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Machines for the production of

Bi-Metallic Clad Pipes Theirapplication and manufacturingmethods

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The Pipe Calibration and Lining Machine, type HFC, is manufactured in varioussizes:

Tool locking pressure from 2,500 100,000 tons Pipe lengths from 2,000 13,000 mm Pipe dia from 12 914 mm Wall thickness from 1,5 38mm Productivity between 4 120 pipes / hour

Our scope of supply includes the complete equipment components from the design ofthe manufacturing process to the acceptable product.

Single machines and tools or alternatively the complete range of equipmentnecessary before and after the core machine.

Example of equipment layout:

An economical comparison between our equipment and other methods is detailedlater in this text.

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Fields of application

Mechanically clad pipes for media transport

Drill pipes

Special pipes for reactors (bundles)

Precision pipes for special application (with internal weld overlay)

Hollow sections: for use in steel Structures

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Functional description of the machine

To enable the manufacture of dimensionally accurate straight and round pipes, thelong seam welded pipe has to be calibrated.

The best results, with respect to dimensional tolerances as well as the manufacturingcosts, can be achieved with the equipment described hereinafter.The equipment so named as, High-pressure- Forming- Centers, have successfullyproved themselves over the last 15 years. The use of these machines allows pipemanufacturers to meet their requirements with respect to quality and quantity.

- The pipes to be processed are inserted in a tool which consists of an upperand a lower form. The bottom tool half travels by means of a sliding table to a

loading position where the pipe to be calibrated is inserted into the lower toolhalf by overhead crane. The sliding table then returns to the calibrationposition. The upper tool half is lowered by means of several hydraulic cylinderssuch that the pipe is enclosed by both, upper and lower tool halves. The actualclosing force exerted by these cylinders must be sufficient to close the tool,taking into account the presence of deflections created during the long seamwelding operation (banana effect).

- Both ends of the pipe are sealed by axial cylinders, which are equipped withextension shafts and sealing heads. The two tool halves are locked againstrising forces and are pre stressed. The pipe is filled from a tank reservoir and

flushed with a water-emulsion mixture until all of the air present has beenremoved.

- The axial force exerted on both pipe ends is controlled directly in relation to thecircular cross sectional area of the pipe and the internal pressure, thusensuring that the system will remain sealed while the pipe circumferenceexpands and the length decreases.

- As internal pressure increases, the pipe being calibrated is gradually forcedagainst the inner tool contour. As soon as this has taken place, the internalpressure is increased to the calculated calibration value and held for apredetermined time.

- The internal pressure is then relieved and the axial cylinders are retracted. Thecalibrated pipe is almost completely emptied. The press water is collected andpumped back to the reservoir tank.

- The tool locking system is opened, the upper tool half is hydraulically elevatedand the sliding table, with the bottom tool half, travels back to the loading / unloading position.

- The calibrated pipe can be unloaded from the tool.

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Machine and tool applications for the manufacture of mechanically cladpipes

In this process, a stainless steel pipe is inserted into a carbon steel pipe. Theinsertion process, as well as respective preparations for the mechanical cladprocedure, are performed manually or semi-automated adjacent to the calibrationmachine. The prepared pipes are inserted into the open tool by means of a liftingdevice. Following tool closure, the inner stainless steel pipe is filled with water, airextracted and sealed up. No water should find its way between the inner and outerpipe. The pressure in the inner pipe is increased to a pre-calculated value, until it isplastically deformed over its full length and surface until it makes full contact againstthe inner contour of the outer pipe.

The water pressure is further increased until the outer pipe is forced against the innercontour of the tool, this being at the limit of the elastic deformation of the pipematerial. After a short, predetermined holding time, the pressure in the inner pipe isrelieved and the pipe is emptied by retracting the two axial cylinders with their endsealing dies.

The difference in behaviors of the elastically deformed outer pipe and plasticallydeformed inner pipe results in the desired compressive stress between both pipes.

The applications and manufacturing method are detailed on the following pages.

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Clad Pipes their application and manufacturing methods

The transportation of crude oil and crude gas within pipeline systems requiresmeasures to prevent corrosion damages due to the aggressiveness of media whichare polluted by hydrogen sulfide, chlorides and water. A traditional method used isthe addition of inhibitors into the media transportation, for example glycerin or othermostly organic compounds. Due to the expenditure necessary for the injection plant,the waste disposal, the continuous breakdown susceptibility, with its maintenancecosts as well as the possible dangers to the environment, this method is normallyonly used on high productive oil and gas fields.

