A ReportonSpiral Pipe Mill

Prepared By:Approved By:Mukesh Kumar SharmaDevraj Khatri(G.E.T.)Standards followed

We produce line pipes for on-shore purpose according to both the standards set by: IS (Indian standards) and API5L (American petroleum institute)-44th edition. IS-3589 is applied to seamless and welded carbon steel pipes for water and sewage of outside diameter from 168.3 to2540mm. This Indian standard is adopted by BIS (bureau of Indian standard). API5L specifies requirements for the manufacture of seamless and welded steel pipes for use in pipeline transportation systems in the petroleum and natural gas industries. 44th edition of ANSI/API is the result of harmonizing the requirements of the following standards: API Spec5L; ISO3183-1:1996; ISO3183-2:1996; ISO3183-3:1999; According to technical requirements for line pipe there are two product specification levels: PSL1 AND PSL2. Level PSL1 provides a standard quality level for line pipe. Level PSL2 has additional mandatory requirements for chemical composition, notch toughness, and strength properties and additional NDE. Material grade range for PSL1 : A25 to X70 Material grade range for PSL2: B to X120 Type of pipe ends in PSL1: plain end, belled end, threaded end and plain end for special coupling.While in PSL2 only plain ended pipe is manufactured. Repair by welding of pipe body, plate and skelp under PSL2. Repair by welding of weld seams with- out filler metal is prohibited in PSL2.

Raw material Main Raw material for pipe making is hot rolled coil of micro alloy steel that shall be made from steel made by the BASIC OXYGEN or ELECTRIC ARC FURNACE. Hot rolling is a metal working process that occurs above the recrystalization temperature of the material. In this process after grain deformation, recystalization takes place; which maintain an equiaxed microstructure and prevent the metal from work hardening. Hot rolled metal have little directionality in their mechanical properties. Steel is micro alloy; which have C, Si, Mn, P, S, V, Nb, Ti, Cr, Mo, Ni, Cu, Al etc. as alloying elements and deoxidizers; the work of these elements is: C- Increases the hardness. Si- Imparts strength. Mn- Reduce formation of Iron Sulphide, make steel hard, tough and wear resisting. V-Increases plasticity and resistance to impact. Nb- improves Welding properties and corrosion resistance. Si- Increases strength and hardness without lowering ductility. Mo- Gives extra Tensile strength. Ni- Improves Tensile strength, Raises elastic limit, imparts hardness, toughness and reduces rust formation. Cr- Improves corrosion resistance. For PSL2 pipe, the steel should be killed and made according to fine grain practice. Steel that is fully deoxidized by strong deoxidizers is known as killed steel. The width of plate used should be between 0.8 times of Outer Dia. to 3 times of Outer Dia.Mill capacity: Dia. range of formed pipe = 18- 84 Main drive max. speed= 14m/min. Auxiliary drive max. speed= 16m/min. thickness of strip that can be formed into a pipe= 6mm to 25mm Width of strip: 800mm- 2000mm Our plants annual capacity is 2.5lac Metric Ton/annum. This can be calculated by the formulaAnnual production= (no. of production hrs in one year) X (main drive speed) X (cross section area of strip) X (DENSITY of metal)Spiral pipe mill is used for making Helical submerged arc welded (HSAW) pipes. Main raw material for this is Hot Rolled coil. We can broadly divide the mill into three sections, namely:-1. Entry line/feeding section2. Forming station3. Exit line

Entry line:This is the section where coil is prepared for forming by means of decoiling, edge milling etc. this consists ofa.) Coil joining wagonDecoiling and online joining of two different coils takes place here. In offline joining we have to stop the forming process for 40 minutes, so by online joining we are saving this much of time per joint, hence increasing the productivity. Wagon can be moved with the max. speed of 20m/min. This wagon is moved on the 130m long rail track. When trolley goes away from the mill, coil unwinds and stays on the idle rollers (82 in nos.) Coil joining wagon is equipped with the following:Hydraulic power pack: power pack has two axial piston pumps which are driven by electric motors. One high pressure and other one low pressure pump. Low pressure pump has higher discharge, and high pressure pump is used for applying the force.The specifications are: High pressure- TYPE- A A10V 0 45 DFR/31R/ PSCR2N00 POWER - 40HP, N = 1475rpm, Q= 45 LPMLow pressure- TYPE- A A10V 00 10 DFR/31R/ PSCR2N00 POWER- 30HP, N = 1475rpm, Q= 100 LPMPower pack also has return line filter to clean the return line oil and cooling radiator filter to cool the oil. Coil car/ coil loading frame: We place the spare coil on it while decoiling the previous coil. Then load the coil to decoiler by means of a hydraulic cylinder.

