There’s a wheel barrow in my pipeline!

Elementary , from Adelaide, South Australia, took an uncommon phone 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 had been used to carry kit for reinstating cement lining throughout gentle metal cement lined (MSCL) pipeline development 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 during the rehabilitation of the Cobdogla Irrigation Area, close to Barmera, South Australia, in 1980’s. It can be 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 consumer 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 12 months in operation, there was about a 10% reduction in pumping output. The client assured me that he had tested the pumps and so they have been 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 locating isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water supply pipelines during the 1980’s.
Recording hydraulic gradients
He recorded accurate stress readings along the pipeline at multiple places (at least 10 locations) which had been surveyed to provide correct elevation data. The sum of the strain reading plus the elevation at each level (termed the Peizometric Height) gave the hydraulic head at each level. Plotting the hydraulic heads with chainage provides a a number of level hydraulic gradient (HG), very comparable to within the graph beneath.
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 in the pipe, the HG would 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 have to be as a outcome of a general friction construct 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% as a outcome of ‘pigging’. Photo: R Welke
The instant enchancment in the pipeline friction from pigging was nothing in need of superb. The system head loss had been nearly totally restored to original efficiency, resulting in a few 10% circulate improvement from the pump station. So, as an alternative of finding a wheel barrow, a biofilm was discovered responsible for pipe friction build-up.
Pipeline efficiency may be at all times be seen from an energy efficiency 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 enhance in system head as a result of biofilm triggered the pumps not solely to operate at a higher head, but that some of the pumping was pressured into peak electricity tariff. The reduced performance pipeline in the end accounted for about 15% extra pumping energy prices.
Not everyone has a 500NB pipeline!
Well, not everyone has a 500mm pipeline of their irrigation system. So how does that relate to the common irrigator?
A new 500NB
System curve (red line) signifies a biofilm build-up. Black line (broken) exhibits system curve after pigging. Biofilm raised pumping prices by up to 15% in a single 12 months. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction worth of about C=155. When lowered to C=140 (10%) by way of biofilm build-up, the pipe will have the equal of a wall roughness of 0.13mm. The identical roughness in an 80mm pipe represents an H&W C worth of a hundred thirty. That’s a 16% discount in move, or a 32% friction loss improve for the same flow! And that’s just within the first year!
Layflat hose can have high energy price
A working example was observed in an power effectivity audit performed by Tallemenco lately on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a delicate hose boom had a head loss of 26m head compared with the producers rating of 14m for the same flow, 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 sizzling solar all summer season, breeding these little critters on the pipe inside wall.
Calculated when it comes to power consumption, the layflat hose was answerable for 46% of total pumping vitality costs via 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 only 6m/200m at the similar circulate, but when that deteriorates as a end result of biofilm, headloss could rise to only about 10m/200m instead of 26m/200m, kinks and fittings excluded. That’s a potential 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 energy financial savings. In some instances, the pump may need to be changed out for a decrease head pump.
Everyone has a wheel barrow of their pipelines, and it solely gets larger with time. You can’t do away with it, however you can control its results, either through vitality environment friendly pipeline design in the first place, or strive ‘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’ in the pipeline when we can’t clarify a pipeline headloss”, said Rob.
Author Rob Welke has been 52 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 the place he performed extensive pumping and pipeline power 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 training courses Internationally to cross on his wealth of data he learned from his fifty two years auditing pumping and pipeline methods throughout Australia.
Rob may be contacted on ph +61 414 492 256, or e-mail . LinkedIn – Robert L Welke

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