译文：
在化工生产中，调节阀是直接接触工艺介质的控制机构，本文以工程实际为背景，讨论了调节阀选型的原则，并介绍了在聚甲醛装置中应用调节阀的情况。 工艺简介 云南云天化股份有限公司的聚甲醛装置系国内{dy}套同类型装置，工艺包从波兰ZAT引进，采用共聚甲醛技术。 30工段甲醛提浓：分为甲醛真空浓缩，甲醇去除，甲醛加压浓缩；原料为40%甲醛，产品为60%甲醛。 40工段三聚甲醛合成：三聚甲醛合成在液相中进行，催化剂为硫酸，原料是60%甲醛液，三聚甲醛平衡浓度为4%。以下经过42工段：去除低沸点物如甲缩醛及甲醇；43工段三聚甲醛浓缩锝 60%三聚甲醛；44工段三聚甲醛结晶分离；46工段提纯：加碱萃取；47工段：蒸馏得99.99%三聚甲醛。 50工段制备二氧五环：原料是60%甲醛和乙二醇，得到二氧五环后用NaOH脱水得到99%DOX；再经过精馏得到99.99%二氧五环。 从工艺流程可知，对原料的纯度要求很高，工业甲醛浓度一般不大于55%，此工艺要求60%；而反应的平衡浓度较低，需要多次分离，其中反复采用精馏塔操作，三聚甲醛和二氧五环产品均要求达到99.99%的浓度。 调节阀是直接接触工艺介质的控制机构，承受着流体的压力，温度，冲刷，腐蚀和磨损。恶劣工况下不乏调节阀卡塞，振动，泄漏，流量特性失真甚至阀芯脱落的现象。在长期的机械疲劳，热冲击和化学腐蚀作用下，调节阀的使用性能逐渐下降。实际上调节阀的使用寿命难以估计，最重要的因素是需要设计者了解工艺要求及使用工况。 调节阀的选用 在调节阀的选用中，必须首先考虑是否能达成工艺目的，满足控制要求以及长期稳定使用。众所周知，调节回路参数的整定耗时费力，其重要的原因便是调节阀的流量特性很难做到理想曲线。控制器采用计算机技术已能使PID算法接近数学期望值，但通过调节阀动作得到的流量特性总是偏离理想值，需要多次调整才能稳定。对于单回路而言，可以放宽控制强度得到较好的稳定性；而串级回路中，副回路需要较好的快速响应及自我稳定性才能跟随主回路的变化。 在聚甲醛工艺中，为保证精馏塔的分离效率，得到高纯度的产品，需要xx、稳定的塔板温度控制。通常采用串级调节：主回路为温度调节，副回路为蒸汽流量调节。 但流量回路响应快速，易造成调节阀振荡，使整个串级回路波动。相对P形阀芯，采用V形阀芯有利于提升控制品质。它具有不对称结构，定点径向力，震动性小，有利于阀芯稳定，延长使用寿命，并且远离流体冲刷区，有利于保护阀芯/座，避免湍流损坏；此外，等百分比流量特性是严格的等百分比曲线，在任何口径下，不改变曲线特性，工作范围20%~90%。 在有机化工装置中，常存在有多种有毒介质。在聚甲醛装置中典型的有毒介质有甲醛，二氧五环。从安全，环保的角度应采用低泄漏阀。调节阀的泄漏源主要为阀杆与填料间隙，为保证阀杆动作自如，必须与填料有一定间隙。对于低沸点介质很容易从此处泄漏出来。 采用波纹管密封可彻底解决这个问题。传统的波纹管受材质和加工工艺限制，使用寿命不长。SAMSON阀门具有金属波纹管专利密封技术，防止了任何有毒及易燃爆气体散逸到大气中，它的设计为2～5层结构，采用一次成型方式，非分段焊接方式，采用软密封的阀芯/座配合，可达到零内泄漏，且使用次数（阀门全开到全关）在160万次以上，同时可以加载波纹管检漏装置，更能保证阀门的安全性，保护人身及环境安全。 作为合成聚甲醛的主要原料三聚甲醛需要逐级提浓至99.99%。在高浓度下须保持70℃左右才能维持液态。如遇冷即结晶，同时伴随有生成多聚甲醛的副反应，且为不可逆反应。工艺上此类管道设计为夹套管，伴随75℃热水。调节阀也必须为夹套阀。许多厂家为降低制造成本，采取夹套外购的方式，将夹套与阀体固定在一起，通过夹套壁传热。金属之间很难作到无间隙，造成传热死角。SAMSON将夹套焊接在阀体上，采用下进上出的方式，独立循环系统使得介质能够均匀分布到阀体的各个部分；不改变原阀门的尺寸，方便安装，拆卸简便；结构小巧独立, 不受管道干扰, 也不对其他管件产生影响。这种夹套必须经过水压试验及探伤，使成本上升，但无保温死角。 以上从工艺角度讨论了调节阀选型的特殊要求，在满足工艺需要的前提下，阀门的使用寿命与工作状况直接相关。在计算书上除了开度、噪声等结果，还应密切注意出口流速的值，原则上液体的出口流速不应大于3m/s，而对于气体或蒸汽则不应大于3Mach，在选型的过程中，如果忽略了这个值而单纯地看开度和噪声，过高的流速会造成对阀门内件的损害，从而使阀门的使用寿命不能得到保障。 阀门的加工工艺中，阀体的制造工艺是非常重要的，SAMSON阀体制造(锻造/铸造)采用计算机应力分析、检测以保证标准的耐温、耐压规格；同时采用机器人手车削阀体内腔确保最小阻力系数；铸造阀体采用专利技术在阀体内腔流路表面形成一氧化膜层，大大提高阀门耐腐蚀性和寿命。 结束语 针对聚甲醛装置的工艺要求，经过市场调研，最终选用SAMSON调节阀。投用4年来，运行非常稳定。解体检查未发现内件磨损现象，使日常维护工作量大幅降低。 在进行增产20%改造以后，现有调节阀不需要更换仍然能够满足要求。除了阀体自身坚固耐用以外，还得益于SAMSON偏于保守的选型风格，Kv值和执行机构均留有较大余量，减少了二次投资。

“ Working knowledge of Control Valves ”是由提供的国际阀门新闻，译文仅供参考。另外，中国调节阀网还提供相关产品搜索：、、、、等。

原文：
In chemical production, process control valve is a direct contact with the control of media institutions, practical engineering background of this paper discussed the principles of control valve selection and describes the application of POM unit control valve situation. Process Overview Yunnan Yuntianhua Inc. POM device of its kind in the Department of Taiwan's first device, process packets from Poland ZAT introduction, using POM techniques. 30 Concentration of construction section Formaldehyde: Formaldehyde is divided into a vacuum concentrated to remove methanol, formaldehyde, concentrated pressure; raw materials 40% formaldehyde, the product of 60% formaldehyde. 40 workshop section trioxane synthesis: trioxane synthesis carried out in the liquid phase, the catalyst for sulfuric acid and raw materials 60% formaldehyde solution, trioxane equilibrium concentration of 4%. After 42 the following system: the removal of low boiling point material, such as A acetal and methanol; 43 workshop section trioxane concentration Technetium 60% trioxane; 44 workshop section trioxane crystallization separation; 46 workshop section purification: alkali extraction; 47 workshop section: distillation was 99.99% trioxane. 