The demand for pipe line systems which encompass the use of corrosive resistantmaterials is on the increase. To cope with the

various degrees of aggressiveness, i.e. thequantity and kind of condensates included inthe respective media to be transported, differenttypes of stainless steel and nickel alloys have tobe utilized. In general, regardless of their topmarket prices, these steels and alloys however,only provide very low strength values whencompared with low alloys, so-called blacksteels. As a result, high pressures can only behandled if very heavy walled pipe is used. Inorder to, at least partially balance out this

apparent disadvantage, the utilization of so-called clad pipe is recommended. These cladpipes are provided with an approx. 3 mm thicklining made from stainless steels or alloys, thus

ensuring corrosion protection. The outside pipe is made from normal high tensileferrite steels.

One can separate the categories of clad pipes into two types:

Type 1 Metallurgically clad pipes

With metallurgically clad pipes, the high alloyed internal cladding and the ferriteexternal material are bonded together metallurgically as one mass with noseparation.Various processes are utilized to produce such pipe:

Seamless pipes

1.1 Seamless clad pipes can be produced by

- Weld Cladding- Centrifugal casting- Extrusion

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1.2 Metallurgically clad welded pipes are manufactured by

- Rolled laminated plates

whereby the metallurgical bond of the different materials is produced during a hotrolling process.

Due to the metallic bond between the inner layer and the outer cladding,metallurgically clad pipes behave similarly in tests - and applications to that of pipesproduced from one material. Special welding procedures have to be considered toguarantee the corrosion resistance of the inner clad layer.

Type 2 Mechanically clad pipes

Mechanically clad pipes are those where the inner cladding is carried out with aninner liner which is mechanically inserted into the outer pipe. A metallurgicalconnection between the inner liner and the outer pipe does not exist. The nature ofthe mechanical contact between the inner and outer pipe varies and is dependant onwhich manufacturing process is utilized.

Due to technical and economic reasons, Seamless clad pipes as in (1.1) are seldomused for pipelines in the common range of between 8 and 24.Only when the volume requirement are low and of an urgent nature are such weldclad pipes utilized.

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Therefore, practically only two alternatives for clad pipelines remain:

- metallurgically clad longitudinally welded pipes (Type 1.2)- mechanically clad pipes (Type 2)

Before one addresses the economic and technical advantage or disadvantage of theabove noted alternatives, the different methods of producing both pipe groups shouldbe clarified.

A prerequisite for metallurgically clad pipes are hot-rolled metallurgically clad plates.The manufacturing of such plates is carried out in a so-called sandwich process,

whereby ferritic steel plate is rolled together with the clad material in a doublepackage, until the desired final thickness is achieved. In the process a solid metallictransition film is rolled between both materials at high temperatures. Following themanufacturing of the double package, the clad plates are polished resp. shot blastedon the clad side and cut to the final dimensions. Following this process, the plates aremachined with the correct weld preparations for the longitudinal welding, formed in apress to the correct pipe dimensions and thereafter welded with a suitable weldingprocess.This manufacturing process has two limitations:Firstly, due to the common heat treatment of ferritic and alloyed material not allcombinations of material are technically feasible. Secondly, this production method,

being economically questionable, is only feasible for the manufacture of larger pipedimensions, preferably starting from 12 OD and upward

Mechanically clad pipes

The manufacturing of double-walled pipes has been in operation for a considerabletime for certain applications such as heat exchangers, roll pipes etc., whereby in arelatively simple manufacturing process one pipe is inserted into the other. Furtherprocesses developed encompass the shrinking or rolling together of one pipe in theother.

For mass production however, these processes are not suitable for pipelines, as onthe one hand they provide only marginal contact between the two metals and on theother hand they cause concern with respect to the uniformity and reliability.

The requirements of mechanically clad pipe are based, in essence, on the features ofmetalurgically clad pipe, i.e. they must be able to be manufactured with a consistentstandard of length and diameter. In addition they must have calculable as well asverifiable characteristic values and must be suitable for circumferential seam weldingon site.

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The development and manufacturing of mechanically clad pipes

The development of mechanically clad pipes, to be used for industrial applications inoil and gas pipelines, started approx. 30 years ago in Japan, with the manufacture ofso-called C II pipe by Nippon. During this process, the telescoped pipe package issubject to hydraulic inner pressure whilst the outer pipe is induction-heated, so thatthe outer pipe shrinks onto the inner pipe during the cooling process.

This process has been replaced by the utilization of the Pipe Calibration and LiningMachine HFC, described below.

The prepared pipe package is expanded with high internal pressure and is

simultaneously ends compressed by the axial cylinders. This process takes place in atool especially designed for the purpose, eliminates the necessity of additional heattreatment.

The inner contour of the tool is manufactured in accordance with the required outercontour of the final product.

In this process, contact is achieved solely by the different elastic and plasticbehaviors of the ferrite outer pipe and the austenitic material of the inner pipe,whereby the spring-back effect of the ferrite outer pipe is greater than that of theinner pipe. The resulting residual pressure stress of the inner pipe is in the region of

50 to 100 N/mm, which not only provides a homogenous high contact level, but alsovery favorable corrosion features.

