Rob Welke, from Adelaide, South Australia, took an unusual phone from an irrigator in the late 1990’s. “Rob”, he stated, “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 were used to carry package for reinstating cement lining throughout delicate metal cement lined (MSCL) pipeline building within the old days. It’s not the primary time Rob had heard of a wheel barrow being left in a large pipeline. Legend has it that it happened during the rehabilitation of the Cobdogla Irrigation Area, close to Barmera, South Australia, in 1980’s. It can also be suspected that it might just have been a plausible excuse for unaccounted friction losses in a brand new 1000mm trunk main!
Rob agreed to help his shopper out. A 500mm dia. PVC rising primary delivered recycled water from a pumping station to a reservoir 10km away.
The downside was that, after a yr in operation, there was a few 10% discount in pumping output. The shopper assured me that he had examined the pumps and they have been OK. Therefore, it simply needed to be a ‘wheel barrow’ in the pipe.
READ: Cheaper irrigation methods for profitable farming
Rob approached this problem a lot as he had during his time in SA Water, the place he had intensive expertise finding isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water provide pipelines in the course of the 1980’s.
Recording hydraulic gradients
He recorded accurate stress readings alongside the pipeline at multiple places (at least 10 locations) which had been surveyed to provide correct elevation info. The sum of the stress studying plus the elevation at each point (termed the Peizometric Height) gave the hydraulic head at each level. Plotting the hydraulic heads with chainage provides a multiple level hydraulic gradient (HG), very similar to within the graph under.
Hydraulic Grade (HG) blue line from the friction exams indicated a constant gradient, indicating there was no wheel barrow within the pipe. If there was a wheel barrow in the pipe, the HG can be like the red 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 alongside the best way, which might be evident by a sudden change in slope of the HG at that time.
So, it was figured that the pinnacle loss should be because of a general friction build up in the pipeline. To affirm this theory, it was decided to ‘pig’ the pipeline. This involved using the pumps to pressure two foam cylinders, about 5cm larger than the pipe ID and 70cm lengthy, alongside 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 prompt enchancment in the pipeline friction from pigging was nothing wanting amazing. The system head loss had been nearly completely restored to authentic performance, resulting in a couple of 10% move improvement from the pump station. So, instead of discovering a wheel barrow, a biofilm was discovered answerable for pipe friction build-up.
Pipeline performance may be at all times be considered from an energy efficiency 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.
READ: 5 Factors to contemplate when selecting irrigation pump
The increase in system head because of biofilm caused the pumps not only to function at the next head, but that a number of the pumping was pressured into peak electricity tariff. The reduced performance pipeline in the end accounted for about 15% additional pumping energy prices.
Not everyone has a 500NB pipeline!
Well, not everyone has a 500mm pipeline of their irrigation system. So how does that relate to the average irrigator?
A new 500NB
System curve (red line) signifies a biofilm build-up. เพรสเชอร์เกจดิจิตอล (broken) reveals system curve after pigging. Biofilm raised pumping costs by up to 15% in one 12 months. Graph: R Welke
PVC pipe has a Hazen & Williams (H&W) friction value of about C=155. When decreased to C=140 (10%) by way of biofilm build-up, the pipe could have the equal of a wall roughness of zero.13mm. The similar roughness in an 80mm pipe represents an H&W C worth of a hundred thirty. That’s a 16% reduction in circulate, or a 32% friction loss increase for a similar flow! And that’s simply within the first year!
Layflat hose can have excessive vitality value
A living proof was noticed in an vitality effectivity audit conducted by Tallemenco recently on a turf farm in NSW. A 200m lengthy 3” layflat pipe delivering water to a delicate hose growth had a head loss 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 surprising considering that this layflat was transporting algae contaminated river water and lay in the sizzling sun all summer time, breeding those little critters on the pipe inside wall.
Calculated by means of vitality consumption, the layflat hose was liable for 46% of complete pumping energy costs via 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 model new pipe head lack of only 6m/200m on the same move, but when that deteriorates as a end result of biofilm, headloss may rise to solely about 10m/200m as a substitute of 26m/200m, kinks and fittings excluded. That’s a possible 28% saving on pumping vitality costs*. In phrases of absolute energy 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 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 will get greater with time. You can’t get rid of it, but you can management its effects, either through energy efficient pipeline design within the first place, or strive ‘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 nonetheless joke concerning the ‘wheel barrow’ within the pipeline when we can’t explain a pipeline headloss”, said Rob.
Author Rob Welke has been fifty two 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 extensive 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 primarily based in Adelaide, South Australia, serving purchasers Australia extensive.
Rob runs common “Pumping System Master Class” ONLINE training programs Internationally to move 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