50 workshop section prepared dioxolane: raw materials is 60% formaldehyde and ethylene glycol, dioxolane obtained after the dehydration with NaOH to be 99% DOX; go through distillation to be 99.99% dioxolane. From the process we can see that very high purity of raw materials, industrial formaldehyde concentration generally not more than 55%, 60% of this process requirements; while the reaction equilibrium concentration of low, require multiple separation, in which repeated use of distillation column operation, trioxane and dioxolane products demand to reach 99.99% concentration. Regulating valve is a direct contact with process media control body fluid to withstand the pressure, temperature, erosion, corrosion and wear. No shortage of harsh operating conditions regulating valve Casey, vibration, leakage, flow characteristics of distortion or even spool off phenomenon. In the long-term mechanical fatigue, thermal shock and chemical corrosion, the control valve using performance declined. In fact the life of incalculable regulating valve, the most important factor is the need for designers to understand the process requirements and the use of working conditions. Control Valve Selection In the selection of control valve, you must first consider whether the technology can reach the purpose to meet the control requirements, as well as the use of long-term stability. As we all know, regulation loop tuning parameters, time-consuming and laborious, its important reason is that the flow control valve is difficult to achieve the ideal characteristic curve. Controller uses PID algorithm for computer technology, has enabled almost mathematical expectation, but by regulating the flow characteristics of valve movements are always deviate from the ideal value, need to be stable and adjusted several times. For the single-loop, we can relax the control intensity to get better stability; the cascade loop, deputy circuit the need for better self-stability of the rapid response and in order to follow the main circuit changes. In the POM process, in order to ensure the separation efficiency of distillation obtain high purity products, require precise, stable temperature control trays. Usually Cascade Control: the main loop for the temperature regulation and vice-loop steam flow regulation. But the flow loop to respond quickly and could easily lead to valve oscillation, so that the whole cascade loop fluctuations. Relative P-shaped spool, using V-shaped spool is conducive to enhancing quality of control. It has asymmetric structure, fixed radial force, vibration of a small spool is conducive to stability and to extend the service life, and away from the fluid erosion area, conducive to the protection spool / seat, to avoid the turbulence damage; In addition, the equal percentage flow characteristic is strictly equal percentage curve, in any caliber, we do not change the curve of the scope of work 20% ~ 90%. In the organic chemical devices, often there is a variety of toxic media. In the POM of toxic media devices typically formaldehyde, dioxolane. From a security and environmental protection point of view should be low-leakage valve. Valve stem the leakage of the source mainly gap-filler, in order to ensure the valve stem moves freely, you must have a certain gap-filler. For low boiling point medium is very easy to leak out from here. With bellows seal can solve this problem. The traditional bellows by the material and processing constraints, life did not last long. SAMSON