A method for on-line repair of emergency shut-off valves for high-sulfur gas fields

Abstract

This invention relates to a method for online maintenance of emergency shut-off valves in high-sulfur gas fields, comprising: S1 Overriding the ESDV signal in the SIS system, setting the bypass valve of the ESDV actuator to local control mode, pressurizing the actuator to ensure sufficient hydraulic pressure, and placing the valve in a forced shielded state; S2 Cutting off the ESDV instrument air supply, depressurizing the actuator air supply line, de-energizing the solenoid valve, disconnecting the instrument air connection line, disconnecting the signal cable, and removing the actuator connecting bolts; S3 Installing a hydraulic jack at each end of the actuator, pushing the actuator, separating the ball valve stem from the actuator coupling sleeve, and using a crane to move the actuator to the maintenance point; S4 Setting the bypass valve of the ESDV actuator to remote mode and releasing the hydraulic cylinder pressure; S5 Measuring the actuator swing shaft distance, disassembling the actuator cylinder, opening the cylinder, and replacing the piston sealing ring; S6 Restoring the actuator. This invention enables online maintenance of ESDVs.

Description

Technical Field

[0001] This invention relates to the field of natural gas extraction technology, and in particular to a method for online maintenance of emergency shut-off valves in high-sulfur gas fields. Background Technology

[0002] In some high-sulfur gas fields, natural gas contains highly toxic hydrogen sulfide acid gas. To ensure the safety of the gathering and transportation process of sulfur-containing natural gas, emergency shut-down valves (ESDVs) are installed on the main process of sulfuric acid gas and fuel gas pipelines during the design and construction of production sites. These valves are used to quickly cut off the sulfur-containing natural gas at the production site in case of pipeline leaks, fires, explosions, or other emergencies, so as to ensure the safe operation of pipeline equipment.

[0003] For example, a gas field's pilot production project and rolling production construction project have hundreds of ESDVs at various stations. These ESDVs mainly use either an instrument air supply system or a dual-acting system of instrument air and hydraulic oil to control the opening and closing of emergency shut-off valves. Under normal circumstances, the valves are open, and in emergencies, they are closed. During daily production operations, the normal operation of the ESDVs mainly depends on whether the instrument air pressure of the pneumatic actuator system is within the normal range. Faults in pipeline components such as solenoid valves, two-position three-way valves, and pressure regulating valves of the pneumatic actuators, as well as aging of the instrument air cylinder seals, lead to reduced valve stability. In particular, the ESDV actuators at the pilot production project stations frequently experience wear on the cylinder end face copper sleeve and lead screw, as well as aging and deformation of the seals, leading to leakage of instrument air from the cylinder. This can easily cause abnormal shutdown of the ESDVs, affecting the normal operation and production of the gas field.

[0004] Therefore, to eliminate potential hazards, it is necessary to replace components such as the instrument air cylinder seals and copper sleeves of the ESDV pneumatic actuator to prevent abnormal ESDV closure due to seal failure in the instrument air cylinder. However, since this valve is a critical self-control valve, there is a risk of abnormal closure during on-site handling, with the following issues:

[0005] Because the ESDV is located at critical points such as the sour gas pipeline outlet and the fuel gas pipeline inlet, maintenance can only be performed by shutting down the ESDV during production shutdowns at the production site or throughout the gas field. Online maintenance during normal production is not possible. Therefore, to minimize the impact of ESDV malfunction handling on gas field production and ensure normal gas field operations, it is necessary to develop an online maintenance method for emergency shut-off valves in high-sulfur gas fields. Summary of the Invention

[0006] The purpose of this invention is to address the problem that existing ESDVs used in the exploitation of high-sulfur gas fields can only be shut down for maintenance when the production station or the entire gas field is shut down, which prevents online maintenance under normal production conditions and affects gas field output. This invention provides a method for online maintenance of emergency shut-off valves in high-sulfur gas fields.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for online maintenance of emergency shut-off valves in high-sulfur gas fields includes the following steps:

[0009] S1. In the SIS (Safety Interlocking System), the ESDV signal is overridden, the bypass valve of the ESDV actuator is set to local control state, the actuator is pressurized, and the hydraulic pressure of the actuator is sufficient, and the valve is in a forced shielding state.

