More information about Osaka Gas Technologies:Osaka Gas-Research&Development

Gas Transmission and Supply Technologies

Stress Measurement and Analysis of Pipeline Behavior

Planning Dept. Pipeline Business Unit

1 . Magnetostrictive Stress Measurement System

The integrity check of gas pipes is carried out by nondestructively measuring the bending stresses occurring in them owing to ground subsidence.

The system nondestructively measures the bending stresses in elastic and plastic ranges occurring in small-diameter steel pipes.
The system measures the stresses when bending deformation occurs on large-diameter pipes accompanied by cross section flattening.

Diameter	100mm - 600mm
Pipe specifications	SGP, STPY400, API5L X52

Stress measurement for a pipeline in an excavation pit

Stress measurement for a pipeline installed under a bridge

When a stress occurs in a steel pipe, the permeability in the direction changes.
This change is proportional to the difference in mean stress（σ1-σ2）
The magnetostrictive sensor measures the change of permeability as a voltage.

σ1：axial stress
σ2：circumferential stress

V＝M（σ1-σ2）
V：output voltage of magnetostrictive sensor
M：magnetostrictive sensitivity

Accurate Stress Measurement
- A sine curve is fitted to circumferential distribution of data measured by magnetostrictive stress sensor.
- A unique data processing method (sine curve fitting method) developed eliminates residual stress.
- Bending stress measurement.
Capable of Stress Measurement
- Plastic strain up to 1% can be measured by application of sine curve fitting method

Capable of Stress Measurement of Bending Deformation with Cross Section Flattening
- Axial and circumferential stresses can be measured by unique data processing method based on Fourier transform.

Easy Stress Measurement
- Demagnetization before measurement is automatically carried out.
- Measurement is possible without removing the paint coating.
- It takes less than 5 minutes to measure the stress at appoint.
- The sensor can be set on the pipe easily by means of a rail.
- Fully automatic processing by a personal computer.
- The system is compact and easy to carry in a van to any site.

2 . Analysis Technique of Pipeline Behavior

To analyze the deformation of pipeline caused by large ground displacement due to earthquackes.
Computer program ,ADINA(Automatic Dynamic Incremental Non-linear Analysis), can compute such deformation in elastic and plastic regions.

A pipeline installed under a bridge subjected to ground subsidence.
A pipeline led into a building on reclaimed land or soft ground.
A pipeline affected by nearby excavation work.
A pipeline installed in the ground ,such as slope area or behind quays, where large ground displacement would occur in case of earthquake.

Behind quays

Ground settlement

Shell Model

To analyze large pipeline deformation incorporating non-linear characteristics of the material of pipeline.

Model	Pipe	Pipe(Beam) element、Shell element
Model	Ground	Spring model
Non-linear characteristics	Pipe	○
Non-linear characteristics	Ground	○
Large pipeline deformation		○