Pressure regulation and overpressure protection process method for oil product receiving terminal

Abstract

The invention discloses a pressure regulation and overpressure protection process method for an oil product receiving terminal, and relates to the technical field of medium and long distance oil pipelines. A pressure regulation and overpressure protection process method of an oil product receiving terminal divides a pressure protection gradient into five levels, the pressure protection gradient is based on a pressure cascade protection principle, a basic process control system, an ESD emergency shutdown system and mechanical protection measures are integrated, and accurate pressure regulation and comprehensive overpressure protection of a pipeline and an equipment system are achieved. The process flow is simple and practical and easy to understand and implement, the functions of split-range pressure adjustment, thermal release mechanical protection, safety interlocking and water attack release protection are achieved, and skid-mounted design, production and manufacturing are easy to achieve.

Description

Technical Field

[0001] This invention relates to the field of medium- and long-distance oil pipeline technology, specifically to a pressure regulation and overpressure protection process for an oil receiving terminal. Background Technology

[0002] As the core carrier for long-distance transportation of crude oil and refined oil, the pressure stability of oil pipelines directly determines transportation efficiency, pipeline safety, and service life. During oil transportation, factors such as terrain undulations, flow fluctuations, pump and valve start-up and shutdown, and water hammer effect within the pipeline can easily cause abnormal pressure fluctuations. Too low a pressure leads to insufficient oil transportation power and air resistance within the pipeline, while too high a pressure exceeds the pipeline's design pressure limit, potentially causing major safety accidents such as pipeline rupture, oil leakage, fire, and explosion.

[0003] Against this backdrop, pressure regulation and overpressure protection technologies have become an indispensable key component of oil pipeline systems, and their development is closely related to the iteration of pipeline transportation technologies and the upgrading of safety standards. Summary of the Invention

[0004] The purpose of this invention is to provide a pressure regulation and overpressure protection process for an oil receiving terminal, aiming to solve the problems of complex process flow and insufficient reliability of overpressure protection in existing oil pipeline systems.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A pressure regulation and overpressure protection process for an oil receiving terminal divides the pressure protection gradient into five levels. The pressure protection gradient is based on the principle of pressure cascade protection and integrates the basic process control system, ESD emergency shutdown system and mechanical protection measures to achieve precise pressure regulation and comprehensive overpressure protection for pipeline and equipment systems. The five pressure levels are in ascending order of numerical value as follows: inlet pressure P1, inlet back pressure valve downstream pressure P2, heat relief pressure P3, safety shut-off pressure P4, and water hammer relief pressure P5, and satisfy P1 < P2 < 0.85P3 < 0.85P4 < P5 < maximum allowable transient operating pressure of the pipeline system.

[0007] The first stage is the inlet pressure regulation, which is used to adjust the oil inlet pressure to be no lower than the pressure set value P1, to meet the metering accuracy requirements of the inlet trade metering flow meter, and to avoid metering deviation caused by insufficient pressure. Closed-loop regulation is achieved through the opening of the back pressure regulating valve and the feedback signal of the pressure transmitter in front of the valve.

[0008] The second stage is the pressure regulation after the inlet back pressure valve, which is used to stabilize the pressure after the valve and ensure that it does not exceed the pressure set value P2. Closed-loop regulation is achieved through the opening of the back pressure regulating valve and the feedback signal of the pressure transmitter after the valve.

[0009] The third level is the thermal relief pressure P3, and the corresponding equipment is the thermal expansion relief valve. It is used to prevent the oil in the closed section from triggering the safety interlock due to thermal expansion. The value is 80% of the safety shut-off valve set pressure P4.

[0010] The fourth level is the safety shut-off pressure P4, and the corresponding equipment is the safety shut-off valve, which is used to urgently isolate the upstream high-pressure area. The P4 pressure setpoint is higher than P2 and P3, but lower than P5. The safety shut-off valve is connected to the user's SIS system or controlled by an independent PLC, and is equipped with 2 or 3 pressure transmitters that meet SIL2 certification to work together to achieve pressure monitoring and interlock control. It is also necessary to verify whether it is connected to the SIS system through HAZOP analysis.

