良工阀门：呼吸阀和安全阀，你了解多少？

　　What do you know about Lianggong Valve: Breathing Valve and Safety Valve?

　　呼吸阀和安全阀都是储罐的安全附件，用于控制储罐的压力，设计原理有很多相似之处，但有一个本质的区别，呼吸阀是化工储罐中常见的气体压力保护装置，应用于正常运行状态下的安全附件，随着储罐日常的日常运行使用而调节动作。安全阀是紧急状态下的安全保护附件，当储罐的安全受到威胁时才会动作。

　　Breathing valves and safety valves are both safety accessories for storage tanks, used to control the pressure of the tank. There are many similarities in design principles, but there is an essential difference. Breathing valves are common gas pressure protection devices in chemical storage tanks, applied as safety accessories under normal operating conditions, and adjust their actions with the daily operation and use of the tank. The safety valve is a safety protection accessory in emergency situations, which only operates when the safety of the storage tank is threatened.

　　1. 呼吸阀

　　1. Breathing valve

　　呼吸阀是一种用于常压或低压储罐(注:操作压力范围在全真空到103.4kPag之间)的安全设施。它可以保持常压或低压储罐中的压力始终处于正常状态,用来降低常压或低压储罐内挥发性液体的蒸发损失,并保护储罐免受超压或超真空度的破坏。

　　A breathing valve is a safety device used for atmospheric or low-pressure storage tanks (note: the operating pressure range is between full vacuum and 103.4kPag). It can maintain the pressure in atmospheric or low-pressure storage tanks in a normal state, reducing the evaporation loss of volatile liquids in atmospheric or low-pressure storage tanks and protecting the tanks from damage caused by overpressure or vacuum.

　　呼吸阀种类很多，但原理基本相同，内部结构是由一个低压安全阀(即呼气阀)和一个真空阀(即吸气阀)组合而成的,习惯上把它称为呼吸阀。常用的呼吸阀可分为两种基本类型:重力式呼吸阀(或称阀盘式)和先导式呼吸阀。

　　There are many types of breathing valves, but their principles are basically the same. The internal structure is composed of a low-pressure safety valve (i.e. exhalation valve) and a vacuum valve (i.e. inhalation valve), which are commonly referred to as breathing valves. The commonly used breathing valves can be divided into two basic types: gravity breathing valves (or valve discs) and pilot operated breathing valves.

　　重力式呼吸阀它利用阀盘的重量来控制储罐的排气正压和吸气负压，呼吸阀不工作时双阀盘关闭处于密闭状态，当罐内补充介质罐内液位升高，上部气体空间减小，内部压力升高，当压力超过呼吸阀的正压阀盘重力时，阀盘被顶开，气体从泄压孔溢出；当罐内流出介质液位下降，上部气体空间增大，压力下降，产生负压，当罐内产生的负压压力大于负压阀盘重力时，外部大气将顶开负压阀盘，进入罐内使罐内压力平衡，保护储罐安全。

　　Gravity breathing valve uses the weight of the valve disc to control the exhaust positive pressure and suction negative pressure of the storage tank. When the breathing valve is not working, the dual valve disc is closed and in a sealed state. When the liquid level in the tank is replenished with medium, the upper gas space decreases and the internal pressure increases. When the pressure exceeds the gravity of the positive pressure valve disc of the breathing valve, the valve disc is pushed open and gas overflows from the pressure relief hole; When the liquid level of the medium flowing out of the tank decreases, the upper gas space increases, the pressure decreases, and negative pressure is generated. When the negative pressure pressure generated in the tank is greater than the gravity of the negative pressure valve disc, the external atmosphere will push open the negative pressure valve disc and enter the tank to balance the pressure inside and protect the safety of the storage tank.

　　先导式呼吸阀由一个主阀和一个导阀组成,两阀先后动作来联合完成呼气和吸气动作。由于导阀采用薄膜结构,薄膜面积大,故在很低的工作压力下,仍可输出足够的作用力来控制主阀的动作。在导阀开启前,主阀不受控制流的作用,关闭严密,无泄漏现象。

　　A pilot operated breathing valve consists of a main valve and a pilot valve, which act sequentially to jointly complete exhalation and inhalation actions. Due to the use of a thin film structure and a large film area, the pilot valve can still output sufficient force to control the action of the main valve at very low working pressures. Before the pilot valve is opened, the main valve is not controlled by the flow and is tightly closed without any leakage.

