There’s a wheel barrow in my pipeline!

เกจวัดแรงดัน300psi , from Adelaide, South Australia, took an unusual cellphone from an irrigator within the late 1990’s. “Rob”, he mentioned, “I suppose 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to hold kit for reinstating cement lining throughout gentle steel cement lined (MSCL) pipeline development within the outdated days.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 happened through the rehabilitation of the Cobdogla Irrigation Area, close to Barmera, South Australia, in 1980’s. It is also suspected that it may just have been a believable excuse for unaccounted friction losses in a brand new 1000mm trunk main!

Rob agreed to assist his client out. A 500mm dia. PVC rising primary 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 shopper assured me that he had tested the pumps and so they had been OK. Therefore, it simply needed to be a ‘wheel barrow’ in the pipe.
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Rob approached this downside much as he had during his time in SA Water, where he had intensive expertise finding isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water provide pipelines through the 1980’s.
Recording hydraulic gradients

He recorded accurate stress readings alongside the pipeline at multiple places (at least 10 locations) which had been surveyed to supply correct elevation information. The sum of the pressure reading plus the elevation at each level (termed the Peizometric Height) gave the hydraulic head at every point. Plotting the hydraulic heads with chainage provides a a quantity of level hydraulic gradient (HG), very like in the graph under.
Hydraulic Grade (HG) blue line from the friction tests indicated a constant gradient, indicating there was no wheel barrow within the pipe. If there was a wheel barrow in the pipe, the HG can be just like the purple line, with the wheel barrow between points three and four km. Graph: R Welke

Given that the HG was pretty straight, there was clearly no blockage alongside the greatest way, which would be evident by a sudden change in slope of the HG at that point.
So, it was figured that the top loss should be due to a basic friction build up within the pipeline. To verify this theory, it was determined to ‘pig’ the pipeline. This concerned utilizing the pumps to drive two foam cylinders, about 5cm bigger 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% because of ‘pigging’. Photo: R Welke

The instant improvement within the pipeline friction from pigging was nothing short of amazing. The system head loss had been almost completely restored to original efficiency, leading to a couple of 10% flow improvement from the pump station. So, as a substitute of finding a wheel barrow, a biofilm was found liable for pipe friction build-up.

Pipeline performance could be at all times be seen from an power effectivity perspective. Below is a graph displaying 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 improve in system head because of biofilm brought on the pumps not only to function at a higher head, however that a variety of the pumping was compelled into peak electrical energy tariff. The decreased efficiency pipeline ultimately accounted for about 15% further pumping power prices.
Not everybody has a 500NB pipeline!

Well, not everyone has a 500mm pipeline of their irrigation system. So how does that relate to the typical 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 one 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 could have the equivalent of a wall roughness of zero.13mm. The similar roughness in an 80mm pipe represents an H&W C value of one hundred thirty. That’s a 16% discount in flow, or a 32% friction loss increase for the same flow! And that’s just in the first year!

Layflat hose can have excessive vitality value

A working example was noticed in an power efficiency audit carried out by Tallemenco lately on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a soft hose increase had a head loss of 26m head in contrast with the producers score of 14m for the same circulate, and with no kinks in the hose! That’s a whopping 85% increase in head loss. Not surprising contemplating that this layflat was transporting algae contaminated river water and lay within the hot sun all summer, breeding these little critters on the pipe inside wall.
Calculated by way of power consumption, the layflat hose was answerable for 46% of complete pumping energy prices 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 lack of solely 6m/200m on the identical flow, but when that deteriorates because of biofilm, headloss may rise to solely about 10m/200m as a substitute of 26m/200m, kinks and fittings excluded. That’s a possible 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 must be trimmed or a VFD fitted to potentiate the energy financial savings. In some circumstances, the pump may need to be changed out for a lower head pump.
Everyone has a wheel barrow in their pipelines, and it solely will get greater with time. You can’t do away with it, but you possibly can control its effects, either via power 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 still joke in regards to the ‘wheel barrow’ within the pipeline when we can’t explain a pipeline headloss”, stated Rob.
Author Rob Welke has been fifty two years in pumping & hydraulics, and never bought product in his life! He spent 25 yrs working for SA Water (South Australia) in the late 60’s to 90’s where he conducted intensive pumping and pipeline energy 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 clients Australia wide.
Rob runs common “Pumping System Master Class” ONLINE training programs Internationally to move on his wealth of knowledge he learned from his 52 years auditing pumping and pipeline techniques throughout Australia.
Rob may be contacted on ph +61 414 492 256, or email . LinkedIn – Robert L Welke


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