Through the utilization of a closed outer tool highest requirements of diameter,roundness and straightness tolerances are guaranteed.

Materials

In general, standard ferritic or low alloyed pipeline steels are used for the outer pipes,e.g. in compliance with API regulations (X65, X70), DIN 17172, GHOST etc.preferably seamless but also welded pipe can be used.Stainless steels, i. e. 316 L, 317 L or similar steels, as well as nickel-base alloys, e. g.Incoloy 825 or Incoloy 625 are used as lining materials in accordance with therespective different corrosion requirements.

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QA Requirements

For strength and safety calculations of the pipe lines, the characteristic values, i.e.yield strength and notched impact strength of the outer pipes, only are verified.Normally this verification takes place prior to the further processing into amechanically clad pipe, as the these values, due to the minimal expansion of theouter pipe, only vary negligibly.

In general, only the chemical analysis of the inner pipe material is established, acorrosion test can also be carried-out.

Various tightness and pressure tests can be carried out on both the outer as well asthe inner pipes.

The certification of the pipe normally encompasses only a pressure test of the finalproduct as well as a control on the respective pipe identity number, ensuring thateach individual pipe can be traced at any time.

This pressure test is carried out immediately following the expansion, in the opentool, in the same HFC AWS Schaefer Machine.

Additional non-destructive tests, e. g. ultrasonic or x-ray tests, can be performed onthe outer and inner pipes either before the or after completion of the clad pipe.cladding process

Pipe End Preparation

In order to present a perfect circumferential weld set-up, when laying themechanically clad pipe, the ends are milled to apredetermined form. To facilitate welding of mechanicallyclad pipe in the same manner as the metallurgically cladpipe, it is recommended to seal weld the theoretical ringgap between the outer and inner pipe.

Seal Weld

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An alternative potential end preparation is to overlay weld the ends to a length ofapprox 100 mm internally, at both pipe ends of the pipe. In this case, the pipe endscorrespond exactly to the weld set up and the shape of metallurgical clad pipes .

Economical aspects

The basic thought behind the use of clad pipe is the fact that all requirements withregard to strength (internal pressure load, tension, torsion and bending stresses) arefulfilled by the cheaper ferrite outer pipe, whereas the requirements regarding

corrosion resistance being complied with by the lining made from (more expensive)high alloy steels or nickel based materials.

For positive corrosion protection, a lining thickness in the range of 2-3 mm will sufficewhilst the wall thickness of the outer pipe depends on the above noted strengthrequirements and can be up to approx. 30 mm.

In addition, it should be taken into account, that the strength values of high alloyedsteels and materials are only half the values of ferrite steels, whereby the applicationof corrosion resistant pipes would lead to a substantial increase of the wall thickness.

Economical comparison (as of January 2007)

The following is a cost comparison of a pipe for the transport of natural gas, which ispolluted by hydrogen sulphide and chlorides, with a pressure of approx. 150 bar. Thepipe has an outer diameter of 12 (323.9 mm), the following assumptions are made:

1. Full pipe of material 316 L2. Welded metallurgically clad pipe API X 65/316 L3. Seamless mechanically clad pipe API X 65/316 L

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Case 1:Taking the previously mentioned circumstances into account, the wall thickness of apipe made from ccorrosion resistant steel 316 L would be approximately 15 mmresulting in a pipe-meter-weight of approx. 120 kg/m.The costs for such a longitudinal seam welded pipe are represented as 100/m.

Case 2:In a combination of API X65 with a lining made from 316L the wall thickness wouldbe approx 10 mm X65 plus 3 mm for the lining, resulting in a pipe meter weight of105 kg/m.

Cost of such a long seam welded pipe: are represented as 80/m against case 1.

Case 3:A combination of a seamless outer pipe X65 with a 3 mm inner liner from 316 Lwould result in a similar wall thickness ratio as noted in Case 2, i.e. 10 mm + 3mm.

The cost for such a mechanically clad pipe are represented as 46/m against case1.

The actual case comparison shows a cost reduction, when utilizing a mechanicallyclad pipe, of over 54 % compared to the full pipe and approx. 42,5% compared to themetallurgically clad pipe.

With increased wall thickness or / and quality of the lining material the economicaladvantage of the mechanic clad pipe is even higher.In addition the reduced welding times for thinner walls when welding thecircumferential seams, compared with the full pipe should not be neglected.

The Pros and Cons of metallurgically and mechanically Clad Pipes Comparison of technical Applications

When considering the high economical advantages, the disadvantages ofmechanically clad pipe compared against metallurgically clad pipe are negligible.

