The Use of Structured Pipeline Pillows Help Control Pipeline … · 2016-10-31 · trench pipeline support called a Structured Pipeline Pillow (SPP). • SPP’s offer the most secure,

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

• 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


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


How has Ovality been controlled?


• 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?


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


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.


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


• Soil 1 – Compacted Silty Sand; Soil 2 – Compacted Clay; Soil 3 –Compacted Low Density Sand

• For the purposes of simulation, Soil 2 was close enough to Soil 1 that it was removed

Results – Modeled Soil Behaviour


• Though it is not readily visible in the image, the pipe is not fully supported at the 6 o’clock position.

• This angle of this gap increases with angle of soil support.

Results – Load Experienced by Soil


Results – Ovality Control

3.3m SPP Spacing 5.2m SPP Spacing

10.4m SPP Spacing

NPS 48, 9.6mm wt, Soil 1




10.4m SPP Spacing





10.4m SPP Spacing





10.4m SPP Spacing





10.4m SPP Spacing





10.4m SPP Spacing



Results – Spacing


Calculation Tool

• Within typical SPP spacings, SPP’s provide superior ovality protection.

• Effects of soil bedding are dependant on soil type, though compacted sand offers the least resistance to ovality.

• Results of this study have been used to generate a tool that may be used to aid in the selection of SPP supports

Conclusions

From this study, we can conclude:


For More Information


Thank You Feel free to contact me for any further questions at: Email - [email protected] Phone - +1 519 472-5080


Documents

The Use of Structured Pipeline Pillows Help Control Pipeline … · 2016-10-31 · trench pipeline support called a Structured Pipeline Pillow (SPP). • SPP’s offer the most secure,