There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an unusual telephone from an irrigator in the late 1990’s. “Rob”, he said, “I suppose there’s a wheel barrow in my pipeline. Can you find it?”
Robert L Welke, Director, Training Manager and Pumping/Hydraulics Consultant
Wheel barrows were used to carry kit for reinstating cement lining throughout mild steel cement lined (MSCL) pipeline construction within the outdated days. It’s not the first time Rob had heard of a wheel barrow being left in a large pipeline. Legend has it that it occurred in the course of the rehabilitation of the Cobdogla Irrigation Area, close to Barmera, South Australia, in 1980’s. It can also be suspected that it could simply have been a plausible excuse for unaccounted friction losses in a model new 1000mm trunk main!
Rob agreed to help his client out. A 500mm dia. PVC rising primary delivered recycled water from a pumping station to a reservoir 10km away.
The problem was that, after a year in operation, there was about a 10% reduction in pumping output. The shopper assured me that he had tested the pumps and so they had been OK. Therefore, it simply needed to be a ‘wheel barrow’ in the pipe.
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Rob approached this drawback much as he had during his time in SA Water, where he had in depth experience locating isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water provide pipelines in the course of the 1980’s.
Recording hydraulic gradients
He recorded accurate pressure readings along the pipeline at multiple places (at least 10 locations) which had been surveyed to offer correct elevation info. The sum of the stress reading plus the elevation at each point (termed the Peizometric Height) gave the hydraulic head at each level. Plotting the hydraulic heads with chainage provides a multiple point hydraulic gradient (HG), very related to within the graph beneath.
Hydraulic Grade (HG) blue line from the friction checks indicated a constant gradient, indicating there was no wheel barrow in the pipe. If there was a wheel barrow within the pipe, the HG can be just like the red line, with the wheel barrow between points three and four km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage along the way, which might be evident by a sudden change in slope of the HG at that point.
So, it was figured that the top loss have to be as a result of a basic friction construct up in the pipeline. To confirm this principle, it was determined to ‘pig’ the pipeline. This involved utilizing the pumps to pressure two foam cylinders, about 5cm larger than the pipe ID and 70cm long, along the pipe from the pump end, exiting into the reservoir.
Two foam pigs emerge from the pipeline. The pipeline efficiency was improved 10% because of ‘pigging’. Photo: R Welke
The instant improvement in the pipeline friction from pigging was nothing short of wonderful. The system head loss had been nearly completely restored to original performance, leading to a few 10% circulate improvement from the pump station. So, as a substitute of finding a wheel barrow, a biofilm was found responsible for pipe friction build-up.
Pipeline efficiency can be always be seen from an vitality effectivity perspective. Below is a graph displaying the biofilm affected (red line) and restored (black line) system curves for the client’s pipeline, earlier than and after pigging.
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The enhance in system head as a end result of biofilm caused the pumps not only to function at the next head, however that a few of the pumping was compelled into peak electricity tariff. The decreased performance pipeline finally accounted for about 15% additional pumping power costs.
Not everybody has a 500NB pipeline!
Well, not everybody has a 500mm pipeline of their irrigation system. So how does that relate to the common irrigator?
A new 500NB
System curve (red line) indicates a biofilm build-up. Black line (broken) reveals system curve after pigging. Biofilm raised pumping costs by up to 15% in one yr. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction worth of about C=155. When decreased to C=140 (10%) through biofilm build-up, the pipe will have the equivalent of a wall roughness of 0.13mm. The same roughness in an 80mm pipe represents an H&W C value of one hundred thirty. That’s a 16% discount in circulate, or a 32% friction loss increase for a similar flow! And that’s just in the first year!
Layflat hose can have excessive power price
A case in point was noticed in an vitality efficiency audit carried out by Tallemenco recently on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a soft hose growth had a head lack of 26m head in contrast with the manufacturers rating of 14m for the same circulate, and with no kinks within the hose! That’s a whopping 85% enhance in head loss. Not stunning considering that this layflat was transporting algae contaminated river water and lay within the scorching solar all summer season, breeding these little critters on the pipe inside wall.
Calculated in terms of energy consumption, the layflat hose was answerable for 46% of complete pumping power costs via its small diameter with biofilm build-up.
Solution is larger pipe
So, what’s the solution? Move to a larger diameter hose. A 3½” hose has a brand new pipe head loss of only 6m/200m at the identical flow, but when that deteriorates as a end result of biofilm, headloss might rise to solely about 10m/200m as an alternative of 26m/200m, kinks and fittings excluded. That’s a possible 28% saving on pumping energy costs*. In terms of absolute energy consumption, if pumping 50ML/yr at 30c/kWh, that’s a saving of $950pa, or $10,seven-hundred over 10 years.
Note*: เพรสเชอร์เกจไฮดรอลิค would need to be trimmed or a VFD fitted to potentiate the vitality financial savings. In some instances, the pump could have to be modified out for a decrease head pump.
Everyone has a wheel barrow of their pipelines, and it solely will get bigger with time. You can’t get rid of it, however you can management its effects, both via vitality environment friendly pipeline design in the first place, or try ‘pigging’ the pipe to get rid of that wheel barrow!!
As for the wheel barrow in Rob’s client’s pipeline, the legend lives on. “He and I nonetheless joke about the ‘wheel barrow’ in the pipeline when we can’t explain a pipeline headloss”, said Rob.
Author Rob Welke has been fifty two years in pumping & hydraulics, and by no means sold product in his life! He spent 25 yrs working for SA Water (South Australia) within the late 60’s to 90’s the place he conducted in depth pumping and pipeline power effectivity monitoring on its 132,000 kW of pumping and pipelines infrastructure. Rob established Tallemenco Pty Ltd (2003), an Independent Pumping and Hydraulics’ Consultancy primarily based in Adelaide, South Australia, serving clients Australia broad.
Rob runs regular “Pumping System Master Class” ONLINE coaching programs Internationally to move on his wealth of data he learned from his fifty two years auditing pumping and pipeline techniques all through Australia.
Rob could be contacted on ph +61 414 492 256, or email . LinkedIn – Robert L Welke

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