原文：
活塞式盘形弹簧安全阀也称带有外加负载的弹簧安全阀。这种安全阀是在一般的弹簧式安全阀的基础上发展的，主要特点有两个：一是弹簧改成盘形，二是阀杆的上部装有活塞，利用压缩空气可推动活塞上下移动。安全阀除靠弹簧的压紧程度控制其起座压力外，还可通过压缩空气推动活塞控制其动作。 这种安全阀在锅炉正常运行时，除靠弹簧将阀芯压紧在阀座上外，还靠压缩空气作用在活塞上部的压力将阀芯压紧，这不改善了安全阀的严密性，减少漏泄现象并延长使用奉命。当锅炉压力升高到安全阀动作压力时，在压缩空气作用下，安全阀迅速开启放汽。当压力降低后，压缩空气又可切换到活塞上部，使安全阀关闭。由于安全阀能迅速启、闭， 可避免或减轻在启、闭过程中对密封面的吹损程度。 活塞式盘形弹簧安全阀具有启、闭灵敏，严密性好，使用奉命长等优点，在一些大容量锅炉上得到使用。

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译文：
Spring safety valve piston disc, also known as spring loaded safety valve with a plus. This safety valve is spring-loaded safety valve in general based on the development, there are two main characteristics: First, change the disc spring, and second, upper valve stem with the piston, using compressed air to push the piston up and down . In addition to compression by a spring safety valve controls the degree of pressure from the seat, push the piston can also control the action of compressed air. This valve in the boiler during normal operation, in addition to the spool by spring pressed on the seat, but also by air pressure acting on the upper piston will compress the spool, this does not improve the tightness of the valve, to reduce leakage and extend the use of the phenomenon of orders. When the boiler pressure increases to the safety valve pressure, under the action of the compressed air, steam release valve to open quickly. When the pressure drops, the compressed air can switch to the piston top, so that safety valve closed. Kai quickly as safety valve, closed, to avoid or mitigate the Kai, closed during the course of the wind damage the sealing surface level. Spring safety valve piston disc with Kai, closed sensitive, tight, good use of advantages such as orders, in some large-capacity boilers are used.