There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an unusual cellphone from an irrigator in 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 throughout delicate metal cement lined (MSCL) pipeline development within the old 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, near Barmera, South Australia, in 1980’s. It is also suspected that it might simply have been a believable excuse for unaccounted friction losses in a brand new 1000mm trunk main!
Rob agreed to help his shopper 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 client assured me that he had tested the pumps and they were OK. Therefore, Priceless had to be a ‘wheel barrow’ within the pipe.
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Rob approached this downside much 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 hydraulic gradients
He recorded accurate strain readings alongside the pipeline at multiple locations (at least 10 locations) which had been surveyed to offer accurate elevation information. The sum of the stress studying plus the elevation at each level (termed the Peizometric Height) gave the hydraulic head at each point. Plotting the hydraulic heads with chainage offers a multiple level hydraulic gradient (HG), very comparable to in the graph beneath.
Hydraulic Grade (HG) blue line from the friction tests indicated a consistent gradient, indicating there was no wheel barrow in the pipe. If there was a wheel barrow within the pipe, the HG could be like the pink line, with the wheel barrow between points three and four km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage alongside 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 should be because of a general friction construct up within the pipeline. To confirm this principle, it was decided to ‘pig’ the pipeline. This involved using the pumps to pressure 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% on account of ‘pigging’. Photo: R Welke
The immediate enchancment within the pipeline friction from pigging was nothing wanting amazing. The system head loss had been virtually totally restored to authentic efficiency, resulting in about a 10% move enchancment from the pump station. So, as a substitute of discovering a wheel barrow, a biofilm was found responsible for pipe friction build-up.
Pipeline performance can be all the time be considered from an power efficiency perspective. Below is a graph exhibiting 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 because of biofilm brought on the pumps not solely to operate at a better head, however that some of the pumping was compelled into peak electricity tariff. The reduced efficiency pipeline in the end accounted for about 15% extra pumping energy costs.
Not everybody 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) shows 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%) through biofilm build-up, the pipe will have the equivalent of a wall roughness of 0.13mm. The same roughness in an 80mm pipe represents an H&W C worth of 130. That’s a 16% discount in move, or a 32% friction loss increase for a similar flow! And that’s just within the first year!
Layflat hose can have excessive power price
A case in point was observed in an energy effectivity audit carried out by Tallemenco lately on a turf farm in NSW. A 200m lengthy 3” layflat pipe delivering water to a soft hose increase had a head loss of 26m head in contrast with the manufacturers rating of 14m for a similar flow, and with no kinks within the hose! That’s a whopping 85% increase in head loss. Not stunning contemplating that this layflat was transporting algae contaminated river water and lay in the scorching sun all summer, breeding these little critters on the pipe inside wall.
Calculated by method of vitality consumption, the layflat hose was liable for 46% of whole pumping vitality prices by way of 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 new pipe head lack of only 6m/200m at the identical circulate, but when that deteriorates due to biofilm, headloss may rise to only about 10m/200m instead of 26m/200m, kinks and fittings excluded. That’s a potential 28% saving on pumping vitality costs*. In phrases of absolute energy 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 vitality financial savings. In some circumstances, the pump could have to be modified out for a lower head pump.
Everyone has a wheel barrow of their pipelines, and it solely gets bigger with time. You can’t eliminate it, however you can management its effects, either by way of power environment friendly 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 nonetheless joke about the ‘wheel barrow’ within the pipeline when we can’t clarify a pipeline headloss”, stated Rob.
Author Rob Welke has been 52 years in pumping & hydraulics, and never 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 conducted in depth 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 mostly in Adelaide, South Australia, serving clients Australia wide.
Rob runs common “Pumping System Master Class” ONLINE coaching programs Internationally to pass on his wealth of data he learned from his fifty two years auditing pumping and pipeline systems throughout Australia.
Rob can be contacted on ph +61 414 492 256, or e mail . LinkedIn – Robert L Welke

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