There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an unusual phone from an irrigator in the late 1990’s. “Rob”, he stated, “I think 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 during gentle metal cement lined (MSCL) pipeline building in the previous days. It’s not the first time Rob had heard of a wheel barrow being left in a large pipeline. Legend has it that it occurred through the rehabilitation of the Cobdogla Irrigation Area, near Barmera, South Australia, in 1980’s. It can additionally be suspected that it may simply have been a plausible excuse for unaccounted friction losses in a model new 1000mm trunk main!
Rob agreed to assist his client out. A 500mm dia. PVC rising main delivered recycled water from a pumping station to a reservoir 10km away.
The drawback was that, after a yr in operation, there was a couple of 10% reduction in pumping output. The shopper assured me that he had examined the pumps they usually had been OK. Therefore, it simply had to be a ‘wheel barrow’ within the pipe.
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Rob approached this drawback much 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 provide pipelines in the course of the 1980’s.
Recording hydraulic gradients
He recorded correct strain readings alongside the pipeline at multiple areas (at least 10 locations) which had been surveyed to offer accurate elevation information. The sum of the pressure reading plus the elevation at every point (termed the Peizometric Height) gave the hydraulic head at every point. Plotting the hydraulic heads with chainage offers a multiple point hydraulic gradient (HG), much like in the graph below.
Hydraulic Grade (HG) blue line from the friction checks indicated a consistent gradient, indicating there was no wheel barrow within the pipe. If there was a wheel barrow within the pipe, the HG could be just like the pink line, with the wheel barrow between factors 3 and four km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage along the way in which, which might be evident by a sudden change in slope of the HG at that point.
So, it was figured that the head loss should be because of a basic friction construct up within the pipeline. To confirm this concept, it was decided to ‘pig’ the pipeline. This involved utilizing the pumps to drive two foam cylinders, about 5cm larger than the pipe ID and 70cm long, along the pipe from the pump finish, exiting into the reservoir.
Two foam pigs emerge from the pipeline. The pipeline efficiency was improved 10% as a end result of ‘pigging’. หลักการทำงานของเกจ์วัดแก๊ส : R Welke
The prompt enchancment within the pipeline friction from pigging was nothing wanting superb. The system head loss had been virtually completely restored to authentic efficiency, leading to about a 10% move enchancment from the pump station. So, instead of finding a wheel barrow, a biofilm was found answerable for pipe friction build-up.
Pipeline efficiency can be all the time be viewed from an energy efficiency 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 due to biofilm triggered the pumps not only to function at a higher head, but that a number of the pumping was compelled into peak electrical energy tariff. The reduced performance pipeline finally accounted for about 15% extra pumping energy 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 typical irrigator?
A new 500NB
System curve (red line) indicates a biofilm build-up. Black line (broken) shows system curve after pigging. Biofilm raised pumping costs by up to 15% in a single yr. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction value of about C=155. When decreased to C=140 (10%) via biofilm build-up, the pipe will have the equivalent of a wall roughness of zero.13mm. The same roughness in an 80mm pipe represents an H&W C value of one hundred thirty. 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 price
A case in point was observed in an energy effectivity audit conducted by Tallemenco recently on a turf farm in NSW. A 200m lengthy 3” layflat pipe delivering water to a soft hose boom had a head loss of 26m head compared with the producers rating of 14m for a similar flow, and with no kinks within 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, breeding those little critters on the pipe inside wall.
Calculated when it comes to vitality consumption, the layflat hose was answerable for 46% of whole pumping vitality costs 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 model new pipe head lack of only 6m/200m at the similar move, however when that deteriorates due to biofilm, headloss could rise to solely about 10m/200m instead of 26m/200m, kinks and fittings excluded. That’s a possible 28% saving on pumping vitality costs*. In terms of absolute power 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 power savings. In some circumstances, the pump might need to be modified out for a lower head pump.
Everyone has a wheel barrow of their pipelines, and it solely will get larger with time. You can’t get rid of it, but you can control its results, either through 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 concerning 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 never sold 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 in depth 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 primarily based in Adelaide, South Australia, serving shoppers Australia wide.
Rob runs common “Pumping System Master Class” ONLINE training courses Internationally to move on his wealth of knowledge he learned from his fifty two years auditing pumping and pipeline methods throughout Australia.
Rob could be contacted on ph +61 414 492 256, or email . LinkedIn – Robert L Welke

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