Decoiler: it has following parts: Coil receiving arm: These are three in numbers. One upper and two are lower arms with one roller at the end and operated hydraulically. These arms are used to receive smoothly the coil when it is loaded on decoiler. Coil lip opener: It is used for opening the packed coil. Hanging guide rollers: This assembly has 6 hanging rows each having 5 rollers. These are used to guide the plate to pinch roll. Radial side guide: These are used to guide the uncoiled plate radially on both edges of the plate. BORE DIA=200mm, PISTON ROD DIA = 125mm, STROKE =660mm Centering disc assembly: These are two in nos. and are used for centering the coil while its opening. Pinch roller: this unit is used to push the opened strip towards main drive. These are two in nos. and driven by electric motor and a planetary gear box. In which 5 stage reductions takes place. Gear box ratio i= 203, 3-phase asynchronous vectorial servo motor having rpm-1800, power- 73kW. We control the speed of motor by using VFD (variable frequency device).One pulley is mounted on motor shaft and other one is mounted on gear box input shaft, first one is twice in dia. in respect of second one. Pinch roller has the same speed as of auxiliary drive irrespective of trolleys moving direction and speed. Max. speed is limited to 16m/min. Pinch roller exit side guide: The side guide is used to prevent the strip movement in direction perpendicular to strip feed direction, this is driven hydraulically. Pinch roller exit guide roller: These rollers guide the strip to leveler. Leveler/Flattener: The work of this unit is to straight the strip by pressing action. This unit carries 7 rollers, 4 on the upper side and 3 on lower side, arranged in staggered form. The lower rollers are fixed whereas upper can be moved up and down hydraulically, for this there are 8 cyls. The up and down motion of cylinders is synchronized by screw jack which is powered by electric motors. No. of screw jack-8,No. of motors-4, Power- .55kW, 1360rpm.Each pair of screw jack is connected by carden shaft which is splined and having universal joint.. We can apply pressure upto 400kg/cm2. After flattener come side guide electrical and then side guide hydraulic. BORE DIA=125mm, PISTON ROD DIA = 90mm, STROKE =750mmStrip clamping moving frame with plasma cutting assly: The width of front and rear end of strip is not uniform (i.e. less than required), so we have to cut the strip from where we get required uniform width, for this the strip is clamped here and cut by plasma cutting torch. The frame can be moved by hydraulic cylinder BORE DIA=125mm, PISTON ROD DIA = 90mm, STROKE =1650mm. Clamping of strip is also carried out by hydraulic cylinders, which are 2 in nos. BORE DIA=200mm, PISTON ROD DIA = 110mm, STROKE =50mm there is a copper saddle to support cutting and welding processes. Plasma head slides on this frame, there are 2 servo motors, one for up/down and second for forward/backward motion. We are using HYPERTHERM-MAX-200 plasma cutting machine. Carriage car is used to carry the cut part of the coil to bin.

Cross miller: this is used to do milling at the end of coil before joining the coils. It can slide on fixed clamping frame with the help of a servo motor.Strip clamping fixed frame with welding accessories: this frame clamp the coil end with the help of 2 cyls. BORE DIA=200mm, PISTON ROD DIA = 110mm, STROKE =50mm. Welding head can slide and can move up and down on this frame with two electric motors each of 90W and 48V DC supply. We are using Lincoln welding set-up of SAW welding. We can control the SAW welding parameters through the man- m/c interaction panel. Welding accessories has flux hopper, wire feeding system, liner and a pointer. Then again there is a side guide with electric motors.

