Title of Invention

CERAMIC LINER

Abstract

The present invention relates to a ceramic liner comprising a single ceramic sleeve (15) housed within a metal liner shell (13), said ceramic sleeve (15) having a compressive strength between 300 and 400 kilo pound per square inch (kpsi); specific gravity between 3.0 and 7.0 and modulus of elasticity ranging between 12500 and 60000 kpsi. A process for forming the said ceramic liner comprising a single sleeve by shrink fitting ceramic sleeve to an outer shell comprises steps of shrink fitting of sleeve by heating the outer shell to high temperature 400 to 550ºC causing sufficiently expansion and dropping the sleeve inside the shell and slow cooling to avoid cracking of sleeve, diamond tool honing to adequately size the inner diameter and diamond tool fine grit finishing to improve surface finish 10 to 50 micro inch.

Full Text

FORM2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10; rule 13) 1. Title of the invention. - CERAMIC LINER 2. Applicant (a) NAME : LARSEN & TOUBRO LIMITED (b) NATIONALITY : Indian (c) ADDRESS : L7 T House, Ballard Estate, Mumbai 400 001, State of Maharashtra, India 3. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed: Field Of Invention The present invention relates to a ceramic liner suitable for high-pressure applications such as in mud pumps used in oil wells. More particularly, the invention relates to a ceramic liner comprising a single ceramic sleeve with high resistance to wear and tear specially during long and continuous use and is cost effective. The invention also relates to a process for forming such ceramic liners by shrink fitting the ceramic sleeve to outer shell and super finishing by diamond honing. Background And Prior Art The ceramic liner is mainly used in mud pumps, which are widely employed in oil drilling industry. Oil drilling basically consists of drilling a suitable hole in the earth crust up to the oil reservoir. In oil hole drilling a synthetically prepared fluid is circulated, which is called mud. The mud circulating system is very vital to oil hole drilling. Mud pumps are at the center of mud circulation system. A mud pump is triplex (with 3 cylinder), horizontal reciprocating, positive displacement piston pump. The pump being an essential part for running of the mud circulation system requires to be operated continuously during oil hole drilling operation. The liner is the component of the mud pump where the pressure is generated. Accordingly the liner performance is very important to working of the mud pump. The liner on its inner diameter has a piston, which reciprocates within it. The piston generally consists of a metal rod over which a piston rubber is fitted. The liner is used as chamber to pressurize the mud. 2 During operation, the piston reciprocates back and forth. Continuous operation leads to wearing of the internal diameter of the liner on friction with the mud. The main performance of the liner is restricted by its wear life. A mud pump consists of two major portion mainly fluid end and power end. The mud is received at the fluid end and then compressed to high pressure and dispatched to discharge line. Power end of the pump receive power from the prime mover, i.e., engine or motor and translate rotating motion to linear motion. The fluid end has a fluid end module or cylinder. Each module has a suction manifold and discharge manifold where suction and discharge piping are attached respectively. The fluid end has internal valves and a cavity to receive the liner. The liners are fitted horizontally in the fluid end module (cylinder). Based on the individual mud pump design, the liner fitment provisions are different. The liner is replaceable hence the design of fluid end module is such that adequate accessibility is provided to replace the liner. Liner for mud pumps may have various designs as described hereunder: It may be of a monolithic liner where a tube of steel is machined to size, carburized and the internal diameter is hardened and then machine finished. A tube may be cut to size and then hard chrome plating is deposited on the internal diameter. 3 Bi-metallic liner consisting of outer thick walled steel shell and an inner thin white C.I (Cast Iron) sleeve. The sleeve is hardened. The steel shell and white C.I. sleeve are assembled and then finish machined. It is known that monolithic, chrome plated liner are having substantially less life compared to known art bimetallic liner. As liner replacement requires mud pump to stop which results in loss of drilling time, it is always desirable that liner life should be long taking into consideration the working condition with increasing pressure and temperature and use of more abrasive mud. US5942353 describes usage of multiple ceramic sleeves (barrels), which result in piston cutting at the edge of sleeves. CN1448365 elaborates a ceramic liner with very low strength. Hence it is not suitable for high-pressure mud pump applications. U6467812, US5924353, US5123439 