IPLOCA Fall Plenary Session Novel Construction Initiative and Onshore Pipeline: The Road to Success October 17-18, 2013 London, UK Presented by : Geoff W. Connors, P. Eng PipeSak® Incorporated London, Ontario, CANADA [email protected]+1 519 472-5080 The Use of Structured Pipeline Pillows Help Control Pipeline Ovality IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
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IPLOCA Fall Plenary Session
Novel Construction Initiative and Onshore Pipeline: The Road to Success October 17-18, 2013
The Use of Structured Pipeline Pillows Help Control Pipeline Ovality
IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
• Two years ago I presented to this group a new type of in-trench pipeline support called a Structured Pipeline Pillow (SPP).
• SPP’s offer the most secure, long term support for pipelines in rocky trenches - an engineered replacement to sand bedding, sand bags and foam.
• A recent study has now shown SPP’s also have the ability to help reduce pipeline ovality – particularly in those pipes with high D/t ratio’s or in difficult construction conditions.
• My talk will briefly address the results of this study
Structured Pipeline Pillows
IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
Ovality Occurs Primarily in two Situations
1. Ovalization resulting from the pipe fabrication process.
2. Ovalization resulting by externally applied loads, including overburden; bending; and poor construction practices.
What Makes a Pipe Vulnerable?
• Ovality occurs most frequently in pipelines with high D/t ratios.
• Two categories of Ovality
1. Symmetric Ovality
2. Arbitrary Out-of-Roundness
When does it occur?
Ovality can have a negative impact on pipeline integrity.
• Ovalized sectional modulus reduces the forces required to resist sectional collapse.
• Ovality may have negative effect on the integrity of the coating, excessive deformation may result in damage.
• Re-rounding the pipe will often leave residual bending stresses.
Dangers of Ovality
IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
How has Ovality been controlled?
IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
• In many cases simply removing the backfill in the area of ovality releases the load allowing the pipe to re-round. This comes at a cost with additional man and equipment hours and commissioning delays.
• Occasionally, hydrostatic testing can pop out minor ovalities – but residual stresses may result.
• Compacted earth/sand bedding has generally been our ‘go-to’ method of support for pipelines we feel are at risk (D/t >85?).
• There may be a better way ...
How Should Ovality be Controlled?
IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
Scope of the Study During this study, we looked at: • 2 Pipeline ODs • 4 Wall Thicknesses • 3 Soil Types • 3 Bedding Angles • 3 SPP Spacings for NPS 36 Pipe • 3 SPP Spacings for NPS 48 Pipe
IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
Methods of Investigation
• Study was conducted using FEA analysis.
• The bedded pipe was subjected to a linearly applied load (Blue).
• Soil behaviour simulated via Drucker and Prager Model (1952) IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
Methods of Investigation
The Ovality (%) of a pipe can be predicted by:
Here, Ovalmin and Ovalmax are minimum and maximum values of Ovality. Ovalpern is
generated from neural network optimization.
IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors
Parameters
Parameters NPS 36 NPS 48
Wall Thickness 7.92mm, 9.6mm, 11.7mm
9.6mm, 11.7mm, 15.6mm
Soil Types Silty Sand Clay Low Density Sand
Silty Sand Clay Low Density Sand
Bedding Angles 60°, 90°, 120° 60°, 90°, 120°
SPP Spacings 3m, 6.9m, 14m 3.3m, 5.2m, 10.4m
Friction
Angle
(deg)
Cohesion
(kPa) Descriptions
Elastic Modulus,
E(MPa)
Soil 1 33 8 Silty-Sand
(SM)
50
Soil 2 33 52 Clay (CL/CH) 50
Soil 3 34 0 Low Density
Sand
10
IPLOCA Fall Plenary Session – Structured Pipeline Pillows vs Ovality – Geoff W. Connors