There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an unusual cellphone from an irrigator within the late 1990’s. “Rob”, he stated, “I think there’s a wheel barrow in my pipeline. Can you locate it?”
Robert L Welke, Director, Training Manager and Pumping/Hydraulics Consultant
Wheel barrows were used to hold package for reinstating cement lining throughout delicate metal cement lined (MSCL) pipeline building 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 through the rehabilitation of the Cobdogla Irrigation Area, close to Barmera, South Australia, in 1980’s. It can also be suspected that it may simply have been a plausible excuse for unaccounted friction losses in a model new 1000mm trunk main!
Rob agreed to assist his shopper out. A 500mm dia. PVC rising primary delivered recycled water from a pumping station to a reservoir 10km away.
The downside was that, after a 12 months in operation, there was a couple of 10% reduction in pumping output. The consumer assured me that he had tested the pumps and so they have been OK. Therefore, it just had to be a ‘wheel barrow’ in the pipe.
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Rob approached this downside much as he had during his time in SA Water, where he had extensive expertise finding isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water supply pipelines in the course of the 1980’s.
Recording hydraulic gradients
He recorded accurate stress readings alongside the pipeline at a quantity of areas (at least 10 locations) which had been surveyed to offer correct elevation information. The sum of the pressure studying plus the elevation at every level (termed the Peizometric Height) gave the hydraulic head at each point. Plotting the hydraulic heads with chainage provides a a quantity of point hydraulic gradient (HG), much like within the graph under.
Hydraulic Grade (HG) blue line from the friction exams indicated a consistent gradient, indicating there was no wheel barrow within the pipe. If there was a wheel barrow within the pipe, the HG could be just like the purple line, with the wheel barrow between factors 3 and four km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage along the way, which would be evident by a sudden change in slope of the HG at that point.
So, it was figured that the head loss must be due to a common friction build up in the pipeline. To affirm this principle, it was determined to ‘pig’ the pipeline. This involved utilizing the pumps to drive two foam cylinders, about 5cm larger than the pipe ID and 70cm long, alongside 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 immediate improvement within the pipeline friction from pigging was nothing in want of amazing. The system head loss had been almost totally restored to unique efficiency, resulting in a couple of 10% flow improvement from the pump station. So, instead of discovering a wheel barrow, a biofilm was found answerable for pipe friction build-up.
Pipeline efficiency can be at all times be viewed from an energy effectivity perspective. Below is a graph exhibiting 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 as a result of biofilm triggered the pumps not only to function at a higher head, however that a few of the pumping was forced into peak electrical energy tariff. The decreased efficiency pipeline ultimately accounted for about 15% additional pumping power prices.
Not everybody has a 500NB pipeline!
Well, not everyone has a 500mm pipeline in their irrigation system. So how does that relate to the typical irrigator?
A new 500NB
System curve (red line) indicates a biofilm build-up. Black line (broken) shows 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%) via biofilm build-up, the pipe will have the equivalent of a wall roughness of zero.13mm. The identical roughness in an 80mm pipe represents an H&W C worth of a hundred thirty. That’s a 16% reduction in flow, or a 32% friction loss improve for a similar flow! And that’s simply within the first year!
Layflat hose can have excessive power price
A working example was observed in an energy effectivity audit carried out by Tallemenco recently on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a gentle hose increase had a head lack of 26m head in contrast with the producers ranking of 14m for the same flow, and with no kinks within the hose! That’s a whopping 85% enhance in head loss. Not surprising considering that this layflat was transporting algae contaminated river water and lay within the hot sun all summer season, breeding those little critters on the pipe inside wall.
Calculated in phrases of energy consumption, the layflat hose was liable for 46% of total pumping power costs by way of its small diameter with biofilm build-up.
Solution is larger pipe
So, what’s the solution? Move to a bigger diameter hose. A 3½” hose has a new pipe head lack of solely 6m/200m at the same move, but when that deteriorates due to biofilm, headloss could rise to only about 10m/200m as an alternative of 26m/200m, kinks and fittings excluded. pressure gauge s a possible 28% saving on pumping energy costs*. In terms of absolute vitality 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 circumstances, the pump may need to be modified out for a lower head pump.
Everyone has a wheel barrow of their pipelines, and it only will get larger with time. You can’t do away with it, however you’ll find a way to control its effects, both by way of vitality efficient pipeline design in the first place, or try ‘pigging’ the pipe to eliminate 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 52 years in pumping & hydraulics, and never sold product in his life! He spent 25 yrs working for SA Water (South Australia) in the late 60’s to 90’s the place he carried out intensive pumping and pipeline energy effectivity monitoring on its 132,000 kW of pumping and pipelines infrastructure. Rob established Tallemenco Pty Ltd (2003), an Independent Pumping and Hydraulics’ Consultancy based mostly in Adelaide, South Australia, serving clients Australia wide.
Rob runs common “Pumping System Master Class” ONLINE training programs Internationally to pass on his wealth of knowledge he discovered from his fifty two years auditing pumping and pipeline techniques throughout Australia.
Rob could be contacted on ph +61 414 492 256, or e mail . LinkedIn – Robert L Welke

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