PIPE JOINT AND PIPE WITH PIPE JOINT

Abstract: The invention provides a pipe joint and a pipe with the pipe joint. The pipe joint has a coupling element (26) of the male and the female parts, and a contact surface (28) wherein the male and the female parts (22), (24) are contacted. Adjacent to the contact surface (28) a groove (30) which contains an O ring (32) is provided wherein the O ring (32) deforms regularly under hydraulic pressure by the effect of the contact surface (28) which leads to the enhancement of the sealing capacity of the joint. The groove (30) of the joint may be provided on one of the male and the female joints (22; 24). The material may be metal, plastic, and fiber reinforced plastic. A pipe with the pipe joint can be applicable to the purpose of the invention.

Description: This invention relates to the field of pipe joint and pipe with pipe joint which are being used in oil field technology or other general purpose areas, wherein a high sealing capability is required to prevent fluid in the piping system from leaking. As for the joints for metallic pipe, plastic pipe, and fiber reinforced plastic pipe, bell and spigot type joint, or glued joint, flanged type joint, screwed type joint, etc are utilized. The glued joint is mainly used for plastic pipes. The inside of the end of a plastic pipe is tapered which constitutes a female joint, whereas the outside of the end of another plastic pipe is tapered which constitutes a male joint. Both joints are jointed together by adhesive painted on the tapered surfaces. In some cases the tapered surfaces are equipped with screw and painted with adhesive. Following problems are reported, as for the above-mentioned glued joint. (1) Disengagement of the joints is impossible since the joints are glued. (2) The resistance to shear on the glued surface is comparatively low, which is 1 to 2 kgf/mm². Therefore the glued surface should be enlarged and the joint be magnified to endure with the high hydraulic pressure of the fluid in the piping system. (3) The jointing operation is done at the operation site, and the operability is significantly worsened. The flanged type joint is widely used in the metallic, plastic, and fiber reinforced plastic pipes. However the hydraulic pressure of the fluid which is within the range of the sealing capacity, is comparatively low; 10 to 35 kgf/cm² for plastic pipe, and about 210 kgf/cm² for metallic pipe. The screwed type joint is widely used one. The screw may be a pair of parallel screws or tapered screws. The sealing is done by an O ring or by using the contact pressure between the thread of the screw in case of the metallic pipe joint. The following problems are pointed out in the joints wherein the materials of the male and female joints are the combination of metal with nonmetal, metal and fiber reinforced plastic, hereinafter FRP. (1) The hydraulic pressure within the sealing capacity is comparatively low; 300 to 350 kgf/cm². (2) The above pressure can be varied due to the inaccuracy of the working of the surface of the thread. (3) The pertinent index for the termination of the screwing operation is difficult to determine, which leads to the damage of the plastic pipe and the FRP pipe by overscrewing. (4) In case of tapered screw type joints the torque for screwing is gradually increased which makes the determination of the termination of the screwing difficult for operators. Figure 1 shows the sectional view of the conventional screwed pipe joint. As shown in Figure 1, the male joint 10 is fitted to the female joint 12 by the tapered screws 14 with the O ring 16. Figure 2A and 2B show the enlarged views of Figure 1 with respect to the parts surrouding the O ring. As shown in Figure 2A a predetermined force "a" is applied on the O ring. As shown in Figure 2B, when hydraulic pressure is applied on the O ring, the ring is deformed and a part of the O ring is pressed in the gap of the joints 18 out of the groove 20. When the force applied on the ring reaches "b" as the combined effect of "a" plus hydraulic pressure, the ring is destroyed and the fluid leaks into the gap 18. As explained above, in case of the joints having the sealing mechanism using O ring, the problem of leakage is inevitable, with the exception of the joints with the materials, metal with metal. It is an object of the invention to provide a pipe joint having high tight sealing capacity. It is an object of the invention to provide a pipe with pipe joint having high tight sealing capacity. According to the invention there is provided a pipe joint according to claim 1 The problem encountered in the conventional pipe joint as described is the deformation which leads to the destruction, of the sealing part, the O ring when it is under the internal hydraulic pressure. To evade the problem, the gap between the male and the female joint members should be nullified. The inventors solved the problem by contacting a part of both joint members adjacent to O ring, which is situated at the opposite side of the pressurized zone. By providing the contact zone, the deformation of the O ring is confined in the groove without the destruction of the ring. The means of coupling the male and female joints may be screws or flanges. The materials of the male and female joints may be metallic, plastic, or of fiber reinforced plastic. The groove may be in to the male or the female joint member. It is quite apparent that a pipe with such type of pipe joint is fitted to the purpose, the function, and the result of the invention. Figure 1 is the sectional view of the conventional screwed pipe joint; Figure 2A and Figure 2B are the enlarged views of Figure 1 with respect to the parts surrouding the O ring; Figure 3 is a typical embodiment of the invention; Figures 4A and 4B are the enlarged views of Figure 3 with respect to the parts surrouding the O ring; Figure 5 is an example of the embodiment of the invention; Figure 6 is another example of the embodiment