valves with metal bellows seal technology patents to prevent any toxic and flammable explosive gas emission into the atmosphere, it's designed for 2 to 5 layer structure, using a molding method, non-sub-welding, using soft-sealed Plug / Block co-ordination can be achieved within a zero leakage, and frequency of use (valve fully open to full-off) of 160 million over the same time can be loaded corrugated pipe leak detection devices, better guarantee the safety valve to protect Personal and environmental safety. As the main raw material for synthesis of POM POM 3 Concentration of the need progressively to 99.99%. At high concentrations should be kept about 70 ℃ in order to maintain the liquid. In case of cold that the crystallization is accompanied by generation of side effects paraformaldehyde, and for non-reversible reaction. Process is designed to clip on the casing of these pipelines, along with 75 ℃ hot water. Control valve must also jacketed valve. Many manufacturers to reduce manufacturing costs, to take jacket purchased way, jacket held together with the valve body, through the jacket wall heat transfer. Metal-free gap between the hard done, resulting in dead heat. SAMSON will be welded to the body jacket, using the next entry on the way out, an independent media, to allow uniform distribution of the circulatory system to the various parts of body; does not change the original valve size, easy installation and removal easy; structure of small and independent without channel interference, nor have an impact on other pipe fittings. This jacket must be water pressure testing and flaw detection, so that rising costs, but no insulation dead. Over from the process control valve discussed in terms of selection of the special requirements to meet the technology needs under the premise of the valve directly related to life and working conditions. In addition to opening the book in the calculation, noise and other results, should also pay close attention to the value of the export flow, in principle, the export of liquid flow rate should not be greater than 3m / s, while for gas or steam should not be larger than 3Mach, in the selection of The process, if this value is ignored and simply look at opening and noise, high flow rate would result in damage to parts inside the valve, so that the life of the valve can not be guaranteed. Processing the valve, the valve manufacturing process is very important, SAMSON valve manufacturing (forging / casting) using a computer stress analysis and testing to ensure that the standard temperature, pressure specifications; the same time, cut valve body with Used Robots cavity to ensure the least resistance coefficient; casting valve body uses proprietary technology in the body cavity flow path formed on the surface an oxide film, corrosion resistance and greatly increased valve life. Conclusion Devices for the POM process requirements through market research, the final selection of SAMSON valve. Vote in 4 years, run very stable. Check the disintegration of wear and tear is not found within the piece, so that routine maintenance workload greatly reduced. After the 20% increase during transformation of the existing control valve does not require the replacement still be able to meet the requirements. In addition to its rugged body, it also benefited from the SAMSON inclined to the conservative selection of styles, Kv value and the implementing agencies have left a larger margin, reducing the second investment.