Auxiliary drive : This total frame weighs 16 tons. It has two drive rollers which are driven by motor-planetary gear box assembly on both sides. Motor shaft is connected to a pulley, which drives the gear box input shaft pulley and hence power is transmitted to the drive roller.motor shaft axis is parallel to the gear box input shaft axis. Gear box ratio i= 233.5Motor has specifications: connections- power 95kW, 2295rpm, 78Hz, 340V, 195.5ampsY connection: power 55kW, 1280rpm, 44Hz, 340V, 115.5amps.Auxiliary drives max. speed is limited to 16m/min. this gear box has 5 stage reduction. Synthetic oil is recommended as a coolant, lubricator and heat remover. For flowing the oil continuously we use a pump having Q= 6lpm which is situated in filtration and air/oil exchange unit. For the proper functioning of the gear box oil should be continuously flown and temperature should not go beyond its optimum working conditions. We used spherical roller bearing with withdrawal sleeve. Bottom roller is fixed and upper drive roller can be moved up/down with the help of 2 hydraulic cylinders. Required Pressure can be applied according to the thickness of the plate. This unit is used to drive the strip at the end of the coil joining wagon towards the main drive. We can apply pressure of 25-30kg/m2. When coil moves on idle rollers in rail track it reaches to the pass line height through the taper arrangement of rollers. They are 4 in nos. the main function of these rollers is that they supports coil to move smoothly while they achieve pass line height. Then coil enters to coil support roller assembly. Which are 4 in nos. and have no drive.b.) Intermediate auxiliary drive Its function is to drive the coil to main drive. It has same arrangement as of auxiliary drive. Gear box ratio= 561.8, motor shaft axis is perpendicular to the gear box input shaft axis.c.) Flattener/ levelerIt has the same functions as of leveler situated on the wagon. It has 4 cylinders. to do up/down to the upper rollers according to the plate thickness. BORE DIA=280mm, PISTON ROD DIA = 200mm, STROKE =80mmd.) Coil UltraSonic TestingIt is also called body Ultrasonic Testing. Ultrasonic testing is one of the NDT known worldwide in the field of material testing. Ultrasounds are the sound having frequencies more than 20,000 Hz, audible sound frequencies range in between 20 Hz to 20,000 Hz. Ultrasonic testing uses high frequency sound energy to conduct examinations and make measurements. Ultrasonic examinations can be conducted on a wide variety of material forms including castings, forgings, welds, and composites. Basic Principal Basic principle of this testing is Reflection & Refraction of the sound from the material / defect boundaries. Working principle of the Ultrasonic Probes is Piezo-Electric effect, i.e, Electrical energy is converted into Mechanical energy in the form of vibrations in the ultrasonic crystals and vice versa.Equipment type: We are using 40 channel TR (transmitter receiver) probe made of EEC Company of size 55 X 5mm. We can use the apparatus to inspect coil of width 2000mm maximum. Micro processor control: The micro processor controller PT receives flaw and de-coupling indication from UFD channel.Alarm module: Audio and visual warning system. Automatic paint marking device: with the help of single color spray gun we mark the defect in the plate.Water coupling circuit: Water is used as couplant. Water is circulated to all 40 probes from common header for acoustic coupling b/w probe and coil. A water tank of capacity 500ltr is there to store water. A blower is there to suck and recirculate the water. 1mtr distance is there between blower and edge miller so that the plate gets dry completely. Ultra sonic sound waves of frequency 5MHz is used to detect any surface and subsurface defect (like lamination etc.) present in coil. Probes located at edges should have 100% (i.e. 55mm) detection capacity, whereas other should have minimum 20% capacity.Ultrasonic sound wave is generated by piezoelectric crystals i.e. probes, and travel through the couplant into the strip. If there is any defect in between then the wave reflect back from the defect, which is seen in the form of high amplitude wave on the screen. Probes are basically the transducers which convert electrical energy to mechanical (i.e. sound energy) and vice-versa. Here, 38 probes are arranged in the staggered arrangement and 2 are on both the edges. Acoustic impedance is the material property by which it reduces the wave signals when passing through it.Advantages of Ultrasonic Inspection Sensitive to both surface and subsurface discontinuities. Depth of penetration for flaw detection or measurement is superior to other methods. High accuracy in determining reflector position and estimating size and shape. Detailed images can be produced with automated systems. Limitations of Ultrasonic Inspection Surface must be accessible to transmit ultrasound. Skill and training is more extensive than with some other methods. Normally requires a coupling medium to promote transfer of sound energy into test specimen. Materials that are rough, irregular in shape, very small, exceptionally thin or not homogeneous are difficult to inspect. Cast iron and other coarse grained materials are difficult to inspect due to low sound transmission and high signal noise. Linear defects oriented parallel to the sound beam may go undetected.

