How to get spiral steel pipes?

What is a spiral steel pipe?

Spiral steel pipe, also called SSAW steel pipe or spiral welded spiral pipe, are made by hot rolled strip, it is made by extrusion forming under the normal temperature, and then welded by taking the technology of double wire and double-faced submerged-arc.
During molding process of spiral steel pipe, steel plate has uniform deformation and light residual stress, thus the surface has no scratches. Spiral steel pipe has more flexible thicknesses and diameters, especially in making high-grade thick pipes with small or medium aperture, these techniques has incomparable advantages in satisfying your needs.
Spiral steel pipe can be widely used in the production of large diameter spiral steel pipes for the following reasons:
1) as long as changing the forming angle, we can use the same width of the strip steel to produce a variety of caliber spiral pipe;
2) Since spiral welded steel pipe is formed by the continuous bending, the specified lengths of spiral steel pipe is not limited;
3) The weld in a spiral shape evenly distributed throughout the circumference of spiral steel pipe, so the dimensional accuracy of spiral pipe is high, and its strength is also high;
4) Spiral steel pipe is easy to change the size, so it is suitable for small batch and multi-species production.

Spiral welded pipe, as the name implies, is a steel pipe which has a seam running its entire length in a spiral form.With the development of the Submerged Arc Welding process, the production of large hot rolled coils of sufficient width and the  development of dependable non-destructive testing methods, it is now possible to produce spiral welded pipe for high pressure service.
Manufacturing process of spiral steel pipe:

ssaw pipe - How to get spiral steel pipes?

1. Coil Probe: steel coil into the production line, the first full board Ultrasonic Inspection.
2. Leveling Milling: through anvil plate leveling machine so that the original curl, and then pass the two edges of steel-sided milling machine milling, so that up to the requirements of the plate width, plate edge parallel groove shape.
3. Cut Type: steel production line along the outer edge of the coiled-coil tube.
4. welding and cutting: the use of advanced technology for pre double submerged arc welding cutting inside from the foot of the welding specification welded steel pipe welded outside use, etc.
5. Visual inspection: some basic parameters by a professional technician check.
6. ultrasonic flaw: the inner and outer sides of the base metal and weld seam 100% inspection.
7. X-ray detection: internal and external welds 100% X-ray television industry checks, the use of image processing system ensures detection sensitivity.
8. Pressure test: hydrostatic testing machine by-root test steel pipe up to the standard requirements to ensure that the test pressure.
9. Chamfer level: steel pipe inspection pipe end processing, up to the requirements of the pipe end beveling size.
10. Check: X-rays and then subjected to ultrasonic testing and magnetic particle inspection conducted pipe end, check whether the deposit welding problems and defects in the pipe ends.

11. Oiled Marking: Qualified oiled steel pipe corrosion and in accordance with user requirements for marking.

Spiral Seam Annealing Systems:
outside diameter control - How to get spiral steel pipes?
Outside Diameter Control
x ray testing online - How to get spiral steel pipes?
X-Ray Testing Online
hydrostatic testing - How to get spiral steel pipes?
Hydrostatic Testing

Thermatool designs and manufactures Spiral Seam Annealing systems for producers of SAW (submerged arc welded) API line pipe.

Offering all the basic features and benefits of Thermatool seam annealing systems designed for operation on longitudinally welded API pipe, Thermatool Spiral Seam Annealing systems, however, require the installation of specially “shaped” inductors.

These are custom designed on CAD systems in order to precisely follow the helix angle for a specific pipe diameter.

Spiral Submerged-arc Welded steel pipe technological process

There are nine modernized product lines in our company with the yield capacity of 1000 thousands tons of B-X80 steel pipe of φ219-φ3200mm, WT5-30mm.

ssaw pipe process - How to get spiral steel pipes?

Listing some notes You must know

Oiled marking: Steel after passing wrer oiled to prevent corrosion,and according to user requirements for making.

Leveling Milling: The flat steel anvil machine so that the origal curl,and then thouth the edge milling machine for two-sided steel milling,so as to meet the requirements of the plate width,plate edge parallelism and groove shape.

Shear molding: The steel plate production line along the outer edge of the spiral curl into a tube.
Butt cut: Double-sided submerged arc welding using advanced technology to pre-welding,internal welding,outside wilding.The welded steel pipe using a plasma-foot cut to specification length.

