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 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 were used to hold equipment for reinstating cement lining during delicate metal cement lined (MSCL) pipeline development in the outdated days.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 happened through the rehabilitation of the Cobdogla Irrigation Area, near Barmera, South Australia, in 1980’s. It can be suspected that it could simply 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 major delivered recycled water from a pumping station to a reservoir 10km away.
The drawback was that, after a year in operation, there was about a 10% reduction in pumping output. The shopper assured me that he had examined the pumps and they were OK. Therefore, it just needed to be a ‘wheel barrow’ within the pipe.
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Rob approached this drawback much as he had during his time in SA Water, the place he had in depth experience locating 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 accurate stress readings along the pipeline at a quantity of locations (at least 10 locations) which had been surveyed to provide correct elevation information. The sum of the pressure studying plus the elevation at every level (termed the Peizometric Height) gave the hydraulic head at every point. Plotting the hydraulic heads with chainage gives a a number of level hydraulic gradient (HG), very like in the graph below.
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 can be like the purple 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 best 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 because of a general friction construct up within the pipeline. To confirm this theory, it was determined to ‘pig’ the pipeline. This concerned utilizing the pumps to force two foam cylinders, about 5cm larger 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 efficiency was improved 10% on account of ‘pigging’. Photo: R Welke
The prompt improvement within the pipeline friction from pigging was nothing wanting wonderful. The system head loss had been almost completely restored to original performance, resulting in about a 10% circulate improvement from the pump station. So, instead of discovering a wheel barrow, a biofilm was found answerable for pipe friction build-up.
Pipeline efficiency could be all the time be seen from an vitality 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 enhance in system head because of biofilm brought on the pumps not solely to operate at a better head, however that a variety of the pumping was forced into peak electrical energy tariff. The decreased performance pipeline finally accounted for about 15% further pumping vitality 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) signifies a biofilm build-up. Black line (broken) shows system curve after pigging. Biofilm raised pumping costs 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 may have the equal of a wall roughness of zero.13mm. The same roughness in an 80mm pipe represents an H&W C worth of 130. That’s a 16% reduction in flow, or a 32% friction loss enhance for the same flow! And that’s simply within the first year!
Layflat hose can have excessive energy value
A case in point was observed in an vitality effectivity audit conducted by Tallemenco recently 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 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 in terms of power consumption, the layflat hose was answerable for 46% of total pumping power prices by way of 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 identical flow, but when that deteriorates due to biofilm, headloss may rise to solely about 10m/200m as an alternative of 26m/200m, kinks and fittings excluded. That’s a potential 28% saving on pumping power 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 power savings. In some instances, the pump might have to be changed out for a lower head pump.
Everyone has a wheel barrow in their pipelines, and it solely gets greater with time. You can’t eliminate it, but you’ll find a way to management its results, either by way of power environment friendly pipeline design within the first place, or attempt ‘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 nonetheless joke about the ‘wheel barrow’ within the pipeline after we can’t clarify a pipeline headloss”, mentioned Rob.
Author Rob Welke has been fifty two years in pumping & hydraulics, and never sold product in his life! He spent 25 yrs working for SA Water (South Australia) within the late 60’s to 90’s where he conducted intensive 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 shoppers Australia extensive.
Rob runs common “Pumping System Master Class” ONLINE training courses Internationally to move on his wealth of data he realized from his 52 years auditing pumping and pipeline systems all through Australia.
Rob can be contacted on ph +61 414 492 256, or e-mail . LinkedIn – Robert L Welke

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