Hydraulic actuators for gas and steam valves用于燃气和蒸汽阀的液压执行器

Planned maintenance can prevent hydraulic actuator failures, high repair costs and downtime.
计划内的维护可以防止液压执行器故障、高昂的维修成本和停机时间。

出处：https://www.flowcontrolnetwork.com/valves-actuators/article/21117689/hydraulic-actuators-for-gas-and-steam-valves

作者：Ralf Bentfeldt and Volker Tenhaeff

翻译：Gordon

Eight out of ten power plant operators do not realize what they are risking if they allow seal wear in hydraulic actuators to simply take its course. This practical guide explains how to cost-effectively prevent damage and production downtime with predictive planning.

80%的发电厂操作员没有意识到如果让液压执行器的密封件磨损顺其自然地走下去会带来什么危险。本实用指南说明了如何通过预测性计划经济有效地防止损坏和生产停机。

In order for gas and steam turbines to generate electricity with the right output and rotational speed, the supply of media must be precisely controlled. Hydraulic actuators ensure exact control of the valves. In the event of a malfunction, they also carry out an important safety function by mechanically moving the valves into a safety position via spring force to disrupt the flow of medium or redirect it. To ensure this in the long term, it is essential that the hydraulic actuators for gas and steam turbines are inspected and maintained at regular intervals in accordance with the relevant legal regulations and manufacturers’ recommendations. The reason: Each hydraulic actuator — no matter the quality — exhibits wear due to operational reasons. The wear starts on the seals and, in the absence of maintenance, may extend to other components. Anyone who disregards this and waits until an obvious failure occurs, risks high repair costs and long waiting periods until unrestricted production can be resumed.

为了使燃气轮机和蒸汽轮机以正确的输出速度和转速发电，必须精确控制介质的供应。液压执行器确保对阀门的精确控制。在发生故障的情况下，它们还可以发挥重要的安全功能，即通过弹簧力将阀门机械地移动到安全位置，以中断介质流动或重新定向。为了长期确保这一点，至关重要的是，应根据相关法律法规和制造商的建议，定期检查和维护用于燃气轮机和蒸汽轮机的液压执行器。原因：每个液压执行器-无论质量如何-都会由于操作原因而出现磨损。磨损开始于密封件，维护缺失的情况下，可能会扩展到其他组件。忽视此问题并等待直到出现明显故障的任何人都将面临高昂的维修成本和漫长的等待时间，直到可以恢复不受限制的生产。

Key insights and considerations
关键见解和注意事项

Damage to actuators can be caused by a variety of events, such as gradual aging and wear, maintenance errors or extreme heat and discharge. Also, poor maintenance may result in diminished quality control and even permanent damage to machine integrity. To reduce costs and avoid damage or prolonged downtime to the machine, long-term maintenance planning and testing are recommended.

各种事件都可能导致执行器损坏，例如逐渐老化和磨损，维护错误或过热和放电。同样，维护不善可能会导致质量控制下降，甚至对机器完整性造成永久性损害。为了降低成本并避免损坏或延长机器的停机时间，建议进行长期维护计划和测试。

Imminent loss of the SIL capability
SIL能力即将丧失

If the specifications from the operating instructions and the safety manual are not complied with — for example, maintenance requirements and proof-test intervals — or if the actuators are not properly used, under certain circumstances, the drive loses its SIL conformity and thus its suitability for safety-related applications. Improper usage includes the use of dirty or contaminated hydraulic oil. This can lead to failure of the solenoid valves and cartridge valves, as well as increased wear on the piston rod seal and the piston rod. In addition, unsuitable placement in the escaping steam can cause damage due to overheating (discussed further in the following section), which can subsequently result in strong corrosion on safety-related components, such as magnetic and cartridge valves, piston rod and spring assembly. Last but not least, a lack of regulation or control poses a risk to the SIL capability, because inadmissible oscillations could cause significant wear in a short time.

