Presentation on theme: "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."— Presentation transcript:
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
A Seismic Design Consideration of 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
Introduction uMost 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. uBecause 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 uCTCI corporation is the leading engineering company in Taiwan. Most of the oil and gas transmission systems in Taiwan are designed by CTCI.
Introduction Earthquakes in Taiwan uTaiwan is located at the border between Eurasian Plate and Phillipine Sea Plate. uThere are 2200 quakes occurred per year and one of which is disastrous in Taiwan. uThe famous 921 Chi-Chi Earthquake of magnitude 7.3 made 2413 people dead.
Introduction The Purpose of Seismic Design uTo 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 Taiwan uOnshore pipelines for gas ： It supplies natural gas from CPC Yuan-an terminal through onshore pipeline to customers. uOffshore pipelines for gas ： The 36” offshore pipeline is approximately 240 km in length from Yuan-an to Tung-shiao and combines with onshore pipeline. uOffshore pipelines for oil ： To transfer the crude oil from offshore of the Saloon and Ta-Lin-Pu to the tanks through offshore pipelines. uOnshore 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 Hazards Seismic Hazards
Identification 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 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 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 Hazards Land Slides ： Land slides always result from seismic shaking and heavy rainfall.
Identification 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 Hazards Example:26 inch Natural Gas Pipeline Cross Cho-Shui River uPipeline systems still keep functionability after 921 Chi-Chi earthquake.
Identification of Seismic Hazards Example:Tai-chung network Piping Systems for Natural Gas near the Southern Location of the Wu-Si Bridge u8 & 4 inch low and moderate pressure transmission pipelines were failure after 921 earthquake. lPiping failure due to differential fault movement and ground rupture. lBending failure of piping supported from bridge structure after bridge crushed. lThreaded 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 design 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 force Technical Rules and Regulation of Building,R.O.C. (Seismic Zone in Taiwan) UBC CODE uUniform 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 force The comparison table for seismic design force
Seismic 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 Geological Investigation Soil Improvement Y Y N N N Finish Countermeasure
Seismic Design Philosophy- Countermeasure for Seismic Design of Piping Countermeasure for Seismic Design of Piping
Seismic Design Philosophy- Countermeasure for Seismic Design of Piping Anti-Seismic Support Design for Aboveground Piping
Seismic Design Philosophy- Countermeasure for Seismic Design of Piping To Install an Isolation Valves
lTo use Response Displacement Method to calculate piping strain within 1% lTo evaluate lique- faction potential lrequired data: soil information, ground acceleration lTo consider effects of soils-piping interaction lTo determine L value lTo use static accel. method to calculate stress in the piping system within allowable stress. lrequired data: soil data, ground acceleration lTo use static accel. method to calculate stress in the piping system within allowable stress. lrequired data: ground acceleration Seismic Design Philosophy- Seismic Analysis for Pipeline 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.
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. lSub-bottom Profiling lSoil Investigations lEcho Sounder/Bathymetric Data lSide -Scan Sonar lMagnetic Anomaly Detection uThe items of seismic analysis for offshore pipeline are same as onshore pipeline
Damage Control During Earthquake uThe 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. uTo take the following methods to minimize the hazard in the event that a leak or rupture occurs in the pipeline after big earthquakes. lTo install a block valve and vent stack l To plan a schedule of periodical surveillance and use smart pigs to check the corrosion condition of the pipe wall. l To design monitor control systems such as SCADA system
Damage Control During Earthquake uTo Develop a Emergency Repaired Plan for Offshore Pipelines lIt 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 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.