EFW Pipe

The EFW pipe divison consists of a JCO forming press, helical / spiral mill, inside and outside welding system, heat treatment furnace and testing facilities.

Welding process employed is gtaw for root-pass and saw/tig for final pass with suitable filler wires as prescribed by aws specifications and asme boiler and pressure vessel code, section-ix. These facilities are capable of manufacturing austenitic and various duplex grades.

Sunny Steel has been supplying EFW Electric Fusion Welded Pipe for many years.

We supply EFW electric fusion welded pipe to the folowing industries on a global scale:

• Oil Industry
• Gas Industry
• Filtration Industry
• Refrigeration Industry
• Refining Industry
• Petrochemical Industry
• Offshore Industry

EFW pipe vs SSAW pipe，ERW pipe

ERW – Electric Resistance Welded

For pipes or tubes size 4 inch (10.2mm) OD and below, strip is fed into a set of forming rolls which consists of horizontal and vertical rollers so placed as to gradually from the flat strip in to a tube which is then allowed to pass the welding electrodes. The electrodes are copper disks connected to the secondary of a revolving transformer assembly.

The copper disk electrodes make contact on each side of the seam and temperature is raised to the welding point. Outside flash is removed by a cutting tool as the tube leaves the electrodes, inside flash is removed either by an air hammer or by passing a mandnel through the welded tube after the tube has been cooled.

This is termed as Electric Resistance welded or ERW tube/pipe. If this ERW is being drawn further to get desired size of tubes or pipes, in cold condition is called as Cold Drawn welded or CDW.

SAW – Submerged Arc Welded

This process is used for pipes from 24″ to 36″ i.e 610mm to 914mm OD. Flat plate is first pressed into U and later O shape.

The O shape is placed in an automatic welder and backed up on the inside by a water cooled copper shoe. Two electrodes in close proximity and used. The electrodes are not in actual contact with the pipe. The current passes from on electrode through a granular flux and across the gap in the pipe to the second electrode. The high temperature of the arc heats the edges of the plate, a welding rod placed just over the seam is thereby melted and metal is deposited in the groove.

After the outside weld has been made, the pipe is conveyed to an inside welder where a similar operation is carried on, except that no backup shoe is need.

Electric Resistance Welding (ERW steel pipe)

welding member combination is applying pressure through the electrodes, the use of current through the joint area of ​​the contact surface and the adjacent heat generating resistance welding process method, Also known as contact welding. It has excellent toughness and dynamic load strength, welding deformation.

Commonly used spot welding, seam welding and butt three.

Fusion welded method of new polyethylene pipe

In the field of fluid medium transmission, polyethylene (PE) pipe is wide attention in recent years and has been the rapid development of new pressure structure.

Compared with the traditional metal pipe, polyethylene piping systems for light weight, strength and specific rigidity, durability, corrosion resistance, insulation, composite capacity and resistance to fracture. Easy to manufacture and installation, and low cost, the typical service life of up to the metal several times and can save a lot of energy production and use. It is used in the field of urban water supply and drainage and gas transportation and distribution system, agricultural irrigation and drainage systems, factories, mines ventilation system and mud, ore pipeline transportation.

Polyethylene piping systems for manufacturing and laying pipe connection between the impact of an important part of its structural integrity and lasting strength. Since polyethylene molecular chain by a methylene group, and having a high degree of symmetry. Determines its polarity is low, so the connection of the polyethylene pipe can not be used solvent bonding method using only mechanical connection or welding. Practice shows that the welding is a high-quality, high-efficiency plastic pipe connection technology. More mature welding techniques include socket weld, butt welding, fusion welded.

Heating wire which are fused welding molten weld has been the development and promotion of the construction is simple, portable field devices, welding speed, and soon. The basic principle is the high resistance of the wire pre-embedded in the plastic casing wall. Plug, Walter current, electric heating wire to make it around the plastic Division Heating and melting into each other, to form a weld cooling. Its main disadvantage is: (1) when the plastic melts and a small amount of current, closely-spaced heating wire are overlapped with each other to cause a short circuit failure often makes welding; (2) the high cost, the heating wire embedded within the plastic injection molding process and mold complex, will inevitably lead to the high production costs of the welded joints; (3) Upon completion of the welding, electric wire remaining in the weld affect performance, on the one hand, on the other hand, cause unnecessary alloy material waste.