Spiral submerged arc welding

Spiral submerged arc welding as raw material is often warm extrusion molding, automatic double -sided wire submerged arc welding process.

The process is normally limited to the flat or horizontal-fillet welding positions (although horizontal groove position welds have been done with a special arrangement to support the flux).

Spiral submerged arc welding process performance:

(1) raw materials that strip, wire, flux. Must go through rigorous testing before being put into the physical and chemical.
(2) strip head and tail docking, using single or double wire submerged arc welding, in rolled steel by automatic submerged arc welding.
(3) Before molding, the strip after flattening, cutting, trimming, planing, surface cleaning and transportation to the curved edge treatment. 
(4) the use of electrical contacts on both sides of the conveyor control the pressure cylinder pressure to ensure the smooth delivery of the strip. 
(5) the use of internal or external control roll forming. 
(6) the weld gap control device to ensure that the weld gap to meet the welding requirements, diameter, volume and the wrong side of the weld gap have been strictly controlled. 
(7) the welding and soldering are used outside the United States Lincoln welding machine for single or double wire submerged arc welding, to obtain stable welding specifications. 
(8) After welding the weld line continuous ultrasonic injury checked to ensure 100% coverage of non-destructive testing of spiral weld. If defective, automatic alarm and spraying tags, production workers so adjusting the process parameters, and remove defects. 
(9) the use of air plasma cutting machine to cut a single tube. 
(10) cut into a single pipe, the first three of each batch of steel to carry out strict inspection system, inspection of weld mechanical properties, chemical composition, fusion status, steel surface quality and after NDT inspection to ensure that the process pipe after passing to formally put into production. 
(11) there is a continuous sonic flaw marks the site of the weld, manual ultrasonic and X-ray review, if there are defects after repair again after destructive testing until confirmation defect has been eliminated. 
(12) strip on the spiral weld seam and intersects with D-type connector where the pipe all through the X -ray television or film examination. 
(13) each pipe hydrostatic test pressure radial seal. Test pressure steel pipe pressure and time by computer testing device strictly controlled. Test parameters are automatically printed record. 
(14) pipe end machining, so that the end vertical, blunt edge bevel and accurate control.

Notes in the process of spiral steel pipe welding
From the aspect of economic benefit, pipe fittings of spiral steel pipes should not only meet the requirements of engineering design, but also reduce the cost as much as possible. But in that case, sometimes the selection of spiral tubes will be a small amount of many varieties on the whole, which is a disadvantage to the overall management of site construction material, control and needed material substitution for design change, etc.
In actual construction, the pipe institutional forms spiral welded pipes used in piping engineering are varied to meet different engineering conditions and the requirements of special engineering is especially stringent. In engineering design and selection, the higher strength grade of pipe fittings is, the higher security is, the greater engineering cost is correspondingly, which will cause unnecessary waste.
So both safety and economy should be considered synthetically when selecting pipe fittings of spiral pipes, as far as possible to reduce pipe varieties. In addition, factors like the site construction conditions, levels, and purchase cycle of pipe fittings also should be focused according to concrete circumstance.

Spiral pipe welding joint

erw pipe - How to get spiral steel pipes?

Double-sided submerged arc spiral steel pipe is that arc method is welding under flux layer, and formed is that the heat generated by the burning of the arc between the wire and flux in the flux layer and melting of the wire solder and base metal.

As for the following reasons it is widely used in the production of large diameter steel pipe:

  • as long as the change of forming the angle, you can use the same broadband strip production of steel pipes of various calibres.
  • is a continuous bending and forming, so the length of steel pipe cut to length unrestricted.
  • weld spiral evenly distributed on the circumference of the entire steel pipe, steel pipe size, high precision, strong also higher.
  • easy to change the size suitable for small quantities of steel pipe production of many varieties.

