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 stated, “I suppose there’s a wheel barrow in my pipeline. Can you locate it?”
Robert L Welke, Director, Training Manager and Pumping/Hydraulics Consultant
Wheel barrows were used to hold equipment for reinstating cement lining throughout mild metal cement lined (MSCL) pipeline construction in 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 occurred during the rehabilitation of the Cobdogla Irrigation Area, close to Barmera, South Australia, in 1980’s. It is also suspected that it might just have been a plausible excuse for unaccounted friction losses in a brand new 1000mm trunk main!
Rob agreed to help his client out. A 500mm dia. PVC rising main delivered recycled water from a pumping station to a reservoir 10km away.
The problem was that, after a year in operation, there was about a 10% discount in pumping output. The consumer assured me that he had examined the pumps and so they were OK. Therefore, it just needed to be a ‘wheel barrow’ in the pipe.
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Rob approached this drawback a lot as he had during his time in SA Water, the place he had intensive experience locating isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water supply pipelines in the course of the 1980’s.
Recording hydraulic gradients
He recorded accurate stress readings along the pipeline at a number of locations (at least 10 locations) which had been surveyed to provide accurate elevation information. The sum of the pressure studying plus the elevation at every point (termed the Peizometric Height) gave the hydraulic head at every point. Plotting the hydraulic heads with chainage provides a a number of level hydraulic gradient (HG), very similar to in the graph below.
Hydraulic Grade (HG) blue line from the friction tests indicated a constant gradient, indicating there was no wheel barrow in the pipe. If there was a wheel barrow within the pipe, the HG would be just like the pink line, with the wheel barrow between points three and 4 km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage along the way 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 should be as a outcome of a general friction construct up within the pipeline. To affirm this concept, it was decided to ‘pig’ the pipeline. This concerned using the pumps to pressure two foam cylinders, about 5cm larger 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 performance was improved 10% because of ‘pigging’. Photo: R Welke
The instant enchancment within the pipeline friction from pigging was nothing short of amazing. The system head loss had been nearly totally restored to original efficiency, resulting in about a 10% flow enchancment from the pump station. So, as a substitute of finding a wheel barrow, a biofilm was discovered liable for pipe friction build-up.
Pipeline ENERGY EFFICIENCY
Pipeline performance could be all the time be considered 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 enhance in system head due to biofilm triggered the pumps not solely to operate at a better head, however that some of the pumping was forced into peak electrical energy tariff. The lowered efficiency pipeline ultimately accounted for about 15% additional pumping energy prices.
Not everybody has a 500NB pipeline!
Well, not everyone has a 500mm pipeline in 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) exhibits system curve after pigging. Biofilm raised pumping prices by as much as 15% in one 12 months. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction worth of about C=155. When reduced 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 worth of 130. That’s a 16% discount in circulate, or a 32% friction loss improve for a similar flow! And that’s just within the first year!
Layflat hose can have high energy cost
A case in point was noticed in an power efficiency audit conducted by Tallemenco lately on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a soft hose growth had a head loss of 26m head compared with the producers score of 14m for a similar flow, and with no kinks in the hose! That’s a whopping 85% increase in head loss. Illusive contemplating that this layflat was transporting algae contaminated river water and lay in the scorching sun all summer season, 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 energy costs by way of its small diameter with biofilm build-up.
Solution is larger pipe
So, what’s the solution? Move to a larger diameter hose. A 3½” hose has a model new pipe head loss of only 6m/200m at the identical flow, but when that deteriorates as a end result of biofilm, headloss may rise to only about 10m/200m as a substitute 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,seven hundred over 10 years.
Note*: The pump impeller would need to be trimmed or a VFD fitted to potentiate the energy savings. In some cases, the pump might need to be modified out for a lower head pump.
Everyone has a wheel barrow of their pipelines, and it solely gets greater with time. You can’t do away with it, but you’ll have the ability to management its results, either through energy environment friendly pipeline design in the first place, or attempt ‘pigging’ the pipe to eliminate that wheel barrow!!
As for Become an insider in Rob’s client’s pipeline, the legend lives on. “He and I nonetheless joke about the ‘wheel barrow’ in the pipeline after 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) within the late 60’s to 90’s the place he performed extensive 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 based mostly in Adelaide, South Australia, serving purchasers Australia broad.
Rob runs regular “Pumping System Master Class” ONLINE coaching programs Internationally to move on his wealth of knowledge he realized from his fifty two years auditing pumping and pipeline systems all through Australia.
Rob can be contacted on ph +61 414 492 256, www.talle.biz or email r.welke@talle.biz . LinkedIn – Robert L Welke
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