Rob Welke, from Adelaide, South Australia, took an unusual cellphone from an irrigator within 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 have been used to carry kit for reinstating cement lining throughout mild steel cement lined (MSCL) pipeline building in the outdated days.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 during the rehabilitation of the Cobdogla Irrigation Area, near Barmera, South Australia, in 1980’s. It can be suspected that it could simply have been a believable 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 12 months in operation, there was a couple of 10% reduction in pumping output. The shopper assured me that he had examined the pumps they usually have been OK. Therefore, it simply needed to be a ‘wheel barrow’ in the pipe.
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Rob approached this problem much as he had during his time in SA Water, where 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 accurate pressure readings alongside the pipeline at multiple places (at least 10 locations) which had been surveyed to provide correct elevation data. The sum of the stress reading plus the elevation at every point (termed the Peizometric Height) gave the hydraulic head at every level. Plotting the hydraulic heads with chainage offers a a quantity of point hydraulic gradient (HG), much like in the graph below.
Hydraulic Grade (HG) blue line from the friction exams indicated a consistent gradient, indicating there was no wheel barrow within the pipe. If there was a wheel barrow within the pipe, the HG can be like the purple line, with the wheel barrow between points 3 and 4 km. Graph: R Welke
Given that the HG was pretty straight, there was clearly no blockage along 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 because of a general friction build up within the pipeline. To verify this principle, it was determined to ‘pig’ the pipeline. This involved using the pumps to force two foam cylinders, about 5cm larger than the pipe ID and 70cm long, along 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 in the pipeline friction from pigging was nothing short of superb. The system head loss had been nearly completely restored to unique efficiency, leading to a few 10% circulate improvement from the pump station. So, as a substitute of finding a wheel barrow, a biofilm was discovered responsible for pipe friction build-up.
Pipeline ENERGY EFFICIENCY
Pipeline efficiency may be always be considered 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 enhance in system head because of biofilm brought on the pumps not only to function at a higher head, but that a few of the pumping was pressured into peak electrical energy tariff. The lowered efficiency pipeline ultimately accounted for about 15% extra pumping vitality costs.
Not everyone 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 as a lot as 15% in a single year. 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 equivalent of a wall roughness of 0.13mm. The similar roughness in an 80mm pipe represents an H&W C worth of one hundred thirty. That’s a 16% reduction in move, or a 32% friction loss enhance for the same flow! And that’s simply within the first year!
Layflat hose can have excessive energy cost
A case in point was noticed in an energy efficiency audit conducted 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 lack of 26m head in contrast with the manufacturers ranking of 14m for the same circulate, and with no kinks within the hose! That’s a whopping 85% increase in head loss. Not surprising considering that this layflat was transporting algae contaminated river water and lay within the hot solar all summer time, breeding these little critters on the pipe inside wall.
Calculated by means of power consumption, the layflat hose was liable for 46% of complete pumping energy costs through 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 same move, however when that deteriorates because of biofilm, headloss could rise to only 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 energy financial savings. In some instances, the pump may have 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, however you presumably can management its effects, either via vitality efficient pipeline design within the first place, or strive ‘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”, said Rob.
Author Rob Welke has been 52 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 power efficiency 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.
เพรสเชอร์เกจไฮดรอลิค runs common “Pumping System Master Class” ONLINE training courses Internationally to cross on his wealth of data he discovered from his fifty two years auditing pumping and pipeline methods all through Australia.
Rob can be contacted on ph +61 414 492 256, www.talle.biz or e-mail email@example.com . LinkedIn – Robert L Welke
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