disclose use of either cement or epoxy adhesive or a bonding layer. This is not advisable for mud pump liner as under high pressure, the adhesive may give way and due to piston movement, the ceramic sleeve may come out which will result in a major accident. Mud pump liner application prefers a mechanical fit like a shrink fit. US5137789 teaches plasma spraying of ceramic on the metal body. This process is highly specialized and is very costly. The ceramic liner of the known art comprises sleeves, which are variously fitted. US6086338 describes a fitment of ceramic liner sleeves into an interior cylinder. The ceramic liner sleeves are fitted by 4 expanding the diameter of cylinder, inserting the liner and then cylinder the diameter of the chamber. US5924353 describes assembling multiple ceramic barrels with outer tube and two metal retainers at two ends of the tube by use of cement or adhesive makes ceramic liner barrel. The adhesive is resistant to pressure and temperature. US6467812 describes the ceramic liner, which is adhesively bonded to the body, made of high strength ductile steel, using epoxy adhesive, which is responsive to heat for release of liner. CN1448365 describes ceramic cylinder liner based on zirconium toughened Alumina ceramic. The main constituents are zirconium, Alumina, silicon powder. The strength of the ceramic cylinder liner is 320Mpa. US5123439 describes ceramic liner (sleeve), which is fitted into the valve bore of valve using the bonding layer. The bonding layer can be of suitable material which has high chemical resistance. US5137789 explains manufacture of composite ceramic and metal article by in situ casting or by plasma spraying. US4376374 describes a metal ceramic composite made by coating a metal grid with viscous ceramic slurry and thereafter firing to form the ceramic into a unitary structure. The ceramic liner known in the art has limitations with respect to hardness and consequently wear/abrasion resistance and such limitation reflects on the performance of the liner and such liners fail 5 to deliver the required performance particularly in high pressure application. Thus there exists a need to provide ceramic liner with high resistance to wear and tear specially during long and continuous use as well as which is cost effective. Further there is need for ceramic liner wherein the sleeve is fitted properly to outer steel shell and the bore is finished to size required having good surface texture (finish) and a process for forming such ceramic liners by shrink fitting the ceramic sleeve to outer shell and super finishing by diamond honing and process of formation of the sleeve. Objects Of Invention Thus the main object of the present invention is to provide a ceramic liner with single sleeve having substantially long liner life as compared to known art. Another object of the present invention is to provide a process for forming ceramic liner by shrink fitting ceramic sleeve to outer shell. Further object of the present invention is to provide a process for forming ceramic liner by shrink fitting ceramic sleeve to outer. One more object of the present invention is to provide a process for super finishing by diamond honing. Another object is to provide a ceramic liner adapted to endure high pressure during working conditions 6 Another object is to provide a ceramic liner such that when in use in mud pump the down time is reduced and thus productivity of oil hole drilling process is increased. The other object of the invention is to provide a ceramic liner with single sleeve that is adapted to be used selectively for pumps used in oil well and water well drilling; plunger pumps for slurry and toxic fluid handling; Internal combustion engine where replaceable cylinder are used. Summary Of Invention Thus according to the basic aspect of the present invention there is provided a ceramic liner comprising a single ceramic sleeve housed within a metal liner shell, said ceramic sleeve having a compressive strength between 300 and 400 kilo pound per square inch (kpsi); specific gravity between 3.0 and 7.0 and modulus of elasticity ranging between 12500 and 60000 kpsi. According to another aspect of the present invention there is provided a ceramic sleeved liner comprising a single ceramic sleeve housed within a metal liner shell, said ceramic sleeve having a thickness of between 5 to 15 mm, interference of between 0.15 to 0.35 mm, a surface finish of the inner diameter of the ceramic sleeve of between 10 to 50 micro inch. According to a further aspect of the present invention there is provided a process for forming ceramic liner comprising a single sleeve by shrink fitting ceramic sleeve to an outer shell comprising the steps of 7 i) Shrink fitting of sleeve by heating the outer shell to high temperature 400 to 550 ° C so that it sufficiently expands and cautiously dropping the sleeve inside the shell and slow cooling to avoid cracking of sleeve; ii) Diamond tool honing to size the Inner Diameter