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 mentioned, “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 have been used to carry kit for reinstating cement lining during gentle metal cement lined (MSCL) pipeline building 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 occurred through the rehabilitation of the Cobdogla Irrigation Area, close to Barmera, South Australia, in 1980’s. It is also suspected that it could just have been a believable excuse for unaccounted friction losses in a model new 1000mm trunk main!
Rob agreed to assist his shopper 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 a few 10% reduction in pumping output. The client assured me that he had examined the pumps they usually were OK. Therefore, it simply had to be a ‘wheel barrow’ within the pipe.
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Rob approached this problem a lot as he had throughout his time in SA Water, the place he had in depth experience finding 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 correct pressure readings along the pipeline at a number of locations (at least 10 locations) which had been surveyed to supply correct elevation data. The sum of the pressure reading plus the elevation at every point (termed the Peizometric Height) gave the hydraulic head at every point. Plotting the hydraulic heads with chainage gives a multiple point hydraulic gradient (HG), much like 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 purple line, with the wheel barrow between points 3 and four km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage along the method in which, which might be evident by a sudden change in slope of the HG at that point.
So, it was figured that the head loss have to be due to a common friction construct up within the pipeline. To affirm this principle, it was determined to ‘pig’ the pipeline. This concerned utilizing the pumps to pressure two foam cylinders, about 5cm bigger 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 performance was improved 10% because of ‘pigging’. Photo: R Welke
The instant improvement in the pipeline friction from pigging was nothing wanting wonderful. The system head loss had been nearly completely restored to original performance, leading to a few 10% circulate enchancment from the pump station. So, as an alternative of finding a wheel barrow, a biofilm was found answerable for pipe friction build-up.
Pipeline efficiency could be always be seen 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 increase in system head as a result of biofilm triggered the pumps not solely to operate at a better head, however that a variety of the pumping was compelled into peak electrical energy tariff. The decreased performance pipeline in the end accounted for about 15% extra pumping energy 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 average irrigator?
A new 500NB
System curve (red line) signifies a biofilm build-up. Black line (broken) reveals system curve after pigging. Efficient raised pumping costs by as much as 15% in one yr. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction value of about C=155. When reduced to C=140 (10%) by way of 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 value of a hundred thirty. That’s a 16% discount in circulate, or a 32% friction loss increase for the same flow! And that’s just in the first year!
Layflat hose can have high energy value
A case in point was noticed in an energy efficiency audit carried out by Tallemenco recently on a turf farm in NSW. A 200m lengthy 3” layflat pipe delivering water to a delicate hose growth had a head loss 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% improve in head loss. Not shocking considering that this layflat was transporting algae contaminated river water and lay within the hot solar all summer season, breeding those little critters on the pipe inside wall.
Calculated in terms of power consumption, the layflat hose was liable for 46% of complete pumping vitality costs through its small diameter with biofilm build-up.
Solution is bigger pipe
So, what’s the solution? Move to a bigger diameter hose. A 3½” hose has a new pipe head loss of solely 6m/200m at the similar flow, however when that deteriorates as a result of biofilm, headloss could rise to solely about 10m/200m as a substitute of 26m/200m, kinks and fittings excluded. That’s a potential 28% saving on pumping power costs*. In phrases of absolute power 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 have to be trimmed or a VFD fitted to potentiate the power savings. In some cases, the pump may have to be modified out for a decrease head pump.
Everyone has a wheel barrow of their pipelines, and it solely gets bigger with time. You can’t get rid of it, however you can control its results, both by way of energy efficient pipeline design within 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 concerning the ‘wheel barrow’ in the pipeline once we can’t explain a pipeline headloss”, mentioned 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 in depth pumping and pipeline vitality 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 purchasers Australia extensive.
Rob runs regular “Pumping System Master Class” ONLINE coaching courses Internationally to pass on his wealth of knowledge he learned from his 52 years auditing pumping and pipeline methods all through Australia.
Rob may be contacted on ph +61 414 492 256, or email . LinkedIn – Robert L Welke

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