During the laying process of mechanically clad pipe, one has to ensure that the pipeis not being subjected to a bending radius of smaller 40 x D. For example, theminimum bending radius of a 12 diameter pipe is approx. 12 m. Bending radii belowthis value may subject the pipe to wrinkling, which, as a result, may cause localiseddetachment of the lining pipe. Normally this requirement does not present a problemfor generic pipe laying methods; only the so-called Reeling of Spools is excluded aspracticable laying method.

In addition, when making works inspections, it should be noted that the wall thicknessof the inner lining cannot be measured from outside using the ultra-sonic measuringmethod. If such an inspection should become necessary, it has to be carried out fromthe inside.

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One of the big advantages of mechanically clad pipe is fact that either seamless orwelded outer pipes can be utilized, the integrity of which having already been ascertained during the pipe production process. In addition, the inner linings can beseparately subject to all necessary tests and inspection, thus ensuring a fault-free,homogeneous lining thickness.

With regard to the circumferential seam welding on site, both pipe types can beevaluated similarly. In both cases, reliable and proven welding methods are required,which ensure that the inner surface of the lining material is not contaminated by otherwelding materials. Using an appropriate pipe ends preparation, e.g. by seal weldingor clad welding, both pipe groups can be regarded as equivalent.

Conclusion

Hundreds of kilometers of mechanically clad line pipe produced on our HFCmachines have, successfully been in use for more than 15 years, both for onshore aswell as for offshore applications. The production method as well as the characteristicsof the pipe have previously been inspected and approved by almost all renowned oilcompanies. The pipes have been produced in section lengths of 12 m, at diametersranging from 6 to 20 with wall thicknesses of up to 30 mm.

From all clad pipe currently in use, the share which has been produced on Schfer

HFC machines is more than 50%. There has been no report on any leakage orcorrosion damage, to date. In the light of the high economic efficiency and technicalreliability of this method, taking into account the increasing requirement, acontinuously growing demand of line pipe produced on HFC machines can beexpected.

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HYDROSTATIC PIPELINING AND CALIBRATION

PRESS

TYPE HFC 380

AWS Schfer Technologie GmbH

Equipment Tools Special Machines

Oberhausener Str. 8, 57234 Wilnsdorf, Germany

Phone: + 49 2739 87003-0

Fax: +49 2739 87003-10

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Description of the machine functions

In order to calibrate the inner stainless steel pipe into the outer carbon steelshell, the inner pipe is initially subject to a high internal water pressure over itsfull length, when contact has been made between the inner lining and the outershell pipe, the water pressure is further increased until the inner piper is forcedagainst the outer shell in a plastic state. The outer shell is also subject to anelastic deformation under such high pressure. The complete pipe length is in-housed in a tool which is machined to the desired pipe size. The pipe to becalibrated is placed into a 2 piece tool by overhead crane. During loading, thebottom tool half travels, by means of a sliding table, into the loading position.Once the pipe is loaded, the table travels back into calibration position. Theupper tool half is thereafter lowered by means of hydraulic cylinders onto thebottom tool half so that the pipe is fully enclosed by the two tool halves.The force to hold both tool halves closed must be sufficient to press thelongitudinally banana-shaped, oval pipe, into the die.

Two axial cylinders equipped with extension rods and sealing heads close thepipe ends hermetically, the two tool halves being mechanically interlocked tocounteract the forces created during the calibration operation.Thereafter, the pipe is filled and flushed with an emulsion, from a tank reservoir,until there is no air left in the pipe. The force transmitted on both ends of thepipe, by the axial cylinders, is increased automatically by the machines controlprogram, in direct relation to the build up of the internal pressure within the pipe,thus ensuring a positive end seal during the process.

As internal pressure increases, the pipe outer surface gradually makes contact

with the internal contours of the tool. As soon as full contact is achieved theinternal pressure is raised to the calculated calibration pressure.On completion of calibration the internal pressure is relieved and the axialcylinders are retracted. At the same time the pipe is almost completely emptiedof fluid, the forming liquid is then filtered and recycled back to the reservoir tank.The tool locking system is opened, the upper tool half moves up and the slidingtable with the bottom tool half, as well as the calibrated pipe, travels to theloading/unloading position. The calibrated pipe is ready to be unloaded by overhead crane.

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Machine Capacities

The machine is basically equipped to handle a pipe length of 12,2 m. To copewith the different pipe diameters the axial cylinder, sealing heads and toolshave to be changed accordingly.The internal contours of the tooling have to be changed out to match with therequired outside diameter of the pipe. We therefore would recommend the useof 1 basic tool for the proposed pipe diameter range:

(Basic machine range - between 101.6 X 8.65 mm and 610.0 x 25.4 mm)

Special Machines: To customers unique requirements.

To handle in between sizes inserts are used.

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Function Events of the Machine

AWS Schfer Technologie GmbH

Equipment Tools Special Machines

Oberhausener Str. 8, 57234 Wilnsdorf, Germany

Phone: + 49 2739 87003-0

Fax: +49 2739 87003-10

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