讨论back pressure？ asme ptc-25 -1994 states the following: asme ptc-25 -1994规定如下： a) superimposed back pressure : the static pressure existing at the outlet of a pressure relief device at the time the device is required to operate. it is the result of pressure in the discharge system coming from other source, and it may be either constant or variable. 附加背压 : 安全阀即将动作前在其出口处存在的静压力。是由其他压力源在排放系统中引起的，它分为恒定和可变两种。 1) variable back pressure is the superimposed back pressure that will vary with time. 可变背压是随时间变化的附加背压。 2) constant back pressure is the superimposed back pressure which is constant with time. 恒定背压是不随时间而变化的附加背压。 b) built -up back pressure : pressure existing at the outlet of a pressure relief device caused by the flow through that particular device into a discharge system. 排放背压 ：由于介质流经该安全阀进入排放系统而在阀出口处形成的压力。 c) back pressure: the static pressure existing at the outlet of a pressure relief device due to pressure in the discharge system. 背压：由于排放系统中的压力而使安全阀出口处存在的静压力。 we can summarize the relationship among all type of backpressures as follows: 我们可以将各种背压之间的关系总结如下： 1. total backpressure = built-up backpressure + superimposed backpressure 总背压 = 排放背压 + 附加背压 2. superimposed backpressure could be either constant or variable for e.g. if a relief device relieves to atmosphere then it is constant and if the relief device relieves into, say, a flare header in which several other relief devices are relieving, then the superimposed backpressure is variable . 附加背压有可能是恒定的，也有可能是可变的。例如，如果安全阀向大气泄放，其附加背压就是恒定的；假如该安全阀向火炬总管泄放，而另外几个安全阀此时也在向火炬总管泄放，则该安全阀的附加背压就是可变的。 查看更多
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