Pressure that spiral steel pipe can withstand

Spiral welded steel pipe refers to the steel strip or steel plate bent and deformed into round, square and other shapes and then welded into a steel pipe with seams on the surface. According to the different welding methods can be divided into electric arc welding pipe, high-frequency or low-frequency resistance welding pipe, gas welding pipe, furnace welding pipe, bonded pipe and so on. According to the shape of welded seam can be divided into straight seam welded pipe and spiral welded pipe. Electric welded steel pipe is used in oil drilling and machinery manufacturing, etc. Furnace welded pipe can be used as water gas pipe. Furnace welded pipe can be used as water and gas pipe, etc. Large diameter straight seam welded pipe is used for high-pressure oil and gas transportation, etc. Spiral welded pipe is used for oil and gas transportation, piles, piers and so on. Welded steel pipe is lower in cost and higher in production efficiency than seamless steel pipe.

Steel Pipe Strength Characteristics When the pipe is subjected to internal pressure, two main stresses are usually generated in the pipe wall, namely, radial stress δY and axial stress δX. The synthetic stress at the weld seam δ = δY(l/4sin2α + cos2α)1/2, where α is the helix angle of the weld seam of the spiral welded pipe.

Spiral welded pipe weld helix angle is generally 50-75 degrees, so the spiral weld synthetic stress is 60-85% of the main stress of straight seam welded pipe. In the same working pressure, the same diameter spiral welded pipe than straight seam welded pipe wall thickness can be reduced.

According to the above characteristics can be seen: A. spiral welded pipe burst, due to the weld seam by the positive stress and the synthetic stress is relatively small, the burst generally does not originate in the spiral weld seam, its security than the straight seam welded pipe high.

B. When the spiral weld near the existence of defects parallel to it, due to the spiral weld is smaller, so the risk of expansion is not as large as the straight weld.

C. Since the radial stress is the maximum stress present on the pipe, the weld bears the maximum load when it is in the direction of the vertical stress. That is, the maximum load on the straight seam, the minimum load on the circumferential weld, the spiral seam between the two.