Device shutdown steam purging
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When the plant is shut down for purging, do the relief valve vent lines of towers and vessels also need to be purged? Also, does the steam go through the control valve or the bypass line? Thank you, points for this!
This post was last edited by ylb913 on 2018-9-27 06:49. Before releasing pressure via the safety valve, let the steam pass through briefly; both the control valve and the bypass line must also be checked to ensure that there is no residual material in either of them. The shutdown purging is different from the initial purging before the start of plant construction or modification; it is not necessary to lower the control valves.
Towers and vessels need to be steamed for a long time, while pipelines are purged with steam. Generally, control valves designed for low temperatures do not allow for prolonged purging, so steam is used for purging through bypass lines.
The last edit to this post was made by longziyun on 2018-9-28 at 11:08. When using a large amount of steam to purge the process medium, it is of course preferable to use a bypass line; however, all control valves should be kept at 30% open. In particular, the drain valves of the main control valves, as well as those of the return control valves located at the lowest points, must remain continuously exposed to steam. Make sure that the vent valve of the safety valve located at a higher position is releasing steam, and also don’t forget to open the bypass valve of the safety valve leading to the flare. Care must be taken when cleaning the steam towers; if the medium inside the pipes escapes, the tower or containers can still be re-steamed. But for those connected to heat exchangers, once the heat exchanger is removed, there are no effective remedies left.