Spiral seam weld is more length than a straight tube, tube length is L, the weld length is L / cos (θ) is the most concentrated of the steel tube defects in the weld and heat affected zone, weld length on the mean the probability of defects, which is the main reason for long-term restricting the spiral welded pipe more widely used, but also long-standing debate in the spiral and straight-seam pipe, especially compared with the UOE steel pipe superior, spiral pipe manufacturing technology to today, we should be comprehensive and correct evaluation and comparison, the idea of a long spiral weld, first of all, due to defects in the weld parallel, on the spiral, the weld defects oblique defects, in the course of the direction of the main stress of the steel pipe, or the equivalent defect length of the pipe axis direction than a straight seam pipe is small;

Second, a larger pipeline steel are rolled steel plate, impact toughness to the opposite sex, than perpendicular to the rolling direction CVN value along the rolling direction of the CVN value is 3 times higher, straight seam pipe principal stress suffered precisely perpendicular to the minimum in the direction of the pipe impact resistance, while the spiral is to stagger the pipe impact minimum capacity of direction, so that the spiral weld disadvantage turned into advantages. Spiral submerged arc welded pipe, hot-rolled strip steel spiral bending forming, automatic submerged arc welding carried out within the seam and the outer seam welded spiral seam steel pipe.

Difference between SSAW steel pipe and LSAW steel pipe

What is a LSAW pipe?
LSAW Pipe (Longitudinal Submerged Arc-Welding Pipe), is taking the steel plate as raw material, mold it by the molding machine, then do double-sided submerged arc welding. Through this process the LSAW steel pipe will get excellent ductility, weld toughness, uniformity, plasticity and great sealing.
What is a SSAW pipe?

Spiral submerged arc welding(SSAW) is its forward direction and forming tube centerline hose reel molding angle (adjustable), side molding edge welding and weld them into a spiral.
(Spirally Submerged Arc Welding pipes) SSAW pipes: SSAW pipes are produced by spiral (helicoidal) welding of steel coil and have a cost advantage over LSAW pipes, as the process uses coils rather than steel plates. As such, in applications where spiral-weld is acceptable, SSAW pipes may be preferred over LSAW pipes. Both LSAW pipes and SSAW pipes compete against ERW pipes and seamless pipes in the diameter ranges of 16”-24”. SSAW pipes are mainly used in petroleum and natural gas industry to transport flammable and non-flammable liquid and steel construction.

Difference between LSAW steel pipe and SSAW steel pipe are followings below:

lsaw pipes - How to get spiral steel pipes?

Metallurgical properties of raw materials
Straight seam submerged arc welding tube is made of steel, but spiral submerged arc welding steel pipe production is usd hot rolled steel coil strip. The hot strip rolling process with a series of advantages, has a metallurgical process for production of high-quality line pipe capacity.

LSAW (Longitudinally Submerged Arc Welded Steel pipes) in leaflets plate as raw material, the steel plate in the mold or molding machine pressure (volume) into using double-sided submerged arc welding and flaring from production.

ssaw pipe 1 - How to get spiral steel pipes?

Spiral submerged arc welding(SSAW) is its forward direction and forming tube centerline hose reel molding angle (adjustable), side molding edge welding and weld them into a spiral.

Welding process

From the welding process, spiral steel pipe welding method is the same as lsaw steel pipe, but the straight seam submerged arc welding tube inevitably will be a lot of T-weld, so the probability of presence of welding defects also greatly improved, and T-welds welding residual stress weld metal are often in a three dimensional stress state, increasing the possibility of cracks.

According to the submerged arc welding process requirements, each weld should have the arc at the extinction,but each steel pipe is unable to meet the conditions in welding girth,which may be at the extinction more welding defects.

1. The welding process is concerned: a consistent spiral welded pipe and Longitudinal welding, straight seam steel pipe will inevitably have a lot of T-weld, and therefore the probability of the existence of welding defects has greatly improved, and welding residual T welds stress is large, the weld metal are often in three-dimensional stress state, increases the likelihood of cracks. Furthermore, according to the provisions of submerged arc process, each weld shall have the arc at the place and extinction, but in each Longitudinal seam welding ring, unable to meet the conditions, which may have a place in the extinction more weld defects.

2. When the pressure in the pipe to withstand, typically produces two main stress on the wall, that the radial and axial stress stress δ . Weld resultant stress δ, wherein the helix angle of the weld.

3. Spiral Weld Pipe degree helix angle is generally, therefore synthetic spiral weld stresses are the principal stresses. Under the same operating pressure, spiral pipe of the same diameter than the Longitudinal wall thickness can be reduced.

