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A Seismic Design Consideration of Oil and Gas Transmission Systems in Taiwan. CTCI Corporation J.S. Chung *1 / C.L. Liu *2 2003/9/3. *1: Piping engineer of CTCI Corporation *2: Manager of Piping Department of CTCI Corporation. Introduction Gas and Oil Transmission Systems in Taiwan

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a seismic design consideration of oil and gas transmission systems in taiwan

A Seismic Design Considerationof Oil and Gas Transmission Systemsin Taiwan

CTCI Corporation

J.S. Chung *1/ C.L. Liu *2

2003/9/3

*1: Piping engineer of CTCI Corporation

*2: Manager of Piping Department of CTCI Corporation

a seismic design consideration of oil and gas transmission systems in taiwan2
Introduction

Gas and Oil Transmission Systems in Taiwan

Identification of Seismic Hazards

The Codes for Seismic Design

Seismic Design Philosophy

Damage Control During Earthquake

Conclusion and Suggestion

A Seismic Design Considerationof Oil and Gas Transmission Systems in Taiwan
introduction
Most of energy resources (such as crude oil and natural gas) must be imported from other countries due to the lack of natural resources in Taiwan. They are stored in storage tanks and transported to customers by pipeline systems after vaporization and refining.

Because of rapid economic gross in Taiwan,today oil and gas transmission systems tend to be underground、concentrated and complicated. The leak of tanks with flammable or explosive contents and damage of oiland gas transmission systems due to earthquake may result in a great loss of human life and property

CTCI corporation is the leading engineering company in Taiwan. Most of the oil and gas transmission systems in Taiwan are designed by CTCI.

Introduction
introduction4
Earthquakes in Taiwan

Taiwan is located at the border between Eurasian Plate and Phillipine Sea Plate.

There are 2200 quakes occurred per year and one of which is disastrous in Taiwan.

The famous 921 Chi-Chi Earthquake of magnitude 7.3 made 2413 people dead.

Introduction
introduction5
The Purpose of Seismic Design

To Ensure Structure Integrity

Introduction
  • To Maintain Functionability
  • In addition to external loading of pressure,deadweight, soil bearing,thermal load and vibration, it is necessary to consider seismic effects for oil and gas transmission systems.
gas and oil transmission system in taiwan
Onshore pipelines for gas:It supplies natural gas from CPC Yuan-an terminal through onshore pipeline to customers.

Offshore pipelines for gas:The 36” offshore pipeline is approximately 240 km in length from Yuan-an to Tung-shiao and combines with onshore pipeline.

Offshore pipelines for oil:To transfer the crude oil from offshore of the Saloon and Ta-Lin-Pu to the tanks through offshore pipelines.

Onshore pipelines for oil:To be built along the highway,the pipelines belong to CPC and FPCC.

Gas and Oil Transmission System in Taiwan
identification of seismic hazards
Seismic HazardsIdentification of Seismic Hazards
  • Note:
  • Offshore pipelines need to be considered on-bottom stability influenced by tsunami and scouring in the nearshore area.
  • The numbers in the table show the hazard degree for pipeline systems and the number 1 means the maximum dangerous degree.
identification of seismic hazards8
Ground Shaking

Ground shaking is a major design consideration for pump stations, tanks and pipeline systems. Ground shaking will induce stress and strain in the piping system due to differential ground movement.

Ground Acceleration

Identification of Seismic Hazards
identification of seismic hazards9
Fault Movement:The fault movement will induce compression or tension stress of pipelines.They can’t withstand this large differential movement by increasing the strength of the structure.Identification of Seismic Hazards
identification of seismic hazards10
Soil Liquefaction : Liquefaction is the transformation of a saturated cohesion-less soil from a solid to a liquid state as a result of increased pore pressure and loss of shear strength. When the soil around a buried pipeline liquefies, the pipeline may be upward or downward. Identification of Seismic Hazards
identification of seismic hazards12
Tsunami :It should be considered about on-bottom stability influenced by tsunami and scouring in the nearshore area for offshore pipeline. Identification of Seismic Hazards
identification of seismic hazards13
Example:26 inch Natural Gas Pipeline Cross Cho-Shui River

Pipeline systems still keep functionability after 921 Chi-Chi earthquake.

Identification of Seismic Hazards
identification of seismic hazards14
Example:Tai-chung network Piping Systems for Natural Gas near the Southern Location of the Wu-Si Bridge

8 & 4 inch low and moderate pressure transmission pipelines were failure after 921 earthquake.

Piping failure due to differential fault movement and ground rupture.

Bending failure of piping supported from bridge structure after bridge crushed.

Threaded piping joints are easier to leak than butt welded joints when subjected to the effect of earthquake.

