Under Pressure Operations on Dense Phase CO2 Pipelines: Issues for the Operator

2014 ◽  
Author(s):  
Julian Barnett ◽  
Richard Wilkinson ◽  
Alan Kirkham ◽  
Keith Armstrong
Keyword(s):  
Natural Gas ◽  
Flow Velocity ◽  
Wall Thickness ◽  
Gaseous Phase ◽  
Operating Conditions ◽  
Cooling Time ◽  
Phase Behaviour ◽  
Pipeline System ◽  
Dense Phase ◽  
Pressure Welding

National Grid, in the United Kingdom (UK), has extensive experience in the management and execution of under pressure operations on its natural gas pipelines. These under pressure operations include welding, ‘hot tap’ and ‘stopple’ operations, and the installation of sleeve repairs. National Grid Carbon is pursuing plans to develop a pipeline network in the Humber and North Yorkshire areas of the UK to transport dense phase Carbon Dioxide (CO2) from major industrial emitters in the area to saline aquifers off the Yorkshire coast. One of the issues that needed to be resolved is the requirement to modify and/or repair dense phase CO2 pipeline system. Existing under pressure experience and procedures for natural gas systems have been proven to be applicable for gaseous phase CO2 pipelines; however, dense phase CO2 pipeline systems require further consideration due to their higher pressures and different phase behaviour. Consequently, there is a need to develop procedures and define requirements for dense phase CO2 pipelines. This development required an experimental programme of under pressure welding trials using a flow loop to simulate real dense phase CO2 pipeline operating conditions. This paper describes the experiments which involved: • Heat decay trials which demonstrated that the practical limitation for under pressure welding on dense phase CO2 systems will be maintaining a sufficient level of heat to achieve the cooling time from 250 °C to 150 °C (T250–150) above the generally accepted 40 second limit. • A successful welding qualification trial with a welded full encirclement split sleeve arrangement. The work found that for the same pipe wall thickness, flow velocity and pressure, dense phase CO2 has the fastest cooling time when compared with gaseous phase CO2 and natural gas. The major practical conclusion of the study is that for dense phase CO2 pipelines with a wall thickness of 19.0 mm or above, safe and practical under pressure welding is possible in accordance with the existing National Grid specification (i.e. T/SP/P/9) up to a flow velocity of around 0.9 m/s. The paper also outlines the work conducted into the use of the Manual Phased Array (MPA) inspection technique on under pressure welding applications. Finally, the paper identifies and considers the additional development work needed to ensure that a comprehensive suite of under pressure operations and procedures are available for the pipeline operator.

Under Pressure Welding and Preheat Temperature Decay Times on Carbon Dioxide Pipelines

2014 ◽  
Author(s):  
Simon Slater ◽  
Robert Andrews ◽  
Peter Boothby ◽  
Julian Barnett ◽  
Keith Armstrong
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Natural Gas ◽  
Cooling Rate ◽  
Gaseous Phase ◽  
Transfer Model ◽  
Dense Phase ◽  
Pressure Welding ◽  
One Dimensional ◽  
Decay Times

