Bjegovic
I have never heard that comment about intake on a double volute pump.
Do you have an explanation or reference?
I will examine this myself, but would appreciate any info you have.
PUMPDESIGNER
This is a great forum, the guys have many excellent comments.
I will add that the radial thrust problem is extremely important unless the pump operates continuously at or near the BEP .
A double volute scroll pump has almost no radial thrust at any point on the curve, from zero flow all the way...
We asked a machine shop to make some parts for a pump intake out of HDPE pipe and 1/2" thick sheet.
The machinist if having severe problems, breaking bits, bending tool shafts, etc.
I know nothing have seen nothing, but that seems strange, very strange.
The machinist has never machined...
1969Grad got it right, get the water tested.
There are both iron and sulfur bacteria, as well as simple elemental sulfur compounds involved.
In our area we have simple sulfur compounds, which we deal with by means of evaporation. Water is dropped into a tank full of wiffle balls, as water...
One note about graphs.
All the software I have seen uses log files that easily import or directly transfer into spreadsheets, perhaps Excel being the most common.
If you want good graphs however you have to do them yourself. The software cannot possibly know what kind of resolution you need in...
Zapster,
You are correct about the term laminar flow, I misused the term, thank you for pointing that out.
So the correct statement would be something like,
Obtain the lowest possible practical velocity and clean flow lines into the impeller.
PUMPDESIGNER
Zapster,
I am aware of the field problems of applications, and I certainly do not condemn those who struggle with this issue due to lack of space, retrofitting, etc.
I helped a guy last year with a 150hp fire engine pump problem.
No way could they get anything close to a flow run onto the...
I agree with Stanier, my post only stated one side of the issue. We find that people usually overdesign the pump because they are not sure of their hydraulics.
But there are other problems to consider also.
We use concentric, modified concentric, and turbines.
The concentric and modified...
JJPellin is exactly correct, although the pumps pass fluid efficiently, they hate to run much below BEP, they can vibrate and have serious recirculation cavitation.
PUMPDESIGNER
Service Factor is used by the majority of commercial pump manufacturers in their standard products, "my 20hp pump pumps more than your 20hp pump", mentality.
As usual, electricpete has the correct scoop, the pump design should not use the service factor, leaving room for field problems such as...
The required straight run of pipe connection to the suction nozzle of a pump can only be determined by modeling, which is not possible in most situations, therefore the rules of thumb trying to protect ourselves.
The concept is simple though, provide a smooth laminar flow with clean flow lines...
Defined by the HI using a chart which can be obtained at this link:
http://www.pumps.org/public/pump_resources/discussion/NPSH_Standard/suction_energy_determination.htm
Follow that link and the pages before and after to learn about high suction energy pumps.
One basic concept:
High suction...
electricpete - Did you get d23s attachment I forwarded to you?
Your explanation is true for volute pumps, not true for turbines, axial flow, etc. There is no radial thrust on turbines (almost none), because the flow through the impeller is concentric, all radial thrust is balanced by the...
So called "turbine" pumps have two distintive features:
1 - concentric flow as opposed to a cutwater
2 - flow from each impeller goes through a diffuser, even if there is only one impeller.
Turbine pumps cover the entire range of specific speeds, low to high, (radial flow all the way up to...
All that the guys above have said is true. Basically, there is no official statement because that cannot be done easily, too many variables.
I do have a scan of a page from Certainteed pipe regarding this issue. You can download the JPG at this link...
sow,
Are you pumping solids or relatively clear water?
Sewage pumps, solids handling pumps, non-clog pumps, all come with a price for the abilities they have to handle solids, rags, etc. If you are pumping relatively clear fluid then you are better off getting away from those pumps.
The price...
If there is one cutwater and the pump is a scroll volute, maximum hydraulic efficiency and hydraulic balance surrounding the impeller occurs at BEP. Radial thrust increases as flow moves away from BEP (above or below BEP).
Explanation & drawings showing radial thrust on scroll volutes at...
