Circuit pressure
Circuit pressure
(OP)
Hi,
I'm facing the following problem: in the project, i've calculated the pressure drop along a closed circuit. The calculations gave me aprox. 3,5 mH2O of pressure drop. This was calculated for a optimal flow of 240 lt/h. After the installation was made, the max flow that the pump was able to provide was 120 lt/h. The first thing that i thought was that the circuit pressure loss was much greater than th one i've calculated in the project and therfor the pump was working in a lour point of the pump curve, so that it could overcome that loss.
After this i've started to think much deeper in this, and i've figured another reason, that i would like to see commented. In this circuit, the pressure vessel is installed after the pump. I wonder if the pressure is limited by the expansion vessel defined pressure, wich may not be enough to overcome the circuit pressure loss.
I would like to hear some comments about this.
Thanks!!
I'm facing the following problem: in the project, i've calculated the pressure drop along a closed circuit. The calculations gave me aprox. 3,5 mH2O of pressure drop. This was calculated for a optimal flow of 240 lt/h. After the installation was made, the max flow that the pump was able to provide was 120 lt/h. The first thing that i thought was that the circuit pressure loss was much greater than th one i've calculated in the project and therfor the pump was working in a lour point of the pump curve, so that it could overcome that loss.
After this i've started to think much deeper in this, and i've figured another reason, that i would like to see commented. In this circuit, the pressure vessel is installed after the pump. I wonder if the pressure is limited by the expansion vessel defined pressure, wich may not be enough to overcome the circuit pressure loss.
I would like to hear some comments about this.
Thanks!!





RE: Circuit pressure
Mike Halloran
Pembroke Pines, FL, USA
RE: Circuit pressure
The circuit head loss (flow resistance) is much higher than you've calculated. That forces the pump back to the left side of the curve and lowers the flow.
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: Circuit pressure
In the top of the circuit. But now it is closed, because the circuit was filled and removed all the air.
BigInch
Ok. That was my cnclusion. But what is the possible reason?
Thank you both!
RE: Circuit pressure
Do you have a schematic you can post?
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: Circuit pressure
It's quite complicate to draw now a schem, but i understand what is your point. You want to confirm if my calculations were correct.
Let's assume yes and if we don't find a reasonable reason, then we assume that was my failure.
Thanks
RE: Circuit pressure
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: Circuit pressure
You are using the wrong pump.
The pump was incorrectly specified.
The wrong pump was delivered and does not meet specifications on the order.
If you could provide a schematic as Biginch requested he may see an error in connecting the pump. Or an unaccounted for system resistance to flow resulting in low pump flow.
Ted
RE: Circuit pressure
Valve not fully open.
Vapor locked.
Welder's gloves left inside the pipe.
Dead armadillo.
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: Circuit pressure
RE: Circuit pressure
I found one glove once, said "well now we'll have to wait for the other one and, sure enough, it turned up a few days later. Also found a hard hat once, said the same thing, but fortunately the guy only had one head.
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: Circuit pressure
For the OP. Check the pump is running correct direction.
RE: Circuit pressure
"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************
http://virtualpipeline.spaces.live.com/
RE: Circuit pressure
It can not be rats or gloves, etc, because is a 15mm pipe.
The pump is installed correctly. I've attached a scheme.
I'm quite lost. The 1st think that i thought is to change the pump, but i'm affraid that may not be this the reason.
RE: Circuit pressure
Ted
RE: Circuit pressure
Since there is a temperature difference around the loop, the location of a clog in the pipework might be found by a slow and careful temperature survey. The other choice is pressure taps at the inlet and outlet of all components.
Speaking of which, I don't see an element that I can identify as a pressure gage or transducer. Have you measured the actual pressure at any single point in the loop? That might give you a clue about the actual operating point.
Mike Halloran
Pembroke Pines, FL, USA
RE: Circuit pressure
RE: Circuit pressure
If you are confimed about the direction of rotation as "correct" (As this is most usually witnessed with wrong cable leads connection on three phase E/motor driven pumps)
Then try to check for physical obstruction alone on the Discharge/suction sides; may be through flush back and local draining if safe?
Best Regards
Qalander(Chem)
RE: Circuit pressure
Might want to look at the possibility that pump intake is being starved by inadequate available volume.
At 74th year working on IR-One PhD from UHK - - -
RE: Circuit pressure
I'm more concerned about the air. Tha guy how made the installation used a filling pump witch has the possibility to remove the air durin the system filling. So, for this reason, he did not install an air purger at the top of the circuit. I wonder if some air could be formed during the time and this would be the problem....
I don't know where do i start to find the problem and oi don't know also what are the methods to look for them...
Thank you!
RE: Circuit pressure
RE: Circuit pressure
RE: Circuit pressure
"If stupidity got us into this mess, then why can't it get us out?" - Will Rogers (1879-1935) ***************
http://virtualpipeline.spaces.live.com/