Both spiral steel pipes and steel plate rolled pipes are welded steel pipes, but they differ significantly in production processes.
Spiral steel pipes are made from steel coil as raw material, formed through extrusion at normal temperature, and welded using the automatic double-wire double-sided submerged arc welding process to create spiral seam steel pipes. The length of spiral steel pipes is typically 12 meters, and they are delivered and measured by length, with specifications generally above 219mm.
Steel plate rolled pipes adopt the tee welding process and can produce steel pipes with diameters above 400mm and wall thicknesses of 8-100mm. They are usually not made to a fixed length and are typically delivered and measured by weight.
The product standards for steel plate rolled pipes include GB/T50205-2001, GB/T3092-2001, etc. Rolled pipes are widely used in petroleum, chemical, natural gas transmission, pile driving, urban water supply, heating, gas supply, and other engineering applications.
The price of steel plate rolled pipes of the same specifications is higher than spiral steel pipes. Steel plate rolled pipes are mainly used in industries that do not conform to standard specifications or require thicker wall thicknesses.
Spiral steel pipes do not have inherent limitations on their service life; the service life is mainly related to the operating environment and production process. To extend the service life of spiral steel pipes operating in harsh environments, corrosion protection is applied to the outer wall and inner diameter of the pipes.
Anti-corrosion spiral steel pipes refer to pipes processed through anti-corrosion techniques, which can effectively prevent or slow down corrosion caused by chemical or electrochemical reactions during transportation and use. Anti-corrosion spiral steel pipes can effectively prevent or slow down corrosion, extend the service life of steel pipes, and reduce operation costs.
Commonly used corrosion-resistant coatings for steel pipelines in China include petroleum asphalt, PE jackets and PE foam jackets, epoxy coal tar, coal tar enamel, epoxy powder, and three-layer composite structures, epoxy coal tar cold-applied tape (PF type), rubber-plastic epoxy coal tar cold-applied tape (RPC type), etc. Currently, the most widely used pipeline corrosion protection methods are three-layer PE composite structures, single-layer epoxy powder, PF type cold-applied tape, and RPC type cold-applied tape.
Petroleum asphalt is widely available and low-priced. However, labor conditions are poor, quality is difficult to guarantee, and environmental pollution is severe.
Epoxy coal tar is easy to operate, but the coating has a long curing time, is greatly affected by the environment, and is not suitable for field operations; it is difficult to construct at temperatures below 10°C.
Epoxy powder corrosion protection adopts electrostatic spraying, which has good fusion and strong adhesion with pipes protected by the same material. However, epoxy powder has poor water resistance (high water absorption rate, reaching 0.83%), posing challenges for cathodic protection design. High requirements for on-site equipment, difficult operation, and quality control.
3PE heat-shrinkable material provides strong sealing, high mechanical strength, strong water resistance, stable quality, convenient construction, good applicability, and no environmental pollution for pipeline corrosion protection. PE has a low water absorption rate (less than 0.01%) and combines high epoxy strength, low PE water absorption, and good flexibility of hot-melt adhesive, offering high corrosion protection reliability. The disadvantage is the high cost compared to other joint coating materials.
PF type and RPC type cold-applied tapes are easy to construct, and the three types of formulated adhesives allow PF type epoxy coal tar cold-applied tape to be used in any environment, season, or temperature condition.
The characteristics of cold-applied tape and 3PE heat-shrinkable tape are that they are suitable for pipelines with various material body corrosion protection layers, while other methods are suitable for pipelines with the same or similar material body corrosion protection layers.
With development, some pipelines require insulation along with corrosion protection. Petroleum is a complex mixture that easily corrodes pipelines, making corrosion protection necessary. However, refined oil pipelines also require insulation in addition to corrosion protection. In northeastern regions and during winter, thermal expansion and contraction can cause pipelines to freeze and crack, affecting stable supply.