Whilst there is extensive industry experience of under pressure welding onto live natural gas and liquid pipelines, there is limited experience for Carbon Dioxide (CO2) pipelines, either in the gaseous or dense phases. National Grid has performed a detailed research programme to investigate if existing natural gas industry under pressure welding procedures are applicable to CO2 pipelines, or if new specific guidance is required. This paper reports the results from one part of a comprehensive trial programme, with the aim of determining the preheat decay times, defined by the cooling time from 250 °C to 150 °C (T250–150), in CO2 pipelines and comparing them to the decay times in natural gas pipelines. Although new build CO2 pipelines are likely to operate in the dense phase, if an existing natural gas pipeline is converted to transport CO2 it may operate in the gaseous phase and so both cases were considered. The aims of the work presented were to: • Determine the correlations between the operating parameters of the pipeline, i.e. flow velocity, pressure etc. and the cooling rate after removal of the preheat, characterised by the (T250–150) cooling time. • Compare the experimentally determined T250–150 cooling times with the values determined using a simple one dimensional heat transfer model. • Define the implications of heat decay for practical under pressure welding on CO2 pipelines. Small-scale trials were performed on a 150 mm (6″) diameter pressurised flow loop at Spadeadam in the UK. The trial matrix was determined using a one dimensional heat transfer model. Welding was performed on a carbon manganese (C-Mn) pipe that was machined to give three sections of 9.9 mm, 19.0 mm and 26.9 mm wall thickness. Trials were performed using natural gas, gaseous phase CO2 and dense phase CO2; across a range of flow velocities from 0.3 m/s to 1.4 m/s. There was relatively good agreement between the T250–150 cooling times predicted by the thermal model and the measured T250–150 times. For the same pipe wall thickness, flow velocity and pressure level, the preheat decay cooling times are longest for gaseous phase CO2, with the fastest cooling rate recorded for dense phase CO2. Due to the fast cooling rate observed on dense phase CO2, the T250–150 times drop below the 40 second minimum requirement in the National Grid specification for under pressure welding, even at relatively low flow velocities. The practical limitation for under pressure welding of pipelines containing dense phase CO2 will be maintaining sufficient preheating during welding. The results from this stage of the technical programme were used to develop the welding trials and qualification of a full encirclement split sleeve assembly discussed in an accompanying paper (1).

Under Pressure Welding on CO2 Pipelines: The Effect of Thermal Decay on Mechanical Properties

2016 ◽  
Author(s):  
Simon Slater ◽  
Julian Barnett ◽  
Peter Boothby ◽  
Robert Andrews
Keyword(s):  
Mechanical Properties ◽  
Natural Gas ◽  
Carbon Capture And Storage ◽  
Cooling Time ◽  
Welding Parameters ◽  
Significant Finding ◽  
Low Carbon ◽  
Dense Phase ◽  
Pressure Welding ◽  
Decay Times

Whilst there is extensive industry experience of under pressure welding onto operational natural gas and liquid pipelines, there is limited experience for Carbon Dioxide (CO2) pipelines, either in the gaseous or dense phase. National Grid has performed a detailed research program to investigate if existing natural gas industry under pressure welding procedures are applicable to CO2 pipelines, or if new specific guidance is required. At IPC 2014 a paper was presented (IPC2014-33223) that dealt with the results from one part of a comprehensive trial program, which defined the cooling time from 250 °C to 150 °C (T250-150) in CO2 pipelines and compared them to the typical decay times for natural gas pipelines. The results from this part of the work identified that maintaining the pre-heat using the established guidance in T/SP/P/9 during under pressure welding on dense phase CO2 pipelines would be very difficult, leading to potential operational issues. The previous paper gave a brief summary of the effect that cooling time had on the mechanical properties. The aim of this paper is to present the findings of the T800-500 weld decay trials in more detail including the full testing programme, detailing the affect that variables such as CO2 phase, CO2 flow velocity and the welding parameters had on the weld and heat affected zone (HAZ) hardness. The main finding is that although there is an indication that a higher cooling rate measured in the weld pool (characterized by the cooling time from 800 °C to 500 °C) leads to increased hardness in the HAZ region, there are no clear correlations. No hardness values were recorded that were considered unacceptable, even for the dense phase CO2 case which delivered the fastest cooling time. A significant finding was the requirement for controlling the buttering run procedure. A discussion of the critical aspects, including the link between weld cooling time and hardness, is presented with guidance on how this essential variables need to be controlled. The paper is aimed at technical, safety and operational staff with CO2 pipeline operators. Read in conjunction, this paper and the previous IPC paper form a comprehensive review of this critical work that is contributing to the development of dense phase CO2 transportation pipelines and will facilitate the implementation of Carbon Capture and Storage (CCS)1 projects which is a critical part of the transition to a low carbon economy.