within tolerance of ±0.13 mm iii) Diamond tool fine grit super finishing to improve surface finish 10 to 50 micro inch. Detail Description Of Invention The thickness of the ceramic liner is a critical feature and determine the hardness and strength properties including resistance to wear/abrasion. The thickness of the ceramic sleeve in the conventional liners is in the region of 4.0 to 6.5 mm and due to manufacturing limitations liners of higher thickness could not be manufactured. The applicants have been able to achieve higher thickness by the aforesaid process. The thickness of the sleeve according to the invention is preferably between 6.5 to 13.0 mm. The thickness of the ceramic liners is determined by the following equation : Thickness = (Outer diameter - Inner diameter) x ½ The interference factor of the ceramic liner a represent the forces which hold the sleeve and shell together. The interference is the difference of the outer diameter of the sleeve and inner diameter of the shell. The ceramic liner according to the invention preferably has interference factor of 0.15 to 0.35 mm 8 The surface finish on the inner diameter of the ceramic liner has a critical bearing on the working life of the liner as well as the working life of the piston. Roughness in the inner surface of the ceramic liner will create greater friction and enhanced abrasion compare to a smoother surface leading to longer working life of the liner and the piston. The ceramic liner according to the invention has a superior surface finish compared to the conventional ceramic liners and this is achieved by the process of the surface treatment of the liner. The surface finish of the ceramic liner according to the invention is preferably between 10 to 50 micro inch. The higher compressive strength of the ceramic liner allows use for longer continuous periods and high pressure applications. Ceramic liner of the present invention comprises steel shell and single ceramic sleeve. Preferably a collar is also present. The collar of steel is either welded or shrink fitted to the shell as is conventional. The ceramic liner of the present invention comprises ceramic sleeve selectively made from alumina, zirconia and mixtures thereof along with conventional materials. Preferably the liners are made of pure alumina with traces of zirconia (Zr203), silicon oxide, magnesium oxide, iron oxide and titanium oxide, or from pure zirconia (Zr203) with traces of alumina, silicon oxide, magnesium oxide, iron oxide and titanium oxide, or mixtures thereof. Conventional additives and/or impurities like oxides of metals as well as non metals, sulphur and phosphorous which are present in lower than 1.00 % cumulatively. The said ceramic sleeve of the present invention has a compressive strength between 300 and 400 kilo per square inch (psi), which is preferably 380 kilo psi; specific gravity between 3.0 and 7.0, preferably 9 3.85 for pure alumina (AI2O3) with traces of zirconia (Zr203), silicon oxide, magnesium oxide, iron oxide and titanium oxide, or 6.0 for pure zirconia (Zr203) with traces of alumina, silicon oxide, magnesium oxide, iron oxide and titanium oxide, and modulus of elasticity ranging between 12500 and 60000 kilo psi, preferably 55000 kilo psi for pure alumina (AI2O3) with traces of zirconia (Zr203),silicon oxide, magnesium oxide, iron oxide and titanium oxide, or 13225 kilo psi for pure zirconia (Zr203) with traces of alumina, silicon oxide, magnesium oxide, iron oxide and titanium oxide. The present invention is also directed to process of forming the ceramic liner by shrink fitting ceramic sleeve to shell. This is done by heating the shell to adequate temperature so that it expands and then cautiously the ceramic sleeve is put within the shell such that it is not damaged. After that the shell is allowed to cool with slow cooling rate such that ceramic sleeve is not cracked or damaged. The bimetallic liner is also assembled by heating the liner shell but here the cooling rate employed are fast so that C.I. (cast iron) sleeve is held by the shell faster. Also the heating temperature is lower than that in case of ceramic liner. Bimetallic liner is honed on the internal diameter to get the required size. The ceramic liner are honed and super finished. Super finishing is done by appropriate finishing tool, preferably diamond and properly controlled parameters on the honing machine so that high surface finish is obtained. The ceramic sleeve can be manufactured by slip casting or centrifugal casting method before machining and firing. The honing process to achieve the bore size may be replaced by cylindrical grinding. The ceramic used in the present process is made from high grade Alumina or Zirconia and thus it has high strength. The shrink fitting 10 process as described earlier has properly selected parameters so that assembly is done without damage to ceramic sleeve. The super finishing process has been designed to impart high surface finish to the ceramic liner bore. These