There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an uncommon telephone from an irrigator within the late 1990’s. “Rob”, he stated, “I assume 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 during gentle steel cement lined (MSCL) pipeline construction in 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, close to Barmera, South Australia, in 1980’s. It can be suspected that it might simply have been a plausible excuse for unaccounted friction losses in a brand new 1000mm trunk main!
Rob agreed to help his client out. A 500mm dia. PVC rising main 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% discount in pumping output. The client assured me that he had examined the pumps and they were OK. Therefore, it simply needed to be a ‘wheel barrow’ within the pipe.
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Rob approached this drawback much as he had throughout his time in SA Water, the place he had extensive 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 strain readings along the pipeline at a quantity of places (at least 10 locations) which had been surveyed to provide correct elevation information. The sum of the stress studying plus the elevation at every level (termed the Peizometric Height) gave the hydraulic head at every level. Plotting the hydraulic heads with chainage gives a a number of point hydraulic gradient (HG), much like in the graph beneath.
pressure gauge น้ำ (HG) blue line from the friction checks indicated a consistent gradient, indicating there was no wheel barrow in the pipe. If there was a wheel barrow within the pipe, the HG could be like the red line, with the wheel barrow between factors three and 4 km. Graph: R Welke
Given that the HG was pretty straight, there was clearly no blockage along the greatest way, which would be evident by a sudden change in slope of the HG at that point.
So, it was figured that the top loss should be due to a basic friction construct up in the pipeline. To verify this concept, it was determined to ‘pig’ the pipeline. This involved using the pumps to pressure two foam cylinders, about 5cm larger than the pipe ID and 70cm lengthy, 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 enchancment within the pipeline friction from pigging was nothing short of amazing. The system head loss had been virtually totally restored to authentic efficiency, resulting in a few 10% move improvement from the pump station. So, as an alternative of discovering a wheel barrow, a biofilm was found responsible for pipe friction build-up.
Pipeline efficiency could be all the time be considered from an energy 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 due to biofilm caused the pumps not solely to function at the next head, however that a few of the pumping was pressured into peak electricity tariff. The reduced efficiency pipeline ultimately accounted for about 15% extra pumping power prices.
Not everybody has a 500NB pipeline!
Well, not everybody has a 500mm pipeline in 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 prices by as much as 15% in one 12 months. 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 may have the equivalent of a wall roughness of 0.13mm. The similar roughness in an 80mm pipe represents an H&W C value of a hundred thirty. That’s a 16% reduction in move, or a 32% friction loss improve for the same flow! And that’s simply within the first year!
Layflat hose can have excessive power value
A living proof was observed in an vitality effectivity audit performed by Tallemenco lately on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a gentle hose increase had a head loss of 26m head in contrast with the producers ranking of 14m for the same circulate, and with no kinks in the hose! That’s a whopping 85% improve in head loss. Not surprising contemplating that this layflat was transporting algae contaminated river water and lay within the hot sun all summer, breeding those little critters on the pipe inside wall.
Calculated in terms of energy consumption, the layflat hose was answerable for 46% of complete pumping energy prices by way of its small diameter with biofilm build-up.
Solution is bigger pipe
So, what’s the solution? Move to a larger diameter hose. A 3½” hose has a new pipe head loss of solely 6m/200m on the identical circulate, but when that deteriorates as a end result of biofilm, headloss might rise to only about 10m/200m instead of 26m/200m, kinks and fittings excluded. That’s a possible 28% saving on pumping power costs*. In phrases of absolute vitality consumption, if pumping 50ML/yr at 30c/kWh, that’s a saving of $950pa, or $10,700 over 10 years.
Note*: The pump impeller would must be trimmed or a VFD fitted to potentiate the power savings. In some cases, the pump could need to be changed out for a decrease head pump.
Everyone has a wheel barrow in their pipelines, and it solely gets bigger with time. You can’t get rid of it, but you’ll be able to control its results, both through vitality efficient pipeline design within the first place, or strive ‘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 in regards to the ‘wheel barrow’ in the pipeline after we can’t explain a pipeline headloss”, stated Rob.
Author Rob Welke has been fifty two years in pumping & hydraulics, and never bought 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 extensive 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 extensive.
Rob runs regular “Pumping System Master Class” ONLINE coaching programs Internationally to cross on his wealth of knowledge he learned from his 52 years auditing pumping and pipeline systems throughout Australia.
Rob may be contacted on ph +61 414 492 256, or e mail . LinkedIn – Robert L Welke

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