Calculation Method of Natural Gas Compressibility Factor and its Application in Pipeline Trade

2014 ◽  
Author(s):  
Xiaocui Tian ◽  
Xiaokai Xing ◽  
Rui Chen ◽  
Shubao Pang ◽  
Liu Yang
Keyword(s):  
Natural Gas ◽  
Compressibility Factor ◽  
Economic Benefits ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Pipeline System ◽  
Natural Gas Pipeline ◽  
Gas Volume ◽  
Gas Compressibility ◽  
Simplified Formula

In the custody transfer metering of natural gas, it’s necessary to transform gas volume from metering state into standard state. Natural gas is non-ideal gas, and its compressibility factor varies with different components, temperature and pressure. So the accuracy of its calculation has direct impact on that of natural gas metering, and then affects the economic benefits of the enterprise [1]. According to related standard of China, in the custody transfer metering of natural gas, the formula stipulated by AGA NO.8 should be adopted to calculate compressibility factor. But the components of natural gas must be monitored at all times when this method is used, and the calculation process is complicated. In practical operation of natural gas trade, compressibility factor changes because of frequent adjustment of pipeline operating conditions. In order to simplify the calculation, simplified formula is applied to calculate compressibility factor generally, but it’s difficult to guarantee the accuracy at the same time. In this paper, the simplified formula, which is used for calculating natural gas compressibility factor of a joint-stock natural gas pipeline of CNPC, is modified with the standard formula stipulated by AGA NO.8. After the modification, an empirical formula of compressibility factor calculation applicable to this pipeline system is proposed, whereby the accuracy of compressibility factor calculation is improved. When the modified one is applied to natural gas trade, the accuracy of metering is improved likewise.

The Decompression Behaviour of Carbon Dioxide in the Dense Phase

2012 ◽  
Author(s):  
Andrew Cosham ◽  
David G. Jones ◽  
Keith Armstrong ◽  
Daniel Allason ◽  
Julian Barnett
Keyword(s):  
Carbon Dioxide ◽  
Natural Gas ◽  
Shock Tube ◽  
Gaseous Phase ◽  
Initial Pressure ◽  
Successful Implementation ◽  
Dense Phase ◽  
Test Programme ◽  
Rich Mixtures ◽  
Arrest Toughness

Pipelines can be expected to play a significant role in the transportation infrastructure required for the successful implementation of carbon capture and storage (CCS). National Grid is undertaking a research and development programme to support the development of a safety justification for the transportation of carbon dioxide (CO2) by pipeline in the United Kingdom. The ‘typical’ CO2 pipeline is designed to operate at high pressure in the ‘dense’ phase. Shock tube tests were conducted in the early 1980s to investigate the decompression behaviour of pure CO2, but, until recently, there have been no tests with CO2-rich mixtures. National Grid have undertaken a programme of shock tube tests on CO2 and CO2-rich mixtures in order to understand the decompression behaviour in the gaseous phase and the liquid (or dense) phase. An understanding of the decompression behaviour is required in order to predict the toughness required to arrest a running ductile fracture. The test programme consisted of three (3) commissioning tests, three (3) test with natural gas, fourteen (14) tests with CO2 and CO2-rich mixtures in the gaseous phase, and fourteen (14) tests with CO2 and CO2-rich mixtures in the liquid (or dense) phase. The shock tube tests in the liquid (dense) phase are the subject under consideration here. Firstly, the design of the shock tube test rig is summarised. Then the test programme is described. Finally, the results of the dense phase tests are presented, and the observed decompression behaviour is compared with that predicted using a simple (isentropic) decompression model. Reference is also made to the more complicated (non-isentropic) decompression models. The differences between decompression through the gaseous and liquid phases are highlighted. It is shown that there is reasonable agreement between the observed and predicted decompression curves. The decompression behaviour of CO2 and CO2-rich mixtures in the liquid (dense) phase is very different to that of lean or rich natural gas, or CO2 in the gaseous phase. The plateau in the decompression curve is long. The following trends (which are the opposite of those observed in the gaseous phase) can be identified in experiment and theory: • Increasing the initial temperature will increase the arrest toughness. • Decreasing the initial pressure will increase the arrest toughness. • The addition of other components such as hydrogen, oxygen, nitrogen or methane will increase the arrest toughness.

