เพรสเชอร์เกจ , from Adelaide, South Australia, took an unusual phone from an irrigator in 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 have been used to carry kit for reinstating cement lining throughout mild metal cement lined (MSCL) pipeline building within the previous days. It’s not the primary 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, near Barmera, South Australia, in 1980’s. It is also suspected that it could simply 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 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% 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’ in 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 expertise finding 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 strain readings along the pipeline at a quantity of locations (at least 10 locations) which had been surveyed to provide correct elevation info. The sum of the strain reading plus the elevation at every level (termed the Peizometric Height) gave the hydraulic head at each level. Plotting the hydraulic heads with chainage provides a multiple point hydraulic gradient (HG), very comparable to in the graph beneath.
Hydraulic Grade (HG) blue line from the friction checks indicated a consistent gradient, indicating there was no wheel barrow in the pipe. If there was a wheel barrow in the pipe, the HG would be like the pink line, with the wheel barrow between points three and 4 km. Graph: R Welke
Given that the HG was pretty straight, there was clearly no blockage along the way, which would be evident by a sudden change in slope of the HG at that time.
So, it was figured that the pinnacle loss should be as a result of a general friction construct up within the pipeline. To confirm this principle, it was decided to ‘pig’ the pipeline. This concerned utilizing the pumps to drive two foam cylinders, about 5cm bigger than the pipe ID and 70cm lengthy, along the pipe from the pump finish, exiting into the reservoir.
Two foam pigs emerge from the pipeline. The pipeline efficiency was improved 10% because of ‘pigging’. Photo: R Welke
The instant enchancment within the pipeline friction from pigging was nothing wanting wonderful. The system head loss had been virtually completely restored to original efficiency, leading to a couple of 10% move 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 efficiency can be always be seen from an power efficiency 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 as a result of biofilm brought on the pumps not solely to operate at the next head, however that a variety of the pumping was compelled into peak electricity tariff. The lowered performance pipeline ultimately accounted for about 15% further pumping energy costs.
Not everybody has a 500NB pipeline!
Well, not everybody has a 500mm pipeline in their irrigation system. So how does that relate to the average irrigator?
pressure gauge (red line) indicates a biofilm build-up. Black line (broken) reveals system curve after pigging. Biofilm raised pumping prices by as a lot as 15% in one 12 months. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction value of about C=155. When lowered to C=140 (10%) through biofilm build-up, the pipe will have the equivalent of a wall roughness of 0.13mm. The same roughness in an 80mm pipe represents an H&W C worth of a hundred thirty. That’s a 16% discount in move, or a 32% friction loss enhance for the same flow! And that’s just within the first year!
Layflat hose can have excessive power value
A case in point was noticed in an vitality effectivity audit performed by Tallemenco 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 producers ranking of 14m for a similar circulate, and with no kinks in the hose! That’s a whopping 85% improve in head loss. Not stunning contemplating that this layflat was transporting algae contaminated river water and lay in the sizzling sun all summer, breeding those little critters on the pipe inside wall.
Calculated by method of energy 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 new pipe head loss of solely 6m/200m on the identical move, but when that deteriorates as a outcome of biofilm, headloss may rise to solely about 10m/200m as an alternative of 26m/200m, kinks and fittings excluded. That’s a potential 28% saving on pumping vitality costs*. In terms of absolute vitality 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 cases, the pump may need to be changed out for a lower head pump.
Everyone has a wheel barrow of their pipelines, and it only will get larger with time. You can’t eliminate it, but you’ll have the ability to control its effects, either via energy environment friendly pipeline design in the first place, or attempt ‘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 still joke in regards to the ‘wheel barrow’ in the pipeline once we can’t clarify a pipeline headloss”, stated 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 conducted intensive pumping and pipeline vitality 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 in Adelaide, South Australia, serving clients Australia wide.
Rob runs regular “Pumping System Master Class” ONLINE coaching courses Internationally to pass on his wealth of knowledge he learned from his 52 years auditing pumping and pipeline methods throughout Australia.
Rob could be contacted on ph +61 414 492 256, www.talle.biz or e-mail r.welke@talle.biz . pressure gauge 10 bar