There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an uncommon cellphone from an irrigator in the late 1990’s. “Rob”, he stated, “I assume 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 hold package for reinstating cement lining during gentle steel cement lined (MSCL) pipeline building within the old days. It’s not the first 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, near Barmera, South Australia, in 1980’s. It is also suspected that it might simply have been a believable excuse for unaccounted friction losses in a brand new 1000mm trunk main!

Rob agreed to help his shopper out. A 500mm dia. PVC rising main 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 client assured me that he had examined the pumps and they have been OK. Therefore, it just had to be a ‘wheel barrow’ in the pipe.
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Rob approached this problem a lot as he had throughout his time in SA Water, where he had intensive 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 pressure readings along the pipeline at a quantity of places (at least 10 locations) which had been surveyed to offer accurate elevation info. The sum of the pressure reading plus the elevation at each point (termed the Peizometric Height) gave the hydraulic head at each point. Plotting the hydraulic heads with chainage gives a a quantity of level hydraulic gradient (HG), much like in the graph below.
Hydraulic Grade (HG) blue line from the friction checks indicated a constant gradient, indicating there was no wheel barrow within the pipe. If there was a wheel barrow in the pipe, the HG would be like the red 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 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 pinnacle loss have to be because of a general friction build up within the pipeline. To affirm this concept, it was decided to ‘pig’ the pipeline. This involved using the pumps to pressure two foam cylinders, about 5cm bigger than the pipe ID and 70cm long, alongside the pipe from the pump end, exiting into the reservoir.
Two foam pigs emerge from the pipeline. The pipeline performance was improved 10% on account of ‘pigging’. pressure gauge : R Welke

The prompt improvement in the pipeline friction from pigging was nothing short of wonderful. The system head loss had been almost completely restored to original performance, resulting in a few 10% circulate enchancment from the pump station. So, as a substitute of discovering a wheel barrow, a biofilm was discovered answerable for pipe friction build-up.

Pipeline performance could be all the time be viewed from an vitality effectivity perspective. Below is pressure gauge octa 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 because of biofilm triggered the pumps not solely to function at a better head, however that a number of the pumping was pressured into peak electrical energy tariff. The decreased efficiency pipeline in the end accounted for about 15% extra pumping power costs.
Not everyone has a 500NB pipeline!

Well, not everybody has a 500mm pipeline in their irrigation system. So how does that relate to the common 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 a lot as 15% in a single yr. Graph: R Welke

PVC pipe has a Hazen & Williams (H&W) friction worth of about C=155. When reduced to C=140 (10%) by way of biofilm build-up, the pipe may have the equivalent of a wall roughness of zero.13mm. The similar roughness in an 80mm pipe represents an H&W C value of a hundred thirty. That’s a 16% reduction in flow, or a 32% friction loss improve for a similar flow! And that’s simply in the first year!

Layflat hose can have high energy cost

A living proof was observed in an vitality efficiency audit conducted by Tallemenco lately on a turf farm in NSW. A 200m lengthy 3” layflat pipe delivering water to a soft hose boom had a head lack of 26m head in contrast with the producers rating of 14m for a similar move, and with no kinks within the hose! That’s a whopping 85% increase in head loss. Not surprising 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 when it comes to vitality consumption, the layflat hose was liable for 46% of whole pumping vitality costs via 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 brand new pipe head loss of only 6m/200m on the similar move, but when that deteriorates as a outcome of biofilm, headloss could rise to solely about 10m/200m as a substitute of 26m/200m, kinks and fittings excluded. That’s a possible 28% saving on pumping power 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 have to be trimmed or a VFD fitted to potentiate the power savings. In some cases, the pump could need to be modified out for a lower head pump.
Everyone has a wheel barrow in their pipelines, and it only will get greater with time. You can’t eliminate it, however you’ll find a way to management its effects, either via 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 nonetheless joke concerning the ‘wheel barrow’ in the pipeline once we can’t clarify a pipeline headloss”, mentioned Rob.
Author Rob Welke has been fifty two years in pumping & hydraulics, and by no means 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 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 primarily based in Adelaide, South Australia, serving purchasers Australia broad.
Rob runs regular “Pumping System Master Class” ONLINE coaching courses Internationally to move on his wealth of knowledge he realized from his fifty two years auditing pumping and pipeline systems throughout Australia.
Rob may be contacted on ph +61 414 492 256, or email . LinkedIn – Robert L Welke


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