Production of Tees Used for Underwater Oil and Gas
Posted: 05/10/2024 07:42:46 Hits: 8
1. Introduction
As underwater oil and gas develop towards deep water, the seabed operating environment faced by underwater production facilities is becoming increasingly severe. The complexity of oil and gas components puts higher and higher requirements for strength and corrosion resistance on underwater production system components. Underwater systems are mainly composed of pipelines, valves, control systems, flow meters and other facilities. Pipe fittings such as tees, elbows, and reducers need to be used to properly plan the design locations of underwater systems and pipe ends due to the requirements for the spatial distribution of valves, process pipelines, and connectors.
2. An introduction to PLET or PLEM
PLEM or PLET is an important part of the underwater production system. It is the equipment used to receive, collect, and control the flow from different underwater production wellheads. They are a necessity developed for deep sea oil and gas fields. As a typical deepwater underwater production facility, the environment, installation, inspection, maintenance, production and other requirements need to be considered when designing underwater manifolds to ensure safe, reliable and stable operation during the service life. The production and manufacturing of related parts must be strictly controlled in accordance with the design and technical requirements due to the high maintenance costs of underwater manifolds and underwater pipe ends. Process pipeline fittings used in underwater manifolds, underwater pipe ends and other facilities are mainly made of ASTM A694 F65 forgings. Forged pipes are processed into pipe fittings using a forming process, and CRA can be used internally to improve corrosion resistance.
3. ASTM A694 F65
ASTM A694 is carbon steel and alloy steel forgings for high-pressure transmission pipe flanges, fittings, valves and parts. It is mainly used for manufacturing flanges for high-pressure pipelines in marine, oil, and natural gas field to transport toxic gases such as hydrogen sulfide (H2S).
The base pipes produced and processed by tees and elbows are forged pipes. The production process includes drawing of forging, inspections of steel ingots, forging, heat treatment, rough turning, fine turning, dimensional inspection and non-destructive inspection. Dimensional inspection and non-destructive inspection after finishing turning should be well paid attention to, which will have a greater impact on subsequent processes.
The manufacturing process of tees
Underwater production systems are essential facilities for offshore oil and gas development and oil and gas transportation processes, especially in deepwater offshore oil and gas field development projects. The underwater pipeline terminals and manifolds are connected to the submarine pipelines. The pipe fittings used include tees, elbows and reducers, and they are made from ASTM A694 F65. In order to improve corrosion resistance, these pipe fittings are mostly made of internal cladding nickel-based alloy 625.
The manufacturing processes of tees are re-inspection of welding materials, re-inspection of forged pipe sizes, mold plus mud pressing, quenching and tempering heat treatment, surfacing welding, non-destructive inspection, dimensional inspection, physical and chemical testing, etc.
4.1 Re-inspection of raw materials
Raw materials mainly include forged pipes and welding materials. Forged pipes are mainly inspected for dimensions, such as wall thickness, length, etc. Welding materials are mainly inspected for chemical composition and mechanical properties. Forged pipes should be inspected one by one, and welding materials should be re-inspected according to batch number. After passing the re-inspection, the material can be used for subsequent production. Considering that the wall thickness of the branch pipe will be thinned in the processing process of tees, the wall thickness of the forged pipe should be slightly greater than that of the finished branch of tees.
4.2 Mud pressing process, quenching and tempering heat treatment
The mud pressing process of the tee is a forming process that expands the branch pipe through the axial compensation of the metal. The process is that after the forged pipe is cut, it is normalized before forming to reduce the hardness of the forged pipe. Fill the tube blank with soil and tamp it down. A special hydraulic press and a special pressing mold are used. Through the movement of the hydraulic press slider, the volume of the soil in the forged pipe becomes smaller after being squeezed. As the volume of the soil becomes smaller, the pressure increases. When the pressure required for the expansion of the tee branch pipe is reached, the metal flows along the inner cavity of the mold by the action of the pressure of the soil in the forged pipe, and then expands the branch pipe. When the slide of the hydraulic press reaches the predetermined stroke, the mud pressing process of the tee is completed. The outer mold is opened; the inner mold is withdrawn, and the internal soil and other media are removed. The specific number of times that mud molding needs to be performed depends on the process, but tempering heat treatment should be performed before each mud molding. Among them, the details of the tee after mud pressing are shown in Figure 1.