4. The hydrostatic burst strength: by the relevant comparison test, to verify the yield pressure and burst pressure measured and theoretical values spiral pipe and Longitudinal basic agreement, deviation close. But neither the yield stress or burst pressure, spiral pipe were lower than Longitudinal. Blasting test also shows spiral steel hoop blasting mouth deformation rate significantly greater than the Longitudinal. It was thus confirmed, spiral pipe plastic deformation than Longitudinal, blasting the mouth is generally confined to within a pitch, which is spiral weld for expansion gap played a powerful role in binding due.

5. Toughness and fatigue strength: pipeline development trend of large diameter, high strength. With the increase of the diameter of the pipe, the steel grade increase, resulting in greater the ductile fracture tip steady expansion trend. Spiral pipe and Longitudinal although the same as a level, but the spiral steel pipe has a high impact toughness.

6. Because of the transfer line output volume changes: in actual operation, the pipe is subjected to random alternating loads of action. Learn low cycle fatigue strength of steel, judging life of the pipeline is of great significance.

7. Press the measuring result: fatigue strength spiral steel seamless and ERW pipe with the same test data and seamless pipe distribution and resistance in the same area, while Longitudinal submerged arc than the average higher.

Ultrasonic Test System for SSAW Pipe Weld Seam

Spiral welded steel pipes are widely used in Oil, Natural Gas, Water and other flammable & nonflammable liquid conveyance and distribution pipelines, steel structures for construction and other general purposes by means of their wide size range.

Ultrasonic inspection of seamless pipes - How to get spiral steel pipes?
Ultrasonic inspection

Widely preferred longer lengths up to 18,5 m. considerably decreases the cost of pipeline construction resulting in less number of girth welds compared to shorter pipe lengths.
When weld ultrasonic testing, in order to track the weld automatic tracking, the probe is always in the frame just above the weld. The system uses laser vision technology to detect traces of the weld, using IPC and motion control components work together to reach out manual control, automatic track welds, adjust the probe holder the right destination location.
Laser weld ultrasonic testing automatic tracking system consists of a laser vision sensor, data processing means for controlling the composition and executing agencies. Laser vision sensor comprises a CCD camera and a semiconductor laser; data processing agencies, including image acquisition card, and industrial control computer; including PLC control mechanism and stepper motor drives; positioning actuator includes a skateboard, a stepper motor and connected institutions.
System in real time using laser vision sensor weld image; industrial control computer through a dedicated software processing to obtain the image feature points to calculate the deviation of the weld, width, and other parameters the wrong side, and then send control commands through PLC, the drive to drive a stepper motor driven skateboard and probe holder back to the correct position. Laser weld ultrasonic inspection system in the design and manufacture of automatic tracking process to fully consider the scene, laser vision sensor uses a high anti-jamming equipment , stable and reliable; data processing bodies and control mechanisms are used for industrial equipment, common good, low failure rate, easy maintenance; executive body of imported ball screw and linear guide rail, high precision, durable, good dustproof performance.
For spiral weld ultrasonic inspection, testing is now more commonly used method, which is to weld pipe arranged on both sides of a number of ultrasonic shear wave probes, parallel motion detection pipe weld seam parallel or perpendicular to the seam weld defects.

Spiral Submerged-arc Welded Quality Assurance

Spiral welded pipe production by submerged arc method is based on using tandem welding technique for joining inside and outside coil edges, which have been trimmed and beveled by carbide milling for high quality weld structure.

Excellent Equipment:
ultrasonic inspecting - How to get spiral steel pipes?
Ultrasonic Inspecting
lincoln welder welding - How to get spiral steel pipes?
Lincoln Welder Welding
ssaw pipe mill - How to get spiral steel pipes?
SSAW pipe mills
supercoil accumulator - How to get spiral steel pipes?
Supercoil Accumulator
high frequency welding - How to get spiral steel pipes?
High Frequency Welding
forming machine - How to get spiral steel pipes?
Forming Machine
normalizing - How to get spiral steel pipes?
Normalizing
off line ultrasonic - How to get spiral steel pipes?
Airport

There are nine modernized product lines in our company with the yield capacity of 1000 thousands tons of B-X80 steel pipe of φ219-φ3200mm, WT5-30mm.