如果不遵守操作说明和安全手册中的规范（例如，维护要求和检验间隔），或者在某些情况下，如果未正确使用执行器，则驱动器将失去其SIL合格性，进而影响和安全相关的应用。不当使用包括使用肮脏或受污染的液压油。这可能导致电磁阀和插装阀故障，以及活塞杆密封件和活塞杆上的磨损增加。此外，不适当地放置在泄漏的蒸汽中可能会因过热（在下一节中进一步讨论）而造成损坏，进而导致对与安全相关的组件（如电磁阀和插装阀，活塞杆和弹簧组件）的强烈腐蚀。最后但并非最不重要的一点是，缺乏调节或控制会对SIL性能造成风险，因为不允许的振荡可能会在短时间内造成严重磨损。

Damage causes
损坏原因

Ongoing seal wear
持续的密封件磨损

If the piston and rod seals are not replaced according to the schedule for the actuator — at the latest, after six years — the wear will lead to functional impairments. First, leakage occurs. Later, there is damage to the piston and the piston housing. Depending on the circumstances, this leads directly to failure. On one hand, the wear ensues regardless of the product quality due to the aging process of the sealing material, which gradually becomes brittle and porous, so the sealing effect decreases. On the other hand, the frequency of the changes in movement, in combination with the stroke length, plays a role. Therefore, the strokes are determined by the control system to ensure an adequate lubricating film and thus low-wear operation for the seals.

如果未按执行机构的时间表更换活塞和活塞杆密封件（最迟六年后），则磨损将导致功能受损。首先，发生泄漏。后来，活塞和活塞外壳受到损坏。根据情况，这直接导致故障。一方面，由于密封材料的老化过程而导致的磨损与产品质量无关，其逐渐变脆和多孔，因此密封效果降低。另一方面，运动变化的频率与行程长度一起起作用。因此，行程由控制系统确定，以确保足够的润滑膜，从而确保密封件的低磨损运行。

In the short-stroke range, constant operation leads to increased seal wear and damage to the mating surfaces. Especially in the case of short strokes at high frequency, the replacement intervals for seals recommended in the maintenance schedule can be significantly reduced. Regular monitoring is essential. In the case of actuators that only extend to short strokes or remain in one position over a longer period of time — depending on the application, this could be several weeks or months — separated seal particles mostly remain in the chamber, as there is hardly any exchange of the oil. Thus, contamination on the inside of the cylinder builds up and the sealing rings wear down more quickly.

在短行程范围内，持续运行会导致密封件磨损增加，并损坏配合表面。特别是在高频短行程的情况下，可以大大减少维护计划中建议的密封件更换间隔。定期监控至关重要。对于仅短行程或较长时间保持在一个位置上的执行器-根据应用情况，可能是数周或数月-分离的密封颗粒大部分保留在腔室内，因为几乎没有换油。因此，缸内部的污染物会堆积，密封环的磨损会更快。

Incorrect maintenance or assembly
不正确的维护或组装

Apart from the wear, maintenance or assembly errors could also be the cause of permanent damage to the actuators. A common source of error is the alignment to the steam or gas valve. If a valve and piston rod are not properly aligned, lateral forces acting on the coupling place stress on the guide belts. Consequently, the guide belts and the seals wear excessively. A further cause of damage resulting from faulty handling is the filling of the hydraulic system with an incorrect fluid. This can trigger a chemical reaction between the seal and the fluid, which accelerates the process of wear and tear.

除了磨损，维护或组装错误也可能是执行器永久损坏的原因。常见的误差来源是与蒸汽或燃气阀的对准。如果阀和活塞杆未正确对准，则作用在联轴器上的侧向力会在导向带上施加压力。因此，导向带和密封件过度磨损。由于处理不当而造成损坏的另一个原因是用不正确的液体填充液压系统。这会触发密封件和流体之间的化学反应，从而加速磨损过程。

Special risks associated with steam valves
与蒸汽阀相关的特殊风险

Power plant operators who generate electricity by means of steam should also observe the leak tightness of the steam valves in the direction of the cylinder. If the hot medium (more than 500°C) flows long enough over the outer coating of the actuator, the coating can “burn off” and the surface becomes corroded. Apart from this obvious damage, the spring assembly inside the cylinder can also be damaged, which, in the event of a malfunction, subjects the valve purely mechanically up to 400 kN force in the locked position.

通过蒸汽发电的电厂操作人员还应注意蒸汽阀在气缸方向上的密封性。如果热介质（高于500°C）在执行机构的外涂层上流动足够长的时间，则涂层会“烧掉”，并且表面会被腐蚀。除了这种明显的损坏外，缸内的弹簧组件也可能损坏，如果发生故障，则在锁定位置，纯机械地使阀承受最大400 kN的力。

At the interface to the armature — the coupling — the ambient temperature must not exceed 200°C. As a result of the effects of excessive heat, the existing anticorrosive coating — consisting of a layer of wax on the Belleville washer system — can be damaged. If a rusty spring cup breaks, the actuator loses its safety function. In this case, the component requires an immediate overhaul in a manufacturer’s certified service center.

