surge pressures in lpg systems!!! 1

[fugassity]

Hello,
Need to explain to a roomfull of unforgiving chemical engineers "surge pressures in lpg systems".Can anybody help me out?
Thank you.

 

[dcasto]

How about billiards. You have a whole group of billiard balls traveling in one direction, toward the end of the pool table. They have momemtum (m*v). They all hit the end bumper and start bouncing back toward where they came. Some will eventually come back mostly by transfer of momemtum to others. This action of coming back increases the pressurre at the starting point. Some even continue back in the original path. Hitting the end again. The momemtum is slowly lost as some balls strick others and go in direction not paralel to the original path.

In LPG versus water, the LPG molecules are larger and the bonds more flexable than water. This makes them absorb and redirect the momemtum more readily than water, so the surge will be a lot less than water.

I workrd on a 120 mile LPG line and we had a very fast SCADA system (about 15 seconds between scans). We could shut the valve 120 miles from the origin and we could see the pressure wave reflec back and forth for several mimutes.