There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an uncommon cellphone from an irrigator within the late 1990’s. “Rob”, he said, “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 have been used to hold equipment for reinstating cement lining during mild metal cement lined (MSCL) pipeline construction in the old 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 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 just 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 main delivered recycled water from a pumping station to a reservoir 10km away.
The drawback was that, after a yr in operation, there was about a 10% discount in pumping output. The consumer assured me that he had tested the pumps they usually had been OK. Therefore, it just had to be a ‘wheel barrow’ in the pipe.
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Rob approached this downside a lot as he had throughout his time in SA Water, the place he had extensive experience 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 correct pressure readings along the pipeline at multiple places (at least 10 locations) which had been surveyed to provide accurate elevation information. The sum of the strain studying plus the elevation at every point (termed the Peizometric Height) gave the hydraulic head at every level. Plotting the hydraulic heads with chainage provides a multiple level hydraulic gradient (HG), very comparable to in the graph below.
Hydraulic Grade (HG) blue line from the friction exams 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 purple line, with the wheel barrow between points 3 and four km. Graph: R Welke
Given that the HG was pretty straight, there was clearly no blockage alongside the way, which would be evident by a sudden change in slope of the HG at that time.
So, it was figured that the top loss should be due to a general friction build up in the pipeline. To confirm this principle, it was determined to ‘pig’ the pipeline. This involved utilizing the pumps to force 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 prompt enchancment in the pipeline friction from pigging was nothing short of wonderful. The system head loss had been nearly completely restored to unique performance, leading to a couple of 10% circulate improvement from the pump station. So, instead of finding a wheel barrow, a biofilm was discovered responsible for pipe friction build-up.
Pipeline performance may be always be viewed from an power effectivity perspective. Below is a graph showing 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 end result of biofilm caused the pumps not only to function at a higher head, but that a few of the pumping was pressured into peak electrical energy tariff. The lowered performance pipeline in the end accounted for about 15% further pumping vitality costs.
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) exhibits system curve after pigging. Biofilm raised pumping costs by as a lot as 15% in a single yr. 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 equal of a wall roughness of zero.13mm. The same roughness in an 80mm pipe represents an H&W C value of one hundred thirty. That’s a 16% reduction in flow, or a 32% friction loss improve for a similar flow! And that’s simply in the first year!
Layflat hose can have excessive energy cost
A working example was noticed in an vitality effectivity audit conducted by Tallemenco just lately on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a gentle hose boom had a head loss of 26m head compared with the manufacturers ranking of 14m for a similar move, 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 in the scorching solar all summer, breeding these little critters on the pipe inside wall.
Calculated by way of vitality consumption, the layflat hose was answerable for 46% of total 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 on the same move, but when that deteriorates because of biofilm, headloss may rise to solely 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,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 might should be changed out for a lower head pump.
Everyone has a wheel barrow in their pipelines, and it only gets bigger with time. Savings can’t eliminate it, but you presumably can management its effects, either via 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 about the ‘wheel barrow’ within the pipeline after we can’t clarify a pipeline headloss”, mentioned Rob.
Author Rob Welke has been 52 years in pumping & hydraulics, and by no means offered 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 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 primarily based in Adelaide, South Australia, serving purchasers Australia broad.
Rob runs common “Pumping System Master Class” ONLINE training courses Internationally to pass on his wealth of knowledge 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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