(6*T/2)mm flat bottom slot(along the width of coil).(6.35*T/2) mm flat bottom hole at distance of 25mm from both edges.T=Thickness, = Dia. of FBH

Fig. Calibration plate for TR normal beam probe.e.) Edge miller Edge miller is used to bevel the edges of the plate so that they make a double V-groove which is the requirement of SAW welding. Its secondary purpose is to trim the strip edges to ensure a constant strip width. Edge miller is basically a milling machine with rotating milling heads. Milling heads are equipped with reversible carbide tools around the circumference of the milling head. Right now we have 2 sets (4 in nos.) of edge millers. Milling cutter has 10 sets of carbide cutting tools. Each cutting tool set has 3 tools. Generally, on each side of the strip, there are one trimming miller and one profile miller. We are using both the millers for making the profile (two faces and a root i.e. double V-groove). We are using here Kennametal cutting tool. Generally after milling 2 coils, we change the orientation of the worn out part of the tool. By this service life of upto 10 processed coils is achieved. For fastening the tool on the cutter we use packing which may vary in thickness. Bevel angle is 30-35. The width of the root face of the bevel shall be 1.60.8mm.Milling cutter 1: gefran 400v asyn motor power-78kW, 1800rpm, encoder- ERN-420Milling cutter2: magnetic 400v 3-phase async. Vectorial servo motor power 78kW, 1800rpm.One edge miller has 2 hydraulic cyls. BORE DIA=80mm, PISTON ROD DIA = 50mm, STROKE =50mm. Which are used to up/down the cutter in order to align the milling unit to the centre of the strip. It also has horizontal guide rollers. Edge miller frame can be moved in/out according to the width of the coil with a lead screw powered by hydraulic motor.Milling head dia-500mm, rpm-1700, and no load current-36amps.f.) Main driveAs the name suggests its function is to drive the strip to the main forming station and centre the strip during the feed process. It has same set-up as of auxiliary drive. Drive rollers have dia. 600mm. Coil is driven with the help of two rollers powered by DC electric motors of power 143kW, and 1150rpm and a break. Distance b/w break and magnet should be 0.4-0.9mm. an encoder is also mounted on the motor shaft to calculate the PPR(pulse per rotation). The planetary gear box has reduction ratio i=288.5. Main drive maximum speed is 12m/min. we can do up/down to the upper roller according to our requirement. There is a separate power pack for this operation in which we inserted a pressure switch with the required max. and min. pressure. Max. rated torque= 2,90,000N-mIn forming the pipe plate only subjected to axial load only. So we can calculate the axial load i.e f=where R= roller radius = max. rated torqueg.) Strip edge prebenderIf helix angle is smaller, the top side of the strip is stretched laterally to a greater extent than the bottom side of the strip. This leads to so-called peaking on the finished pipe body in order to compensate this effect strip edges are prebent in the opposite directions prior to the pipe forming process. Prebending is done by prebender rolls on both the edges of the coil to control peaking at the weldment. These are three in nos. one on upper and two on the lower side of the strip. In which third roller is just for the support. The profiles of these rollers are shown below. Upper roller can be moved up/down manually with the hand wheel. Lower roller can be moved in/out w.r.t coil with the help of screw jack. These prebending rollers can be adjusted precisely that any radius can be achieved. The whole frame can be shifted to in/out according to the width of the coil with a screw jack. In this diagram coil is fed inside and perpendicular to the plane of the paper. Here we can clearly see that edges of the strip will be bent slightly when coil passes through it. It is necessary to do tack welding and matching both the V- grooves of the meeting edges. After edge prebender there is a horizontal strip guide which supports the strip to the forming place. These strip guides are 6 in nos. in which 3 are on upper side and 3 on lower side. Each strip guide has rollers which roll with the moving plate. We press these strip guides to press the coil with the help of inside threaded stud rod.

