Rob Welke, from Adelaide, South Australia, took an uncommon phone from an irrigator within the late 1990’s. “Rob”, he said, “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 had been used to hold package for reinstating cement lining throughout delicate steel cement lined (MSCL) pipeline construction in the previous 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 during the rehabilitation of the Cobdogla Irrigation Area, near Barmera, South Australia, in 1980’s. It can be suspected that it may just have been a plausible excuse for unaccounted friction losses in a model new 1000mm trunk main!
Rob agreed to help his client out. A 500mm dia. PVC rising major 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% reduction in pumping output. The shopper assured me that he had examined the pumps they usually have been OK. Therefore, it simply had to be a ‘wheel barrow’ within the pipe.
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Rob approached this drawback a lot as he had throughout his time in SA Water, where he had in depth experience finding isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water supply pipelines during the 1980’s.
Recording hydraulic gradients
He recorded accurate stress readings alongside the pipeline at multiple locations (at least 10 locations) which had been surveyed to provide correct elevation information. The sum of the stress studying plus the elevation at every point (termed the Peizometric Height) gave the hydraulic head at each point. Plotting the hydraulic heads with chainage gives a multiple level hydraulic gradient (HG), very like within the graph below.
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 within the pipe, the HG would be just like the red line, with the wheel barrow between factors three and 4 km. Graph: R Welke
Given that the HG was pretty straight, there was clearly no blockage alongside the means in which, which might be evident by a sudden change in slope of the HG at that point.
So, it was figured that the top loss should be due to a common friction build up within the pipeline. To affirm this principle, it was determined to ‘pig’ the pipeline. This concerned 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% on account of ‘pigging’. Photo: R Welke
The instant enchancment in the pipeline friction from pigging was nothing in need of amazing. The system head loss had been virtually totally restored to original efficiency, resulting in a couple of 10% circulate 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 ENERGY EFFICIENCY
Pipeline performance may be always be viewed 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 increase in system head as a end result of biofilm caused the pumps not solely to function at a higher head, but that a few of the pumping was forced into peak electrical energy tariff. The reduced efficiency pipeline ultimately accounted for about 15% extra pumping power prices.
Not everyone has a 500NB pipeline!
Well, not everyone has a 500mm pipeline of their irrigation system. So how does ไดอะแฟรม to the average irrigator?
A new 500NB
System curve (red line) signifies a biofilm build-up. Black line (broken) exhibits system curve after pigging. Biofilm raised pumping costs by as much as 15% in a single year. 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 may have the equal of a wall roughness of 0.13mm. The same roughness in an 80mm pipe represents an H&W C value of one hundred thirty. That’s a 16% discount in move, or a 32% friction loss improve for the same flow! And that’s just within the first year!
Layflat hose can have high energy value
A living proof was observed in an energy efficiency audit carried out by Tallemenco just lately on a turf farm in NSW. A 200m lengthy 3” layflat pipe delivering water to a delicate hose growth had a head lack of 26m head compared with the manufacturers rating of 14m for a similar flow, and with no kinks in 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 within the hot solar all summer time, breeding those little critters on the pipe inside wall.
Calculated in phrases of vitality consumption, the layflat hose was liable for 46% of whole pumping power prices via its small diameter with biofilm build-up.
Solution is bigger pipe
So, what’s the solution? Move to a larger diameter hose. A 3½” hose has a new pipe head loss of solely 6m/200m at the same flow, but when that deteriorates because of biofilm, headloss might 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 terms of absolute vitality 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 must be trimmed or a VFD fitted to potentiate the energy savings. In some circumstances, the pump could should be modified out for a lower head pump.
Everyone has a wheel barrow in their pipelines, and it only gets greater with time. You can’t do away with it, however you’ll be able to management its results, either through energy environment friendly pipeline design in the first place, or strive ‘pigging’ the pipe to do away with 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 once we can’t explain a pipeline headloss”, mentioned Rob.
Author Rob Welke has been fifty two 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 carried out intensive 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 wide.
Rob runs common “Pumping System Master Class” ONLINE training courses Internationally to cross on his wealth of data he discovered from his 52 years auditing pumping and pipeline systems throughout Australia.
Rob could be contacted on ph +61 414 492 256, www.talle.biz or e-mail firstname.lastname@example.org . LinkedIn – Robert L Welke
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