Pipeline engineers must have heard the term “flow lines” over and over again. In the oil and gas industry, Flowlines transport fluids between wellheads and collection stations such as RMS or MSV or refineries and vice versa. In a larger well field, multiple flow lines connect separate wells to a manifold. The current is then transferred from the manifold by a collection line to the pre-process stage or to the transport facility or ship. Flow lines can pass over land or wells under the sea. Flow lines may be buried on the ground or seabed or graded. Pipelines that collect current from multiple flow lines are known as collection lines.
The flow lines are to a specific well and are therefore located at the well site. It may be a metal or non-metal pipe or hose. Most flow lines are usually very short. However, they can run miles on land applications. Collection lines are used when fluid flow lines are routed to a manifold or other process equipment. Flow lines are built on land and may go down to the seabed and have terminal connections that make installation at the wellhead easier.
Flowline design considerations
In general, the following guidelines for flow line design are followed:
1. Temperature and pressure of flow lines:
The operating temperature for flow lines is usually lower. However, the design pressure is very high. Design pressure can be up to 238 bar. The design temperature of flow lines is usually determined by environmental conditions because the process temperature is usually low (in the range of 60 ° C).
The selected design pressure must be greater than the maximum pressure that can be generated at any time during the complete life cycle of the flow line.
2. Flowline design code:
The typical design code followed for flow lines is ASME B31.4 or ASME B31.8. Click here to find the differences between ASME B31.4 and ASME B31.8.
3. mechanical strength:
Depending on the process requirements, the size of the flow lines varies. The wall thickness of these flow lines is determined using the Barlow formula with a design factor of 0.72. In all places, including road crossings. Barlow’s formula assumes a metal tube. Carbon steel flow lines are usually installed above ground, which creates additional flexural and thermal stresses (expansion) not considered by Barlow’s formula. To ensure that the allowable code stresses do not exceed the flow lines due to these additional stresses, the support opening, the size of the expansion loop and the distance between the limit stops, etc. should be designed and checked by pipeline stress engineers.
4. Stream routing:
To create new flow lines, walkways or designated flow lines are followed to minimize land use. For this purpose, flow city maps showing the specified flow line paths are created for each field, and flow lines are programmed to follow these paths only. Opportunities for large audible lines and headlines should always be considered.
Inspection / maintenance access should be considered when planning flow routes. Flowline crossovers should be provided where necessary. The number of roads must be minimized. Space for future flow lines must be maintained. A minimum distance of at least 250 mm between adjacent flow lines is usually required to allow inspection by external MFL instruments. Marker plates to identify the flow line must be provided every 200 meters at the crossings (before and after crossing). Welding on coated flow lines is not permitted.
For GRP or composite pipelines, the following requirements must be considered:
- Check the route
- Topographic data
- Proximity to occupied buildings
- Location and floors of valleys, sand dunes, road crossings, types and densities of traffic, etc. if necessary.
- environmental effects.
- Bending radius recommended by the manufacturer.
- Flow line optimization
5. Flow line material:
Generally, a standard line pipe (API 5L) is used as the metal flow material. Common grades that help metallic materials are API 5L Grade B. Grade X42, X52, and Grade X60.
6. Flow line expansion loops:
Expansion or contraction occurs when the temperature of the flow line material is different from the temperature at the time of installation or due to the effect of pressure and the end cap on the change of direction. Appropriate expansion loops must be considered when designing flow lines. To prevent preferential expansion in one direction, anchors must be provided to ensure that each expansion loop absorbs only the propulsive force for which it is designed.
7. Flowline Connections:
Hook-up refers to the piping required to connect the flow line to the wellhead and production facility. Hook-up piping is designed with ANSI B31.3 standard.
8. Install Flowline:
All flow lines must be properly supported below the pipe support ports to maintain a drop of less than 15 mm. For flow lines that have two-phase current, it is better to have a depression of less than 3 mm. Therefore, the distance should be reduced accordingly. Support should also be provided when crossing existing buried lines.
Buried sections of pipelines passing through existing pipelines and other services should be arranged with a standard ramp or walkway to maintain access to those services. Where the power line passes by the mast, access should be maintained using a standard ramp or walkway.
To absorb expansion stresses at road junctions, it is recommended that carbon steel lines follow a configuration that allows thermal stresses (expansion) to be directed to the rings on both sides of the intersection instead of through the pipe.
The use of low-radius bends in passages (except for those used in ring configuration) is not recommended, as the goose neck interferes with inspection and repair.
New construction lines should be subjected to leakage strength and leakage tests after construction. Flow lines are usually tested at a pressure of 1.25 times the design pressure.
GRP flow lines must always be buried. Particular attention should be paid to support and anchoring where GRP is mounted on supports in places on the pallet.
9. Setting up flow lines:
When the water line has successfully completed the water test, it is connected at both ends and prepared for operational operation, it is operated according to specific start-up methods.
What is a pipeline?
A system of pipes and other components used to transport fluids between factories / facilities. A pipeline extends from the pig trap to the pig trap (including the pig trap), or, if a pig trap is not installed, to the first separation valve within the factory boundaries or a more internal valve, if selected. Pipelines are designed and constructed based on ASME B31.4, ASME B31.8 or ISO 14692 codes.
Difference between pipeline and flowline
Both pipelines and flow lines are designed according to ASME codes B31.4 or B31.8. However, there are certain differences between a flow line and a pipeline.
* All flow lines are part of pipelines. However, pipelines that run between the wellhead and the RMS or MSV or treatment plant are called flow lines.
* In a complete pipeline system, pipelines cover a small part of the pipeline system. Hence, the flow line is a special pipeline whose length is limited to the oil field area. Pipelines, on the other hand, run for miles and sometimes cross different countries.
* Pipelines carry unprocessed crude oil while pipelines carry semi-refined or fully refined fluids.
What is an underwater flow line?
Pipelines that carry fluids between submarine wellheads and surface or manifold installations are called submarine flow lines. They are made of rigid or flexible tubes and generally carry a mixture of refined oil and gas.
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