Fig. schematic diagram of edge prebender rollers arrangement

Forming stationThe hot rolled coil is formed into spiral pipe in the three-roll bending machine which permits a large no. of adjustments according to the pipe dia., thickness of coil and material quality. There is a pivot/pin around which all the rotating frames and run-out table can be moved according to the helix angle. Pin centre is 6425mm distant from the main drive roller centre. And the height of the pass line (along which strip is fed.) from the ground level is 1500mm. the deformation forces are approx. 300Ton. Forming bed can rotate around the pin according to helix angle, with the help of a hydraulic cylinder, having stroke 500mm.forming bed can also be moved horizontally in the direction of exit line, with the help of a hydraulic cylinder. Forming station consists of:a.) Front roller beam: This is the beam that strip faces firstly. It has 10-15 no. of rollers. The individual rollers are made of rolling- bearing steel and are equipped with special bearings and are auto-lubricated. The calculated service life of the individual rollers is the 1500 production hrs. there are 4 adjustments in this beam namely:1. Roller beam front IN/OUT adjustment: motor- 1.1kW, 1370 rpm, no. of screw jack-22. Roller beam front swivel adjustment: motor-0.37kW, 1380rpm, no. of screw jack- 23. Roller beam front height(up/down) adjustment: motor-0.37kW, 1370rpm, screw jack-44. Roller beam front approach(left/right) adjustment: motor-1.1kW, 1380rpmFor measuring all the above adjustments there are encoders. All the rollers are to be placed on the cradle which has curvature on one side and can swivel on split bearings. Cradle angle in general: 18-25 (set according to dia. of pipe). All the rollers are connected to each other through tie rod. These rollers can also be moved in horizontal plane and front boom angle we have to set to our requirements. In the diagram below, cradle axis is perpendicular to the plane of paper.

Vertical plane (18- 25) Fig. cross section of cradle and roller arrangementb.) Rear roller beam/buttress:There are 15 rollers in this beam and no. can be reduced or increased according to the width and other requirements. There are 4 adjustments:1. Roller beam rear IN/OUT adjustment: motor -2.2kW, 1420rpm no. of screw jack-22. Roller beam rear swivel adjustment: motor-2.2kW, 1420rpm no. of screw jack-23. Roller beam rear height(up/down) adjustment: no. of screw jack-44. Roller beam rear approach(left/right): motor- 2.2kW, 1420rpmThis whole beam arrangement with approach has been put on the support which is 10 taper towards the front roller beam. Approach frame has 4 concave curvature plates on which screw jack mounted on convex curvature plates on the lower side swings.

c.) Boom: Work of this unit is to provide sufficient deformation force for the cold forming of the plate to manufacture a spiral pipe. This is the upper roller beam. Boom can have upto 14 rollers. Boom is mounted on lever plate which can slide up/down on the lever plate mounting structure. Lever plate is connected to a screw through a 2.5m long arm. So we can say that boom can be adjusted up/down with this screw jack. Screw jack has 100ton capacity and pitch=16mm. screw jack is powered by a electric motor: dual pole squirrel cage induction motor which has two rpm 2950/118 fast and slow respectively. We run it at high speed when we do up/down to the boom and slow speed when we press the plate for the formation of pipe or we can say to do cold forming. This screw jack is also called a jaquator. This motor has power of 16kW, torque- 1360/1290N-m, current- 13.5/45 amps, gear box ratio i= 24.92:1 There is also one more motor-screw jack assly. to adjust the lever plate. The structure on which lever plate slides is tied through two beams to a closed (in shape) supporting plate structure which has been made up of 19 plates of 60mm thickness. d.) Invert roller: it is used to provide the required backing for the tack welding while forming the pipe. This roller is placed on a separate frame. e.) Tack welding:We use iSAM/ LINCOLN set-up for continuous tack welding on inside. This is mounted on the boom as an extension of it, like an arm, projects into the pipe to be formed.. The frequency of tacking is 1000 per sec. and current it can draw upto 14ooamps. Welding set-up comprises: wire feed system, LASER tracking, shield gas unit, chiller unit. Wire feeding speed is controlled by servo motor according to the main drive speed. LASER senses outside groove. We use co2 as a shielding gas for the tack welding because it is the most cost effective shielding gas. We preheat the gas before using otherwise cold gas will produce cracks in HAZ. If we use the mixture of inert and active gas then improved metal transfer, more stable arc and lesser spatters can be achieved. Heavier the gas is more effective in arc shielding action. If we use 80% Ar+20% O2 then there wont be any spatter. Since we are only tacking, so most of our purpose is fulfilled by using CO2. Metal is transferred through the pulsed transfer which is controlled method of spray transfer. For this highly sophisticated power source and wire feed system is required. Here current and heat inputs are also higher. This mode of transfer can be used on micro, low alloy steel and mild steel. Visible stick-out is generally maintained at 25mm. Water cooling is provided for the welding holder. Automatic LASER tracking is also there which senses the outside V-groove. We also provide air and water cooling for the LASER. We can operate the welding system in both auto and manual mode. Tack welds shall be melted and coalesced into the final weld seam.