Quality Control:
x ray testing online - How to get spiral steel pipes?
X-Ray Testing Online
outside diameter control - How to get spiral steel pipes?
Outside Diameter Control
hydrostatic testing - How to get spiral steel pipes?
Hydrostatic Testing
Pipe Test Centre:
chemical analysis - How to get spiral steel pipes?
Chemical Analysis
universal testing machine - How to get spiral steel pipes?
Universal Testing Machine
metallurgical analysis - How to get spiral steel pipes?
Metallurgical Analysis
Note:

Welding of hot rolled steel coils takes spiral form after passing through preforming and forming rolls. Excellent exterior weld quality at high production speeds is provided by double submerged arc welding process. Manufactured pipes are cut to the desired lengths at the exit of the pipe machine. Pipe ends are beveled by means of carbide machining for accurate on-site welding.

After the pipe is conveyed to hydrostatic testing and off-line ultrasonic testing and/or real time X-ray inspection, the pipe will be subject to final inspection for the compliance to customer requirements.

Starting from incoming control up to the final inspection stage; entire process is monitored and supported by computerized system. Traceability is achieved by input controls and barcodes through entire production lines.

The Causes of Errors Spiral Steel Pipe
Spiral steel pipe production at the wrong side have occurred, many influencing factors in the production practice, often by a dry wrong side super differential leaving the steel pipe downgrade. Reason and Preventive Measures therefore Spiral Pipe wrong side analysis is generated Necessary.
1. Edge strip poor health is another important reason for the wrong side.
2. Because the poor are not trimming the strip head and tail shape and size precision, easy to cause docking strip hard bend caused by the wrong side.
3. When the strip head and tail docking welding weld reinforcement larger when overmolding if not handled properly, likely to cause greater wrong side.
4. The camber of the strip is the most important factor causing the wrong side of the pipe in the spiral welded pipe forming, the strip camber angle will constantly change shape, leading to changes in the weld gap, resulting in open seam, wrong side or even take side. seriously affected the quality of the steel, so the observation strip coil-camber situations after, by controlling the vertical roll of the continuous control and corrective disc shears can cut and molding department camber angle is to reduce the production of steel in the process effective way to produce the wrong side of the camber.
Advantages of Spiral Steel Pipe

Spiral pipe is widely used in natural gas, petroleum, chemical industry, power industry, heating industry, water supply and drainage industry, steam heating, hydropower pressure steel pipe, thermal energy, water and other long-distance transmission pipeline and piling, dredging, bridges, steelstructure and other projects. 
In the use and production process of spiral steel pipe, humans have invented a lot of good welding and production methods, and contributed greatly to the steady and rapid development of this industry, but also makes this industry optimization in the development. Automatic submerged arc welding is a new welding method invented in 1940, and in front of the manual welding it or slag protection, but this residue is not the electrode coating is melting out of welding flux . Into a wire device to send wire and wire reel, continuously gave welding wires, welding method is a continuous feeding wire arc ignition fusible granular flux coverage, so that the wire, base metal and part of the flux melting and evaporation to form a cavity, the arc of stable combustion in the cavity inside, so call it automatic submerged arc welding. The arc is buried in a cavity inside. Coat system consists of a funnel filled with welding flux transported through a pipe to be welded in front of the second difference is that using electrodes, wire, because wire can give continuous; electrode, we burn an electrode must have a give an electrode head throw, and operating to stop, change the electrode before welding. 
Such welding method compared with other methods is a great advantage of spiral pipes, the first advantage: completely realize the automation; second advantage, which is submerged arc under welding, heat exchange and protection performance is relatively strong, the welding quality is relatively high; third advantage, due to the automatic submerged arc welding arc buried beneath the coat, so it can use high-current welding efficiency high.

  • Customize size that meet exact design requirement (Diameter, Thickness, Length).
  • Greater strength, double welded seam has the effect of a spiral band around the pipe.
  • Greater pressure resistant, Stress, and Friction. The spiral band has the effect of adding greater structural strength, 25% higher pressures than longitudinally welded pipes and ERW Pipes.

How to Choose a Spiral Steel Pipe?

