There’s a wheel barrow in my pipeline!

Rob Welke, from Adelaide, South Australia, took an uncommon phone from an irrigator in the late 1990’s. “Rob”, he stated, “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 have been used to carry package for reinstating cement lining throughout mild steel cement lined (MSCL) pipeline building within the outdated days.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, near Barmera, South Australia, in 1980’s. It is also suspected that it could just 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% discount in pumping output. The shopper assured me that he had examined the pumps they usually have been OK. Therefore, it simply had to be a ‘wheel barrow’ within the pipe.
READ: Cheaper irrigation strategies for worthwhile farming
Rob approached this drawback a lot as he had during his time in SA Water, where he had intensive expertise finding isolated partial blockages in deteriorated Cast iron Cement Lined (CICL) water provide pipelines through the 1980’s.
Recording hydraulic gradients
He recorded correct stress readings alongside the pipeline at a quantity of places (at least 10 locations) which had been surveyed to provide correct elevation information. 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 offers a a quantity of level hydraulic gradient (HG), much like in the graph below.
Hydraulic Grade (HG) blue line from the friction tests indicated a constant gradient, indicating there was no wheel barrow in the pipe. If there was a wheel barrow within the pipe, the HG would be like the pink line, with the wheel barrow between factors three and four km. Graph: R Welke
Given that the HG was fairly straight, there was clearly no blockage along the way, which might be evident by a sudden change in slope of the HG at that time.
So, it was figured that the top loss must be as a result of a basic friction construct up in the pipeline. To verify this concept, it was determined to ‘pig’ the pipeline. This involved using the pumps to pressure two foam cylinders, about 5cm larger than the pipe ID and 70cm long, 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 instant improvement in the pipeline friction from pigging was nothing in need of wonderful. The system head loss had been virtually totally restored to authentic performance, leading to a few 10% move 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 performance could be all the time be seen from an power effectivity perspective. Below is a graph showing 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 choosing irrigation pump
The enhance in system head because of biofilm triggered the pumps not only to operate at a higher head, but that some of the pumping was forced into peak electrical energy tariff. The reduced efficiency pipeline finally accounted for about 15% additional pumping vitality costs.
Not everyone has a 500NB pipeline!
Well, not everybody has a 500mm pipeline of 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. Biofilm raised pumping prices by as much as 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%) through biofilm build-up, the pipe could have the equivalent of a wall roughness of 0.13mm. The identical roughness in an 80mm pipe represents an H&W C value of 130. That’s a 16% discount in flow, or a 32% friction loss increase for a similar flow! And เกจแรงดัน in the first year!
Layflat hose can have high power cost
A working example was observed in an vitality effectivity audit carried out by Tallemenco recently on a turf farm in NSW. A 200m lengthy 3” layflat pipe delivering water to a soft hose boom had a head loss of 26m head compared with the producers ranking of 14m for a similar move, and with no kinks in the hose! That’s a whopping 85% enhance in head loss. Not surprising contemplating that this layflat was transporting algae contaminated river water and lay in the scorching solar all summer, breeding those little critters on the pipe inside wall.
Calculated by method of power consumption, the layflat hose was responsible for 46% of whole pumping energy prices via its small diameter with biofilm build-up.
Solution is bigger pipe
So, what’s the solution? Move to a larger diameter hose. A 3½” hose has a brand new pipe head loss of solely 6m/200m on the same move, but when that deteriorates as a end result of biofilm, headloss might rise to only about 10m/200m as a substitute of 26m/200m, kinks and fittings excluded. That’s a potential 28% saving on pumping energy costs*. In phrases of absolute power 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 need to be trimmed or a VFD fitted to potentiate the power financial savings. In some instances, the pump might need to be changed out for a decrease head pump.
Everyone has a wheel barrow of their pipelines, and it only gets bigger with time. You can’t do away with it, but you presumably can control its effects, both through energy efficient pipeline design in the first place, or strive ‘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 nonetheless joke in regards to the ‘wheel barrow’ in the pipeline after we can’t explain a pipeline headloss”, mentioned Rob.
Author Rob Welke has been fifty two years in pumping & hydraulics, and by no means bought product in his life! He spent 25 yrs working for SA Water (South Australia) within the late 60’s to 90’s where he conducted extensive 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 extensive.
Rob runs common “Pumping System Master Class” ONLINE coaching programs Internationally to move on his wealth of knowledge he discovered from his 52 years auditing pumping and pipeline methods all through Australia.
Rob can be contacted on ph +61 414 492 256, or e mail . LinkedIn – Robert L Welke