Pipelines are Safe

Pipelines are used to transport gases and fluids, both onshore and subsea, Figures 1. Large diameter, long distance pipelines are called ‘transmission’ pipelines, and can be very large diameter (e.g., up to 1422 mm (56 in)), operate at very high flow rates, and very high pressures (e.g., 69 bar (1000 lbf/in2)).

Pipe ready for use in a buried, onshore pipeline.

Figure 1. Onshore pipeline being constructed.

Photographs copyright and courtesy of Penspen Ltd., UK.

Pipelines carrying hydrocarbons such as oil and gas are a safe form of transportation compared to other transportation modes, Table

Mode

Fatalities (2016)

Highways

37,461

Rail

733

Air

412

Marine (Sea)

730

Pipeline

16

Table 1. Fatalities by mode of transportation in USA [1].

There are long pipeline systems in most countries around the world: between three and four million kilometres in total. Most of these pipeline systems are over 40 years of age, Table 2. This means they are an ageing asset, and it means more attention to safety, but it is worth emphasising the age of transmission pipelines, in and of itself, is not the most important factor affecting the safety of that pipeline (for example [4]).

Pipelines are essential for the transport of most nations’ energy. They are irreplaceable – unless billions of dollars are invested in new constructions. How much would it cost to replace the world’s 3,500,000 km of ageing pipelines? Pipelines typically cost four million US dollars/mile (1.6 km) to construct. So, replacement is expensive….

Vintage

Mileage
(% of total)

Built before 1940

15,000 miles (5%)

Built between 1940 and 1970

185,000 (62%)

Built since 1970

100,000 (33%)

Table 2. Age of natural gas transmission pipelines in the USA [2, 3].

Pipeline Failures

No engineering system is perfect, and some failures of the system will occur; therefore, there is an inevitable need to accept both the benefits of using pipelines, and the associated risks of failures.

Pipelines do not want to fail – they need a reason; for example, they can fail due to:

  • corrosion: the corrosion can be from the outside of the pipeline (external corrosion), or from the inside (internal corrosion);
  • ‘external interference’ (e.g., by earthmoving equipment damaging an onshore pipeline, or an anchor hitting a subsea pipeline).

This corrosion and external interference are known as ‘threats’ to a pipeline. Pipelines fail because they are subjected to these threats, and many other. The most common threats to pipelines are:

  • corrosion (on the internal surface or external surface of the pipeline);
  • external interference (e.g., earth excavating equipment hitting buried pipelines of anchors dropped on subsea pipelines);
  • material defects (in the pipe and associated welds);
  • cracks (e.g., caused by cyclic pressures in the pipeline);
  • natural environmental force/hazard (e.g., cold weather or floods);
  • man-made environmental force/hazard (e.g. mining subsidence);
  • design errors;
  • equipment error (e.g., pumps, valves, etc.;
  • operation/operator (human) error;
  • vandalism/theft/sabotage/terrorism.

Examples of external interference and corrosion are given in Figure 2. Major causes of pipeline failures vary from country to country: ‘external interference’ is a major cause in the developed world. Product theft is a major cause in the developing world, but this is an increasing threat throughout the world.

Figure 2. Dent in excavated pipeline (left), and corrosion (crossing a girth weld) in excavated pipeline (right).

Photographs copyright and courtesy of Penspen Ltd., UK.

Pipelines do fail, and these failures can cause fatalities and injuries, Figure 3.

Figure 3. Fatalities and injuries (i.e., injuries requiring hospital treatment) in USA natural gas pipelines (top) and liquid pipelines (bottom), 1995 – 2017 [5, 6].

Summary

Pipelines transporting hydrocarbons are a relatively safe form of energy transportation, but they sometimes fail, causing casualties and environmental damage.

A major challenge for the pipeline industry is ‘ageing pipelines’: most transmission pipelines are over 40 years old.

There are many causes of pipeline failures, including damage caused by impact (anchors, excavating machines, etc.), corrosion, and theft.

Pipeline failure rates are decreasing in the developed world (Table 3), but serious failures still occur.

Average

Product

Incident Count

Fatalities

Injuries

3 year average

(2015-2017)

Gas

3

4

7

Liquid

2

2

3

5 year average

(2013-2017)

Gas

3

3

5

Liquid

2

1

3

10 year average

(2008-2017)

Gas

3

2

11

Liquid

2

2

3

20 year average

(1998-2017)

Gas

5

3

9

Liquid

3

2

5

Table 3. Failure rates in natural gas and liquid transmission pipelines in the USA [7, 8].

References

  1. http://www.ntsb.gov/investigations/data/Pages/Data_Stats.aspx
  2. E Clark, B Leis, R Eiber, ’Integrity Characteristics of Vintage Pipelines’, Interstate Natural Gas Association of America. INGAA. Report F-2002-50435. USA. 2004
  3. ’Building Safe Communities: Pipeline Risk and its Application to Local Development Decisions’, PHMSA Office of Pipeline Safety. October, 2010.
  4. J F Kiefner, M J Rosenfeld, ‘The Role of Pipeline Age in Pipeline Safety’ Interstate Natural Gas Association of America. INGAA Foundation Inc.. Final Report No. 2012.04. November 8, 2012.
  5. https://hip.phmsa.dot.gov/analyticsSOAP/saw.dll?Portalpages
  6. https://hip.phmsa.dot.gov/analyticsSOAP/saw.dll?Portalpages
  7. https://hip.phmsa.dot.gov/analyticsSOAP/saw.dll?Portalpages
  8. https://hip.phmsa.dot.gov/analyticsSOAP/saw.dll?Portalpages