[0011] The fifth level is the water hammer pressure relief pressure P5, and the corresponding equipment is the water hammer pressure relief valve, which is used to deal with the risk of rapid pressure rise caused by transient water hammer. The set pressure of the water hammer pressure relief valve must be confirmed by the transient hydraulic calculation report and must be higher than P4 and lower than the maximum allowable transient working pressure of the pipeline system.

[0012] Furthermore, the first-stage pressure P1 and the second-stage pressure P2 can be controlled separately using the same regulating valve. When the upstream pressure of the back pressure regulating valve is ≤ P1, the back pressure regulating valve is controlled by the upstream pressure transmitter to reduce its opening and increase the upstream pressure. When the downstream pressure of the back pressure regulating valve is ≥ P2, the back pressure regulating valve is controlled by the downstream pressure transmitter to reduce its opening and decrease the downstream pressure. Here, P1 must meet the flow meter accuracy requirements, following the formula:

[0013] P1≥2ΔP+1.25Ps,

[0014] Where ΔP is the pressure loss of the flow meter, and Ps is the saturated vapor pressure of the oil at the operating temperature.

[0015] Furthermore, the fourth-stage safety shut-off valve is equipped with two or three pressure transmitters that meet SIL2 certification to work together to achieve pressure monitoring and interlock control, and it is necessary to verify whether it is connected to the SIS system through HAZOP analysis.

[0016] Furthermore, for the fifth-stage water hammer relief valve, either nitrogen-loaded or pilot-operated type should be selected. If pilot-operated type is selected, the impact of the delay on the protection effect must be verified through transient calculation.

[0017] Furthermore, the discharge medium of the thermal expansion relief valve, the isolation range of the safety shut-off valve, and the discharge path of the water hammer relief valve are all preset through pipelines, and the discharge medium of the water hammer relief valve assembly can be introduced into a receiving tank or a sludge tank.

[0018] Furthermore, the basic process control system collects real-time parameters through pressure transmitters and flow meters, and combines them with a pressure indicator controller to achieve automatic adjustment of P1 and P2, while maintaining the metering accuracy of the flow meter during the adjustment process.

[0019] Furthermore, the oil products include light gasoline, jet fuel, and diesel, suitable for terminal unloading scenarios in medium- and long-distance oil pipelines.

[0020] Furthermore, the set pressure P3 of the thermal expansion relief valve and the set pressure P4 of the safety shut-off valve satisfy P3 < 0.85P4, thus preventing the safety shut-off valve from being triggered under thermal expansion conditions.

[0021] The beneficial effects of this invention are as follows: the process flow of this application is simple, practical, easy to understand and implement, and it realizes the functions of segmented pressure regulation, thermal venting mechanical protection, safety interlock and water hammer venting protection respectively, and it is easy to realize skid-mounted design, production and manufacturing.

[0022] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the overall process of an embodiment of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Please refer to a preferred embodiment of this application for a pressure regulation and overpressure protection process method for an oil receiving terminal. The pressure protection gradient is divided into five levels. The pressure protection gradient is based on the principle of pressure cascade protection and integrates the basic process control system, ESD emergency shutdown system and mechanical protection measures to achieve precise pressure regulation and comprehensive overpressure protection for pipeline and equipment systems. The five pressure levels are in ascending order of numerical value as follows: inlet pressure P1, inlet back pressure valve downstream pressure P2, heat release pressure P3, safety shut-off pressure P4, and water hammer pressure relief pressure P5, and satisfy P1 < P2 < 0.85P3 < 0.85P4 < P5 < maximum allowable transient operating pressure of the pipeline system.

