Merge Lines of Different Pressures In Maniy

[FaizanAMalik]

Hello All,

I have a question regarding merging of pipes which have varying pressures. The lines in question are drain lines from different vessels currently discharging to a trench. The trench needs repair so the lines are to be combined and rerouted to a manhole temporarily so trench can be repaired. My issue is how to ensure no back flow occurs in lines as the drain flow is intermittent and some drain lines discharge at higher pressure than others. Any advice is appreciated.

We are thinking of using hoses to reroute the lines but since manhole size is small the goal is to combine flow first and then take one hose to manhole.

Thank you

 

[georgeverghese]

Presume the existing lines to the trench go direct to the open trench without manifolding ? Are these drain fluids flammable or potentially flammable if there is poor degassing or poor liquid liquid separation operation of the upstream sources? Are solids or corrosion debris present in any of these drain streams that can block a manifold ?
What is the highest operating source pressure of these drain lines, and the lowest?

 

[LittleInch]

If the line runs only party full and the vapour space is connected to a vent (atmospheric pressure, then there should be no backflow.

Only if the drain pipe becomes full of liquid and ending up with positive pressure. So just make the line continuously draining with no pockets and big enough to always be open channel flow

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