| 摘要 |
A system for automatically purging heating mantles and other apparatus including an enclosed volume capable of low level pressurization. The system comprises a pressure sensor for sensing the fluid pressure within the enclosure, which may be the space between a heating mantle poncho and the enclosed flask, and a fluidic logic circuit which is responsive to a low pressure condition within the enclosure to deactivate the heating element in the mantle. At the same time, the logic circuit causes a predetermined volume of purging gas to flow through the enclosure and, after this has been accomplished, reactivates the heating element and reestablishes the minimum pressure conditions by flowing a small volume of purging gas into the enclosure. The system is particularly intended for use in hazardous locations where explosion-proof electrical equipment enclosures are normally mandatory. In order to avoid the enclosing of the purging system in an explosion-proof enclosure, all of the control functions are accomplished by fluidic-mechanical logic and control components, thereby virtually eliminating the necessity for electrical control equipment. In cases where electrical switches and relays are used to disconnect the heating element from its source of supply, these may be located remotely from the hazardous location and controlled by fluid pressure signals transmitted thereto over control tubing.
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