散的培训，测试和监督的要求, 周围的建筑起重机给这些工作的人树立了一种虚假的安全感，在我们的行业。最近塔式起重机倒塌在一个繁忙的纽约市建筑地盘应敲响警钟，提醒我们问题的存在，并加强我们目前安全的做法。当谈到安全问题时，训练和测试是关键。不过，建造业是把不合格人员放在建筑起重机的驾驶位上，甚至没有通过今天的测试。在许多地方，没有任何经验必须合格的通过标准化的测试。一周的学习将给予一些人足够的知识足以通过认证考试，然后他们可以跳转到的起重机的驾驶室。想象一下一个商业航空公司飞行员和一个认证的起重机操作员有相同的训练。你会如何感觉，下一次你决定要坐飞机？在加利福尼亚州，掌握一对剪刀在头发沙龙比操作有潜在危险的起重机械需要更多的时间训练。如何，这是否合理？装配工人和发信号的人也需要标准的培训和测试，以确保安全下钩。雇主通常允许任何工人发信号指挥起重机上工地 ，尽管最佳做法是需要合格的人这样做。怎么能允许那么无证和未受过训练的人来代替有工作证或经核证的操作者呢？塔式起重机是特别危险的，尤其是在市区用地变得更加拥挤时。攀登行动更是一个风险的行动，其灾难性非常高。然而，大多数塔式起重机攀登员的训练，在一个非传统的方式，通过二手知识已流传一段时间。问题与这种类型的现成的知识是，多年来，留下来的非常少，但最重要的细节却丢失了。这种“渗透”的知识，导致操作者只能发展自己的技巧攀登起重机，往往放弃基本的安全，企图以节省时间和能源.在许多情况下没有安全装置或警报来提醒严重的问题的存在。攀登人员容易遭受到影响安全性至关重要的决策所带来的压力。攀登时，使用损坏或泄漏的液压系统，没有任何的调整，这并不鲜见。在黑暗中工作和延长工作时间是时有发生的。这种攀登方法，其中的每一次攀登都会成为新的冒险，不应该作为规范被采纳。攀爬架的设计，在制造商之间存在不同，但设计的步骤在原则上是相似的。攀登过程中是相对比较明了的，配合着的体力劳动和技术程序。这是并不复杂，它是更多地了解知道正确的序列需要做什么，然后按照下列步骤，一个又一个，确保每一步在做下一步前成功完成。这是十分重要，每个人都清楚的知道事情进展的怎么样，在每一个阶段存在什么样的危险。这就是为什么业界需要规范的培训，测试和监督，其中包括一个实际的评估能力。技术人员应该随着实际经验的提升，直接从制造商哪里获得标准训练。视察员同样也也须有具体的技术培训。他们应独立于安装和维修的各方面，
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