Relief valves trayed towers

Tower trays were repeatedly upset due to pressure surges resultii from water accumulating in the tower during short unit outages. The source of water was condensation of purge steam used under the cohmm relief valves to prevent their inlets from plugging. 

I have never seen or heard about tray failure due to a relief valve opening. However, in a packed distillation tower, I am aware of at least one such incident, also at the Whiting Refinery. 

For such a tower, tray decks should be sieve or grid trays, and never valve cap trays. I will typically use a grid tray with a 1 -inch lift. Also, using 10-gauge rather than 14-gauge trays (which is the industry standard) will double the tray resistance to collapse, due to the relief valves lifting at the bottom of the tower. 

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