The Dynamic Simulation of a Long Distance Natural Gas Pipeline

2012 ◽  
Vol 268-270 ◽  
pp. 1244-1248
Author(s):  
Shan Bi Peng ◽  
En Bin Liu ◽  
Xiao Chun Du ◽  
Rong Lin Hong
Keyword(s):  
Natural Gas ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Pipeline System ◽  
Long Distance ◽  
Natural Gas Pipeline ◽  
Operation Conditions ◽  
Condition Change ◽  
Gas Market ◽  
The One

With the growth of the natural gas market, the long distance natural gas pipeline system is getting more and more important in nowadays. As a united and enclosed hydraulic system, the operation conditions of the whole line will be changed by the influence of the condition change in one station. On the one hand, the condition change made people analyze operation scheme more difficult, on the other hand, pipeline system operating conditions directly affect the relationship between the production and the sales of natural gas. Therefore, the operation of the gas pipeline must be optimized, which brings huge economic and social benefits. This paper constructed a simulation model of a long distance natural gas pipeline by TG.net, and then analyzed the change of the operating condition of the pipeline after a compressor station shut down, found out the regularity.

Energy Usage in Natural Gas Pipeline Applications

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Augusto Garcia-Hernandez ◽  
Klaus Brun
Keyword(s):  
Natural Gas ◽  
Fuel Consumption ◽  
Transport System ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Pipeline System ◽  
Entire System ◽  
Energy Usage ◽  
Natural Gas Pipeline

Energy required to transport the fluid is an important parameter to be analyzed and minimized in pipeline applications. However, the pipeline system requirements and equipment could impose different constraints for operating pipelines in the best manner possible. One of the critical parameters that it is looked at closely, is the machines’ efficiency to avoid unfavorable operating conditions and to save energy costs. However, a compression-transport system includes more than one machine and more than one station working together at different conditions. Therefore, a detailed analysis of the entire compression system should be conducted to obtain a real power usage optimization. This paper presents a case study that is focused on analyzing natural gas transport system flow maximization while optimizing the usage of the available compression power. Various operating scenarios and machine spare philosophies are considered to identify the most suitable conditions for an optimum operation of the entire system. Modeling of pipeline networks has increased in the past decade due to the use of powerful computational tools that provide good quality representation of the real pipeline conditions. Therefore, a computational pipeline model was developed and used to simulate the gas transmission system. All the compressors’ performance maps and their driver data such as heat rate curves for the fuel consumption, site data, and running speed correction curves for the power were loaded in the model for each machine. The pipeline system covers 218 miles of hilly terrain with two looped pipelines of 38″ and 36″ in diameter. The entire system includes three compressor stations along its path with different configurations and equipment. For the optimization, various factors such as good efficiency over a wide range of operating conditions, maximum flexibility of configuration, fuel consumption and high power available were analyzed. The flow rate was maximized by using instantaneous maximum compression capacity at each station while maintaining fixed boundary conditions. This paper presents typical parameters that affect the energy usage in natural gas pipeline applications and discusses a case study that covers an entire pipeline. A modeling approach and basic considerations are presented as well as the results obtained for the optimization.

Energy Usage in Natural Gas Pipeline Applications

2011 ◽  
Author(s):  
Augusto Garcia-Hernandez ◽  
Klaus Brun
Keyword(s):  
Natural Gas ◽  
Fuel Consumption ◽  
Transport System ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Pipeline System ◽  
Entire System ◽  
Energy Usage ◽  
Natural Gas Pipeline

