A Seismic Design ConsiderationA Seismic Design Considerationof Oil and Gas Transmission Systemsof Oil and Gas Transmission Systems

in Taiwanin Taiwan

CTCI CorporationJ.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 ConsiderationA Seismic Design Considerationof Oil and Gas Transmission Systems in Taiwanof Oil and Gas Transmission Systems in Taiwan

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

IntroductioIntroductionn 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 oil and 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.

IntroductioIntroductionn

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.

IntroductionIntroduction The Purpose of Seismic Design

To Ensure Structure Integrity

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.

To Maintain Functionability

Gas and Oil Transmission System in TaiwanGas 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.

Note: 1. Offshore pipelines need to be considered on-bottom stability influenced

by tsunami and scouring in the nearshore area. 2. The numbers in the table show the hazard degree for pipeline systems

and the number 1 means the maximum dangerous degree.

Identification of Seismic HazardsIdentification of Seismic Hazards

Seismic HazardsTYPE

ITEMGroundShaking

FaultingLique-faction

Landslides

Tsunami

TransportationPipelines

3 1 2 1－

NOTE*1

Pipelines/facilitiesin Booster Station orDistribution Station

or Terminal

1 － － － －

Identification of Seismic HazardsIdentification of Seismic Hazards 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 HazardsIdentification of Seismic Hazards 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 HazardsIdentification of Seismic Hazards

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 HazardsIdentification of Seismic Hazards Land Slides ：

Land slides always result from seismic shaking and heavy rainfall.

Identification of Seismic HazardsIdentification of Seismic Hazards Tsunami :

It should be considered about on-bottom stability influenced by

tsunami and scouring in the nearshore area for offshore pipeline.

Identification of Seismic HazardsIdentification of Seismic Hazards Example:26 inch Natural Gas Pipeline Cross Cho-Shui River

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

Identification of Seismic HazardsIdentification of Seismic Hazards 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.

Note :1. 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.

2. 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.

The Code for Seismic The Code for Seismic designdesign The Major Code use for Seismic Design

Four sections ： (0.33g,0.28g,0.23g,0.18g)

Two Sections ：

0.33g(black),0.23g(white)

Seismic Design Philosophy-Seismic Design forceSeismic Design Philosophy-Seismic Design force Technical Rules and Regulation of Building,R.O.C.

(Seismic Zone in Taiwan)

UBC CODE Uniform Building Code specifies Taiwan in seismic zone-4 and it defines 0.4g

of ground acceleration to design the structure.

Three sections ：High,moderate,low

BEFORE 921 AFTER 9211995 YEAR

Piping code such as ASME B31.4/B31.8 doesn’t specify the seismic intensity for piping systems

Seismic Design Philosophy-Seismic Design forceSeismic Design Philosophy-Seismic Design force The comparison table for seismic design force

Publication

Date

Item

Technical rules and regulations of building -1995

Technical rules and regulations of building- 1999

UBC-1997

Design Base Shear

ZKCIWV

Z :Seismic zone factor(0.6,0.8,1.0)

:I Importance factor=1.5

C :Seismic coefficient

15.08

1 T

K =0.8

0.18WV

WF

ZICV

uy4.1

：Z Seismic zone factor

=0.33g

：I Importation factor

=1.5(Second Type)

：C Seismic coefficient=2.5

1.2 y

2.27uF

1uF

C

0.295WV

WR

CV a0.3

aC :Seismic coefficient(0.44x1.3)

R :Numerical coefficient representative of the inherent overstrength and global ductility capacity of lateral-force-resisting systems

0.477WV

Seismic Design Philosophy-Design ProcedureSeismic Design Philosophy-Design Procedure Design Procedure for Seismic Design

of Oil and Gas Transmission Systems

Y Crossing

Faulting line

Landslides

Area

Liquefaction Area

Seismic Design

Preliminary Route Selection

Start

GeologicalInvestigation

Soil Improvement

Y

Y

N

N

N

Finish

Countermeasure

Seismic Design Philosophy- Countermeasure for Seismic Design Philosophy- Countermeasure for Seismic Design of PipingSeismic Design of Piping

Countermeasure for Seismic Design of PipingHazards

Item Ground Shaking Fault Movement Soil liquefaction Landslides Tsunami

Counter-measure

To design anti-seismic piping support based on ground acceleration.

1. To design rigid guide or anchor supports to provide more stiffness of piping.

2. To use rubber sheet to increase viscous value of piping systems.

To avoid crossing the fault line.

The shut-off valves should be installed at the two sides of the crossing line in case the piping routing must cross the fault line.

To avoid crossing soil liquefaction area

To improve soil condition

To determine weight of pipeline

To determine pipe support spans to design pile structure.

To avoid crossing slope instability areas.

To improve slope stability or avoid crossing in small potential areas.

To check on-bottom stability of offshore pipelines

To determine the burial depth or add concrete weight for offshore pipelines.

To check burial depth in the nearshore areas

Seismic Design Philosophy- Countermeasure for Seismic Design Philosophy- Countermeasure for

Seismic Design of PipingSeismic Design of Piping Anti-Seismic Support Design for Aboveground Piping

Seismic Design Philosophy- Countermeasure for Seismic Design Philosophy- Countermeasure for

Seismic Design of PipingSeismic Design of Piping To Install an Isolation Valves

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 Analysis for Seismic Design Philosophy- Seismic Analysis for PipelinePipeline 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.

Virtual AnchorVirtual Anchor

Fully Restri

ction

Fully Restri

ction

Underground Piping

Interaction AreaInteraction Area

Soil and Pipeline Interactive Zone

Soil FrictionSoil Friction

LL

Aboveground Piping

Pig Station

Physical AnchorPhysical Anchor

Seismic Design Philosophy- Seismic Design for Offshore Seismic Design Philosophy- Seismic Design for Offshore PipelinePipeline

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

Damage Control During Damage Control During EarthquakeEarthquake 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 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 Damage Control During EarthquakeEarthquake 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.

Conclusion and Conclusion and SuggestionSuggestion 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.