　　呼吸阀在日常的维护中要保持阀座、阀盘的清洁，带阻火器的呼吸阀还要保持阻火器的部分的通畅，否则容易造成事故。

　　In daily maintenance, the valve seat and disc of the breathing valve should be kept clean, and the breathing valve with a flame arrester should also keep the flame arrester part unobstructed, otherwise accidents may occur.

　　2. 安全阀

　　2. Safety valve

　　安全阀是一种自动机构，原理与呼吸阀类似，在介质压力超过工作压力时自动打开，在压力回降到工作压力或低于工作压力后又能自动关闭。常用与压力容器，压缩机、容积泵的管道中。

　　A safety valve is an automatic mechanism that operates similarly to a breathing valve. It opens automatically when the medium pressure exceeds the working pressure and closes automatically when the pressure drops back to or below the working pressure. Commonly used in pipelines of pressure vessels, compressors, and positive displacement pumps.

　　按照结构类型分类主要有重力式安全阀、弹簧式安全阀、先导式安全阀。

　　Classified by structural type, there are mainly gravity safety valves, spring safety valves, and pilot operated safety valves.

　　重力式安全阀利用重锤的重力来封闭通道和控制设定压力，如图所示。

　　The gravity type safety valve uses the weight of a heavy hammer to close the channel and control the set pressure, as shown in the figure.

　　弹簧式安全阀依靠弹簧弹力用阀盘施加压力来封闭通道和控制设定压力。如果出口有一定的压力，需要带背压平衡装置的安全阀，按照其形式又可分为活塞式和波纹管式。

　　Spring type safety valves rely on the elastic force of the spring to apply pressure to the valve disc to close the channel and control the set pressure. If there is a certain pressure at the outlet, a safety valve with a back pressure balancing device is required, which can be divided into piston type and bellows type according to its form.

　　先导式安全阀

　　Pilot operated safety valve

　　先导式安全阀也称脉冲式安全阀，原理与先导式呼吸阀相似，其设定压力由导阀控制,动作特性基本不受背压影响。由两部分组成导阀和主阀，主阀作用于压力容器的泄压通道，导阀用于控制主阀的启闭，导阀其实就是一个小号的弹簧式安全阀，通过平衡管将主阀上下连通，两端形成稳定状态，当容器内压力上升，压力通过平衡管传导至导阀，当压力超过导阀设定值，导阀关闭平衡管至主阀上气室的通道，并同时打开主阀上气室对空泄压，让主阀上下形成压差从而打开主阀。先导式安全阀体积小，压力控制范围广，精度高，不受背压影响。但其系统回路相对较复杂，耐用度受介质影响，成本较高。

　　Pilot operated safety valve, also known as pulse operated safety valve, has a principle similar to that of pilot operated breathing valve. Its set pressure is controlled by the pilot valve, and its operating characteristics are basically not affected by back pressure. The main valve consists of two parts: a pilot valve and a main valve. The main valve acts on the pressure relief channel of the pressure vessel, and the pilot valve is used to control the opening and closing of the main valve. The pilot valve is actually a small spring-loaded safety valve, which connects the upper and lower parts of the main valve through a balance pipe, forming a stable state at both ends. When the pressure in the container rises, the pressure is transmitted to the pilot valve through the balance pipe. When the pressure exceeds the set value of the pilot valve, the pilot valve closes the channel from the balance pipe to the upper chamber of the main valve, and at the same time opens the upper chamber of the main valve to release air pressure, creating a pressure difference between the upper and lower parts of the main valve and opening the main valve. Pilot operated safety valves have small volume, wide pressure control range, high accuracy, and are not affected by back pressure. But its system circuit is relatively complex, durability is affected by the medium, and the cost is high.

　　安全阀在使用中如果发现有动作需引起重视，尽快查找原因，防止出现超压事故。且安全阀需要每年交由有资质单位进行校验。

　　If there is any movement of the safety valve during use, it should be taken seriously and the cause should be identified as soon as possible to prevent overpressure accidents. And the safety valve needs to be verified annually by a qualified unit.

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