f.) OD CAGE: In order to stabilize the very tight tolerances, the produced pipe is guided and supported by an outside guide cage. This additional device prevents uncontrolled shifting of the strip edges during the welding process. Without the pipe guide cage it would not be possible to ensure perfect welding or compliance with the tolerances for the pipe dia. or for the roundness and straightness of the pipe strand. This OD cage encloses the formed pipe. The outside guide cage consists of individual roller beams with swiveling single rollers. In the case of dimension changes, the roller beams can be adjusted by motors. In this respect, the data which has been set on one time is reproducible by electronic data storage. OD cage has following adjustment:1. Column assembly(up/down)2. Support roller beam vertical adjustment(up/down)3. Support roller beam horizontal adjustment(in/out)4. Adjusting unit-I horizontal(in/out)5. Adjusting unit-II vertical(up/down)6. Pipe caging base(up/down)We can adjust all these according to pipe diameter.

Exit lineRun out table: this part of exit line is used to handle and support the pipe coming out from the forming station. Pipe run-out section can be swiveled in order to set the pipe diameter. Run-out table is connected to the forming base through a rod and hinge frame. Earthing brushes are also fastened on run-out table. Run out table has two V-gates having two motor driven rollers each. Then to cut the pipe strand to the required length we have on -board plasma cutting trolley. After plasma trolley there is a pipe lifting device with hydraulic cylinder. Then to support the rotating pipe, pipe lowering device is also there which are 5 in nos. which is hydraulically operated : BORE DIA=125mm, PISTON ROD DIA = 70mm, STROKE =465mm. each pipe lowering device has two electrically powered rollers. In between there is also a skid arrangement for transporting the pipe to the swivel trolley. Gap control unit: Curvature in the longitudinal axis (strip camber), in particular at the front and rear ends of the strip, result in permanent deviation in the helix angle and in the length of the two strip edges. Deviation in the strip edges lengths also caused strip edge offset since one larger and one smaller circumference are welded together. Any angle deviation which arises must be corrected in order to obtain a constant pipe diameter. So to match perfectly the edges of two strips while tack welding we need a gap control unit which moves the run-out with the small changes in the helix angle. Gap control hydraulic cylinder: BORE DIA=160mm, PISTON ROD DIA = 100mm, STROKE =600mm. There is a power pack provided for it.Plasma cutting platform: The endless pipe strand is cut into single pipe lengths in a cutting unit. The cutting equipment used is a plasma cutting unit accommodated on a carriage which moves with the pipe at the corresponding run-out speed.Plasma the fourth state of matter. The first three states are solid, liquid and gas. For the most commonly known substance-water- these states are ice, water and steam. If we add heat energy, the ice will change from a solid to liquid, and if more heat is added, it will change to steam. When substantial heat is added to a gas, it gets ionized, and its state changes from gas to plasma, the fourth state of matter. Plasma is an electrically conductive gas. The ionization of gases causes the creation of free electrons and positive ions among the gas atoms. When it occurs, the gas becomes electrically conductive with current carrying capabilities. Thus, it becomes a plasma. One example of plasma, as seen in nature, is lightening. Just like plasma torch the lightening moves electrically from one place to another. Plasma cutting is a process that utilizes an optimized nozzle orifice to generate a very high temp., ionized gas so that it can be used to melt and cut sections of electrically conductive metals. The cut is very clean and heat affected zone is negligible; however it must be ensured that the gases escaping from the plasma unit are discharged. In plasma cutting we use two gases one is plasma gas and other one is shielding gas. Plasma gases are: air, N2, O2, Ar-H2. Shielding gas surrounds the arc and cools the torch. Shielding gases are: air, CO2, O2-N2, N2, and CH4.