在电枢的接口（联轴器）上，环境温度不得超过200°C。由于过热的影响，现有的防腐蚀涂层（由Belleville弹簧垫圈系统上的一层蜡组成）可能会损坏。如果生锈的弹簧杯破裂，执行器将失去其安全功能。在这种情况下，该组件需要立即在制造商认证的服务中心进行大修。

In addition, uncontrolled steam discharge can damage the actuator due to overheating of the hydraulic fluid, because the fluid temperature must not exceed 70°C in circulation. If the system cannot compensate for the influx of heat, the hydraulic oil will be “burnt.” This means it becomes viscous and sticky. The seal wear increases, while valves and other components lose their freedom of movement and function.

另外，由于液压油的温度在循环中不得超过70°C，因此不受控制的蒸汽排放会由于液压油过热而损坏执行器。如果系统无法补偿热量的流入，则液压油将“燃烧”。这意味着它会变得粘稠。密封件磨损增加，同时阀门和其他组件失去其运动和功能的自由度。

Consequences of inadequate maintenance
维护不足的后果

Reduced control quality
控制质量降低

Even before the seals lose their originally intended function through continued wear, increasing internal or external leakage leads to energy losses. The accompanying temperature rise promotes wear and tear in other areas of the hydraulic system. Another consequence of the increased leakage is diminished control quality. Therefore, under certain circumstances, the system would no longer be able to adjust the required performance of the turbine with sufficient accuracy.

即使在密封件由于持续磨损而失去其最初的预期功能之前，内部或外部泄漏的增加也会导致能量损失。随之而来的温度升高会加剧液压系统其他区域的磨损。泄漏增加的另一个结果是控制质量下降。因此，在某些情况下，该系统将不再能够以足够的精度来调节汽轮机的所需性能。

Mechanical damage: Worst-case scenario
机械损坏：最坏的情况

If the damage of the seal system has deteriorated to such an extent that it leads to mechanical contact between the piston rod and cylinder housing, the main components suffer permanent damage. Due to the leakage that occurs, the actuator can no longer properly perform its regulatory function. Although this is not safety-relevant with the Belleville spring washer system intact, the damage is much greater. The seal wear increases, while valves and other components lose their freedom of movement and function. The reason: The main components of the actuator, such as the cylinder housing and piston, are generally not stockable items for the manufacturer due to the large variance. Some parts must even be cast and then machined. In the worst case, this could take weeks or months. If the waiting period occurs during the high season, operators must possibly accept painful constraints to production.

如果密封系统的损坏恶化到导致活塞杆和油缸壳体之间机械接触的程度，则主要部件将遭受永久性损坏。由于发生泄漏，执行器将无法正常执行其调节功能。尽管这与完好无损的Belleville弹簧垫圈系统无关，但造成的损失更大。密封件磨损增加，同时阀门和其他组件失去其运动和功能的自由度。原因：执行器的主要部件，例如油缸壳和活塞，由于差异较大，通常对于制造商来说不是库存产品。有些零件甚至必须铸造然后再加工。在最坏的情况下，这可能需要数周或数月的时间。如果等待期发生在旺季，操作员可能必须接受痛苦的带病运行。

Recommendations for practical use
实用建议

Preventing the worst-case scenario
预防最坏的情况

To avoid the worst-case scenario in a cost-efficient manner, operators should not only comply with the maintenance rules and instructions, but also schedule major inspections in a timely manner. This way, the manufacturer has enough time to provide the necessary parts, carry out repairs and perform the final functional test.

为了以节省成本的方式避免出现最坏的情况，操作员不仅应遵守维护规则和说明，还应及时安排大检查。这样，制造商就有足够的时间提供必要的零件，进行维修并执行最终的功能测试。

If the actuator must be repaired, it is essential that the power plant operator ensure that the final examination also includes the safety functionality and that everything is documented in detail. This is the only way to ensure that, in the event of a malfunction, the actuator operates perfectly and the SIL capability is maintained. However, only the original manufacturer can guarantee this, as they have the original specification, e.g., for the spring tension. Alternative providers cannot guarantee this, because they do not have the same materials, nor do they have specific information regarding rigidity, for example. Only with the right combination of hydraulic fluid, piston rod, spring assembly, corrosion protection, etc., can the manufacturer achieve the same longevity and the same safety level as with the initial delivery.