processes are essential to ceramic liner performance. Ceramic liner Shell is made by either centrifugal steel casting or from seamless steel tubes. According to preferred aspect the ceramic liner manufacturing may be carried out by the process as indicated below A. Shrink fitting by heating the shell to 475 to 525°C , preferably 500°C so that it sufficiently expands and cautiously dropping the sleeve inside the shell and slow cooling in controlled atmosphere to avoid cracking of sleeve. B. Diamond tool honing to size the ID to 165.227 ± 0.127 mm. Honing is done at low speed and high pressure. C. Diamond tool fine grit super finishing to improve surface finish up to 0.15 to 0.6 microns. Super finishing is done at high speed and low pressure. D. Finish machining the outer profile with respect to finished internal diameter (ID) to achieve the fitment diameter and feature required. According to preferred aspect the sleeve may be formed by the process as indicated below 11 1. The raw material used here is 99.5% Alumina (AI2O3) and traces of silicon oxide, Magnesium oxide iron oxide and titanium oxide. Iso press in the mould. 2. Machine to the size and shape in green condition 3. Fire/Sinter at very high temperature (> 1650°C) in high temperature furnace 4. Diamond wheel grinding and honing to size ID 165 x OD 189x length 437 mm. According to another preferred aspect the sleeve may be formed by the process as indicated below 1. The raw material used here is zirconia (Zr203) and traces of silicon oxide, Magnesium oxide iron oxide and titanium oxide. Iso press in the mould. 2. Machine to the size and shape in green condition 3. Fire/Sinter at very high temperature (> 1650°C) in high temperature furnace 4. Diamond wheel grinding and honing to size ID 165 x OD 189x length 437 mm. Honing process consists of a rotating tool head, which also moves up and down, in the bore of the components. This twin motion also with radial pressure applied on the tool through the tool head gives the cutting action. The honing process can achieve fairly good surface finish but to achieve a super finish, different tools like diamond etc are 12 used. The parameters viz. speed, RPM pressure are remarkably different then those employed for the honing process. The time interval for this operation is also different then for honing. The actual process in the super finishing is burnishing (the high spot on the working surface are pressed so that high surface finish is achieved) and not material cutting. Operation Of Ceramic Liner Ceramic liner is fitted in the fluid end module of the mud pump. Depending upon the mud pump design there are various provision for fitment of ceramic liner into the fluid end module. Once fitted the piston is inserted into the ceramic liner. Piston rod is connected to the power end of the mud pump. Once the pump is started, the piston moves back so that mud is taken into the liner and when piston moves forward, the mud is pumped out under high pressure. The ceramic liner can be fitted with Polyurethane pistons rather than conventional rubber pistons for higher performance. To enhance life of ceramic liner as well as piston, abundant cooling water should be used. Additional cooling line for ceramic liner is of advantage. Alignment between fluid end module and power end is of prime importance. To accommodate mismatch, self-aligning piston rod with ceramic liner is used. This further increases life. Piston is rotated at regular interval so that the wear pattern is spread uniformly. This also increases life of piston as well as ceramic liner. 13 The following description relating to this invention are illustrative and should not, be construed as specifically limiting the invention. Moreover, such variations of the invention, now known or later developed, that are within the purview of one skilled in the art are to be considered to fall within the scope of the present invention hereinafter claimed. Ceramic liner is used in mud pump. It is fitted in the fluid end module of the mud pump. A schematic view of a typical mud pump is shown in figure 1. The ceramic liner is located in the bore of fluid end module. The clamping of ceramic liner is done by various means, which depends the models of the mud pump. For sealing, a ring of rubber or polyurethane is used as packing ring around the liner front face, as shown in accompanying Figure 4. After the ceramic liner is fitted to the fluid end module, a piston with piston rod is inserted into the bore of the ceramic liner. The other end of the piston rod is connected to the power end of the mud pump. Once the mud pump is ready for operation, the pump is started. The piston moves back & forth in the ceramic liner. When piston moves backward, the mud is sucked for the suction line, the valve assembly in the suction port is opened and mud fills the cavity of ceramic liner as well as fluid end module. When the piston moves forward, the valve on the suction port closes thus, mud cannot go back to suction