PLASMA GASSHIELDING GAS(-)ELECTRODE (+)WORK PIECE

Fig. plasma cutting processWe are using plasma cutting machine designed by HYPERTHERM, model-MAX200 and HT4400. MAX200 is used to cut MS plate of thickness upto 20mm and with speed upto 2mtr/min. Current used is 200amps and air plasma and air shielding is used. Plasma gas inlet pressure and shield gas inlet pressure is set to 90psi. Water is used as coolant. Many warning indicators essential for cutting are displayed. Plasma trolley is synchronized with the main drive speed and powered by two electric servo motors, one on each side. Servo motor specifications are: power- 1.467kW, 4000rpm, and gear box ratio i=138.63. Servo motors are used for high precision. In stop condition we cant rotate motor shaft freely as the magnetic field generated inside it by permanent magnets doesnt allow it to rotate. All cutting parameters like torch to work distance, arc voltage, travel speed etc. are selected by using cut chart. As cutting speed increases arc voltage decreases and vice-versa.Swivel trolley: this is used as a transport carriage to carry the pipe from run-out skids to the starting line of conveyors. There is a power pack on swivel trolley for two lifters on both sides. Trolley moves on two curved skids, one is larger in radius and other one is smaller in radius. So to reach at run-out the wheels which move on larger radius have to travel longer path. The wheels velocity ratio= 1.6. As skids are not perpendicular to the swivel trolley so to centre and balance the pipe according to swivel trolley, there are two ejectors, one on each end. When trolley receives pipe it carry it to the lifter-cum-conveyors and stops when limit switch has been cut. Then lifters rise the pipe above the height of swivel trolley lifters. Now trolley is free and it moves back to the run-out and wait for the next pipe. Swivel trolley motor details are: 50Hz-1450rpm, 60Hz- 1710rpm, rpm of gear box output shaft= 33, power of motor- 5.5kW.

FORMING PROCESS

First of all we receive the process and product sheet from quality department. Then we set the forming bed and run-out as per helix angle with the help of hydraulic cylinders, helix angle is the angle between pipe axis and spiral weld seam. Which is calculated from the formula:= Cos-1 {coil width / (OD-t)}

Coil width Strip feed

Fig. pictorial view of coil showing helix angle calculationDuring the pipe forming process the C point meets with point A. hence AC will be the circumference of the pipe. And AB will be the spiral weld seam; BD will be the pitch which is parallel to the pipe axis. So angle between AB and BD will be helix angle, which is equal to angle ACB. AC is perpendicular to BD. So in ACBCos= coil width/circumferenceIn CBD Cos(90-)=coil width/pitch pitch=coil width/Sin If strip feed speed is Vf and pipe forming speed is Vp thenVp = Vf CosThis formula is used to synchronize plasma trolley speed with strip feeding speed.

Fig. cross section of pipe

Where: t= thickness of the strip = helix anglehelix angle can vary between 45-80 Angle of front beam rollers, rear beam rollers and boom rollers is set according to the below formulas:f= Cos-1 {coil width / (OD-t)}r= Cos-1 {coil width / (OD)} b= Cos-1 {coil width / (OD-2t)} Where f is angle of front beam rollers r is angle of rear beam rollers b is angle of boom rollers dmin=210mm(assumed) for 18 pipe dia., for every 2 increase in dia, d is increased by 10mm. it advisable that the line joining centers of front roller and pipe should be tangent to the boom roller for greater roller life. Set cradle angle, Check all the drive conditions, Load the coil on decoiler, open the coil with lip opener and forward it through pinch roller. Center the coil using side guides, Adjust the leveler according to the strip thickness, Adjust the milling cutter as per the weld geometry and strip width, Strip is fed to the three roll bending machine through the main drive, Push the lever plate to get a desired curvature, and match it by Template which is made according to required dia. If dia. is more than the required, down the boom. In process sheet three dia. min., nominal and max. are specified. So starting formation of pipe should be with min. dia., because max. Probability is of that pipe dia. will increase till it reaches to the run-out. Once the required dia. is attained the feeding is stopped after every 25 to 30mm feeding and edges of strip are tack welded manually, do it until the pipe reaches to first V-gate roller. Set the shielding gas flow to 80lpm, also set voltage as required, Now start iSAM system in Auto/Manual mode, Control the strip edge gap while tacking and pipe dia. using gap control cylinder, In each pitch length measure the circumference twice, Cut the pipe in required length by plasma cutting machine. Cut pipe is moved on rollers of pipe lowering device and slightly rotated pipe is dropped on skid, Take this pipe on swivel trolley, Carry it to the starting of conveyor line. Through the conveyor line it is transported to initial inspection section.