[0010] S2. Cut off the air supply to the ESDV instrument, depressurize the air supply line to the actuator, de-energize the solenoid valve, disconnect the instrument air connection line, disconnect the signal cable, and remove the actuator connection bolts.

[0011] S3. Install a hydraulic jack at each end of the actuator to push the actuator, separate the ball valve stem from the coupling sleeve of the actuator, and use a crane to move the actuator to the maintenance point;

[0012] S4. Set the bypass valve of the ESDV actuator to remote mode to release the hydraulic cylinder pressure;

[0013] S5. Measure the distance of the actuator swing shaft, disassemble the actuator cylinder, open the cylinder, and replace the piston sealing ring;

[0014] S6. Reinstate the enforcement agency.

[0015] As a preferred embodiment of the present invention, in step S1, the actuator is pressurized by a hand-operated pump until it can no longer be pressurized.

[0016] As a preferred embodiment of the present invention, in step S2, the quick-release valve on the actuator panel is opened to release the instrument air pressure in the actuator cavity to 0MPa. After observing for a period of time, the next step is performed. After the actuator has no abnormal movement and the hydraulic pressure has not dropped significantly, the solenoid valve is de-energized on the SIS cabinet.

[0017] In a preferred embodiment of the present invention, in step S3, a crane is first used to attach the actuator, and the mechanism is slowly raised to allow the hoisting rope to bear force. Then, a hydraulic jack is used to push the actuator, and the crane straightens the hoisting rope to assist in the process.

[0018] In a preferred embodiment of the present invention, in step S3, a level is placed on the actuator to cooperate with the hydraulic jacks to push, and the two hydraulic jacks lift steadily.

[0019] As a preferred embodiment of the present invention, in step S5, when disassembling the cylinder, two tie rods on the cylinder are removed in advance and replaced with two extended tie rods, and the thrust of the spring cylinder is relieved by the extended tie rods.

[0020] As a preferred embodiment of the present invention, after step S5, an action test and a sealing test are performed on the actuator.

[0021] As a preferred embodiment of the present invention, in step S6, before reinstalling the actuator, the actuator is set to the open state under no-load conditions, and then the actuator coupling sleeve is connected to the ball valve stem.

[0022] As a preferred embodiment of the present invention, before step S1, the valve position indicator of the ESDV is disassembled, the connection between the bushing and the actuator is derusted and lubricated, and a mobile scaffold and a simple platform are erected according to the height of the cylinder of the ESDV actuator for maintenance.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] Through principle analysis and experimental verification of pneumatic actuators, the method for online maintenance of emergency shut-off valves in high-sulfur gas fields described in this invention avoids the risk of abnormal closure during online maintenance of ESDVs, ensures maintenance of valves under normal operating conditions, greatly reduces the limitations of subsequent ESDV fault maintenance, reduces the impact of fault handling on gas field production, ensures timely elimination of potential faults, improves the stability of ESDVs, and guarantees stable and safe production of gas fields. Detailed Implementation

[0025] The present invention will now be described in detail.

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] Example

[0028] The present invention provides a method for online maintenance of emergency shut-off valves in high-sulfur gas fields, comprising the following steps:

[0029] Step 1: Remove the valve position indicator from the ESDV.

[0030] Remove the valve position indicator from the top of the ESDV actuator along with the bolts on its mounting bracket to disassemble the valve position indicator.

[0031] Step 2: Lubrication and rust removal.

[0032] Because the ESDV actuator has been in use for a long time, severe rust may occur at the connection between the bushing and the actuator, which may cause adhesion. Therefore, the day before the maintenance work, the actuator shift fork cover is opened, and rust remover is used to remove rust at the connection between the bushing and the actuator. After the rust removal is completed, lubricant is added, and then the actuator is restored.

[0033] Step 3: Place the mobile scaffolding and simple platform.

[0034] Based on the height of the ESDV actuator cylinder at the site (approximately 2.7m), mobile scaffolding and a simple platform were used on-site to ensure that maintenance personnel could perform online maintenance on the actuator.

[0035] Step 4: Signal overshoot.

[0036] The host computer of the Instrument Safety Interlocking System (SIS) overrides the signal of the ESDV and confirms the completion of the override action before proceeding to the next step.

[0037] Step 5: Manually apply hydraulic pressure.