1. For pipelines with high requirement for peak regulation, due to the uneven gas consumption of users and the frequent fluctuation of pipeline pressure, the alternating stress that spiral steel pipe is subjected to is large. Existing defects in pipe materials will expand under alternating stress. If Selection of weld, defect probability of spiral steel pipe, the safe operation of the pipeline will not be guaranteed.
2. Pipeline passes through the seismic fault zone or through the local high-intensity seismic area. Due to the frequent geological activities in these areas, longitudinal or axial alternating stress will be generated on the pipeline. Under the long-term stress, the probability of accidental spiral welded steel pipe is much higher than that of Q195 Galvanized Welded Spiral Steel Pipe. Therefore, in this zone, the straight Submerged arc spiral steel pipe.
3. For pipes with high requirements for inner and outer coating,spiral steel pipes shall be adopted. Spiral submerged arc welded steel pipe weld more than the height of the weld seam than the vertical submerged arc spiral steel pipe, the steel pipe for internal and external corrosion, corrosion resistance and bare metal pipe joints than the spiral steel pipe close, Anticorrosion effect is not straight seam submerged arc welded pipe is good.
4. For the important wear across the project, should use spiral steel pipe. As the future maintenance and management are more difficult than the general line section, therefore, the use of excellent performance spiral steel pipe is particularly necessary.
5.For the pipeline of weak links, such as hot simmer elbow pipe, should be used spiral steel pipe. Hot simmer elbow due to changes in direction, the internal and external force than its normal line straight pipe to large, due to various factors in the simmering process, the stress is not easy to eliminate, is the weak link in the long-distance pipeline , Using a good overall performance of spiral steel pipe can make up for these deficiencies.
Usage of spiral steel pipe is relatively high, the application is very wide, it should be how to choose before in the selection to pay attention to quality.
The first method is a more professional detection method, that is, by the strength of the pressure vessel to be detected. Commonly, we use atmospheric pressure and water pressure to detect, in this way can detect the working conditions of the spiral steel pipe in the pressure working environment, but also to detect the tightness of the spiral steel pipe, generally take the atmospheric pressure detection, because such security Relatively high, and if the water vapor pressure through the test, then the need to remove the spiral pipe after the water, too much trouble.
The second method is also relatively simple, that is, through the surface of observation. With the naked eye found in the spiral steel pipe in the welding and size of the problem, if necessary, you can also use the standard sample and the products to be compared to find the problem. In general, formal steel pipe company in the production is relatively perfect, on the other hand to beat the metal pipe, if the sound is very crisp and the echo is not very dirty, then the name is the latest selection of steel pipe, rather than scrap steel recycling.
These two methods are commonly used, we can choose a way to test, more secure way is the best to the regular manufacturers, can reduce the use of the process of abuse.

We choose the spiral steel pipe for its larger probability and long-term constraints. Those are the reasons why spiral steel pipe are widely used in varies fields. Compared to the UOE steel pipe, spiral steel pipe can divide to long vexed spiral pipe and straight seam pipe. Nowadays the technology to produce spiral pipe is rapidly developing. We should evaluate Spiral pipe accurately and compares Spiral pipe and rediscover long spiral weld. We can direct the tube of the main stress when we use them. For example, Compared to the straight seam, the length and the axial direction of steel pipe are smaller. Pipeline can be affected on the tough of anisotropy and steel which is rolled. These advantages of spiral steel pipe are the reasons we choose spiral steel pipe.