Energy required to transport the fluid is an important parameter to be analyzed and minimized in pipeline applications. However, the pipeline system requirements and equipment could impose different constraints for operating pipelines in the best manner possible. One of the critical parameters that is looked at closely, is the machines’ efficiency to avoid unfavorable operating conditions and to save energy costs. However, a compression-transport system includes more than one machine and more than one station working together at different conditions. Therefore, a detailed analysis of the entire compression system should be conducted to obtain a real power usage optimization. This paper presents a case study that is focused on analyzing natural gas transport system flow maximization while optimizing the usage of the available compression power. Various operating scenarios and machine spare philosophies are considered to identify the most suitable conditions for an optimum operation of the entire system. Modeling of pipeline networks has increased in the past decade due to the use of powerful computational tools that provide good quality representation of the real pipeline conditions. Therefore, a computational pipeline model was developed and used to simulate the gas transmission system. All the compressors’ performance maps and their driver data such as heat rate curves for the fuel consumption, site data, and running speed correction curves for the power were loaded in the model for each machine. The pipeline system covers 218 miles of hilly terrain with two looped pipelines of 38″ and 36″ in diameter. The entire system includes three compressor stations along its path with different configurations and equipment. For the optimization, various factors such as good efficiency over a wide range of operating conditions, maximum flexibility of configuration, fuel consumption and high power available were analyzed. The flow rate was maximized by using instantaneous maximum compression capacity at each station while maintaining fixed boundary conditions. This paper presents typical parameters that affect the energy usage in natural gas pipeline applications and discusses a case study that covers an entire pipeline. A modeling approach and basic considerations are presented as well as the results obtained for the optimization.

Hydrogen in Pipelines: Impact of Hydrogen Transport in Natural Gas Pipelines

2020 ◽  
Author(s):  
Rainer Kurz ◽  
Matt Lubomirsky ◽  
Francis Bainier
Keyword(s):  
Natural Gas ◽  
Gas Turbines ◽  
Supply And Demand ◽  
Operating Conditions ◽  
Pipeline System ◽  
Pure Hydrogen ◽  
Hydraulic Simulation ◽  
Natural Gas Pipelines ◽  
Natural Gas Pipeline ◽  
The Impact

Abstract The increased use of renewable energy has made the need to store electricity a central requirement. One of the concepts to address this need is to produce hydrogen from surplus electricity, and to use the existing natural gas pipeline system to transport the hydrogen. Generally, the hydrogen content in the pipeline flow would be below 20%, thus avoiding the problems of transporting and burning pure hydrogen. The natural gas – hydrogen mixtures have to be considered both from a gas transport and a gas storage perspective. In this study, the impact of various levels of hydrogen in a pipeline system are simulated. The pipeline hydraulic simulation will provide the necessary operating conditions for the gas compressors, and the gas turbines that drive these compressors. The result of the study addresses the impact on transportation efficiency in terms of energy consumption and the emission of green house gases. Further, necessary concepts in the capability to store gas to better balance supply and demand are discussed.

Pipe Length Limit Analysis to Tunnel Vertical Well of Natural Gas Pipeline

2013 ◽  
Vol 457-458 ◽  
pp. 633-638
Author(s):  
Xin Tian ◽  
Chi Yuan Ren
Keyword(s):  
Natural Gas ◽  
Stress Analysis ◽  
Wall Thickness ◽  
Gas Pipeline ◽  
Operating Conditions ◽  
Normal Operation ◽  
Tube Length ◽  
Operating Pressure ◽  
Pipe Length ◽  
Natural Gas Pipeline

In practical applications, often using natural gas pipeline through the pipe shaft way, so conditions for shaft pipe stress analysis has a very important practical significance and economic value, and limit the tube length calculation is one of the key issues. Take advantage of this stress analysis software, combined with program design, the shaft condition of the pipeline depth simulation. The results show that: gas pipeline tunnel shaft limit pipe length and pipe material, wall thickness and operating conditions are closely related, the greater the steel yield strength and wall thickness, the smaller the operating pressure, the longer the tube length limit. In the actual design pipeline crossing, it should fully take into account the limits of the tube length limit, the limit calculated under different conditions, to ensure the normal operation of gas pipelines provide pipeline reliability and economic benefits.

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