Advantages and Disadvantages of Welded Steel Pipe

The technology of welded steel pipe is continuous online production. So the thicker the wall thickness is, the greater the investment in the unit and welding equipment is, and welded steel pipe will have less economical efficiency and practical applicability. The wall thickness is thinner, its input-output ratio will be decreased accordingly. The process of the product determines its advantages and disadvantages. In general, the welded steel pipe with high precision, uniform wall thickness, high brightness of tube inside and outside (surface grade of steel plate determines the surface brightness of steel pipe), can be fixed length wilfully. Therefore, welded steel pipe reflects its economy and aesthetics in the high-precision, low-pressure fluid applications.

The production process of welded steel pipe is simple, the production efficiency is high, the cost is low, and develops rapidly. The strength of the spiral welded pipe is generally higher than that of the straight seam welded pipe. The pipe with larger diameter can be produced with the narrow billet and the pipe with different diameter can also be produced with the same width billets. However, compared with the same length of the straight pipe, the length of weld seam increased by 30% to 100%, and the production rate is low. Therefore, the pipes with smaller diameter are mostly used straight welding, the welded steel pipes with large diameter are mostly used spiral welding.

Prime Steel Pipe is positioned as a steel pipe manufacturer and exporter for all kinds of welded steel pipes in different standard and dimension, including ERW steel pipe, LSAW steel pipe, SSAW steel pipe, etc..


Material and Standard Classification of SSAW Steel Pipe

Material of SSAW steel pipe:

SSAW steel pipe (also called spiral welded pipe) is the steel pipe with spiral seam that using strip coil as raw material, extrusion forming under normal temperature, and welding by automatic Double wire double-sided submerged arc welding process. The material of it includes: Q235A, Q23b, 0Cr13, 1Cr17, 00Cr19Ni11, 1Cr18Ni9, 0Cr18Ni11Nb, Q345, L245(B), L290(X42), L320(X46), L485(X70), L555(X80).

Standard classification of SSAW steel pipe:

1. Spiral welded pipe (SY5036-83) used for pressurized fluid transportation is mainly used for conveying oil and natural gas pipeline.
2. Spiral seam high-frequency welded steel pipe (SY5038-83) used for pressurized fluid transportation, it is welded with high-frequency welding method. The loading capacity of it is powerful, the plastic is good, and it is easy to weld and machine shaping.
3. Spiral welded pipe (SY5037-83) used for general low-pressure fluid transmission, it is welded with double-sided automatic submerged arc welding method or one-side welding method, it is mainly used for water, gas, air and steam and other general low-pressure fluid delivery.

Now general standards for SSAW steel pipe is generally divided into: SY/T5037-2000 (ministerial standard, also known as spiral submerged arc welded steel pipe for ordinary fluid transportation pipeline), GB/T9711.1-1997 (Chinese standard, also known as pipe for oil and gas industry transportation, API-5L (American Petroleum Institute, also known as pipeline steel pipe; which is divided into PSL1 and PSL2), SY/T5040-92 (spiral seam submerged arc welded pipe for pile).

Prime Steel Pipe as a excellent manufacturer and exporter of steel pipe, will provide the spiral welded pipe with highest quality and the most comprehensive service for our customer. If you are interested in our products, you can click the hyper-link to view details.

The Welding Quality of Welded Steel Pipe

Welding quality of welded steel pipe refers to the degree to which the welding product meets the design technical requirements. Welding quality not only affects the use performance and life of welding products, more importantly, affects personal and property safety. Welding quality is usually ensured by design quality, processing quality, quality inspection and post-weld treatment and other links of the product.

Design Quality

The type of joint used in the welding product and its calculated strength should meet the actual carrying capacity. Welding method should be suitable for the characteristics of components, and its economical efficiency should be good. The welding process should be able to minimize stress, deformation and stress concentration. Production labor and material consumption should be as small as possible, the convenience of flaw detection should also be taken into consideration when design the joint.

