A Seismic Design Consideration of Oil and Gas Transmission Systems in Taiwan

1. 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

2. 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

3. 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

4. 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

5. 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.

6. 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

7. Seismic Hazards Identification 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.

8. 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

9. 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

10. 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

11. Land Slides：Land slides always result from seismic shaking and heavy rainfall. Identification of Seismic Hazards

12. 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

13. Example:26 inch Natural Gas Pipeline Cross Cho-Shui River Pipeline systems still keep functionability after 921 Chi-Chi earthquake. Identification of Seismic Hazards

14. 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

15. 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.

16. 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

17. The comparison table for seismic design force Seismic Design Philosophy-Seismic Design force

18. 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

19. Countermeasure for Seismic Design of Piping Seismic Design Philosophy- Countermeasure for Seismic Design of Piping

20. Anti-Seismic Support Design for Aboveground Piping Seismic Design Philosophy- Countermeasure for Seismic Design of Piping

21. To Install an Isolation Valves Seismic Design Philosophy- Countermeasure for Seismic Design of Piping

22. 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

23. 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

24. 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

25. 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

26. 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