原文：
            调节阀在过程控制中的作用是人所共知的，在许多控制过程中要求调节阀在故障时处于某一个位置，以保护工艺过程不出现事故，这就要求调节阀在设计上实现故障—安全的三断（断气、断电、断信号）保护措施。对于电动调节阀来说，比较简单，断信号时，可以根据控制模块的设定而停留在全开、全关、保持中的任一位置，而断电时，自然停留在故障位置，或带有复位装置的电动执行器也可将阀位运行到全开或全关。 对于气动调节阀来说，情况就比较复杂了，所以我们主要讨论气动调节阀的三断保位方法。一般来说，我们在选择气动薄膜调节阀时，都要先确定选气开还是气闭，这就是选择调节阀断气时的保护位置，如果工艺要求断气时阀门打开，过滤器则选择常开（气闭）式调节阀，反之则选常闭（气开）式调节阀。这只是一个粗浅的方案，如果工艺要求断气、断电、断信号的三断保护，则调节阀就需要配置一些附件来组成一个保护系统才能实现控制要求，这些附件主要有保位阀、电磁阀、气罐等。以下是单作用气动薄膜调节阀和双作用气动调节阀的两种保位方案。

       一、气动薄膜调节阀方案（调节阀配用电－气阀门定位器） 本方案主要由气动调节阀、电－气阀门定位器、失电（信号）比较器、单电控电磁换向阀、气动保位阀、阀位信号返回器等组成。其工作原理如下：

          1、断气源：当控制系统气源故障（失气）时，平衡阀气动保位阀自动关闭将定位器的输出信号压力锁定在气动控制阀的膜室内，输出信号压力与控制阀弹簧产生的反力相平衡，气动控制阀的阀位保持在故障位置。该保位阀应设定在略低于气源的最小值时启动。

          2、断电源：当控制系统电源故障（失电）时，失电（信号）比较器控制单电控电磁换向阀的输出电压消失，单电控电磁换向阀失电，单电控电磁换向阀内的滑阀在复位弹簧的作用下滑动，电磁阀换向，将气动保位阀的膜室压力排空，气动保位阀关闭，将定位器的输出信号压力锁定在气动控制阀的膜室内，输出信号压力与控制阀弹簧产生的反力相平衡，气动控制阀的阀位保持在故障位置。

          3、断信号：当控制系统信号故障（失信号）时，失电（信号）比较器检测到后，断掉单电控电磁换向阀的电压信号，单电控电磁换向阀失电，单电控电磁换向阀内的滑阀在复位弹簧的作用下滑动，电磁阀换向，将气动保位阀的膜室压力排空，气动保位阀关闭，将定位器的输出信号压力锁定在气动控制阀的膜室内，针型阀输出信号压力与控制阀弹簧产生的反力相平衡，气动控制阀的阀位保持在故障位置。 位置反馈信号由阀位信号返回器给出。 本方案的优点：“三断”保护启动时，系统反应较快，动作迅速。整体造价比较便宜。 本方案的缺点：电磁阀长期带电，影响使用寿命。配用附件较多，安装、调试复杂一些，阀位反馈需另配阀位信号返回器，在配用手轮的情况下，比较复杂。

             二、双作用气动调节阀方案（调节阀配用电－气阀门定位器） 本方案主要由控制阀、气控换向阀、定位器、自锁阀、单向阀、减压阀、储气罐等组成。其工作原理如下： 当控制系统气源故障（失气）时，自锁阀锻钢阀门（其作用方式与保位阀相反）自动打开，将气控换向阀的控制气源撤消，气控换向阀的滑阀在弹簧的作用下复位，两个气控换向阀中的其中一个排气，另一个进气，单向阀关闭，气源由储气罐中储存的气源向阀门供气，从而实现阀门的全关或全开。全关或全开的转换可通过调整气控换向阀的连接方式实现。 如果要实现阀门保位，加装气动保位阀并改变管路连接，用自锁阀直接控制保位阀，取消气控换向阀、单向阀、储气罐即可。 若要实现断气源时，能够保证阀门有若干次的动作，可采用以下方案。 本方案由储气罐、单向阀、闭锁阀、截止阀等组成。其工作原理如下： 当气源故障（失气）时，单向阀关闭， 液位计闭锁阀失气，在闭锁阀的滑阀在弹簧的作用下复位，气路换向，断开系统的气源管路，接通储气罐管路，由储气罐向阀门供气，以保证阀门有若干次动作，实现连续控制的目的。由于储气罐的容量有限，且储气罐中的气源压力随着阀门动作不断下降，不可长期使用储气罐为阀门供气。本方案配用储气罐的容量应比一般保护用储气罐的容量大。本方案在断气源时，阀门动作的次数与储气罐的容量有关。 对于气动薄膜调节阀的保位方案，还有一个可供参考：在定位器和执行器之间串联保位阀和两位三通电磁阀各一，在断气时用保位阀来保位，在断信号时，用电磁阀来保位，不过，电磁阀必须与定位器进行连锁（在控制程序中设定），即定位器有信号，电磁阀必有电，定位器一旦失信号，电磁阀必须立即断电。

“ Valve failure with that of several security bit program ”是由中国安全阀网提供的国际阀门新闻，译文仅供参考。另外，中国安全阀网还提供相关产品搜索： 弹簧式安全阀、 脉冲式安全阀(先导式安全阀)、 杠杆式安全阀、 微启式安全阀、 全启式安全阀等。