[0028] The first stage is the inlet pressure regulation, which is used to adjust the oil inlet pressure to be no lower than the pressure set value P1, to meet the metering accuracy requirements of the inlet trade metering flow meter, and to avoid metering deviation caused by insufficient pressure. Closed-loop regulation is achieved through the opening of the back pressure regulating valve and the feedback signal of the pressure transmitter in front of the valve.

[0029] The second stage is the pressure regulation after the inlet back pressure valve, which is used to stabilize the pressure after the valve and ensure that it does not exceed the pressure set value P2. Closed-loop regulation is achieved through the opening of the back pressure regulating valve and the feedback signal of the pressure transmitter after the valve.

[0030] The third level is the thermal relief pressure P3, and the corresponding equipment is the thermal expansion relief valve. It is used to prevent the oil in the closed section from triggering the safety interlock due to thermal expansion. The value is 80% of the safety shut-off valve set pressure P4.

[0031] The fourth level is the safety shut-off pressure P4, and the corresponding equipment is the safety shut-off valve, which is used to urgently isolate the upstream high-pressure area. The P4 pressure setpoint is higher than P2 and P3, but lower than P5. The safety shut-off valve is connected to the user's SIS system or controlled by an independent PLC, and is equipped with 2 or 3 pressure transmitters that meet SIL2 certification to work together to achieve pressure monitoring and interlock control. It is also necessary to verify whether it is connected to the SIS system through HAZOP analysis.

[0032] The fifth level is the water hammer pressure relief pressure P5, and the corresponding equipment is the water hammer pressure relief valve, which is used to deal with the risk of rapid pressure rise caused by transient water hammer. The set pressure of the water hammer pressure relief valve must be confirmed by the transient hydraulic calculation report and must be higher than P4 and lower than the maximum allowable transient working pressure of the pipeline system.

[0033] The first-stage pressure P1 and the second-stage pressure P2 can be controlled separately using the same regulating valve. When the upstream pressure of the back pressure regulating valve is ≤ P1, the back pressure regulating valve is controlled by the upstream pressure transmitter, reducing its opening to increase the upstream pressure. When the downstream pressure of the back pressure regulating valve is ≥ P2, the back pressure regulating valve is controlled by the downstream pressure transmitter, reducing its opening to decrease the downstream pressure. P1 must meet the flow meter accuracy requirements, following the formula:

[0034] P1≥2ΔP+1.25Ps,

[0035] Where ΔP is the pressure loss of the flow meter, and Ps is the saturated vapor pressure of the oil at the operating temperature.

[0036] The fourth-level safety shut-off valve is equipped with two or three pressure transmitters that meet SIL2 certification to work together to achieve pressure monitoring and interlock control, and needs to be verified by HAZOP analysis to determine whether it is connected to the SIS system.

[0037] For the fifth-stage water hammer relief valve, either nitrogen-loaded or pilot-operated type should be selected. If pilot-operated type is selected, the impact of the delay on the protection effect must be verified through transient calculation.

[0038] The discharge medium of the thermal expansion relief valve, the isolation range of the safety shut-off valve, and the discharge path of the water hammer relief valve are all preset through pipelines. The discharge medium of the water hammer relief valve group can be introduced into the receiving tank or the sludge tank.

[0039] The basic process control system collects real-time parameters through pressure transmitters and flow meters, and combines them with a pressure indicating controller to achieve automatic adjustment of P1 and P2, while maintaining the metering accuracy of the flow meter during the adjustment process.

[0040] The petroleum products include light gasoline, jet fuel, and diesel, suitable for terminal unloading scenarios in medium- and long-distance oil pipelines.

[0041] The set pressure P3 of the thermal expansion relief valve and the set pressure P4 of the safety shut-off valve satisfy P3 < 0.85P4 to avoid triggering the safety shut-off valve under thermal expansion conditions.

[0042] Because the safety shut-off valve has a closing response time on the order of seconds, it cannot cope with the millisecond-level pressure rise caused by water hammer and is only suitable for overpressure protection caused by other reasons.