Identification of Seismic Hazards
the code for seismic design
The Major Code use for Seismic Design The Code for Seismic design
  • Note :
  • Since Code B31.4 & B31.8 don’t provide calculation method of seismic analysis for pipeline systems, hence guidelines and recommendations by ASCE/ASME committee are used for design.
  • After 921 earthquake, Professors and specialists are invited by the Public Construction Commission to research and provide some recommendations and seismic design guides for lifeline system.
seismic design philosophy seismic design force
Technical Rules and Regulation of Building,R.O.C.

(Seismic Zone in Taiwan)

Three sections:

High,moderate,low

Four sections:

(0.33g,0.28g,0.23g,0.18g)

Two Sections: 0.33g(black),0.23g(white)

Seismic Design Philosophy-Seismic Design force

1995 YEAR

BEFORE 921

AFTER 921

  • UBC CODE
    • Uniform Building Code specifies Taiwan in seismic zone-4 and it defines 0.4g of ground acceleration to design the structure.
  • Piping code such as ASME B31.4/B31.8 doesn’t specify the seismic intensity for piping systems
seismic design philosophy design procedure
Design Procedure for Seismic Design of Oil and Gas Transmission Systems

Start

Preliminary Route Selection

Geological

Investigation

Countermeasure

Crossing Faulting line

Y

N

Liquefaction Area

Y

N

Soil Improvement

Landslides Area

Y

N

Seismic Design

Finish

Seismic Design Philosophy-Design Procedure
seismic design philosophy seismic analysis for pipeline
Seismic analysis models for oil and gas pipelines can be divided into three sections based on location of piping :(1)U/G Piping (2)Soil and Piping Interactive Zone (3)A/G Piping.

Pig Station

L

L

Physical Anchor

Physical Anchor

Soil Friction

Soil Friction

Virtual Anchor

Virtual Anchor

Fully Restriction

Fully Restriction

Interaction Area

Interaction Area

Underground Piping

Soil and Pipeline Interactive Zone

Aboveground Piping

Seismic Design Philosophy- Seismic Analysis for Pipeline
  • To use Response Displacement Method to calculate piping strain within 1%
  • To evaluate lique- faction potential
  • required data: soil information, ground acceleration
  • To consider effects of soils-piping interaction
  • To determine L value
  • To use static accel. method to calculate stress in the piping system within allowable stress.
  • required data: soil data , ground acceleration
  • To use static accel. method to calculate stress in the piping system within allowable stress.
  • required data: ground acceleration
seismic design philosophy seismic design for offshore pipeline
Seismic design for offshore Pipeline:

To perform seabed investigation in preliminary route selection stage is necessary to choose a safety route.

Sub-bottom Profiling

Soil Investigations

Echo Sounder/Bathymetric Data

Side -Scan Sonar

Magnetic Anomaly Detection

The items of seismic analysis for offshore pipeline are same as onshore pipeline

Seismic Design Philosophy- Seismic Design for Offshore Pipeline
damage control during earthquake
The seismic design for the oil and gas transmission pipelines can withstand a seismic capability to earthquake magnitude of 6(0.33g).If we use actual seismic value (approximately 1g) of 921 earthquake to design pipeline, it is too conservative from economical view due to occurring seldom.

To take the following methods to minimize the hazard in the event that a leak or rupture occurs in the pipeline after big earthquakes.

To install a block valve and vent stack

Damage Control During Earthquake
  • To plan a schedule of periodical surveillance and use smart pigs to check the corrosion condition of the pipe wall.
  • To design monitor control systems such as SCADA system
damage control during earthquake25
To Develop a Emergency Repaired Plan for Offshore Pipelines

It is difficult to repair an offshore pipeline due to require to mobilize repair equipment such as lay-barge,mechanical connectors and survey vessel,etc. A small pinhole or puncture in pipeline can use a special clamp to control leakage.But,a full rupture resulting in a shutdown must cut a spool pipe to replace it.

Damage Control During Earthquake
conclusion and suggestion
Oil and gas transmission systems damage due to earthquake may cause by liquefaction、landslides 、fault movement and ground shaking,etc. To ensure safety of pipeline operation, it is necessary to get more geological information along the pipeline routing during design stage. The owner should have a detail emergency plan and operation manual that covers various types of man-made and natural disasters,such as earthquakes, and practice periodically to make the operators acquainted with the procedure if earthquakes occur.

Now, new installed pipeline systems have been designed to withstand a seismic capability to earthquake magnitude of 6(0.33g). To ensure the integrity and maintain functionability of existing pipeline systems is considerably difficult during big earthquakes occur. It is necessary to make further assessment of existing pipeline systems.

Up to now, there isn’t a standard or code to specify the design methods , parameters, and design criteria of the seismic design for the oil and gas pipelines in the industry, excluding of some guidelines provided by Committee of ASCE. The engineers can follow its instruction for seismic design.

Conclusion and Suggestion