of the invention; Figure 7 is another example of the embodiment of the invention; and Figure 8 is another example of the embodiment of the invention; The problem encountered in the conventional pipe joint as described in Figures 1, 2A, and 2B, is the deformation which leads to the destruction, of the sealing part, the O ring when it is under the internal hydraulic pressure. To evade the problem, the gap between the male and the female joints denoted as the gap 18 in Figure 2B, should be nullified. The inventors solved the problem by contacting parts of both joint members adjacent to O ring, which are situated at the opposite side of the pressurized zone. By providing the contact zone, the deformation of the O ring is confined in the groove 20 denoted in Figure 2B without the destruction of the O ring. Figure 3 is the sectional view of the screw joint of a typical embodiment of the invention. The male joint 22 is coupled with the female joint 24 by the screw 26. Both joint members are contacted at the contact surface 28. To ensure the contact the unthreaded zone 29 is provided between the screw and the contact surface. Adjacent to the contact surface on the side of the male joint 22, the groove 30 for accomodating the O ring 32 is provided. Adjacent to the groove 30 the gap 31 between both joint members is provided to fit the male joint 22 into the female joint 24. Figures 4A and 4B are the enlarged views of Figure 3 with respect to the parts surrouding the O ring. As shown in Figure 4A, a predetermined force "a" is applied on the O ring. As shown in Figure 4B, when hydraulic pressure is applied on the ring, the ring is deformed. When the force applied on the ring reaches "c" as the combined effect of "a" plus hydraulic pressure, the ring is deformed and pressed to the wall of the groove. But the fluid does not leak into the unthreaded zone 29, since no irregular deformation of O ring is initiated to allow the fluid to come into the unthreaded zone. The angle made by the contact zone 28 and the axial direction of the joints is denoted as Θ. The angle may vary between 0 to 90 degree. However the angle is pertinent between 20 to 80 degree to ensure the good contact. In this embodiment, the O ring and the groove are provided on the side of the male joint. However the effect is the same when the O ring and the groove are provided on the female side. The above explained technical thoughts are further explained in the following examples. It is quite apparent that this invention is applicable in case of the pipe with the invented pipe joint. Figure 5 is an example of the embodiment of the invention. The male joint 33 is coupled with the female joint 34 by the thread 36. The both joints are contacted at the contact surface 38. To ensure the contact the unthreaded zone 40 is provided between the screw and the contact surface. Adjacent to the contact zone on the side of the male joint 33, the groove 42 for accomodating the O ring 44 is provided. Adjacent to the groove 42 the gap 46 between the both joint is provided to ensure the good contact. In this embodiment, the O ring and the groove are provided on the side of the male joint. However the effect is the same when the O ring and the groove are provided on the female side. Figure 6 is another example of the embodiment of the invention. The male joint 50 is coupled with the female joint 52 by the tapered thread 54. The both joints are contacted at the contact surface 56. To ensure the contact the unthreaded zone 58 is provided between the screw and the contact surface. Adjacent to the contact zone on the side of the female joint 52, the groove 60 for accomodating the O ring 62 is provided. Adjacent to the groove 60 the gap 61 between the both joints is provided to ensure the good contact. In this case the shape of the section of the groove 60 is triangular. In this embodiment, the O ring and the groove are provided on the side of the female joint. However the effect is the same when the O ring and the groove are provided on the male side. Figure 7 is another example of the embodiment of the invention. The flanged male joint 64 is coupled with the flanged female joint 66 by the bolt 68 and the nut 70. The both joints are contacted at the contact surface 72. To ensure the contact the clearance 73 is provided between the joints. Adjacent to the contact zone on the side of the flanged male joint 64, the groove 74 for accomodating the O ring 76 is provided. Adjacent to the groove 74 the gap 78 in between the both joint is provided to ensure the good contact. In this case the shape of the section of the groove 74 is square. In this embodiment, the O ring and the groove are provided on the side of the male joint. However the effect is the same when the O ring and the groove are provided on the female side. Figure 8 is another example of the embodiment of the invention. The flanged male joint 80 is coupled with the flanged female joint 82 by the means of engaging the flanges, in this case, by shrinkage fitting fixture 84. The both joints are contacted at the contact surface 86. To ensure the contact the clearance 88 is provided between the joints. Adjacent to the contact zone on the side of the flanged male joint 80, the groove 90 for accomodating the O ring 92 is provided. Adjacent to the groove 90 the gap 94 between the both joint is provided to ensure the good contact. In this case the shaped of the groove 90 is square sectional shape. In this embodiment, the O ring and the groove are provided on the side of the male joint. However the effect is the same when the O ring and the groove are provided on the female side. Examples Hydraulic Pressure Test The hydrulic pressure tests are carried out to guarantee the invention. The test is conducted by the method described in ASTM D-1599 " THE SHORT TIME HYDRAULIC FAILURE PRESSURE OF PLASTIC PIPE, TUBING, AND FITTING " . The invented joints are used in tests from 1 to 5, and conventional joints are used in tests 6 