Casing Pipe: The Circular Guardian Of Modern Infrastructure

Core Concept Analysis

What is Casing Pipe

Casing Pipe is a ring-shaped cross-section protection pipe specially designed for wrapping critical pipelines. Its main purpose is to provide structural protection, which is different from traditional transmission pipelines. According to the API 5CT standard, the casing range is 4 inches to 48 inches, and the sealing pipe body must have a compressive strength of ≥10,000 psi.

Difference from collecting main

A brief history of material evolution

Materials have evolved from traditional carbon steel to modern composite materials, and the protective performance has been greatly improved. Compared with the original materials, the improvement has reached 300%.
First generation (1950s): ASTM A53 Gr.B carbon steel pipe was the most commonly used structural material at the time. Although the yield strength reached ≥240MPa, it was still far from enough in a highly corrosive environment.
Second generation (1980s): The introduction of N80 alloy steel was a milestone in major progress in materials science, and the hydrogen sulfide stress corrosion resistance index was increased to ≥85%.
Third generation (2010s): The rise of glass fiber reinforced epoxy resin reduced weight and extended life to five times the previous one. Current mainstream material selection matrix:

Oil and gas extraction: The “Great Wall of Steel” of thousand-meter-deep wells

In shale gas mining, the casing system needs to build a four-level protection system:
Conductor casing (30-150 meters): ensure the stability of the well wall during excavation and prevent surface collapse.
Surface casing (300-800 meters): prevent possible pollution during mining
Technical casing (1500-3000 meters): block the high-pressure layer to prevent high-pressure gas or fluid from penetrating upward.
Production casing (>3500 meters): It is the deepest casing and needs to be designed for H2S corrosion.

Urban underground pipe network: the “flexible joints” of the earthquake-resistant system

In underground pipe networks in seismically active zones, casings must achieve level 3 seismic resistance
Base isolation: In order to absorb the vibration caused by seismic waves, rubber bearings are usually used to achieve ±15 cm displacement compensation during earthquakes.
Joint flexibility: The design of the joint must be flexible enough to cope with the displacement during earthquakes, and the design of the bellows allows 30° angle deflection.
Stress dissipation: The introduction of a tapered transition section effectively reduces 90% of stress concentration.

Coking equipment: “Life channel” in high temperature and highly toxic environment

In the gas purification system, the casing must meet the following requirements:
Temperature control: 50mm ceramic fiber layer lining to maintain the outer wall temperature ≤80℃
Tilt accuracy: 6-10° precise slope to ensure smooth tar diversion
Anti-leakage design: double-layer casing structure, interlayer filled with nitrogen to monitor pressure changes