Pressure drop along a line.

[v8landy]

Hi

I have been posed a question by my EH&S manger, so looking for quick reply!

I have calculated pressure required to move a slurry along a line by pressurising a pressure rated tank, connected to a 6" line approx 100m long and 18m head, to a tank vented to atms.

The MAX pressure I have calculated (inc bend,valves etc and 18m) is ~5Bar g.

His question is will we still have 5 bar at the exit of the pipe into the open tank???

I do not belive so becuse the pressure tankes into account the pressure drop along the line etc?

Can someone verify that given statment, assuming that material moves and not sealed?

Thanks

 

[rbcoulter]

Pressure is often confused, and it looks so here. You said the pipe empties into a vented atmospheric tank so the pressure at the end of the pipe is atmospheric pressure. What you are not mentioning is the flow rate through the pipe. What flow rate did you assume when you calculated the pressure? The equations (Darcy, HW, etc.) actually calculates a pressure drop for a particularly flow rate. The end of the pipe pressure is known so the needed pressure at the pipe entrance is the pressure drop calculated plus the end of the pipe pressure (gauge = 0).

 

[v8landy]

Hi

I used a flow rate of 30,000 L/hr.

Based on transfering approx 8,000 L in ~15 mins.

 

[Compositepro]

Moving fluid, or anything, with air pressure involves some hazards. Pressurized gas contains stored energy and its release must be controlled. When your slurry tank empties and the pipe runs dry, the last slug of slurry will be shot out of the pipe if you haven't taken steps to avoid it.

 

[v8landy]

We are blowwing up into the base of the tank (12m high) i.e through the slurry.

The tank is vented to atms, with plenty of open area.

Only when the tank is nearing full would there be any possiblty on entrainment.

 

[Compositepro]

So it seems to me you have the possibility of blowing 5 bar air though a 6" pipe supplied by a very large pressure vessel into the bottom of a nearly full tank 12m tall. That sound like a potential volcano to me.

When the pipe is empty of slurry there will be very little pressure drop in the air flow.

 

[zerosum]

What is the difference in the line pressure drop when conveying slurry as opposed to the line pressure drop of the motivating gas only (air?). Compositepro makes a point that needs to be considered. There will possibly be a lot of energy to be dissipated thru the slurry.

 

[v8landy]

3 points why we will NOT have a volcano!

1 In directly we already preform this task! We currently vac out from one tank into a road tanker. Road tanker drives to other side of site, and blows slurry up into tank. Project is to remove need for tanker i.e install pipeline. Therfore we already preform this task with no issues!

2 We have level control and ultra high linked to block valves with set points with a max fill of 90%

3 Mist eliminator pads will be fitted to the to as a final precation.