Prepared using the carbon felt polyethylene laminated composite conductive composites as fusion welded materials is feasible during power-up, the resistance of the composite rate of change is very small, can be heated to the melting temperature of polyethylene. Composite molding process parameters temperature of 160 ° C, time 10 min, pressure 10 MPa, the resistance of the composite control in a 100 W. Factors affect the weld strength of the fused heating power, heating time, they impact on the weld strength is mainly attributed to the influence of the temperature of the heating layer, when the temperature of the heating layer is controlled within the range of 140 220 ° C, to obtain satisfactory weld strength. Therefore, the type of input power, it is possible to select an appropriate heating time to achieve the desired welding effect. Electrofusion welding, the presence of a heat affected zone in the vicinity of the heating layer in the melted layer and the heat-affected zone, the degree of crystallinity of the polyethylene, the crystal size will be changed, so that the properties of the material affected.

Coating

Pipeline coating is the most consistent and successful solution for protecting ERW pipes from corrosion, from moisture, other harmful chemicals.

Anti-corrosion steel pipe is processed through the preservation process, which can effectively prevent or slow down the process in the transport and use of chemical or electrochemical corrosion reaction of steel pipe.

Therefore pipe anti-corrosion layer is an important barrier to prevent soil erosion. A well-known foreign scholar put forward” 3PE france protective layer”, so far, anti-corrosion methods is widely used.

Coated pipes offer high resistance to corrosion on pipes and provide many benefits such as:

1. Increased Flow Capacity – A coating on pipes helps provide a smoother surface thus improving gas and liquid flow within pipes.
2. Reduced Cost – The pipeline coating increases the pipes durability so they can be deployed with minimum maintenance cost even in the harshest environments.
3. Lower energy usage – Various studies have shown that pipelines that are internally coated use less energy for pumping and compression of products through pipes. This helps in increased saving over time.
4. Clean delivery of products – The inhibitors used for the protection products can also be minimized by the use of coated pipes for delivery of products.
5. Thus, coating of pipelines can help you in reducing your maintenance cost and at the same time providing a corrosion free reliable protection.

Basic functions of erw pipe coating

1. making the surface of ERW steel pipes free from electrochemical corrosion of the soil medium, the basic physics of bacterial corrosion protection.
2. resisting the move of the soil medium creep stress, static stress and abrasion force method and structure of the basic machinery protection.

The basic principles of urban gas pipeline coating selection:

• good insulating and mechanical properties;
• good resistance to cathodic disbondment performance;
• good resistance to water, gas permeability;
• good chemical resistance soaking performance and anti-aging properties;
• resistance to low temperature and high temperature performance;
• easy mending and mending;
• at reasonable prices.

Types of coating

Delivery

Measurement size

Packing

Advantage of ERW pipe

The alloy content of the coil is often lower than similar grades of steel plate, improving the weldability of the spiral welded pipe. Due to the rolling direction of spiral welded pipe coil is not perpendicular to the pipe axis direction, the crack resistance of the spiral welded pipe materials.

What is welded steel pipe?

Welded steel pipe refers to a steel pipe with seams on the surface that is welded by bending and deforming a steel strip or steel plate into a circular, square or other shape. The blanks used for welded steel pipes are steel sheets or strips.

Since the 1930s, with the rapid development of continuous rolling production of high-quality strip steel and the advancement of welding and inspection technology, the quality of welds has been continuously improved, and the varieties and specifications of welded steel pipes have been increasing.

When the T-shaped welded steel pipe contains Ni, it has strong corrosion resistance in an acidic environment. In an environment containing sulfuric acid or hydrochloric acid, the higher the Ni content in the T-shaped welded steel pipe, the stronger the corrosion resistance. Under normal circumstances, only adding Cr to the T-shaped welded steel pipe can prevent the phenomenon of corrosion. The poor edge condition of the strip is another important cause of misalignment. The effects of changes in mass flow, heat flow density and structural parameters (ratio of helical curvature diameter to T-shaped welded steel pipe diameter Dc/D) on the heat transfer coefficient of saturated bubble boiling in vertical spiral pipes.

During the production of T-shaped welded steel pipes, misalignment occurs from time to time, and there are many influencing factors. In production practice, the steel pipe is often degraded by the wrong side and out of tolerance. Therefore, it is necessary to analyze the reasons for the misalignment of the spiral steel pipe and its preventive measures.