如果必须维修执行器，则至关重要的是，发电厂操作员应确保最终检查还包括安全功能，并且所有内容均已详细记录在案。这是确保发生故障时执行器能够完美运行并保持SIL能力的唯一方法。但是，只有原始制造商才能保证这一点，因为它们具有原始规格，例如弹簧张力。替代提供者不能保证这一点，因为它们没有相同的材料，例如，他们也没有有关刚性的特定信息。只有正确组合液压油，活塞杆，弹簧组件，防腐蚀剂等，制造商才能达到与初次交付时相同的寿命和安全等级。

Performing proof-tests 
进行证明测试

To ensure the SIL conformity in the long term after five years — at least every six years or after 50,000 hours of operation — a proof-test must be performed. During this test, the manufacturer inspects all safety-related components in accordance with the maintenance requirements. If components with restricted functionality are discovered, or during preventive maintenance, they will be replaced. Furthermore, a functional test is always performed in accordance with the instructions for commissioning of the system and its safety-related functions, as well as according to the manufacturer’s operating instructions and documentation. The actuator is tested the same as during the initial commissioning of the system. The reason is, before every recommissioning, the user is required to validate the safety function, including the safety period of the safety system, and to traceably document it.

为确保五年后（至少每六年一次或运行50,000小时后）的长期SIL符合性，必须进行一次证明测试。在此测试期间，制造商会根据维护要求检查所有与安全相关的组件。如果发现功能受限的组件，或在预防性维护期间，将对其进行更换。此外，始终要根据系统调试及其安全相关功能的说明以及制造商的操作说明和文档进行功能测试。执行器的测试与系统初次调试时相同。原因是，在每次重新调试之前，都要求用户验证安全功能，包括安全系统的安全期限，并对其进行追溯记录。

Predictive planning
预测性计划

In terms of risk minimization, the standard overhaul with seal replacement should be a matter of course – every two to six years, depending on the maintenance schedule and load stress. Power plant operators should plan approximately 10 working days for the duration of this measure, including functional testing, plus transport as well as import and export from the country, as the case may be. If the accompanying inspection reveals damage to the actuator, the manufacturer will inform the customer with corresponding photographic proof and submit a subsequent offer. The further procedure will be jointly discussed. If there is still time for the repair, replacement parts can be ordered or manufactured at an early stage for a later maintenance step. In addition to the regular seal replacement, the condition of the spring assembly should be a major focal point. This can be done in advance of a maintenance operation by a specialist, checking the spring force and apparent condition (e.g., rust formation).

在最大程度降低风险方面，采用密封件更换的标准大修应该是顺理成章的事情-每两到六年，这取决于维护计划和负载压力。电厂运营商应在此措施期间计划大约10个工作日，包括功能测试，运输以及从该国的进出口（视情况而定）。如果随附的检查发现执行器损坏，则制造商将通知客户相应的照相证明并提交后续报价。进一步的程序将共同讨论。如果仍然有维修时间，则可以在早期订购或制造替换零件，以进行后续维护。除了定期更换密封件外，弹簧组件的状况应成为主要重点。这可以在专业人员进行维护操作之前完成，检查弹簧力和外观状况（例如，生锈）。

A good point in time for major overhauls or repairs is during a low-output phase of the power plant — in spring, summer or winter, depending on the geographical location. After the overhaul, OEM manufacturers typically offer a 12-month guarantee on the entire drive. 

进行大修或维修的好时机是在电厂的低负荷阶段-在春季，夏季或冬季，具体取决于地理位置。检修后，OEM制造商通常会对整个驱动器提供12个月的保修。

Maintenance backlog
维护积压

If the maintenance has been neglected in the past, the operator should lose no time and immediately contact the manufacturer. Discussing matters with experts makes it possible to better assess the condition of the actuators to minimize time and financial risks. Typically, the manufacturer first informs about the technical interrelationships and then explains the various options for action. Based on age and maintenance history, it can now be decided as to whether the device needs to be returned for a standard overhaul or whether it is sufficient to inspect the device within the scope of an on-site visit to the power plant. There, field service specialists assess the current condition of the system and, if necessary, carry out additional measurements. If there are several actuators of the same type in the same power plant, under certain circumstances, it is worthwhile to stock a spare device to bridge a gap in maintenance times.

