Rob Welke, from Adelaide, South Australia, took an unusual phone from an irrigator in the late 1990’s. “Rob”, he mentioned, “I suppose there’s a wheel barrow in my pipeline. Can you find it?”
Robert L Welke, Director, Training Manager and Pumping/Hydraulics Consultant
Wheel barrows were used to hold package for reinstating cement lining during mild steel cement lined (MSCL) pipeline development 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 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 believable 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 downside was that, after a yr in operation, there was a couple of 10% discount in pumping output. The client assured me that he had tested the pumps and so they had been OK. Therefore, it just needed to be a ‘wheel barrow’ within the pipe.
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Rob approached this drawback much as he had throughout his time in SA Water, the place he had intensive expertise 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 correct strain readings alongside the pipeline at a quantity of locations (at least 10 locations) which had been surveyed to provide correct elevation data. The sum of the strain reading plus the elevation at each point (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), very like in 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 within the pipe, the HG could be like the pink line, with the wheel barrow between factors 3 and 4 km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage along the greatest way, which would 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 general friction build up in the pipeline. To verify this concept, it was determined to ‘pig’ the pipeline. This concerned using the pumps to drive two foam cylinders, about 5cm bigger 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 performance was improved 10% as a result of ‘pigging’. Photo: R Welke
The immediate improvement within the pipeline friction from pigging was nothing short of wonderful. The system head loss had been almost totally restored to authentic performance, leading to about a 10% move improvement from the pump station. So, instead of finding a wheel barrow, a biofilm was found liable for pipe friction build-up.
Pipeline efficiency can be always be considered from an energy efficiency perspective. Below is a graph exhibiting 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 as a end result of biofilm triggered the pumps not solely to function at a higher head, but that a number of the pumping was forced into peak electrical energy tariff. The decreased performance pipeline ultimately accounted for about 15% additional pumping power costs.
Not everybody has a 500NB pipeline!
Well, not everyone has a 500mm pipeline in their irrigation system. So how does that relate to the average irrigator?
A new 500NB
System curve (red line) signifies a biofilm build-up. เกจไนโตรเจนsumo (broken) exhibits system curve after pigging. Biofilm raised pumping prices by as a lot as 15% in a single 12 months. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction worth of about C=155. When decreased to C=140 (10%) by way of biofilm build-up, the pipe will have the equivalent of a wall roughness of zero.13mm. The similar roughness in an 80mm pipe represents an H&W C value of one hundred thirty. That’s a 16% discount in flow, or a 32% friction loss increase for the same flow! And that’s just within the first year!
Layflat hose can have excessive power cost
A living proof was observed in an vitality efficiency audit conducted by Tallemenco just lately on a turf farm in NSW. A 200m long 3” layflat pipe delivering water to a gentle hose boom had a head lack of 26m head compared with the producers rating of 14m for the same circulate, and with no kinks within the hose! That’s a whopping 85% improve in head loss. Not shocking contemplating that this layflat was transporting algae contaminated river water and lay in the scorching solar all summer season, breeding these little critters on the pipe inside wall.
Calculated by means of energy consumption, the layflat hose was answerable for 46% of total 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 bigger diameter hose. A 3½” hose has a new pipe head lack of solely 6m/200m at the similar move, however when that deteriorates due to biofilm, headloss could rise to solely about 10m/200m instead of 26m/200m, kinks and fittings excluded. That’s a possible 28% saving on pumping vitality costs*. In phrases 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 have to be trimmed or a VFD fitted to potentiate the energy savings. In some instances, the pump might should be changed out for a lower head pump.
Everyone has a wheel barrow in their pipelines, and it only will get larger with time. You can’t eliminate it, but you probably can control its effects, either by way of power efficient pipeline design within the first place, or try ‘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’ in the pipeline once we can’t clarify a pipeline headloss”, mentioned Rob.
Author Rob Welke has been 52 years in pumping & hydraulics, and never offered 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 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 extensive.
Rob runs regular “Pumping System Master Class” ONLINE training courses Internationally to cross on his wealth of information he learned from his 52 years auditing pumping and pipeline systems all through Australia.
Rob could be contacted on ph +61 414 492 256, or email . LinkedIn – Robert L Welke