Lined pipe from the inner lining is the wear layer, the insulating layer, steel wall. Currently lined pipeline network to use more double-lined shells, no shells steel and fiber-reinforced double lining, no single hexagonal mesh of steel fiber reinforced lining and other forms. Because after using the lining of the pipeline stress, stiffness had a significant impact.
Pressure from the pipe, weight hoop stress and external load generated axial stress (collectively positive stress) and shear stress external force and moment equilibrium conditions should be met. Excessive stress deformation generated by the unrestricted increases (ie, no self-limiting), resulting in damage. This stress state belongs to a membrane stress. Bending stress caused by the weight and the external load is a bending stress. Bending stresses in the pipe section is a straight line distribution. A side cross-sectional tensile stress, compressive stress and the other side, the neutral axis through the center of the stress is zero. When the pipe wall began to enter the yield, near the neutral axis is still in elastic state. So can continue to carry the load, and stress redistribution. This stress can be applied to analyze the concept of ultimate load, allowing a higher state than the last film allowable stress values. Generally for safety reasons, the provisions can not exceed pipe stress once the allowable stress. A stress value of less than or equal to the allowable operating temperature stress, the pipeline can operate safely.
Due to the weight of the pipe lining increases, leading to a sustained external load stress pipelines have very different before and after the liner, therefore, need to be checking. In the continuous external load stresses, bending stress weight caused the greatest impact on pipe stress. In the design of large-diameter pipe temperature, cold-wall design is the use of thermal insulation lining materials to make pipe wall temperature far below the temperature of the medium. Pipe thermal stress levels due to the decrease of temperature dropped significantly after the liner according to the strength properties of concrete lining material shows its minimum tensile strength, compressive strength greater. Thermal expansion of the liner pipe stress is shared pipe and liner materials in thermal expansion stress is tensile stress, tensile strength due to poor lining materials, thermal stress of steel tubes little effect. When the thermal expansion stress is compressive stress, the compressive strength of the liner material is better due to the compressive stress is mainly composed of the lining material balance, thermal stress of steel greater impact.
Post time: Aug-28-2019