1 New Concept and Test Method on Running Ductile Fracture Arrest for High Pressure Gas Pipeline Ryota Higuchi, Hiroyuki Makino Sumitomo Metal Industries Ltd., Corporate Research& Development Laboratories Izumi Takeuchi Sumitomo Metal Industries Ltd., Pipe & Tube Company, Tokyo Head Office Key words；Running Ductile Fracture, Natural Gas, X80, X100, Crack Arrestability, Full Scale Burst Test, Gas Pipeline, Battelle Two Curve Method, HLP Method Introduction The world energy demand is continuously increasing. The environment preservation has become a more important and urgent issue for our life in twenty first century. In this context, energy efficiency and less CO 2 emission is getting fo- cused than ever before. Renewable energy such as solar and wind are expected to increase its share, though the major part of energy shall be supplied by the fossil fuel such as oil, coal and gas in coming at least 30 years. Natural gas, which is known as clean energy due to less CO 2 emission and less pollutant among them, should increase its share in primary energy in the world. The large reserve of natural gas, which is expected to develop, is generally far from the market. The efficiency of nat- ural gas transportation is one of the key factors to increase the usage of natural gas. LNG is established its status to convey natural gas for long distance. At the same time gas pipeline has been expanded to transport natural gas. The pipe strength and pipe diameter of gas pipeline has been increased, which has contributed the cost reduction of natural gas [1]. High strength line pipes of X80 has been commercialized and applied in long distance gas pipeline such as 2 nd East to West gas pipeline in China [2]. X90, X100 and X120 grade have been specified in ISO3183 and API 5L for fur- ther increase of transportation efficiency by high-pressure operation. The stringent property of such high strength line pipe is required as the safety of pipeline in high-pressure operation is the first priority. One of the concerns in high pressure gas pipeline is the RDF (Running Ductile Fracture) propagation, which is a unique fracture mode in high pressure gas pipelines. Gas pipelines must be designed to ensure the crack ar- rest together with crack initiation prevention. High strength line pipe for high pressure gas pipeline is required the crack arrestability of RDF in operating condition. The crack arrestability of RDF is defined by the absorbed energy of steel. The required energy to arrest RDF is the common interest among steel makers and pipeline designers. The arrest energy has been obtained by the full scale burst test with incremental energy arrangement, which is an arrangement with energy gradient from center to the ends. BTC(Battelle Two Curve) method enforces this procedure [3]. But recent test results on X80 and X100 revealed that the expected arrest energy by BTC method could not be enough to arrest RDF. The crack arrestor is proposed when the high pressure gas pipeline is constructed with high strength line pipe. That is unfavorable situation on the application of high strength line pipes. The simulation method was developed on RDF propagation and arrest by HLP (High Strength Line Pipe Committee in ISIJ) which revealed that fracture length changes depending on the toughness of steel [4]. The energy gradient in full scale burst test affects the propagation length of RDF. The new concept of crack arrestability of line pipe, which is defined by the energy to arrest RDF within 24 m in each side, is proposed instead of Go or No-Go judgment by single 12 m pipe. This is a more realistic criterion on RDF arrest in gas pipeline. Full scale burst test of X100 was conducted to prove the new concept of crack arrestability of high strength line pipes. The new concept of crack arrestability of high strength line pipe gives a chance to design high pressure gas pipeline without crack arrestor, which reduces pipeline construction cost and is expected to reduce gas price in the market. Traditional definition of crack arrestability of line pipe It is reported that RDF propagation became a keen technical issue in late 1960s, when the pipe diameter and opera- tion pressure was increased for transportation efficiency [5]. The toughness of steel pipe was generally low at that era comparing the toughness of present steel due to the early stage of advancement of clean steel making technology. Charpy absorbed energy of 100J was hardly to obtain in mass production [6]. In this context, the original full scale burst
New Concept and Test Method on Running Ductile Fracture Arrest for High Pressure Gas Pipeline
May 30, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
