There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an unusual phone from an irrigator in 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 have been used to carry kit for reinstating cement lining during mild metal cement lined (MSCL) pipeline building in the previous days. It’s not the primary 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 plausible excuse for unaccounted friction losses in a brand new 1000mm trunk main!
Rob agreed to assist his client out. A 500mm dia. PVC rising main delivered recycled water from a pumping station to a reservoir 10km away.
The downside 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 have been OK. Therefore, it just needed to be a ‘wheel barrow’ within the pipe.
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Rob approached this drawback a lot as he had during his time in SA Water, where he had in depth experience locating isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water supply pipelines during the 1980’s.
Recording Dependable recorded accurate stress readings alongside the pipeline at a number of locations (at least 10 locations) which had been surveyed to offer accurate elevation information. The sum of the pressure studying plus the elevation at every level (termed the Peizometric Height) gave the hydraulic head at every level. Plotting the hydraulic heads with chainage offers a multiple level hydraulic gradient (HG), very similar to within the graph beneath.
Hydraulic Grade (HG) blue line from the friction exams indicated a constant gradient, indicating there was no wheel barrow in the pipe. If there was a wheel barrow in the pipe, the HG would be just 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 way, which might be evident by a sudden change in slope of the HG at that time.
So, it was figured that the pinnacle loss must be due to a general friction construct up in the pipeline. To affirm this principle, it was decided to ‘pig’ the pipeline. This concerned utilizing the pumps to drive two foam cylinders, about 5cm larger than the pipe ID and 70cm lengthy, along the pipe from the pump finish, exiting into the reservoir.
Two foam pigs emerge from the pipeline. The pipeline efficiency was improved 10% because of ‘pigging’. Photo: R Welke
The instant improvement in the pipeline friction from pigging was nothing wanting superb. The system head loss had been nearly completely restored to original performance, leading to about a 10% circulate improvement from the pump station. So, as an alternative of discovering a wheel barrow, a biofilm was found liable for pipe friction build-up.
Pipeline performance could be always be viewed from an power effectivity perspective. Below is a graph exhibiting the biofilm affected (red line) and restored (black line) system curves for the client’s pipeline, before and after pigging.
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The increase in system head as a end result of biofilm caused the pumps not only to operate at a better head, but that some of the pumping was forced into peak electrical energy tariff. The decreased efficiency pipeline ultimately accounted for about 15% extra pumping power costs.
Not everyone has a 500NB pipeline!
Well, not everyone has a 500mm pipeline of their irrigation system. So how does that relate to the average 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 up to 15% in one 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 could have the equivalent of a wall roughness of zero.13mm. The same roughness in an 80mm pipe represents an H&W C worth of one hundred thirty. That’s a 16% reduction in circulate, or a 32% friction loss improve for a similar flow! And that’s simply within the first year!
Layflat hose can have high energy value
A working example was noticed in an vitality efficiency audit conducted by Tallemenco recently on a turf farm in NSW. A 200m lengthy 3” layflat pipe delivering water to a gentle hose boom had a head lack of 26m head compared with the producers rating of 14m for a similar flow, and with no kinks within the hose! That’s a whopping 85% enhance in head loss. Not shocking considering that this layflat was transporting algae contaminated river water and lay in the sizzling solar all summer, breeding those little critters on the pipe inside wall.
Calculated by method of vitality consumption, the layflat hose was liable for 46% of complete pumping power prices through 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 model new pipe head loss of solely 6m/200m at the similar circulate, however when that deteriorates because of biofilm, headloss might rise to solely about 10m/200m instead of 26m/200m, kinks and fittings excluded. That’s a potential 28% saving on pumping vitality 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 have to be trimmed or a VFD fitted to potentiate the energy financial savings. In some circumstances, the pump may need 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 do away with it, however you’ll be able to management its effects, either via power efficient pipeline design in the first place, or try ‘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 about the ‘wheel barrow’ within the pipeline when we can’t explain a pipeline headloss”, said Rob.
Author Rob Welke has been fifty two years in pumping & hydraulics, and by no means sold 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 intensive pumping and pipeline vitality efficiency monitoring on its 132,000 kW of pumping and pipelines infrastructure. Rob established Tallemenco Pty Ltd (2003), an Independent Pumping and Hydraulics’ Consultancy based in Adelaide, South Australia, serving purchasers Australia broad.
Rob runs regular “Pumping System Master Class” ONLINE coaching courses Internationally to cross on his wealth of information he learned from his fifty two years auditing pumping and pipeline techniques all through Australia.
Rob may be contacted on ph +61 414 492 256, or email . LinkedIn – Robert L Welke

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