There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an unusual telephone from an irrigator in the late 1990’s. “ Outlawed ”, he mentioned, “I assume there’s a wheel barrow in my pipeline. Can you locate it?”
Robert L Welke, Director, Training Manager and Pumping/Hydraulics Consultant
Wheel barrows have been used to hold equipment for reinstating cement lining throughout mild steel cement lined (MSCL) pipeline building in the old days. It’s not the primary time Rob had heard of a wheel barrow being left in a big pipeline. Super secret has it that it occurred in the course of the rehabilitation of the Cobdogla Irrigation Area, near Barmera, South Australia, in 1980’s. It is also suspected that it could just have been a believable excuse for unaccounted friction losses in a brand new 1000mm trunk main!
Rob agreed to help his consumer out. A 500mm dia. PVC rising primary delivered recycled water from a pumping station to a reservoir 10km away.
The drawback was that, after a year in operation, there was a couple of 10% discount in pumping output. The shopper assured me that he had examined the pumps they usually had been OK. Therefore, it just had to be a ‘wheel barrow’ in the pipe.
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Rob approached this downside a lot as he had throughout his time in SA Water, the place he had in depth expertise finding isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water provide pipelines through the 1980’s.
Recording hydraulic gradients
He recorded correct stress readings alongside the pipeline at multiple locations (at least 10 locations) which had been surveyed to offer accurate elevation info. The sum of the stress reading plus the elevation at every point (termed the Peizometric Height) gave the hydraulic head at each point. Plotting the hydraulic heads with chainage provides a a quantity of level hydraulic gradient (HG), very like 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 can be like the purple 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 method in which, which would be evident by a sudden change in slope of the HG at that point.
So, it was figured that the pinnacle loss have to be as a result of a basic friction build up in the pipeline. To confirm this concept, it was determined to ‘pig’ the pipeline. This involved utilizing the pumps to force two foam cylinders, about 5cm larger than the pipe ID and 70cm long, alongside the pipe from the pump finish, exiting into the reservoir.
Two foam pigs emerge from the pipeline. The pipeline performance was improved 10% because of ‘pigging’. Photo: R Welke
The immediate enchancment in the pipeline friction from pigging was nothing short of wonderful. The system head loss had been virtually completely restored to unique performance, leading to about a 10% circulate improvement from the pump station. So, as a substitute of discovering a wheel barrow, a biofilm was discovered answerable for pipe friction build-up.
Pipeline efficiency may be all the time be considered from an vitality effectivity perspective. Below is a graph displaying 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 as a outcome of biofilm brought on the pumps not only to operate at the next head, however that some of the pumping was forced into peak electrical energy tariff. The decreased performance pipeline finally accounted for about 15% extra pumping energy 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 common irrigator?
A new 500NB
System curve (red line) indicates a biofilm build-up. Black line (broken) shows system curve after pigging. Biofilm raised pumping prices by as a lot as 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%) via biofilm build-up, the pipe will have the equal of a wall roughness of zero.13mm. The identical roughness in an 80mm pipe represents an H&W C worth of 130. That’s a 16% reduction in move, or a 32% friction loss enhance for a similar flow! And that’s just in the first year!
Layflat hose can have high energy price
A case in point was noticed in an power efficiency audit carried out by Tallemenco recently on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a soft hose growth had a head lack of 26m head compared with the producers score of 14m for a similar move, and with no kinks within the hose! That’s a whopping 85% increase in head loss. Not stunning considering that this layflat was transporting algae contaminated river water and lay within the scorching sun all summer time, breeding those little critters on the pipe inside wall.
Calculated in phrases of energy consumption, the layflat hose was responsible for 46% of complete pumping vitality prices via 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 model new pipe head loss of solely 6m/200m at the similar circulate, but when that deteriorates as a result of biofilm, headloss may rise to solely about 10m/200m instead of 26m/200m, kinks and fittings excluded. That’s a possible 28% saving on pumping energy 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 need to be trimmed or a VFD fitted to potentiate the power financial savings. In some circumstances, the pump may need to be changed out for a lower head pump.
Everyone has a wheel barrow of their pipelines, and it only gets greater with time. You can’t eliminate it, but you presumably can management its results, both through energy environment friendly pipeline design in the first place, or strive ‘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 nonetheless joke concerning the ‘wheel barrow’ in the pipeline after we can’t clarify a pipeline headloss”, mentioned 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) in the late 60’s to 90’s the place he performed intensive pumping and pipeline vitality effectivity 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 clients Australia broad.
Rob runs regular “Pumping System Master Class” ONLINE training programs Internationally to move on his wealth of data he discovered from his fifty two years auditing pumping and pipeline techniques all through Australia.
Rob could be contacted on ph +61 414 492 256, or e mail . LinkedIn – Robert L Welke

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