Processing Quality

The performance of adopted the base metal, wire, flux or welding electrodes and other welding materials should meet the design requirements. The performance of welder, auxiliary equipment and testing equipment should be good. Before welding, the welding material should be dried according to the provisions, the welding groove of workpiece should meet the requirements and remove the cutting residue, cracks and dirt.

Quality Inspection

Quality inspection runs through the whole production process from design to finished product, we must ensure that the test method used in the quality inspection process is rationality, the reliability of the testing instrument and inspection staff technical level. The properties of the joints, physical properties, mechanical properties, microstructure, chemical composition, corrosion resistance, appearance dimensions and welding defects of products after welding should be checked by means of various inspection methods.

Welding defects can be divided into external defects and internal defects. External defects include: excess height does not meet the requirements, welding tumor, undercut, crater, arc burns, surface pores, surface cracks, welding deformation and warping. Internal defects include: cracks, not penetration, not fused, slag and porosity. The most harmful in welding defects is the crack, the followed is lack of penetration, incomplete fusion and slag inclusion, pores and structure defect. Individual flaws are allowed to exist. The number and the nature of allowed defects are determined by the using conditions and the quality assessment criteria of the product. If the surplus height of welding line is too high, it is allowed for those products by the static load, but it is not allowed for those products by cyclic fatigue loading in high frequency, even the normal excess weld metal also has to be cut off. The presence of welding defects is related to the groove processing and assembly accuracy, the rigor degree of the welding process, the technology of the welder and other factors.


What is Welded Steel Pipe?

Welded steel pipe, also known as welded pipe, is the steel pipe that made of steel plate or steel strip after crimped and welded. The production process of welded steel pipe is simple, production efficiency is high, variety specifications are many, the investment of equipment is little, but its general strength is lower than the seamless steel pipe. Since the 1930s, with the rapid development of high-quality strip continuous rolling line and the improvement of welding and inspection technology, the quality of welding line has been increasing continuously, and the specifications of welded steel pipes have been increasing. And welded pipe have replaced the seamless steel pipe in more and more field. Sewing steel pipe. The welded steel pipe is divided into straight seam welded pipe(also called LSAW steel pipe) and spiral welded pipe(also called SSAW steel pipe) according to the form of welding line.

Production process of LSAW steel pipe is simple, production efficiency is high, cost is low, and it develops rapidly. The strength of the SSAW steel pipe is generally higher than that of the LSAW steel pipe, and the SSAW steel pipe with larger diameter can be produced with the narrow billet. And it also can use the billet with the same width to produce t SSAW steel pipe with different diameter. However, compared with the straight seam welded pipe in identical length, the length of welding line increased by 30 to 100%, and the production rate was low.

Therefore, pipe manufacturers usually use straight seam welding to produce the smaller diameter of the pipe, use spiral welding to produce large diameter welded pipe.


Connection Modes of Oil Pipelines

Several days ago, we introduced the types of tube that used in oil pipeline, today, we will share the connection modes of oil pipelines for people those interested in this aspect.

Oil pipeline must use a certain connection to form a complete system. Connection methods of pipeline are mainly three categories, including screw thread, welding and flange connection.

When the pressure is not high, the pipe with small diameter can be connected by using screw thread this method. This connection method is very convenient, but most of the diameter of oil pipelines are generally larger, so other two connection methods are used commonly.

The pipeline that DN≥50 basically uses welding method to connect. Welding has many advantages, such as convenient construction, strong, tight and saving steels. The general straight pipe or bends those parts do not need to tear down can use this method.

The connection of pipes and valves or other equipment (such as: pump) and the parts those need to disassemble of pipeline need to use flange to connect. In order to ensure the tightness of the flange connection, we also need to use a relatively soft flange grommet to assist on both sides of the flange. According to the production process, flange can be divided into flat welding, thread, butt welding, loose tube and blind plate and other types. Except blind plate flange, others are all used in interconnection between the pipeline. If you need to connect different diameters of the pipeline, you can use the adapter flange that two diameter corresponding. The blind plate flange is used to close the end of the pipe head. Therefore design of it make it can withstand greater bending stresses.