Determining the venting time of a gas trunk pipeline segment provides an important basis for formulating an emergency plan in the advent of unexpected accidents.As the natural gas venting process corresponds to the tr...Determining the venting time of a gas trunk pipeline segment provides an important basis for formulating an emergency plan in the advent of unexpected accidents.As the natural gas venting process corresponds to the transient flow,it is necessary to establish a transient hydraulic-thermal simulation model in order to determine the venting time.In this paper,based on two kinds of venting scenarios in which there is only one venting point in the venting system of a gas trunk pipeline segment—namely,where the venting point is either at one of the two ends or at the junction of two gas trunk pipeline segments—transient hydraulic-thermal simulation models are established.The models consist of gas flow governing equations,the gas state equation,gas physical property equations,initial conditions,and appropriate boundary conditions.The implicit central difference method is used to discretize the gas flow partial differential equations,and the trust-region-dogleg algorithm is used to solve the equations corresponding to each time step,in order to dynamically simulate the whole venting process.The judgment condition for the end of the venting process is that the average pressure of gas trunk pipeline segment is less than 0.11 MPa(actual pressure).Comparing the simulation results of the proposed model with those of the OLGA software and real operational data,we find that the venting time error is less than 10%.On this basis,a venting valve opening control principle is proposed,which prevents the venting noise from exceeded the specified noise value(85 d B)in the venting design of domestic gas pipeline projects.The established calculation model for venting time(dynamic simulation model)for a gas trunk pipeline segment and the proposed opening control principle of venting valve provide reference for the optimal operation of gas pipeline venting systems.展开更多
Modern processing plants use a variety of control loop networks to deliver a finished product to the market.Such control loops,like control valves,are designed to keep process variables such as pressure,temperature,sp...Modern processing plants use a variety of control loop networks to deliver a finished product to the market.Such control loops,like control valves,are designed to keep process variables such as pressure,temperature,speed,flow,etc.within the appropriate operating range and to ensure a quality product is produced.All control valves have a bypass so that production can proceed if maintenance is needed for the control valve as part of the control loop.The important point is that in both operation and maintenance situations,the bypass valve and the control valve should have approximately the same flow capacity to provide nearly the same amount of pressure.This paper presents a case study in seawater service on the selection of manual bypass valves for a 16″control valve in class 150 and titanium material.A 16″butterfly valve of class 150 was chosen for the control valve bypass,which provided a much higher flow capacity than the control valve.In this paper,four solutions are recommended to achieve the same coefficient value(Cv)for the control and bypass valve.Using the reduced size butterfly valve could be the cheapest and best solution.On the other hand,selecting the same control valve for bypass line is the most expensive but maybe the most reliable solution.Using a flow orifice for throttling could be ranked as the second expensive option and the second reliable one.Selection of butterfly valve for throttling is the second cheapest option,but it has the least reliability.Different parameters such as space and weight saving,cost as well as reliability have been considered in evaluation of different solutions.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52174064)
文摘Determining the venting time of a gas trunk pipeline segment provides an important basis for formulating an emergency plan in the advent of unexpected accidents.As the natural gas venting process corresponds to the transient flow,it is necessary to establish a transient hydraulic-thermal simulation model in order to determine the venting time.In this paper,based on two kinds of venting scenarios in which there is only one venting point in the venting system of a gas trunk pipeline segment—namely,where the venting point is either at one of the two ends or at the junction of two gas trunk pipeline segments—transient hydraulic-thermal simulation models are established.The models consist of gas flow governing equations,the gas state equation,gas physical property equations,initial conditions,and appropriate boundary conditions.The implicit central difference method is used to discretize the gas flow partial differential equations,and the trust-region-dogleg algorithm is used to solve the equations corresponding to each time step,in order to dynamically simulate the whole venting process.The judgment condition for the end of the venting process is that the average pressure of gas trunk pipeline segment is less than 0.11 MPa(actual pressure).Comparing the simulation results of the proposed model with those of the OLGA software and real operational data,we find that the venting time error is less than 10%.On this basis,a venting valve opening control principle is proposed,which prevents the venting noise from exceeded the specified noise value(85 d B)in the venting design of domestic gas pipeline projects.The established calculation model for venting time(dynamic simulation model)for a gas trunk pipeline segment and the proposed opening control principle of venting valve provide reference for the optimal operation of gas pipeline venting systems.
文摘Modern processing plants use a variety of control loop networks to deliver a finished product to the market.Such control loops,like control valves,are designed to keep process variables such as pressure,temperature,speed,flow,etc.within the appropriate operating range and to ensure a quality product is produced.All control valves have a bypass so that production can proceed if maintenance is needed for the control valve as part of the control loop.The important point is that in both operation and maintenance situations,the bypass valve and the control valve should have approximately the same flow capacity to provide nearly the same amount of pressure.This paper presents a case study in seawater service on the selection of manual bypass valves for a 16″control valve in class 150 and titanium material.A 16″butterfly valve of class 150 was chosen for the control valve bypass,which provided a much higher flow capacity than the control valve.In this paper,four solutions are recommended to achieve the same coefficient value(Cv)for the control and bypass valve.Using the reduced size butterfly valve could be the cheapest and best solution.On the other hand,selecting the same control valve for bypass line is the most expensive but maybe the most reliable solution.Using a flow orifice for throttling could be ranked as the second expensive option and the second reliable one.Selection of butterfly valve for throttling is the second cheapest option,but it has the least reliability.Different parameters such as space and weight saving,cost as well as reliability have been considered in evaluation of different solutions.
