Mythbusters

 

Real Water Losses & Precise In-Line Leak Detection of Bulk Water Pipelines 

Mythbusters

 
The following misunderstandings and myths are frequently encountered on why bulk water pipeline leak detection inspections are not required: 

 “Our bulk pipelines don’t leak”

 “Our losses are less than 5% - we have bigger problems to worry about”

 “You will see it immediately when a bulk pipeline leaks” in other words “Your leaks will find you, you don’t have to find them!”  

 “We perform regular route inspections

 "We use conventional methods”

 

Failure caused by prolonged leakage under high pressure

With a local inspection database fast approaching 2 000 km of bulk pipeline inspections, coupled with an additional 10 000 km of international experience performed by our North American based licensor, the above myths are easily refuted.  Figure 1 below is but one example of actual inspection statistics disputing the notion that bulk pipelines do not leak based on almost 6 000 km of inspections using the revolutionary in-line Sahara™ tethered leak detection technology.

Leak Frequency

Internationally, we are seeing average leak frequencies (refer to Figure 2) varying from as high as 150 leaks per 100 km (i.e. 1.5 leak/km) in the United Kingdom to 23 leaks / 100 km in South Africa. This implies that for every 4 km of bulk pipelines in South Africa, a minimum of one (1) leak can be expected.

Leakage Rates

Real-time leak sizing is by no means an exact science and leak sizes are affected by several factors including operating pressure, leak geometry and physical dimensions, type and consistency of bedding material etc.  As an example Figure 3 below illustrates the relationship between hole size, pressure and leakage rate expressed as kilolitres/day based on calculations using the simple orifice equation. 

Figure 3 highlights the pressure range we most often encounter in bulk pipelines varying between 5 and 25 bar.  What is evident from this figure is that it does not take a big hole (i.e. 7 mm) at a low operating pressure of 10 bar to lose 100 kilolitres per day (35 Ml/year)!  Also, at the same 10 bar operating pressure, a slightly larger 10 mm hole will lose 200 kilolitres / day (70 Ml/year). 

Also shown in Figure 3 are actual measured average leakage rates for several counties and cities around the world.  Typical leakage rates seem to vary from as little as 10 kl/day to over 225 kl/day.  From experience, a minimum daily leakage rate of 150 kl/day is used locally (55 Ml/year).  As we know, most leaks go undetected for years and unless pro-active leak detection inspections are carried out, will go undetected indefinitely.

  

Figure 1 International Sahara In-Line Leak Detection Inspection Statistics

  

Figure 2 Geographical Average Leak Frequency for Bulk Water Pipelines per 100 km Inspected

  

Figure 3 Relationship Between Leakage Rate, Hole and Operating Pressure

  Through our relationship with Pure Technologies, SSIS offers a suite of innovative inspection technologies backed up by sound engineering judgment and international best practice to pro-actively manage risk, reduce cost for the pipeline owner and extend the service life of pipeline assets. Please contact us to find out how we can assist you to Assess and AddressTM your pipeline problems and extend the life of your buried assets.
   

 

 

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