There are some other advantages of spiral steel pipe. In water engineering, we usually use the spiral steel pipe. The spiral steel pipe also can use in various fields, such as urban construction, power industry, petrochemical industry and so on. There are 20 major products developed by spiral steel pipe. They deliver liquids like drainage or water. Steam, gas, liquefied petroleum gas and other gas transportation are also transported by spiral steel pipe. There are some structural purposes for us choose spiral steel pipe. These structural purposes include buildings, docks, and bridges and so on. However, the process of welding steel pipe is high efficiency. These are some advantages of spiral steel pipe.
In order to improve the arrest ability and toughness, we should reduce the sulfur content which is a body of the steel pipe. In order to achieve one goal that delivers fewer inclusions to the swap, we also need to reduce inclusions. But the content of phosphorus is lower than other content. The phosphorus on the walkability and steel toughness are a hazard. We can increase numbers of added titanium and the content of vanadium niobium and move walkability through reduces the content of phosphorus. The quality of the spiral can be influenced by defects of welding. These are some advantages of spiral steel pipe.
In conclusion, consumers choose product for its benefit. While spiral steel pipe have a number of advantages. These are reasons why people choose them. These advantages of spiral steel pipe are the reasons we choose steel pipe.
The Advantages of Spiral Steel Pipe Strength
Pipe under internal pressure, usually on the wall there are two main stress, namely the radial stress delta Y and delta X axial stress. Synthetic stress of the weld of the delta delta Y = (l / 4 sin2 alpha + cos2 alpha) 1/2, among them, the alpha for spiral welded pipe weld spiral Angle.
Weld spiral Angle of SSAW is generally 50-75 degrees, so the spiral seam synthesis stress is straight seam welded pipe 60-85% of principal stress. Under the same working pressure, spiral welded pipe of the same diameter than the wall thickness can reduce the straight seam welding.
According to the above characteristics:
A. spiral welded tube blasting occurs, due to the weld is smaller, the normal stress and synthetic stress by blasting mouth does not generally originated in the spiral seam, its security is higher than straight seam welded pipe.
B. when screw near the weld are in parallel with the defect, due to the spiral weld stress is small, so its extension risk than straight weld.
C. because the radial stress is exist in the maximum stress on steel tube, so the weld in the vertical stress direction under maximum load. The straight seam under load, the largest ring to carry the load a minimum seamComputer Technology Articles, spiral seam between the two.
Defects and disadvantages of Spiral Steel pipe
Spiral pipe is a very widely used pipe, sometimes it may require welding, but spiral pipe exsit welding defects.
Under normal circumstances, weld defects of spiral pipe has porosity, undercut and crack phenomena.
Helical tube bubble defects: conducting spiral welded, in the center of the weld bead, there will be the situation of bubble defects, will produce this situation? Main reason is that, in the welding process is hydrogen bubbles form of residue inside the metal. How to solve this failure? Welding process, we need to clear weld the inside of the oil, water and other ingredients, but also need good drying and removing moisture, so that hydrogen does not remain inside the weld . Increasing the welding current in the welding process and the generation of the bubble can be avoided yet.
Spiral undercut: v-shaped groove weld edge, and along the weld centerline, said undercut. Usually undercut is inappropriate because of the current, voltage and welding speed, therefore, the need to control the welding process good speed, so as to effectively avoid the biting edge phenomenon.
The crack of the spiral welded pipe: spiral cracks may be because of the direction of the spiral weld problems, in order to effectively avoid the spiral cracks in the welding process, the need for strict accordance with the welding process to operate the job.
Spiral pipe for the specific requirements of the strip is advancing the weldability of the steel pipe, to reduce the sulfur content in the steel to improve the toughness of the steel pipe and arrestability are useful. It also reduce the sulfide inclusions to the swap, forward the crack resistance of the steel. The phosphorus content in the hot rolled strip is as low as possible, because, thus lowering the phosphorus content of phosphorus on the toughness and weldability of the steel strip are harmful weldability can advance directly, may be appropriate to add increased titanium, vanadium , the niobium content.
Spiral pipe is containing Ni corrosion resistance in an acidic environment, in the environment containing sulfuric acid or hydrochloric acid, the solenoid the Ni content in the higher the corrosion resistance of the stronger. Under the environment in general, simply adding Cr in the spiral can be prevented the phenomenon of erosion.

