bimr:
The pipe is 1/2 inches in diameter. I just did the calculations on the capillary rise, and at worst case (wetting angle of 0 degrees) the rise is 0.0460 inches. I believe the gradations are in inches, and thus there is no way 5 inches of difference in water columns can be attributed to...
I have updated information on this project....
We let the force main sit unused for a week or so and took static readings at all of the ARVs again. ARV #s 2-5 all where right on the correct HGL, while ARV #1 was 7.8ft higher. The first round of readings showed ARV #1 as 7.9ft higher than the...
bimr:
The pumps were sized for the 16" FM based on state regulations which states a minimum of 2fps in a FM. That is where the ~1250gpm number comes from. The pumps are set-up as a series of lead-lag floats. #1 ON, then #1 and #2 ON, etc. State regulations say that a station's "firm...
There are 4 pumps in the stations, typically only 1 is required, sometimes 2. The pumps are Myers 4VC 10"-impeller 30-hp 1750rpm. One pump should be operating in the 1200gpm range, based on design numbers and that is conservative.
The pump reps have been on-site and checked the amp draws...
On the pump side of ARV #2 there is a low point of (-)1.65'ELV(top of pipe) and on the discharge side there is a low point of (-)2.0'ELV. ARV #2, 7.3'ELV, is in a high spot between 2 swampy areas.
That explanation works for the additional static head, it just doesn't seem to explain the static head being 20ft below what it should be at ARV #2. If there is a backpressure then I could see the static head being significantly higher, but would it not be flat as well (look like a stair step...
Now this project has taken another wierd turn.
The client sent their operations guys out to take pressure readings at the ARVs along the pipeline, and the attached graph is the information obtained.
I have no idea how to explain what is going on. There is 850gpm coming out of the pumps...
bimr:
The gauge elevation is 20.5' and the average water elevation during the drawdown was -0.875', thus the static head the pumps themselves were seeing was 63.375' (42' + 21.375'). Then subtracting that from the 77' of TDH, that the pumps were seeing, the friction losses were approx. 13.6'...
The more I think about this the more it makes sense to me.
It seems like if there is an unequal water surface around a high point with pressurized air between them, you "stack" the water columns. Using your intial sketch, at point B the air is getting the pressure from the water column on the...
To bimr:
Our surveyors have run re-run this route 3 different times and they come back as correct.
To semo:
This force main is dedicated solely to this pump station, so the static this station should see would just be the elevation difference.
I agree this concept seems illogical, I just...
Thanks for all of the insight SteveWag. Looking back through the plans it seems that there are several places that the FM should have been laid to a grade and not follow the ground profile. My guess is they followed the ground profile more than the grade and put several high points without ARVs...
Thanks for the insight SteveWag! I am really interested in seeing your sketch, because I think I understand but a visual would help. The re-profiling based on radar or "pot-holing" is likely where we are headed with this project.
Would we be able to narrow down where the issues might be...
Thanks for the comment bimr. We have the operations guys going out to check that, but even if it was surcharged it theoretically wouldn't account for the full 20'. The top of the discharge manhole is approx. elevation 47.5', thus the gauge should read approx. 27' of head not 42'.
If the...
I am working on a pump station that has everybody scratching their heads. This was an existing pump station with a forcemain that trended downward to the discharge. Our clients decided to send the flow to a different portion of the system, so we tapped the existing 16" FM and routed a new FM...
