利用所測容器中水和蒸汽的導(dǎo)電率差異的特性進(jìn)行測量，由于液位的變化使部分電極浸入水中，部分電極置于蒸汽中，浸入爐水中的電極對筒體阻抗減小，而置于蒸汽中的電極對筒體的阻抗增大。利用這一特性，可將非電量的水位轉(zhuǎn)化為電量，送給智能二次儀表，從而實現(xiàn)水位的顯示、報警、保護(hù)、聯(lián)鎖之功能。

For the convenience of piping engineers, the following pages show the allowable pressure rating at temperature of various piping materials including Stainless Steel Type 304 and 316 in sizes ?” through 24” in popular wall schedules. Stress values shown at various temperatures are as given in Appendix A of ANSI B31.3-Code for Pressure Piping for Petroleum Refinery Piping. The allowable pressure ratings have been calculated from the basic formula given in ANSI B31.3 as

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