Breakage of Spiral Steel Pipe
Breakage of spiral pipe according to the material after the destruction of anti-corrosion steel case and metal material is substantially the same divided into three types, namely: ① cleavage fracture, ② tie troglobites anti-fracture, ③ slip surface separation fracture.
Cleavage fracture along a section strictly crystal – product surface separating the planes called cleavage plane. When the fracture along the crystal plane, the theoretical minimum breaking strength. Decision cleavage plane of factors specific surface energy y, the surface of the crystal plane spacing mountains and modulus of elasticity along the normal direction. Cleavage fracture with almost no plastic deformation, is a brittle fracture occurs in the body-centered cubic, hexagonal close-packed gold center. Fcc metals is generally not cleavage fracture occurs. The nature of the genus L ductile material gold sessions, shear fracture is the main fracture mechanism. Such as anti-corrosion steel alloy second phase particles to impede slippage, increasing the resistance to plastic deformation; when the plastic deformation increases, the second phase particles and the matrix interfacial peeling occurs Aung, produce tiny hole; hole formed, grew up with the merger will form a shear section. For high-purity metals, for there is no second phase particles, double metal wear-resistant composite pipe and will not yield: Health and tiny holes, the results of the battle was only shifted along the surface area is increasing, and finally the formation of slip planes separate section. Anti-corrosion steel composite spinning technology under special equipment for precise control, re-pressed wheel rotation and liner friction generates heat quickly reach the softening point of stainless steel, roller squeeze out of the outer tube is elastically deformed, the two create an interference together to achieve closely. From gold session histological point of view, it is divided into the fracture and transgranular fracture along the fracture goods.
Lamination Defect Control Measures of Spiral Steel Pipe
Lamination defect control measures of spiral steel pipe is following below:
1, to improve the toughness of plastic tube
Improve the cleanliness of molten steel, to reduce the harmful inclusions; increase the proportion of the slab crystal axis, to reduce the center segregation and center porosity; the use of reasonable cooling system to avoid cracks occur within the slab; billet or rolling slab to be taken offline slow cooling process, reduce internal stress, thus ensuring the microstructure and mechanical properties of the finished tube and pipe meet the technical standards.
2, the reasonable control of the heating temperature
By measuring the thermoplastic curve, choose the best heating temperature. Note also that there is enough heating tube holding time, in order to reduce and improve plastic deformation resistance and toughness.
3, lower roll speed
Roll speed is a key parameter piercing process, the roll speed from low to high variations in the process, there is a critical stratification began the roll speed. Lower roll speed, easy to form tube bore; higher roll speed, tube and capillary easily form a layered defects. In order to eliminate delamination defects and capillary tube, roll speed should be reduced to the beginning of the critical delamination roll speed or less.
Corrosion Insulation Performance of Spiral Steel Pipe
Anti-corrosion insulation pipe with corrosion resistance of steel, and has good insulation properties, has been widely used and promoted in building construction, and constantly improve and spread. Corrosion pipe insulation having different processing types and methods, different processing method to determine the pipe have different properties and functions, and the use range also changes. As the name suggests, it is to increase the number of external spiral steel pipe corrosion insulation class protection, in order to achieve low temperature can be used. In general, the use of second degree pipe insulation inorganic zinc-rich paint, which temperature ≥400 ℃, belonging to corrosion coating, conduit port is used polyethylene film called 3-layer PE or using cold sealing tapes to achieve the previously installed to prevent moisture entering into the water or construction.
Spiral steel pipe insulation for high temperature, water and fuel pumps, chemical pump corrosive. Insulation pipeline centrifugal pump series products with low noise, performance, energy efficient and reliable. The insulation material used is a multi-layer bandaging wrong seam, so it is effective to reduce the heat loss, but also able to control the jacket surface measures to prevent the generation of cold bridges, so that the outer coating of temperature control is guaranteed. Spiral steel pipe wrapped with insulation material multilayer reflective layer of aluminum foil, which can effectively reduce the loss of heat, and can make the steam pipe can be more economical and reasonable. Anti-corrosion steel pipe insulation is a good corrosion resistance, along with good insulation properties, has been widely used and promoted in the design and construction, the current and constantly perfected and popularized. Spiral steel also have different types and methods of processing, while the different processing method to determine the pipe have different properties and functions, and range will change.

3PE Spiral Steel Pipe use in Oil and Gas Pipelines
3PE anti-corrosion steel pipe for buried pipeline life is critical, the same material pipes buried in the ground for decades and some non-corrosive, and some years it leaks occur. Because they use different outer coating.
In which ordinary steel for use in harsh environmental conditions, there will be severe corrosion, which will reduce the life of the steel pipe, steel pipe anti-corrosion insulation life is relatively long, generally, it can be used under normal circumstances for 30-50 years, and the proper installation and use is also possible to make the pipe network maintenance costs low, anti-corrosion pipe insulation can also set an alarm system, automatic leak detection pipe network failures, accurate knowledge of fault location and will automatically alarm.
3PE anti-corrosion steel pipe insulation performance is good, heat loss is only 25 per cent of the traditional pipe, long run can save relatively large resources, significantly reduce energy costs, and still has a relatively strong waterproof and corrosion resistance, and has no need trench directly on the ground or water can be purchased, but also easily and quickly on the construction, relatively low cost integrated, also at low temperatures and has good corrosion resistance, impact resistance, and in certain circumstances You can also directly embedded in permafrost.

Source: China Spiral Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

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Reference:

  • https://www.yaang.com

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