[0043] Explanation of the attached image:

[0044] FT: Oil Trade Metering Flow Meter

[0045] PV: Pressure regulating valve, used for basic process control. It employs a split-range control scheme: 1) When the upstream pressure is less than or equal to P1, PV is controlled by PT1, reducing the opening and increasing the upstream pressure. This is often used in low-flow or low-pressure conditions where the oil level in the tank is low; 2) When the downstream pressure is greater than or equal to P1, PV is controlled by PT2, reducing the opening and increasing the downstream pressure. This is useful for situations where downstream fluid flow is obstructed, causing pressure buildup or other issues.

[0046] XV: Emergency shut-off valve, used for high-pressure safety interlock protection to protect downstream low-pressure system pipelines and equipment; used in downstream high-pressure situations, often in emergency situations where downstream flow is rapidly increasing, to quickly shut off and isolate high-pressure fluid.

[0047] TSV: Thermal relief safety valve, used for thermal relief in a closed section. Prevents high-pressure safety interlocks from being triggered by external factors such as solar radiation.

[0048] SV: Water hammer relief valve, used to prevent rapid pressure increases in pipelines caused by water hammer, with changes typically on the order of milliseconds. In such cases, traditional fast-acting shut-off and regulating protection devices, whose actions are usually on the order of seconds, cannot be used for water hammer protection.

[0049] III. Explanation of the Core Logic of the Attached Drawings

[0050] 1) Adjustment process:

[0051] Oil enters the station → FT metering (P1 is required to ensure accuracy) → PV valve split-range adjustment (PT1 / PT2 feedback) → stabilizes at P2 and enters the downstream pipeline network;

[0052] 2) Protection Logic:

[0053] Normal overpressure (operational fluctuation): PV valve adjustment → P2 over-limit trigger, TSV (P3) depressurization;

[0054] Fault overpressure (regulating valve jamming / hysteresis): P4 over-limit trigger, XV valve emergency shut-off;

[0055] Transient water hammer (millisecond-level pressure rise): P5 over-limit triggers SV valve for rapid pressure relief to prevent pipeline rupture;

[0056] Equipment coordination: Three-level protection of split-range regulation (PV) + mechanical venting (TSV / SV) + safety interlock (XV) covers overpressure risks in all scenarios of steady state / transient, operation / fault.

[0057] In summary, this invention provides a pressure regulation and overpressure protection process for an oil receiving terminal. This method has a simple and practical process flow, is easy to understand and implement, and achieves functions such as segmented pressure regulation, thermal venting mechanical protection, safety interlocking, and water hammer venting protection. Furthermore, it is easy to implement in skid-mounted design, production, and manufacturing.