[0038] Ensure that the bypass valve of the actuator is set to local control mode. Use a hand pump to pressurize until it can no longer be pressurized to ensure that the hydraulic pressure of the actuator is sufficient and that the valve is in a forced shielded state.

[0039] Step 6: Disconnect the air supply to the instrument panel.

[0040] Close the air inlet valve of the ESDV instrument to cut off the air supply to the instrument.

[0041] Step 7: Depressurize the air supply line of the actuator and de-energize the solenoid valve.

[0042] Open the quick-release valve on the actuator panel to release the instrument air pressure in the actuator cavity to 0MPa. Observe for a period of time (30min) before proceeding to the next step. After the actuator does not have any abnormal movement and the hydraulic pressure does not drop significantly, disconnect the power to the solenoid valve on the SIS cabinet.

[0043] Step 8: Disconnect the instrument air connection pipeline.

[0044] Disconnect the ESDV actuator from the instrument air connection line in the station to facilitate the disassembly of the actuator.

[0045] Step 9: Disconnect the signal cable.

[0046] Remove the cables and glands from the ESDV air circuit panel.

[0047] Step 10: Disassemble the connecting bolts of the actuator.

[0048] Remove the bolts connecting the actuator to the ball valve.

[0049] Step 11: Secure the suspension rope.

[0050] Use a crane hook to secure the crane to the lifting fixture of the actuator, and slowly raise it to allow the lifting rope to bear the load.

[0051] Step 12: Install the hydraulic jack to separate the ball valve from the actuator.

[0052] Install one hydraulic jack at each end of the actuator, place them on the support frame, and place a level on top of the actuator to assist in lifting. Throughout the lifting process, continuously monitor the level for balance and adjust it promptly if tilted. When separating the actuator from the valve body, use the hydraulic jacks to slowly push the actuator upwards while maintaining horizontality at both ends. Simultaneously, straighten the lifting ropes with a crane to assist in separating the actuator from the valve body, ensuring the actuator is subjected to balanced forces to prevent jamming and swaying due to uneven lifting. After separating the ball valve stem from the actuator's coupling sleeve, use a crane to place the actuator at a designated maintenance location outside the station.

[0053] Step 13: Release the pressure in the hydraulic cylinder.

[0054] Switching the bypass valve of the actuator to the remote state will release the pressure of the hydraulic oil in the hydraulic cylinder and restore the spring to its normal state.

[0055] Step 14: Measure the distance of the actuator's swing axis.

[0056] After the actuator disengages from the valve, open the fork box cover, measure and record the travel distance of the rocker arm slider at the rocker arm. The purpose is to adjust the slider to its offline position during reinstallation, so as to easily find the center point between the actuator mechanism and the bushing during reinstallation.

[0057] Step 15: Cylinder disassembly.

[0058] When disassembling the cylinder, although the spring cylinder has returned to the fully closed position, the spring is not fully extended. At this time, there is still thrust inside the spring cylinder. In order to prevent the cylinder head from suddenly popping out when the cylinder head is removed, two tie rods on the cylinder are removed in advance and replaced with two extended tie rods. The thrust of the spring cylinder is slowly relieved through the extended tie rods.

[0059] Step 16: Open the cylinder and replace the piston seal ring.

[0060] The direct cause of cylinder leakage is a defect in the cylinder's piston rings, allowing air from the instrument panel to pass through the piston rings and leak out through the breather. After disassembling the actuator, open the cylinder and replace the piston rings.

[0061] Step 17: Motion test and sealing test.

[0062] After replacing the piston rings, perform maintenance on the cylinder and replace the relevant seals. Conduct operational and sealing tests on the actuator at the service location. The test method involves injecting compressed air into the actuator's instrument air duct to check for normal operation and to inspect for any external air leaks.

[0063] Step 18: Reinstate the enforcement agency.

[0064] After the actuator passes the operation and sealing tests, the actuator is reinstalled. Before installation, the actuator is set to the open state under no-load conditions (that is, the bypass valve is switched to the LOCAL state and the hydraulic oil is pressurized by hand pump), and then the actuator coupling sleeve is connected to the ball valve stem.

