Development and Engineering Applications of High-pressure Underwater Valves
Jun 07, 2023
Overview
A subsea valve is one of the indispensable devices in the development of underwater production systems, and have the characteristics of wide applications, high technical content, high requirement for reliability, and long service life. A subsea valve is widely used in gas and liquid medium mining and pipeline systems due to its small flow resistance, reliable sealing and long service life, especially in the process of offshore oil and gas exploration or development, high-pressure underwater gate valves and ball valves are widely used in various underwater production equipment. Offshore Oil Engineering Co., Ltd has gradually mastered the selection, design, manufacture, testing and the key technology of the certification, and the relevant results were applied to the localization of high-pressure underwater valves required for a gas field development project in the South China Sea, which played a vital role in the quality control of localized products of high-pressure underwater valves.
Development and engineering applications of high-pressure underwater valves
Demand for localization
A development project of a gas field group in the South China Sea needs to build a new set of underwater pipelines. Eight underwater gate valves of 6 inches and two underwater ball valves of 8 inches are required. The working water depth is 142 meters, and the design service life is 20 years. The product specification is PSL 3G; the requirement for performance is API 6A PR2, and the material level is HH level. The design temperature is P level (-29 to 82℃). Among them, the design pressure of the underwater gate valve is 41.4MPa (corresponding to the pressure in the API 6A is Class 6000psi). The design pressure of the underwater ball valve is 43.1MPa (corresponding to the pressure in the API 6DSS is Class 2500LB). It is a typical high-pressure valve, and the valve can be operated by ROV (underwater robots) carrying torque tools or divers carrying special handwheels.
Requirements
The design of the underwater ball valve should be based on API 6DSS, which adopts the opening and closing at an angle of 90 and the trunnion ball floating seat structure. The top entry or side entry can be selected. The downstream of the valve seat is designed as a double piston effect seal (DPE), and the upstream of the valve seat is designed as a self-discharging seal (SPE). Detailed information and reliability data on the relevant valve seat must be provided. The valve design must ensure the concentricity of the valve seat and the valve ball. At the same time, to avoid impurities in the medium and damage to the valve seat during the passage of the ball, corresponding measures should be considered. The pressure difference at the self-bleeding sealing end shall be identified, and it shall be verified by calculation that there is sufficient spring force during the passing of the ball to ensure that the seal between the valve seat and the ball is not damaged by the pigging ball.
The design of the underwater gate valve shall be straight-through type according to API 17D standards. For the main seal of the gate valve, a metal-to-metal seal should be used between the wedge and the valve seat, and no lubricant is required on the sealing surface. Wedges and seats shall be coated with tungsten carbide (TCC) with a minimum thickness of 250μm. The wedge should move in the vertical plane, and special consideration should be given to the possibility of sand accumulation or hydrate formation inside the valve cavity. Override operation of the valve shall be actuated directly through the extension shaft, and a visual position indicator on the operating port shall indicate full travel. The spindle of the mechanical actuator and the spindle for override operation should rotate clockwise to close the valve and counterclockwise to open the valve.
Implementation results
According to the technical requirements provided by COOEC, domestic valve manufacturers have completed the trial production of underwater ball valves and underwater gate valve engineering prototypes, and passed a series of tests such as the hyperbaric chamber, PR 2 and life tests, and have been approved by international authoritative third-party organizations. The product’s quality meets the requirements of relevant standards and specifications. The underwater valve developed in this project was integrated into the underwater pipelines, and was applied to the seabed at a water depth of 142 meters together with the pipeline, realizing the localization of underwater valve products and initially forming a domestic technical system for design, manufacturing, testing and certification of underwater valves, and solving the problem of the monopoly of foreign technology, which is of great significance to ensuring China's independent development of deep-water oil and gas fields.
A subsea valve is one of the indispensable devices in the development of underwater production systems, and have the characteristics of wide applications, high technical content, high requirement for reliability, and long service life. A subsea valve is widely used in gas and liquid medium mining and pipeline systems due to its small flow resistance, reliable sealing and long service life, especially in the process of offshore oil and gas exploration or development, high-pressure underwater gate valves and ball valves are widely used in various underwater production equipment. Offshore Oil Engineering Co., Ltd has gradually mastered the selection, design, manufacture, testing and the key technology of the certification, and the relevant results were applied to the localization of high-pressure underwater valves required for a gas field development project in the South China Sea, which played a vital role in the quality control of localized products of high-pressure underwater valves.
Development and engineering applications of high-pressure underwater valves
Demand for localization
A development project of a gas field group in the South China Sea needs to build a new set of underwater pipelines. Eight underwater gate valves of 6 inches and two underwater ball valves of 8 inches are required. The working water depth is 142 meters, and the design service life is 20 years. The product specification is PSL 3G; the requirement for performance is API 6A PR2, and the material level is HH level. The design temperature is P level (-29 to 82℃). Among them, the design pressure of the underwater gate valve is 41.4MPa (corresponding to the pressure in the API 6A is Class 6000psi). The design pressure of the underwater ball valve is 43.1MPa (corresponding to the pressure in the API 6DSS is Class 2500LB). It is a typical high-pressure valve, and the valve can be operated by ROV (underwater robots) carrying torque tools or divers carrying special handwheels.
Requirements
The design of the underwater ball valve should be based on API 6DSS, which adopts the opening and closing at an angle of 90 and the trunnion ball floating seat structure. The top entry or side entry can be selected. The downstream of the valve seat is designed as a double piston effect seal (DPE), and the upstream of the valve seat is designed as a self-discharging seal (SPE). Detailed information and reliability data on the relevant valve seat must be provided. The valve design must ensure the concentricity of the valve seat and the valve ball. At the same time, to avoid impurities in the medium and damage to the valve seat during the passage of the ball, corresponding measures should be considered. The pressure difference at the self-bleeding sealing end shall be identified, and it shall be verified by calculation that there is sufficient spring force during the passing of the ball to ensure that the seal between the valve seat and the ball is not damaged by the pigging ball.
The design of the underwater gate valve shall be straight-through type according to API 17D standards. For the main seal of the gate valve, a metal-to-metal seal should be used between the wedge and the valve seat, and no lubricant is required on the sealing surface. Wedges and seats shall be coated with tungsten carbide (TCC) with a minimum thickness of 250μm. The wedge should move in the vertical plane, and special consideration should be given to the possibility of sand accumulation or hydrate formation inside the valve cavity. Override operation of the valve shall be actuated directly through the extension shaft, and a visual position indicator on the operating port shall indicate full travel. The spindle of the mechanical actuator and the spindle for override operation should rotate clockwise to close the valve and counterclockwise to open the valve.
Implementation results
According to the technical requirements provided by COOEC, domestic valve manufacturers have completed the trial production of underwater ball valves and underwater gate valve engineering prototypes, and passed a series of tests such as the hyperbaric chamber, PR 2 and life tests, and have been approved by international authoritative third-party organizations. The product’s quality meets the requirements of relevant standards and specifications. The underwater valve developed in this project was integrated into the underwater pipelines, and was applied to the seabed at a water depth of 142 meters together with the pipeline, realizing the localization of underwater valve products and initially forming a domestic technical system for design, manufacturing, testing and certification of underwater valves, and solving the problem of the monopoly of foreign technology, which is of great significance to ensuring China's independent development of deep-water oil and gas fields.
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