[0058] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A process for pressure regulation and overpressure protection in an oil receiving terminal, characterized in that, The pressure protection gradient is divided into five levels. Based on the principle of pressure cascade protection, the pressure protection gradient integrates the basic process control system, ESD emergency shutdown system and mechanical protection measures to achieve precise pressure regulation and comprehensive overpressure protection for pipeline and equipment systems. The five pressure levels are in ascending order of numerical value as follows: inlet pressure P1, inlet back pressure valve downstream pressure P2, heat relief pressure P3, safety shut-off pressure P4, and water hammer relief pressure P5, and satisfy P1 < P2 < 0.85P3 < 0.85P4 < P5 < maximum allowable transient operating pressure of the pipeline system. The first stage is the inlet pressure regulation, which is used to adjust the oil inlet pressure to be no lower than the pressure set value P1, to meet the metering accuracy requirements of the inlet trade metering flow meter, and to avoid metering deviation caused by insufficient pressure. Closed-loop regulation is achieved through the opening of the back pressure regulating valve and the feedback signal of the pressure transmitter in front of the valve. The second stage is the pressure regulation after the inlet back pressure valve, which is used to stabilize the pressure after the valve and ensure that it does not exceed the pressure set value P2. Closed-loop regulation is achieved through the opening of the back pressure regulating valve and the feedback signal of the pressure transmitter after the valve. The third level is the thermal relief pressure P3, and the corresponding equipment is the thermal expansion relief valve. It is used to prevent the oil in the closed section from triggering the safety interlock due to thermal expansion. The value is 80% of the safety shut-off valve set pressure P4. The fourth level is the safety shut-off pressure P4, and the corresponding equipment is the safety shut-off valve, which is used to urgently isolate the upstream high-pressure area. The P4 pressure setpoint is higher than P2 and P3, but lower than P5. The safety shut-off valve is connected to the user's SIS system or controlled by an independent PLC, and is equipped with 2 or 3 pressure transmitters that meet SIL2 certification to work together to achieve pressure monitoring and interlock control. It is also necessary to verify whether it is connected to the SIS system through HAZOP analysis. The fifth level is the water hammer pressure relief pressure P5, and the corresponding equipment is the water hammer pressure relief valve, which is used to deal with the risk of rapid pressure rise caused by transient water hammer. The set pressure of the water hammer pressure relief valve must be confirmed by the transient hydraulic calculation report and must be higher than P4 and lower than the maximum allowable transient working pressure of the pipeline system.

2. The pressure regulation and overpressure protection process method for an oil receiving terminal as described in claim 1, characterized in that, The first-stage pressure P1 and the second-stage pressure P2 can be controlled separately using the same regulating valve. When the upstream pressure of the back pressure regulating valve is ≤ P1, the back pressure regulating valve is controlled by the upstream pressure transmitter, reducing its opening to increase the upstream pressure. When the downstream pressure of the back pressure regulating valve is ≥ P2, the back pressure regulating valve is controlled by the downstream pressure transmitter, reducing its opening to decrease the downstream pressure. P1 must meet the flow meter accuracy requirements, following the formula: P1≥2ΔP+1.25Ps, Where ΔP is the pressure loss of the flow meter, and Ps is the saturated vapor pressure of the oil at the operating temperature.

3. The pressure regulation and overpressure protection process method for an oil receiving terminal as described in claim 1, characterized in that, The fourth-level safety shut-off valve is equipped with two or three pressure transmitters that meet SIL2 certification to work together to achieve pressure monitoring and interlock control, and needs to be verified by HAZOP analysis to determine whether it is connected to the SIS system.

4. The pressure regulation and overpressure protection process method for an oil receiving terminal as described in claim 1, characterized in that, For the fifth-stage water hammer relief valve, either nitrogen-loaded or pilot-operated type should be selected. If pilot-operated type is selected, the impact of the delay on the protection effect must be verified through transient calculation.

5. The pressure regulation and overpressure protection process method for an oil receiving terminal as described in claim 1, characterized in that, The discharge medium of the thermal expansion relief valve, the isolation range of the safety shut-off valve, and the discharge path of the water hammer relief valve are all preset through pipelines. The discharge medium of the water hammer relief valve group can be introduced into the receiving tank or the sludge tank.

6. The pressure regulation and overpressure protection process method for an oil receiving terminal as described in claim 1, characterized in that, The basic process control system collects real-time parameters through pressure transmitters and flow meters, and combines them with a pressure indicating controller to achieve automatic adjustment of P1 and P2, while maintaining the metering accuracy of the flow meter during the adjustment process.

7. The pressure regulation and overpressure protection process method for an oil receiving terminal as described in claim 1, characterized in that, The petroleum products include light gasoline, jet fuel, and diesel, suitable for terminal unloading scenarios in medium- and long-distance oil pipelines.

8. The pressure regulation and overpressure protection process method for an oil receiving terminal as described in claim 1, characterized in that, The set pressure P3 of the thermal expansion relief valve and the set pressure P4 of the safety shut-off valve satisfy P3 < 0.85P4 to avoid triggering the safety shut-off valve under thermal expansion conditions.

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