Figure 1 Tees formed by mud pressing
After the tee is formed by mud pressing, a preliminary dimensional inspection is carried out, focusing on checking whether the length of the straight pipe meets the requirements. After passing the inspection, mechanical cutting and tempering heat treatment are performed. Quenching and tempering heat treatment include quenching and tempering, focusing on key parameters such as heating rates, holding temperatures, and holding time.
In the production process, a tee is used for destructive testing of mechanical properties. The tested tee should be installed at the same time as the product tee. The test tee should undergo normalizing heat treatment, quenching and tempering heat treatment and other processes at the same time as the product tee before mud pressing.
3. ASTM A694 F65
ASTM A694 is carbon steel and alloy steel forgings for high-pressure transmission pipe flanges, fittings, valves and parts. It is mainly used for manufacturing flanges for high-pressure pipelines in marine, oil, and natural gas field to transport toxic gases such as hydrogen sulfide (H2S).
The base pipes produced and processed by tees and elbows are forged pipes. The production process includes drawing of forging, inspections of steel ingots, forging, heat treatment, rough turning, fine turning, dimensional inspection and non-destructive inspection. Dimensional inspection and non-destructive inspection after finishing turning should be well paid attention to, which will have a greater impact on subsequent processes.
The manufacturing process of tees
Underwater production systems are essential facilities for offshore oil and gas development and oil and gas transportation processes, especially in deepwater offshore oil and gas field development projects. The underwater pipeline terminals and manifolds are connected to the submarine pipelines. The pipe fittings used include tees, elbows and reducers, and they are made from ASTM A694 F65. In order to improve corrosion resistance, these pipe fittings are mostly made of internal cladding nickel-based alloy 625.
The manufacturing processes of tees are re-inspection of welding materials, re-inspection of forged pipe sizes, mold plus mud pressing, quenching and tempering heat treatment, surfacing welding, non-destructive inspection, dimensional inspection, physical and chemical testing, etc.
4.1 Re-inspection of raw materials
Raw materials mainly include forged pipes and welding materials. Forged pipes are mainly inspected for dimensions, such as wall thickness, length, etc. Welding materials are mainly inspected for chemical composition and mechanical properties. Forged pipes should be inspected one by one, and welding materials should be re-inspected according to batch number. After passing the re-inspection, the material can be used for subsequent production. Considering that the wall thickness of the branch pipe will be thinned in the processing process of tees, the wall thickness of the forged pipe should be slightly greater than that of the finished branch of tees.
4.2 Mud pressing process, quenching and tempering heat treatment
The mud pressing process of the tee is a forming process that expands the branch pipe through the axial compensation of the metal. The process is that after the forged pipe is cut, it is normalized before forming to reduce the hardness of the forged pipe. Fill the tube blank with soil and tamp it down. A special hydraulic press and a special pressing mold are used. Through the movement of the hydraulic press slider, the volume of the soil in the forged pipe becomes smaller after being squeezed. As the volume of the soil becomes smaller, the pressure increases. When the pressure required for the expansion of the tee branch pipe is reached, the metal flows along the inner cavity of the mold by the action of the pressure of the soil in the forged pipe, and then expands the branch pipe. When the slide of the hydraulic press reaches the predetermined stroke, the mud pressing process of the tee is completed. The outer mold is opened; the inner mold is withdrawn, and the internal soil and other media are removed. The specific number of times that mud molding needs to be performed depends on the process, but tempering heat treatment should be performed before each mud molding. Among them, the details of the tee after mud pressing are shown in Figure 1.
Figure 1 Tees formed by mud pressing
After the tee is formed by mud pressing, a preliminary dimensional inspection is carried out, focusing on checking whether the length of the straight pipe meets the requirements. After passing the inspection, mechanical cutting and tempering heat treatment are performed. Quenching and tempering heat treatment include quenching and tempering, focusing on key parameters such as heating rates, holding temperatures, and holding time.
In the production process, a tee is used for destructive testing of mechanical properties. The tested tee should be installed at the same time as the product tee. The test tee should undergo normalizing heat treatment, quenching and tempering heat treatment and other processes at the same time as the product tee before mud pressing.
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