如果过去没有进行过维护，则操作员应立即花费时间并立即与制造商联系。与专家讨论问题可以更好地评估执行器的状况，从而最大程度地减少时间和财务风险。通常，制造商首先会告知技术上的相互关系，然后说明采取的各种措施。现在，根据使用年限和维护历史记录，可以确定是否需要退回设备进行标准大修，或者是否足以在现场访问电厂的范围内检查设备。现场服务专家在那里评估系统的当前状况，并在必要时执行其他测量。如果在同一发电厂中有多个相同类型的执行器，则在某些情况下，值得购买备用设备以弥补维护时间的不足。

Standard overhaul at the manufacturer’s facility with original spare parts includes:
使用原始备件在制造商工厂进行的标准大修包括：

• Visual inspection of the condition in the delivered state with photographic documentation
  用摄影文件目视检查交付状态下的状况
• Disassembly: Cylinder housing, piston rod, piston, spring unit, add-on components and measuring unit
  拆卸：缸体，活塞杆，活塞，弹簧单元，附加组件和测量单元
• Verification:
  验证：
  • Cylinder housing, piston rod and piston and the measurement of the running surfaces and adherence to permissible wear limits, in accordance with the design requirements, and the chrome layer in terms of minimum thickness
    根据设计要求，缸体，活塞杆和活塞以及工作表面的测量和对允许磨损极限的粘附性以及最小厚度的镀铬层
  • Spring unit: visual inspection of the Belleville spring washers and protective pipe
    弹簧单元：目视检查Belleville弹簧垫圈和保护管
  • Add-on components (e.g., control block, valves and filters)
    附加组件（例如，控制块，阀门和过滤器）
  • Measurement units: position transducer and limit switch
    测量单位：位置传感器和限位开关
• Drafting of findings report with photo documentation
• 草拟调查结果报告并附照片文件

Repair by the manufacturer with original spare parts includes:
制造商使用原始备件进行的维修包括：

• Cleaning of all components
  清洁所有组件
• Resealing of the sealing elements of the cylinder and all components with certified OEM spare parts, ensuring operational safety
  使用经过认证的OEM备件重新密封气缸和所有组件的密封元件，从而确保操作安全
• Finishing of the running surfaces by polishing with precision processing machinery
  通过精密加工机械抛光对工作表面进行精加工
• Maintenance of the filters by replacing the seals, filter elements and the clogging indicator
  通过更换密封件，过滤器元件和堵塞指示器来维护过滤器
• Replacement of all wear parts, e.g., air filters, measuring ports, plug screws, bolts, locking rings and guide rings.
  更换所有易损件，例如空气过滤器，测量口，堵头螺钉，螺栓，锁紧环和导向环。
• Assembly with manipulators and state-of-the-art lifting devices
  配备机械手和最先进的提升装置
• Functional testing of all assembly components according to specified criteria and with settings per the initial delivery to ensure operational safety
  根据指定标准对所有组件进行功能测试，并在首次交付时进行设置，以确保操作安全
• Full functional test of all specified values according to the initial delivery state
  根据初始交付状态对所有指定值进行全功能测试
• Creating a test protocol
  创建测试协议

Conclusion
结论

It is advisable for power plant operators with steam or gas valves to protect hydraulic actuators against unplanned downtime and avoid the ensuing costs. The easiest way to do this is to adhere to the manufacturer’s maintenance schedules from the first day of operation. In addition, regular condition analyses by field service specialists can help discover unusual damage and the error sources and initiate immediate countermeasures or plan them in a timely manner. In case of a maintenance backlog, it is urgently recommended to immediately contact the manufacturer to jointly assess the situation and discuss the next steps. This ensures that power plant operation can continue unrestricted or with planned maintenance.

建议使用蒸汽或燃气阀的电厂操作员保护液压执行器以防意外停机，并避免随之而来的成本。最简单的方法是从生产的第一天开始遵守制造商的维护时间表。此外，现场服务专家的定期状况分析可以帮助发现异常的损坏和错误源，并立即采取对策或及时计划。如果发生维护积压，强烈建议立即与制造商联系，以共同评估情况并讨论下一步。这确保了发电厂的运行可以不受限制地进行或按计划进行维护。