Regarding the differences between welded pipes and seamless pipes
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Our factory manufactures lubrication equipment. Usually, the pipelines used are ordinary carbon steel pipes (seamless pipes). Recently, a new purchasing manager was appointed, and for one particular system, all the pipelines were purchased as welded pipes; the dimensions and materials are the same. I work in production and have no prior experience with welded pipes. I would like to ask what the difference between welded pipes and ordinary pipes is – I only know that welded pipes are cheaper... PS: Added in green after reading the reply on the first floor. The working medium is lubricating oil and water. This post was last edited by fahaio on 2009-3-6 at 14:43
Your description is inaccurate. ““Carbon steel pipe” is a type of pipeline material; it can be either seamless steel pipe or welded steel pipe. “\"Screw welded pipe\" is a type of welded steel pipe. If by “ordinary pipelines usually use standard carbon steel pipes” you mean seamless steel pipes, then care should be taken regarding the timing of replacing them with welded steel pipes. It mainly depends on your medium and operating conditions. Some media cannot be used with welded steel pipes! If it is necessary to replace it with welded steel pipes, it is recommended to conduct a strength check!
Spiral-welded steel pipes are generally used for water pipelines, while seamless steel pipes should be employed for pipelines carrying process media.
When the pressure is not high, spiral-welded steel pipes are used, such as for water pipes and gas pipes, etc.; whereas for applications with a pressure of more than 1 kilogram, seamless steel pipes are used
Steel pipes used for chemical process pipelines to transport process media must not be welded pipes!
Lubricating oil and water pose neither corrosion nor pressure issues, so welded steel pipes can be used.
It depends on the pressure you are using; seamless tubes can only be used under pressure
I have serious doubts about what the people upstairs said regarding the use of seamless steel pipes for processes, materials, and pipelines that are under pressure. :funk:
Spiral welded pipes aren’t necessarily unusable under pressure; it depends on the operating conditions, the medium, and the material of the spiral welded pipe, among other factors.
Please check the 3rd edition of the ＜Chemical Process Design Manual＞, Part 4, Metal Pipes and Fittings. It provides detailed information on the differences between seamless steel pipes and welded steel pipes, as well as an explanation of what spiral welded pipes are and in what situations they can be used. Spiral welded steel pipe (sY5036), also known as spiral-welded pipe, is suitable for use in steam, water, air, oil, and oil-gas pipelines. In China, its available diameter range is Φ219~2220mm, and its quality is equivalent to that of steel plate-coiled pipes.
Take a look at “Technical Conditions for the Delivery of Steel Pipes Used in the Oil and Gas Industry GBT9711.1-3”. When selecting seamless pipes, pay attention to the positive and negative deviations; for spiral-welded pipes, deviations generally need not be considered ； It has become difficult to purchase seamless pipes with a diameter of DN250 or larger; spiral-welded pipes are used for larger diameters. Production capacity of domestic steel pipe manufacturers for various pipe types: Spiral submerged arc welded steel pipes: 273～1422mm ； Semi-automatic submerged arc welded steel pipes: 406～1422mm ； Seamless high-frequency resistance welded steel pipes (ERW) ≤610mm ； Seamless steel pipes ≤630mm.
Steel pipes are classified into seamless pipes and welded pipes based on their manufacturing methods. Welded steel pipes are formed by welding steel plates rolled into tubular shapes together with butt joints or spiral joints. In terms of manufacturing methods, they are further classified into welded steel pipes for low-pressure fluid transport, spiral-welded electric welding steel pipes, directly rolled and welded steel pipes, electric welding pipes, etc. Seamless steel pipes can be used for various liquid and gas pipelines, etc. Welded pipes can be used for water supply pipelines, gas pipelines, heating pipelines, etc. Seamless steel pipes are classified into hot-rolled pipes and cold-drawn (rolled) pipes according to their manufacturing methods. The maximum nominal diameter of cold-drawn (rolled) tubes is 200 mm, while that of hot-rolled tubes is 600 mm. In piping projects, hot-rolled pipes are commonly used when the pipe diameter exceeds 57 mm, while cold-drawn (rolled) pipes are typically used when the diameter is less than 57 mm. Generally, seamless steel pipes are simply referred to as seamless pipes. They are made from ordinary carbon steel, high-quality carbon steel, ordinary low-alloy steel, and alloy structural steel, and are used for constructing pipelines for transporting liquids or for making structural components and parts.