L represents the nominal pressure level code, A represents 150LB (2Mpa). According to the different dimensions of the pipe cross-section shape can be divided into equal wall thickness profiled seamless steel pipe (code D), unequal wall thickness profiled seamless steel pipe (code BD), variable diameter profiled seamless steel pipe (code BJ).
Seamless profiled tubes are widely used for various structural components, tools and mechanical parts. Compared with round pipe, shaped pipe generally have larger moment of inertia and section modulus, have larger bending and torsion resistance, can greatly reduce the weight of the structure, saving steel.
Pipe - pipe diameter determination when the fluid flow rate is known, the size of the pipe diameter depends on the allowable flow rate or allowable frictional resistance (pressure drop). The pipe diameter is small for high flow rates, but the pressure drop value increases. Therefore, when the flow rate is large, you can save the pipeline infrastructure investment, but pumps and compressors and other power equipment operating energy costs increase.
In addition, if the flow rate is too large, there may bring some other unfavorable factors. Therefore, the pipe diameter should be based on construction investment, operating costs and other technical factors to consider the decision.
Expanded Information:
Pipe - Pipe Laying p>Pipeline - pipeline laying of the city's water supply, drainage, heating, gas pipeline trunk and long-distance oil and gas pipelines are mostly laid in the ground, while the factory's process pipeline for ease of operation and maintenance more laid on the ground. Pipeline passage, support, slope and drainage exhaust, compensation, insulation and heating, corrosion and cleaning, identification and painting and safety, whether for the ground or underground laying is an important issue. The pipeline may be subjected to many kinds of external forces, including its own weight (pipe, valve, pipe joints, insulation and the weight of the fluid inside the pipe), the pressure of the fluid acting on the end of the pipe thrust, wind and snow load, soil pressure, thermal expansion and contraction of thermal stress caused by thermal expansion and contraction, vibration load and seismic hazards and so on. In order to ensure the strength and rigidity of the pipeline, it is necessary to set up a variety of support (hanging) frame, such as movable bracket, fixed bracket, guided bracket and spring bracket. The setting of the bracket is decided according to the pipe diameter, material, pipe wall thickness and load and other conditions. Fixed bracket is used to control the thermal elongation of the pipe in segments and make the expansion joint work evenly. The guide bracket makes the pipe move only axially. Baidu Encyclopedia - Pipelines