Due to the poor shape and dimensional accuracy of the head and tail of the uncut steel strip, it is easy to cause the steel strip to bend hard and cause misalignment during butt joint. Simulation parameter range: vertical pipe: pipe diameter D=10mm, pipe length L=660mm; three types of vertical T-shaped welded steel pipe: pipe diameter D=10mm, the change of the ratio of the curvature diameter of the T-shaped welded steel pipe to the spiral pipe diameter is Dc /D=15, 20, 25, helical pitch Pt=20mm, tube lengths are L=503mm, L=660mm, L=817mm respectively. Mass flow G=200~400Kg/(m'2 s), heat flux density q=5~15KW/m'2, saturation pressure p, saturation=0.414880MPa, saturation temperature T, saturation=283.15K.

Technical requirements for welded pipes

The technical requirements and inspection of welded pipes are based on the provisions of the GB3092 "Welded Steel Pipes for Low-Pressure Fluid Transmission". It can be delivered according to fixed length or double length. The surface of the steel pipe should be smooth, and defects such as folds, cracks, delamination, and lap welding are not allowed. The surface of the steel pipe is allowed to have minor defects such as scratches, scratches, weld misalignment, burns and scars that do not exceed the negative deviation of the wall thickness. The thickening of the wall thickness and the presence of inner seam weld bars are allowed at the weld.

Welded steel pipes should be subjected to mechanical performance test, flattening test and flaring test, and must meet the requirements of the standard. When the steel pipe should be able to withstand the internal pressure, carry out a pressure test of 2.5Mpa, and keep it for one minute without leakage. The method of eddy current flaw detection is allowed to replace the hydrostatic test. The eddy current flaw detection is carried out according to the standard of GB7735 "Steel tube eddy current flaw detection inspection method". The eddy current flaw detection method is to fix the probe on the frame, keep a distance of 3~5mm between the flaw detection and the weld seam, and conduct a comprehensive scan of the weld seam by the rapid movement of the steel pipe. The flaw detection signal is automatically processed and sorted by the eddy current flaw detector. To achieve the purpose of flaw detection. The welded pipe after the flaw detection is cut off according to the specified length with a flying saw, and it is rolled off the assembly line through the turning frame. Both ends of the steel pipe should be chamfered with flat ends, printed with marks, and the finished pipes are packed in hexagonal bundles before leaving the factory.

Straight seam steel pipe processing method:

Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. Generally, its strength is higher than that of straight seam welded pipe. Narrower billets can be used to produce welded pipes with larger diameters, and the same width of billets can be used to produce welded pipes with different pipe diameters. But compared with the straight seam pipe of the same length, the weld length is increased by 30~100%, and the production speed is lower. So what are its processing methods?

1. Forging steel: a pressure processing method that uses the reciprocating impact force of the forging hammer or the pressure of the press to change the blank into the shape and size we need.
2. Extrusion: It is a processing method in which steel puts metal in a closed extrusion box and applies pressure at one end to make the metal extrude from the specified die hole to obtain a finished product with the same shape and size. It is mostly used for the production of non-ferrous metals material steel.
3. Rolling: A pressure processing method in which the steel metal billet passes through the gap between a pair of rotating rolls (various shapes), and the cross-section of the material is reduced due to the compression of the rolls, and the length is increased.
4. Pulling steel: it is a processing method in which the rolled metal blank (type, pipe, product, etc.) is pulled through the die hole to reduce the cross section and increase the length. Most of them are used for cold processing.

Quenching Technology for Straight Seam Welded Pipe

The surface quenching and tempering heat treatment of straight seam welded pipe is usually carried out by induction heating or flame heating. The main technical parameters are surface hardness, local hardness and effective hardened layer depth. Vickers hardness tester can be used for hardness testing, and Rockwell or superficial Rockwell hardness tester can also be used. When the surface heat treatment hardened layer is thick, the Rockwell hardness tester can also be used. When the thickness of the heat-treated hardened layer is 0.4-0.8mm, the HRA scale can be used, and when the thickness of the hardened layer exceeds 0.8mm, the HRC scale can be used.

If the parts require high local hardness, local quenching heat treatment can be carried out by means of induction heating. Such longitudinal welded pipes usually need to mark the location of local quenching heat treatment and local hardness value on the drawing. Hardness testing of longitudinally welded pipes shall be carried out in the area. The hardness testing instrument can use a Rockwell hardness tester to test the HRC hardness value. If the heat-treated hardened layer is shallow, a surface Rockwell hardness tester can be used to test the HRN hardness value.

The three hardness values of Vickers, Rockwell and Superficial Rockwell can be easily converted to each other and converted into hardness values required by standards, drawings or users. The corresponding conversion tables are given in the international standard ISO, the American standard ASTM and the Chinese standard GB/T.