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51316-7575-Reinforcement Assesment of Natural Gas Road Crossings Using Composite Repair

Product Number: 51316-7575-SG
ISBN: 7575 2016 CP
Author: Davie Peguero
Publication Date: 2016
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There was a recent change in class location along a section of a natural gassystem in Ontario. An analysis as per CSA Z662determined the allowable MAOP on the lines due to the change in the design factor. The change to a Class 2 location reduced the calculated MAOP from 802 psi to 767 psi for threeroad crossings. The reduction in the pipeline pressure due to these three smallsections at road crossings prompted the search for a solution to reinforce the sections to prevent a pressure reduction along the entire length of line.In order to maintain the 802 psi MAOP the three 12in OD road crossings will require additional hoopreinforcement. Possible solutions were casing the line reducing the pressure or use of metallic or nonmetallic sleeves. Areinforcement design was requested which would allow to maintain a MAOP of 802 psi (the calculated MAOP of the system prior to the class location change). Apre-impregnated carbon fiber composite system with a hybrid carbon and glass fiber architecture was selected. The matrix was amoisture-cured polyurethane system. ViThe system has been tested and complies with regulations set forth by ASME PCC-2-2011 Part 4 “Nonmetallic and Bonded Repairs”. The advantages of a composite repairover other methods of reinforcement are ease of application avoidance of hot work conformability and the application of the composite under live conditions. In addition this method avoids the cathodic protection issues presented by the installation of casings. In order for the steel to share its load with the composite and hence reduce the stresses on the pipe a partial depressurization will need to take place. This will allow for the stress in the steel to be reduced and the composite system applied. As the pipe is re-pressurized the load will be shared between the steel and composite. The repair thickness will be dependent on the amount of pressure reduction possible. The higher the pressure reduction possible the thinner the composite thickness needs to be. The partial depressurization will allow for the stress level on the steel to be less than or equal to the SMYS with the desired MAOP of 802psi.This paperhas also expanded the analysis to find the maximum allowable live pressure during the composite application such that the stresses on the pipe for the new MAOP of 802 psi after Viper-Skin is applied are less than the stresses that the pipe is under at a current MAOP of 767psi.
There was a recent change in class location along a section of a natural gassystem in Ontario. An analysis as per CSA Z662determined the allowable MAOP on the lines due to the change in the design factor. The change to a Class 2 location reduced the calculated MAOP from 802 psi to 767 psi for threeroad crossings. The reduction in the pipeline pressure due to these three smallsections at road crossings prompted the search for a solution to reinforce the sections to prevent a pressure reduction along the entire length of line.In order to maintain the 802 psi MAOP the three 12in OD road crossings will require additional hoopreinforcement. Possible solutions were casing the line reducing the pressure or use of metallic or nonmetallic sleeves. Areinforcement design was requested which would allow to maintain a MAOP of 802 psi (the calculated MAOP of the system prior to the class location change). Apre-impregnated carbon fiber composite system with a hybrid carbon and glass fiber architecture was selected. The matrix was amoisture-cured polyurethane system. ViThe system has been tested and complies with regulations set forth by ASME PCC-2-2011 Part 4 “Nonmetallic and Bonded Repairs”. The advantages of a composite repairover other methods of reinforcement are ease of application avoidance of hot work conformability and the application of the composite under live conditions. In addition this method avoids the cathodic protection issues presented by the installation of casings. In order for the steel to share its load with the composite and hence reduce the stresses on the pipe a partial depressurization will need to take place. This will allow for the stress in the steel to be reduced and the composite system applied. As the pipe is re-pressurized the load will be shared between the steel and composite. The repair thickness will be dependent on the amount of pressure reduction possible. The higher the pressure reduction possible the thinner the composite thickness needs to be. The partial depressurization will allow for the stress level on the steel to be less than or equal to the SMYS with the desired MAOP of 802psi.This paperhas also expanded the analysis to find the maximum allowable live pressure during the composite application such that the stresses on the pipe for the new MAOP of 802 psi after Viper-Skin is applied are less than the stresses that the pipe is under at a current MAOP of 767psi.
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