What is the difference between ERW pipe and SSAW?

1) Different concepts

1. ERW pipe, also known as "electric resistance straight seam welded pipe", ERW straight seam welded pipe is mainly divided into two types: ERW AC welded steel pipe and ERW DC welded steel pipe. ERW longitudinal welded pipes are divided into low frequency welding, intermediate frequency welding, super intermediate frequency welding and high frequency welding according to the different frequency. High-frequency welding is mainly used in the production of thin-walled steel pipes or ordinary thick-walled steel pipes. High-frequency welding is divided into contact welding and induction welding;

2. SSAW refers to spiral welded pipe. Low-carbon carbon structural steel or low-alloy structural steel strip is rolled into a tube blank at a certain spiral angle (called forming angle), and then the tube seam is welded together to make it. Use narrower strip steel to produce large-diameter steel pipes. Its specifications are expressed by outer diameter * wall thickness, and the welded pipe shall be ensured that the hydraulic test, the tensile strength and cold bending performance of the weld meet the requirements.

2) Different advantages and disadvantages

1. Compared with spiral welded pipe, ERW has the advantages of short welding seam, high dimensional accuracy, uniform wall thickness, good surface quality, and high pressure resistance; but the disadvantage is that it can only produce small and medium-diameter thin-walled pipes, and it is easy to produce gray spots at the welding seam. Unfused, groove-like corrosion defects.

2. The advantage of SSAW is that the strip steel of the same specification can produce steel pipes of various diameters. The raw material has a large range of adaptability, the welding seam can avoid the main stress, and the stress is better; the disadvantage is that the geometric size is poor and the welding seam length Compared with the long straight seam pipe, it is prone to welding defects such as cracks, pores, slag inclusion, and welding deviation, and the welding stress is in a state of tensile stress. The general design code for long-distance oil and gas pipelines stipulates that spiral submerged arc welded pipes can only be used in Type 3 and Type 4 areas. After improving this process in foreign countries, the raw material is changed to steel plate to separate the forming and welding. After pre-welding and precision, and cold expansion after welding, the welding quality is close to UOE pipe. At present, there is no such process in China. It is a spiral pipe in my country. The direction of plant improvement. The spiral pipe used in the "West-East Gas Pipeline" is still produced according to the traditional technology, but the pipe end has been expanded in diameter. The United States, Japan, and Germany generally reject SSAW and believe that SSAW should not be used on the main trunk line; Canada and Italy use SSAW in some cases, and Russia uses SSAW in a small amount, and they have formulated very strict supplementary conditions. Due to historical reasons, most domestic trunk lines still use SSAW. 

3) Different uses

1. ERW is currently widely used in domestic areas such as city gas, crude oil and refined oil transportation, etc.; it is generally used to make wire sleeves in the power industry. Performance characteristics: 100% ultrasonic testing of the base material ensures the internal pipe body Quality; no unwinding-disc shearing process, the base material has less pitting and scratches; there is basically no residual stress in the finished pipe after the stress is eliminated; the welding seam is short, and the probability of defects is small; it can be transported conditionally Wet sour natural gas; after the diameter is expanded, the steel pipe has a high geometric dimension accuracy; the welding is carried out in a straight line in a horizontal position after the forming is completed, so the staggered edges, slits, and the pipe diameter and circumference are better controlled, and the welding quality is excellent .

2. SSAW is mainly used in water supply engineering, petrochemical industry, chemical industry, electric power industry, agricultural irrigation and urban construction in China. Used for liquid transportation: water supply and drainage. Used for gas transportation: coal gas, steam, liquefied petroleum gas. For structural purposes: as piling pipes and bridges; pipes for docks, roads, and building structures.

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