译文：
        Valve's role in the process control is well known, many of the control process in the requested valve in the failure in a certain position Yi Baohugongyi process Bu occurring which requires valve failure in the implementation She Jishang - Safety of three off (breathe, power, off signals) protection measures. The electric control valve, the relatively simple, off signal, can control the settings of the module remain open, fully closed, to keep in any position, and power outages, naturally, remain in the fault location, or with devices are reset actuator valve position can also be run to open and close. The pneumatic control valve, the situation is more complicated, so we focused on three pneumatic valve positionBalance Valves termination method. In general, we select the pneumatic membrane valves, they must first determine the open air or gas close election, this is to choose the protection of the breath control valve position, if the technological requirements of the breath to open the valve, then select the normally open (gas closed) type control valve, otherwise select normally closed (open air) Control Valve. This is only a crude program, if the process requirements breathe, power, off three break protection signal, the control valve will need to configure a number of annexes to the formation of a protection system to achieve control requirements of these accessories are mainly security position valve, solenoid valve , gas cylinders, etc.. The following is a single action pneumatic membrane valves and double acting pneumatic control valve of the two security bit program. 1, pneumatic control valve film program (with electric control valve - gas valve positioner) The program mainly by the pneumatic control valve, electric - gas valve positioner, loss of power (signal) comparator, a single electronic control solenoid valve, pneumatic valve to secure his position, valve position signal to return devices and other components. It works as follows: 1, expire Source: When the control system of air supply failure (loss of gas), the air valve automatically closes to secure his position and orientation, the output signal pressure to lock the film room air control valve, the output signal pressure and control valve spring reaction force generated equilibrium, pneumatic valve position control valve to maintain the fault position. The valve should be set to secure his position slightly lower than the minimum air supply when the start. 2, broken power supply: When the control system power failure (loss of power), the loss of power (signal) to compare a single electronic control device controls the output voltage electromagnetic valve disappeared, electronically controlled solenoidInstrumentation Ball Valves valve single loss of electricity, electromagnetic single electronic control valve within the spool under the action of the reset spring sliding, reversing valve, the pneumatic valve protection bit empty film chamber pressure, pneumatic protection valve closed position, the positioning, the output signal pressure to lock in the pneumatic control valve membrane interior, the output signal pressure control valve spring reaction force generated by phase equilibrium, pneumatic valve position control valve to keep the fault location. 3, off the signal: when the control signal failure (loss of signal), the loss of power (signal) detected by the comparator, the broken single-electric control solenoid valve voltage signal, a single electronically controlled solenoid valve energized, single electronicSafety Relief Valves control slide valve within the solenoid valve in the reset slide under the action of the spring, reversing valve, the pneumatic valve of the film to secure his position emptying chamber pressure, pneumatic valve closure to secure his position, the positioning, the output signal pressure lock pneumatic control valve in the membrane interior, the output signal pressure control valve spring reaction force generated by phase equilibrium, pneumatic control valve of the valve position to maintain in the fault location. Position feedback signal from the valve position signal back to device is given. The program's benefits: "Three down" protection starts, the system response to fast, move fast. The overall cost cheaper. The program's shortcomings: long-term electric solenoid valve, affecting life. Equipped with more accessories, installation, commissioning complex, valve position feedback signal to return need to reprovision valve device, in the case with hand wheel, the more complicated. Second, double acting pneumatic valve program (with electricity Valve Air - Valve Positioner) The program mainly by the control valve,Needle & Gauge Valves gas control valve, locator, self-locking valve, check valve, relief valve, tank etc.. It works as follows: When the control system of air supply failure (loss of gas), the self-locking valve (its mode of action contrary to secure his position valve) automatically open the gas control valve to control gas source removed, the slide valve gas control valve in the spring reset under the action of the two air control valve in one of the exhaust, the other into the air, one-way valve closed, air source is stored in tank of gas supply source to the valve to achieve the valve the fully closed or fully open. Fully closed or fully open conversion can be controlled by adjusting the gas valve connection ways. If the goal of preserving the valve position, the installation of pneumatic valves and change the protection bit pipe connections, with self-locking valve direct control of the security position valve to remove air control valve, check valve, air tank can be. To achieve breathe source, to ensure the valve has a number of actions, can use the following program. The program consists of gas tank, check valve, latch valve, cut-off valve. It works as follows: When the air supply failure (loss of gas), the one-way valve closed, closed gas valve failure, the slide valve in the closed valve under the action of the spring reset, pneumatic commutation, disconnected the gas supply piping system, connected to storage cylinder tube, gas from the gas tank to the valve to ensure that the valve has a number of actions to achieve continuous control. As the tank's capacity is limited, and Instrument Manifoldsthe tank of gas supply pressure with the valve falling action, can not use the tank for the long-term gas supply valve. The program is equipped with tank capacity should be higher than the general protection of large capacity gas tank. The program expire source, the number of valve movements and the capacity of the gas tank. Pneumatic Diaphragm Control Valve for Paul-bit programs, there is a reference: the positioner and actuator in series between the two links to secure his position solenoid valve and one each in the breath is out of place with the security valve to protect its position, In the off signal, with the solenoid valve to protect its position, but the valve must be linked with the locator (in the control program in the set), that is, a signal locator, there must be electric solenoid valves, positioners, once lost the signal, electromagnetic valve must be immediately power off.

原文来源：http://www.1anquanfa.com/

2010-07-26 07:56

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