line. Pressure is generated in the ceramic liner because of compression of mud. After pressure is generated, the valve in discharge port is opened and thus the mud under high pressure is transferred to the discharge line. This process continues as piston reciprocates back and forth in the ceramic liner. As piston rubs against the bore of the ceramic liner, heat is generated hence the temperature of the piston goes up. After certain temperature, piston rubber may fail because of high temperature. Hence liner-cooling system is provided. A cooling line is put with a nozzle such that cold 14 water is directed in form of a jet at the piston liner interface from the back, as shown. The cooling line ensures that the temperature of piston as well as ceramic liner is kept near to atmosphere temperature. The main component of the ceramic liner is the ceramic sleeve. This is because the liner life is the wear life in the bore. Ceramic sleeve has very high wear life because of its inherent hardness and wear resistance. Thus exceptionally high working life of ceramic liner is because of ceramic sleeve. Super finishing operation done at the internal diameter (bore) of the ceramic liner also helps to increase life of liner as well as life of piston. This is because high surface finish results in less friction and thus less heat is generated and wear life increases. The invention is now described by non limiting exemplanary illustrations. Brief description of accompanying figures Figure 1 illustrates the cross-sectional view of a generalized mud pump with different functional components. Figure 2 illustrates a liner consisting of steel shell and liner sleeve of the known art. Figure 3 illustrates the ceramic liner of the present invention consisting of liner shell and ceramic sleeve. Figure 4 illustrates a schematic view of the fluid end of a typical mud pump. Figure 5 illustrates the plan view of a monolithic liner. 15 Figure 6 illustrates a plan view of a chrome-plated liner. Figure 7 illustrates the plan view of a bi-metallic liner. Detailed Description Of Accompanying Figures Figure 1 illustrates a mud pump (1) consisting of two portions: a fluid end (2) and a power end (3). The fluid end (2) is where the mud is received and then compressed to high pressure and dispatched to the discharge line (4). The power end (3) of the pump (1) receive power from the prime mover i.e. engine or motor and translate the rotating motion to linear motion. The fluid end (2) has a cylinder like structure (5) consisting of a number of manifolds. From figure 1 it is realizable that a suction manifold (6) and a discharge manifold (7) are present with suction pipe (8) and discharge pipes (9) attached to the respective manifolds (6 and 7). It has internal valves and a cavity to receive the liner (10). The liner (10) is fitted horizontally in the cylinder (5). The mode of embedding the liner (10) depends on the design of the mud pump (1). From figure 1 it is also observed that there is a piston (11) inside the liner (10). The metallic piston (11) can perform a reciprocating motion inside the liner (10). From figure 1 it is also realizable that when the piston (11) moves back, it sucks in the mud through the suction manifold (6). In figure 2 the liner of the known art is illustrated. In the figure the sleeve (12) is encompassed by the liner shell (13). The collar (14) is located on the surface of the shell (13). 16 In figure 3 liner of present invention is illustrated. The ceramic sleeve (15) is encapsulated by the liner shell (13). In figure 4 schematic view of the fluid end of a typical mud pump is illustrated. In figure a valve assembly at the port of the suction manifold (6) illustrated. On moving the piston (11) back the mud is sucked in on opening of the valve (16) of the suction manifold (6). The valve (16) is hinged in such a way that only unidirectional opening is possible. So, now the inner volume of the liner is filled with mud. When the piston (11) is moved forward the mud is pressed giving rise to enormous amount of pressure. Thus, a huge thrust is created on the discharge valve (17), which also can be opened in one direction. So, the valve (17) in the port of the discharge manifold (7) is opened and the mud under high pressure is transferred to the discharge manifold (7). From the schematic arrangement of the fluid end as shown in figure 4, it is observed that a space (18) is left in between the liner (10) and the piston (11). This space (18) is provided to circulate cold water so that the rise in temperature of the piston (11) due to its reciprocating motion can be controlled. In figure 5 a monolithic liner is illustrated. From the figure it is clear that a tube of steel is machined to size inside the shell. Since the percentage of carbon steel in the monolithic liner (19) is less, it is carburized to heat the metal component above its ferrite-austenite transition in a suitable carbonaceous atmosphere. The hardening of the internal diameter is done by gradual diffusion of carbon into the surface of the liner increasing the carbon concentration gradient. 