[0065] For example, the online maintenance method for emergency shut-off valves in high-sulfur gas fields described in this invention was applied to a leak at the vent of the ESDV (gas-liquid linkage actuator) on the A-line of the gas gathering station in the Yuanba Gas Field in Sichuan Province. This ESDV is located in a critical position; offline maintenance would require reducing the acid gas production of the entire gas field by 6 million cubic meters per day before the operation could proceed. Through demonstration and research, online maintenance was achieved, and on-site verification confirmed the feasibility of the online maintenance method. This significantly reduced the limitations of subsequent ESDV fault maintenance, minimized the impact of fault handling on gas field production, ensured timely elimination of potential faults, improved ESDV stability, and guaranteed stable and safe production in the gas field.

[0066] This invention describes a method for online maintenance of emergency shut-off valves in high-sulfur gas fields. This method is applicable to the online maintenance of cylinder failures in the ESDV pneumatic control systems of natural gas field production stations. Against the backdrop of the national new energy strategy, green resource development, and the rapid development of natural gas, its application scenarios are wide-ranging. For example, the Yuanba Gas Field pilot production project and rolling production construction project have a total of 56 such ESDVs. This online maintenance method can also be used for the online maintenance of other similar emergency shut-off valve pneumatic actuator systems, demonstrating good application results and ensuring that potential faults in ESDV pneumatic actuators can be addressed promptly.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for online maintenance of emergency shut-off valves in high-sulfur gas fields, characterized in that, Includes the following steps: S1. Override the ESDV signal in the SIS system, set the bypass valve of the ESDV actuator to local control state, pressurize the actuator to ensure sufficient hydraulic pressure, and put the valve in a forced shielding state. S2. Cut off the air supply to the ESDV instrument, depressurize the air supply line to the actuator, de-energize the solenoid valve, disconnect the instrument air connection line, disconnect the signal cable, and remove the actuator connection bolts. S3. Install a hydraulic jack at each end of the actuator to push the actuator, separate the ball valve stem from the coupling sleeve of the actuator, and use a crane to move the actuator to the maintenance point; S4. Set the bypass valve of the ESDV actuator to remote mode to release the hydraulic cylinder pressure; S5. Measure the distance of the actuator swing shaft, disassemble the actuator cylinder, open the cylinder, and replace the piston sealing ring; S6. Reinstate the enforcement agency.

2. The method for online maintenance of emergency shut-off valves in high-sulfur gas fields according to claim 1, characterized in that, In step S1, the actuator is pressurized by a hand-operated pump until it can no longer be pressurized.

3. The method for online maintenance of emergency shut-off valves in high-sulfur gas fields according to claim 1, characterized in that, In step S2, open the quick relief valve on the actuator panel to release the instrument air pressure in the actuator cavity to 0MPa. After observing that the actuator has no abnormal movement and the hydraulic pressure has not dropped, de-energize the solenoid valve on the SIS cabinet.

4. The method for online maintenance of emergency shut-off valves in high-sulfur gas fields according to claim 1, characterized in that, In step S3, first use a crane to attach the actuator, raise it to allow the hoisting rope to bear the force, and then use a hydraulic jack to push the actuator, with the crane straightening the hoisting rope for assistance.

5. The method for online maintenance of emergency shut-off valves in high-sulfur gas fields according to claim 1, characterized in that, In step S3, a level is placed on the actuator to cooperate with the hydraulic jacks to push, and the two hydraulic jacks lift steadily.

6. The method for online maintenance of emergency shut-off valves in high-sulfur gas fields according to claim 1, characterized in that, In step S5, when disassembling the cylinder, two tie rods on the cylinder are removed in advance and replaced with two extended tie rods. The thrust of the spring cylinder is relieved by extending the tie rods.

7. The method for online maintenance of emergency shut-off valves in high-sulfur gas fields according to claim 1, characterized in that, After step S5, an action test and a sealing test are performed on the actuator.

8. The method for online maintenance of emergency shut-off valves in high-sulfur gas fields according to claim 1, characterized in that, In step S6, before reinstalling the actuator, the actuator is set to the open state under no-load conditions, and then the actuator coupling sleeve is connected to the ball valve stem.

9. The method for online maintenance of emergency shut-off valves in high-sulfur gas fields according to any one of claims 1-8, characterized in that, Before step S1, remove the valve position indicator of the ESDV, remove rust and lubricate the connection between the bushing and the actuator, and set up a mobile scaffold and a simple platform according to the height of the ESDV actuator cylinder for maintenance.