Rob Welke, from Adelaide, South Australia, took an uncommon telephone from an irrigator within the late 1990’s. “Rob”, he said, “I assume 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 package for reinstating cement lining throughout mild steel cement lined (MSCL) pipeline construction within 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 happened through the rehabilitation of the Cobdogla Irrigation Area, close to Barmera, South Australia, in 1980’s. It can be suspected that it could just have been a believable excuse for unaccounted friction losses in a model new 1000mm trunk main!
Rob agreed to assist 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 12 months in operation, there was a couple of 10% discount in pumping output. The shopper assured me that he had tested the pumps and they were OK. Therefore, it just needed to be a ‘wheel barrow’ within the pipe.
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Rob approached this downside much as he had throughout 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 through the 1980’s.
Recording hydraulic gradients
He recorded accurate stress readings along the pipeline at a number of areas (at least 10 locations) which had been surveyed to offer accurate elevation info. The sum of the strain reading plus the elevation at each level (termed the Peizometric Height) gave the hydraulic head at every point. Plotting the hydraulic heads with chainage gives a a quantity of point hydraulic gradient (HG), much like within the graph under.
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 in the pipe, the HG could 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 way, which would be evident by a sudden change in slope of the HG at that point.
So, it was figured that the head loss should be due to a common friction build up within the pipeline. To affirm this concept, it was determined to ‘pig’ the pipeline. This involved utilizing the pumps to pressure two foam cylinders, about 5cm larger than the pipe ID and 70cm lengthy, alongside the pipe from the pump end, exiting into the reservoir.
Two foam pigs emerge from the pipeline. The pipeline efficiency was improved 10% as a end result of ‘pigging’. Photo: R Welke
The prompt enchancment in the pipeline friction from pigging was nothing wanting wonderful. The system head loss had been nearly totally restored to unique performance, leading to about a 10% flow improvement from the pump station. So, as an alternative of finding a wheel barrow, a biofilm was found responsible for pipe friction build-up.
Pipeline ENERGY EFFICIENCY
Pipeline efficiency could be all the time be viewed from an energy 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 because of biofilm brought on the pumps not only to function at a higher head, however that a few of the pumping was compelled into peak electricity tariff. The lowered efficiency pipeline in the end accounted for about 15% additional pumping power 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 typical irrigator?
A new 500NB
System curve (red line) signifies a biofilm build-up. Black line (broken) exhibits system curve after pigging. เกจวัดแรงดันแก๊สอาร์กอน raised pumping costs by as much 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%) by way of biofilm build-up, the pipe will have the equal of a wall roughness of 0.13mm. The similar roughness in an 80mm pipe represents an H&W C worth of 130. That’s a 16% reduction in circulate, or a 32% friction loss improve for the same flow! And that’s just in the first year!
Layflat hose can have excessive energy price
A case in point was noticed in an vitality efficiency audit performed by Tallemenco recently on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a delicate hose boom had a head loss of 26m head in contrast with the manufacturers score of 14m for the same circulate, and with no kinks within the hose! That’s a whopping 85% increase in head loss. Not shocking 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 power consumption, the layflat hose was responsible for 46% of whole pumping energy prices through 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 solely 6m/200m at the identical circulate, but when that deteriorates as a result of biofilm, headloss may rise to only 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 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 vitality financial savings. In some cases, the pump might should be modified out for a decrease head pump.
Everyone has a wheel barrow in their pipelines, and it solely will get bigger with time. You can’t do away with it, however you can control its results, both by way of energy 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 in regards to the ‘wheel barrow’ within the pipeline once we can’t clarify a pipeline headloss”, said 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 where he performed intensive pumping and pipeline energy efficiency 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 clients Australia broad.
Rob runs regular “Pumping System Master Class” ONLINE training programs Internationally to cross on his wealth of knowledge he discovered from his 52 years auditing pumping and pipeline techniques all through Australia.
Rob may be contacted on ph +61 414 492 256, www.talle.biz or e-mail firstname.lastname@example.org . LinkedIn – Robert L Welke