and 7. Test 1 The test sample is made of FRP male screwed joint and 13 Cr steel female screwed joint. The FRP tube has the dimensions; 50 mm in internal diameter and 8 mm in thickness. The test was interrupted since the FRP tubing was destructed at the pressure of 840 kgf/cm². Test 2 The test sample is made of FRP male and female screwed joints. The FRP tube has the dimensions; 50 mm in internal diameter and 8 mm in thickness. The test was interrupted since the FRP tubing was destructed at the pressure of 820 kgf/cm². Test 3 The test sample is made of metallic male screwed joint and FRP female screwed joint. The FRP tube has the dimensions; 50 mm in internal diameter and 12 mm in thickness. The test pressure without the destruction of the joints was more than 1050kgf/cm², which is the target value. Test 4 The test sample is made of metallic male flanged joint and FRP female flanged joint. The FRP tube has the dimensions; 50 mm in internal diameter and 12 mm in thickness. The test pressure without the destruction of the joints was more than 1000 kgf/cm², which is the target value. Test 5 The test sample is made of polyethyrene male screwed joint and polyethyrene female screwed joint. The polyethyrene tube has the dimensions; 48 mm in internal diameter and 6 mm in thickness. The test was interrupted since the polyethyrene tubing was destructed at the pressure of 40 kgf/cm². Test 6 The test sample is made of FRP male screwed joint and 13 Cr steel female screwed joint. The test was interrupted since the leakage was found at the joint at the pressure of 450 kgf/cm². Test 7 The test sample is made of FRP screwed joint. The test was interrupted since the leakage was found at the joint at the pressure of 480 kgf/cm². Reference signs in the claims are intends for better understanding and shall not limit the scope.

Claims: 1. A pipe joint having coupled male and female joint members (22), (24) , comprising: a contact surface (28) on the male member; a contact surface on the female member, which is contacted with the contact surface of the male member in coupling the male member with the female member; a groove (30) situated in one member adjacent to one said contact surface, of which groove the opening faces a surface of the opposite member, and is connected to fluid in pipe via a clearance (31) between surfaces of the members next to the groove; and an O ring (32) which is contained in said groove, of which ring portions ends are contacted with the male and female members. 2. The pipe joint of claim 1, characterized in that the coupling means is screws, the thread of the screw of the male joint member being coupled with the thread of the screw of the of the female joint member, wherein the screwing action is hampered by the contact surfaces. 3. The pipe joint of claim 1, characterized in that the coupling means is flanges attached to the male and female joint members, which are pressed together by combination of bolts and nuts, wherein the pressing action is hampered by the contact surfaces. 4. The pipe joint of claim 1, characterized in that the coupling means is flanges attached to the male and female joint members, which are pressed together by a shrinkage fitting fixture, wherein the pressing action is hampered by the contact surfaces. 5. The pipe joint of claim 1, characterized in that said groove is in the male joint member. 6. The pipe joint of claim 2, characterized in that said groove is in the male joint member. 7. The pipe joint of claim 3, characterized in that said groove is in the male joint member. 8. The pipe joint of claim 4, characterized in that said groove is in the male joint member. 9. The pipe joint of claim 1, characterized in that said groove is in the female joint member. 10. The pipe joint of claim 2, characterized in that said groove is in the female joint member. 11. The pipe joint of claim 3, characterized in that said groove is in the female joint member. 12. The pipe joint claim 4, characterized in that said groove is in the female joint member. 13. The pipe joint of claim 1, characterized in that the material of the male joint is metal and the material of the female joint member is plastic. 14. The pipe joint of claim 1, characterized in that the material of the male joint member is metal and the material of the female joint member is fiber reinforced plastic. 15. The pipe joint of claim 1, characterized in that the material of the male joint is plastic and the material of the female joint member is metal 16. The pipe joint of claim 1, characerized in that the material of the male joint is plastic and the material of the female joint member is plastic. 17. The pipe joint of claim 1, characterized in that the material of the male joint is plastic and the material of the female joint member is fiber reinforced plastic. 18. The pipe joint of claim 1, characterized in that the material of the male joint member is fiber reinforced plastic and the material of the female joint member is metal. 19. The pipe joint of claim 1, characterized in that the material of the male joint member is fiber reinforced plastic and the material of the female joint member is plastic. 20. The pipe joint of claim 1, characterized in that the material of the male joint member is fiber reinforced plastic and the material of the female joint member is fiber reinforced plastic. 21. An assembly comprising a pipe joint according to claim 1 having a pipe connected to said pipe joint. 22. The assembly of claim 21, characterized in that the pipe is connected to the male joint member. 23. The assembly of claim 21, characterized in that the pipe is connected to the female joint member.

Inventors: AKIYAMA, HIROSHI, ISHIHARA, TOSHIO, NAKANO, TAKASHI, Akiyama, Hiroshi, c/o Patent &amp; Licence Dept., Ishihara, Toshio, c/o Patent &amp; Licence Dept., Nakano, Takashi, c/o Patent &amp; Licence Dept.
Applicants: NKK CORPORATION
Application year: 1990
Main classification: F16L15
IPC codes: F16L15, E21B17, F16L17