How To Choose The Size of Steel Casing Pipe?

Steel casing pipe size is a key factor to consider when selecting and using steel casing pipe. The size specification parameters directly affect the performance and installation requirements of steel casing pipe. The size of steel casing pipe for different purposes will also be different. Generally speaking, the size of steel casing pipe follows national or regional standards, such as the American National Standard (ANSI), the American Society of Mechanical Engineers Standard (ASME) or the German Industrial Standard (DIN), etc., to ensure the quality and compatibility of the product.

Length selection

The length of the steel casing pipe should be determined according to the length of the protected object and the installation environment. When passing through building structures such as floors and walls, the length of the steel casing pipe should be slightly longer than the part of the protected pipe or cable passing through the structure, generally about 100-200mm longer, to ensure that the passing part is fully covered and plays a good protective role. For example, in a building, when the pipeline passes through a 300mm thick floor, the length of the steel casing pipe can be selected from 500-600mm, so that the steel casing pipe has a certain extension length above and below the floor.

Inner diameter selection

1. Consider the outer diameter of the protected object

The inner diameter of the steel casing pipe should be larger than the outer diameter of the protected object (such as pipes, cables, etc.). Generally speaking, a gap of 10-20mm should be reserved to facilitate installation and possible subsequent maintenance operations. For example, if you want to protect a pipe with an outer diameter of 50mm, the inner diameter of the steel casing pipe can be selected as 60-70mm. Such a gap can prevent the pipe from being squeezed between the pipe and the steel casing pipe when the pipe expands or contracts due to temperature changes, and also provide space for operations such as applying anti-corrosion materials and wrapping insulation materials.

2. Consider the flow rate and permeability of the internal fluid or object

If the steel casing pipe is used to protect the pipeline that transports fluids, the flow requirements of the internal fluid also need to be considered. Too small an inner diameter may limit the flow rate of the fluid and increase the flow velocity and resistance of the fluid. For example, in chemical pipelines, according to the flow formula of the fluid (flow rate, flow velocity, and pipe cross-sectional area), when a certain flow rate needs to be guaranteed, a too small inner diameter will lead to too high a flow velocity and excessive pressure drop, so the appropriate inner diameter should be calculated according to the flow rate to ensure that the fluid can pass smoothly.

Outer diameter selection

1. Consider the limitation of installation space

For example, in places with limited space such as building pipe wells and underground pipeline corridors, the outer diameter of the steel casing pipe should be determined according to the actual installation space. When the installation space is narrow, a steel casing pipe with a smaller outer diameter must be selected to ensure that it can be placed in the predetermined position. At the same time, the operating space of the installation tool should also be considered. For example, when using a crane or forklift to install the steel casing pipe, it is necessary to ensure that there is enough space around for the equipment to operate normally.

2. Consider external loads and protection requirements

When the steel casing pipe needs to withstand external pressure, impact force or protect against harsh external environments, a larger outer diameter can provide better strength and stability. For example, in order to withstand the pressure generated by vehicle driving, the steel casing pipe of the pipeline crossing under the road or railway needs to select a steel casing pipe with a larger outer diameter and sufficient wall thickness to ensure the safety of the pipeline. According to empirical formulas or finite element analysis and other methods, the minimum outer diameter required under a given external load can be calculated to select the appropriate specification.

Wall thickness selection

1. Consider strength requirements

Determine the wall thickness according to the working environment and load of the steel casing pipe. If the steel casing pipe is used for oil wells or chemical pipelines that withstand high pressure, it needs to have sufficient wall thickness to resist the internal pressure. According to the strength theory formula of thin-walled cylinders (for hoop stress, for internal pressure, for outer diameter, for wall thickness), the minimum required wall thickness can be calculated when the internal pressure and allowable hoop stress are known. Generally speaking, the wall thickness of steel casing pipe under high pressure environment may reach 10-20mm.

2. Consider corrosion resistance and service life

In corrosive environments, appropriately increasing the wall thickness can extend the service life of steel casing pipe. Because corrosion usually starts from the surface and gradually erodes inward, thicker wall thickness can provide more margin for corrosion. For example, in marine environments or chemical corrosive media environments, the wall thickness may need to be increased by 2-5mm compared to steel casing pipe in ordinary environments to ensure that the steel casing pipe will not fail due to corrosion within a certain service life. At the same time, measures such as anti-corrosion coatings can also be considered to further improve the corrosion resistance of steel casing pipe.

Summary

Choosing the right steel casing pipe size is essential to ensure the normal operation of the system. Too large or too small a size may lead to installation difficulties, performance degradation or safety hazards. Therefore, when selecting steel casing pipe, be sure to determine the appropriate size specifications based on actual needs and national or regional standards (such as ANSI, ASME, DIN, etc.).