There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an uncommon telephone from an irrigator in the late 1990’s. “Rob”, he stated, “I suppose there’s a wheel barrow in my pipeline. Can you locate it?”
Robert L Welke, Director, Training Manager and Pumping/Hydraulics Consultant
Wheel barrows have been used to hold kit for reinstating cement lining throughout delicate steel cement lined (MSCL) pipeline construction within the previous days. It’s not the first time Rob had heard of a wheel barrow being left in a big pipeline. Legend has it that it happened in the course of the rehabilitation of the Cobdogla Irrigation Area, near Barmera, South Australia, in 1980’s. It is also suspected that it might simply have been a plausible excuse for unaccounted friction losses in a brand new 1000mm trunk main!
Rob agreed to assist his shopper out. A 500mm dia. PVC rising major delivered recycled water from a pumping station to a reservoir 10km away.
The drawback was that, after a 12 months in operation, there was a few 10% reduction in pumping output. The client assured me that he had tested the pumps and they have been OK. Therefore, it simply needed to be a ‘wheel barrow’ in the pipe.
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Rob approached this problem much as he had throughout his time in SA Water, the place he had intensive experience locating isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water supply pipelines through the 1980’s.
Recording hydraulic gradients
He recorded accurate stress readings alongside the pipeline at multiple locations (at least 10 locations) which had been surveyed to offer correct elevation information. The sum of the strain reading plus the elevation at every point (termed the Peizometric Height) gave the hydraulic head at every point. Plotting the hydraulic heads with chainage offers a multiple point hydraulic gradient (HG), much like within the graph under.
Hydraulic Grade (HG) blue line from the friction tests indicated a constant gradient, indicating there was no wheel barrow within the pipe. If there was a wheel barrow in the pipe, the HG could be like the pink line, with the wheel barrow between points three and 4 km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage along the finest way, which might be evident by a sudden change in slope of the HG at that point.
So, it was figured that the pinnacle loss should be as a result of a basic friction build up in the pipeline. To confirm this principle, it was determined to ‘pig’ the pipeline. This concerned using the pumps to force 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% on account of ‘pigging’. Photo: R Welke
The instant improvement within the pipeline friction from pigging was nothing short of amazing. The system head loss had been virtually completely restored to original performance, resulting in about a 10% circulate improvement from the pump station. So, as an alternative of discovering a wheel barrow, a biofilm was discovered answerable for pipe friction build-up.
Pipeline efficiency can be at all times be considered from an energy efficiency 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 improve in system head because of biofilm brought on the pumps not solely to operate at the next head, but that a few of the pumping was forced into peak electricity tariff. The decreased efficiency pipeline ultimately accounted for about 15% additional pumping power costs.
Not everybody has a 500NB pipeline!
Well, not everyone 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) exhibits system curve after pigging. Biofilm raised pumping costs by as much as 15% in one year. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction value of about C=155. When decreased to C=140 (10%) by way of biofilm build-up, the pipe will have the equivalent of a wall roughness of zero.13mm. The same roughness in an 80mm pipe represents an H&W C worth of a hundred thirty. That’s a 16% discount in flow, or a 32% friction loss improve for the same flow! And that’s just within the first year!
Layflat hose can have excessive energy price
A case in point was noticed in an vitality efficiency audit performed by Tallemenco recently on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a gentle hose growth had a head lack of 26m head in contrast with the producers rating of 14m for the same flow, and with no kinks in the hose! That’s a whopping 85% improve in head loss. Not stunning contemplating that this layflat was transporting algae contaminated river water and lay in the scorching sun all summer season, breeding those little critters on the pipe inside wall.
Calculated by means of power consumption, the layflat hose was responsible for 46% of whole pumping energy costs by way of its small diameter with biofilm build-up.
Pay zero is larger pipe
So, what’s the solution? Move to a bigger diameter hose. A 3½” hose has a brand new pipe head lack of only 6m/200m at the identical move, however when that deteriorates due to biofilm, headloss might rise to only about 10m/200m as an alternative of 26m/200m, kinks and fittings excluded. That’s a potential 28% saving on pumping vitality 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*: The pump impeller would need to be trimmed or a VFD fitted to potentiate the power savings. In some instances, the pump might have to be modified out for a lower head pump.
Everyone has a wheel barrow in their pipelines, and it solely will get greater with time. You can’t eliminate it, but you probably can management its results, either through energy efficient pipeline design in the first place, or strive ‘pigging’ the pipe to do away with that wheel barrow!!
As for the wheel barrow in Rob’s client’s pipeline, the legend lives on. “He and I still joke concerning the ‘wheel barrow’ in the pipeline once we can’t explain a pipeline headloss”, said Rob.
Author Rob Welke has been fifty two years in pumping & hydraulics, and by no means bought product in his life! He spent 25 yrs working for SA Water (South Australia) within the late 60’s to 90’s where he performed extensive pumping and pipeline power efficiency 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 purchasers Australia broad.
Rob runs regular “Pumping System Master Class” ONLINE training courses Internationally to move on his wealth of data he discovered from his 52 years auditing pumping and pipeline systems throughout Australia.
Rob could be contacted on ph +61 414 492 256, or e-mail . LinkedIn – Robert L Welke

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