17 Fig. 6 illustrates cutting a tube to size and then chromium is plated on the internal diameter. Fig. 7 illustrates a plan view of a bimetallic liner consisting of thick walled steel shell and an inner thin white C.I sleeve. 18 We claim 1. A ceramic liner comprising a single ceramic sleeve housed within a metal liner shell, said ceramic sleeve having a compressive strength between 300 and 400 kilo pound per square inch (kpsi); specific gravity between 3.0 and 7.0 and modulus of elasticity-ranging between 12500 and 60000 kpsi. 2. A ceramic liner as claimed in claim 1, wherein said ceramic sleeve being made of material selected from alumina (AI2O3), zirconia (Zr203) and mixtures thereof along with silicon oxide, magnesium oxide, iron oxide, titanium oxide and conventional additives and/or impurities. 3. A ceramic liner as claimed in claims 1 and 2, wherein the ceramic sleeve is preferably made from pure alumina (AI2O3) with traces of Zirconia(Zr203), silicon oxide, magnesium oxide, iron oxide, titanium oxide and conventional additives and/or impurities. 4. A ceramic liner as claimed in claims 1 to 3, wherein the ceramic sleeve is preferably made from pure zirconia (Zr203) with traces of alumina, silicon oxide, magnesium oxide, iron oxide, titanium oxide and conventional additives and/or impurities. 5. A ceramic liner as claimed in claims 1 to 4, wherein the compressive strength of the sleeve is preferably 380 kpsi. 19 6. A ceramic liner as claimed in claim 3, wherein the ceramic sleeve made from pure alumina preferably having specific gravity of 3.85 and modulus of elasticity 55000 kpsi. 7. A ceramic liner as claimed in claim 4, wherein the ceramic sleeve made from pure zirconia preferably having specific gravity of 6.0 and modulus of elasticity 13225 kpsi. 8. A ceramic liner as claimed in any preceding claims, wherein ceramic sleeve having a thickness of between 5 to 15 mm, interference of between 0.15 to 0.35 mm, a surface finish of the inner diameter of the ceramic sleeve of between 10 to 50 micro inch. 9. A process for forming ceramic liner comprising a single sleeve by shrink fitting ceramic sleeve to an outer shell comprising the steps of (i) shrink fitting of sleeve by heating the outer shell to high temperature 400 to 550 ° C for sufficient expansion, cautiously dropping the sleeve inside the shell and slow cooling to avoid cracking of sleeve; (ii) diamond tool honing to size the Inner Diameter within tolerance of ±0.13 mm; and (iii) diamond tool fine grit super finishing to improve surface finish 10 to 50 micro inch. 10. A process as claimed in claim 9, wherein shrink fitting temperature is preferably 500°C. 20 11. A process as claimed in claims 9 and 10, wherein diamond tool honing at low speed and high pressure is adapted to achieve the adequate size the internal diameter. 12. A ceramic liner as claimed in claims 1 to 8 adapted selectively for pumps for oil well and water well drilling; slurry, toxic fluid and all other types of fluid handling; Internal combustion engine with replaceable cylinders. 13. A ceramic liner comprising a single ceramic sleeve housed within a metal liner shell and the process for forming the said ceramic liner as substantially herein described and illustrated with reference to accompanying figures. 21 ABSTRACT Title : Ceramic Liner The present invention relates to a ceramic liner comprising a single ceramic sleeve (15) housed within a metal liner shell (13), said ceramic sleeve (15) having a compressive strength between 300 and 400 kilo pound per square inch (kpsi); specific gravity between 3.0 and 7.0 and modulus of elasticity ranging between 12500 and 60000 kpsi. A process for forming the said ceramic liner comprising a single sleeve by shrink fitting ceramic sleeve to an outer shell comprises steps of shrink fitting of sleeve by heating the outer shell to high temperature 400 to 550 ° C causing sufficiently expansion and dropping the sleeve inside the shell and slow cooling to avoid cracking of sleeve, diamond tool honing to adequately size the inner diameter and diamond tool fine grit super finishing to improve surface finish 10 to 50 micro inch. Figure 3

Documents:

759-mum-2004-abstract(19-02-2008).doc

759-mum-2004-abstract(19-02-2008).pdf

759-mum-2004-abstract(complete).doc

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759-mum-2004-cancelled pages(19-02-2008).pdf

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759-mum-2004-correspondance-received-300704.pdf

759-mum-2004-correspondance-received.pdf

759-mum-2004-correspondence(19-02-2008).pdf

759-mum-2004-correspondence(ipo)-(03-04-2008).pdf

759-mum-2004-description (complete).pdf

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759-mum-2004-form 3(16-06-2004).pdf

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759-mum-2004-others document(16-07-2004).pdf

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