A METHOD OF TESTING THE JOINTS FOR LEAKS IN A THIN PLATE LINED STORING ROOM AND A JOINT ADAPTED TO THE PERFORMANCE OF THE METHOD

Abstract: The present invention relates to a method of testing the joints for leaks in a thin plate lined storing room, in particular an underground storing room, for a fluid, a gas or a liquid. Said joints (3) are welded standing joints having at least one exterior folded fold portion (12), which is folded in such a way, that a closed duct (17) is formed in a space between said exterior folded fold portion (12) and longitudinal welding seams (13, 16), which mutually connect all the elements of said joint. A leak-testing fluid can be fed into said duct (17) thus formed, leaks being detected by sensing leak-testing fluid, which passes a welding seam (16), by means of which said folded fold portion (12) is welded. The present invention also relates to a joint adapted to the performance of the method.

Description: A METHOD OF TESTING THE JOINTS FOR LEAKS IN A THIN PLATE LINED STORING ROOM AND A JOINT ADAPTED TO THE PERFORMANCE OF THE METHOD The technical field The present invention relates to a method of testing the joints for leaks in a thin plate lined storing room, par¬ ticularly an underground storing room,-for a fluid, e.g. a gas or a liquid. The present invention also relates to a joint, which is adapted to the performance of the meth¬ od and provided between plates mutually connected in the thin plate lined storing room, which joint comprises an upright joint including edge folds of the edge portions of said plates mutually connected, which folds in an up¬ right position are turned towards the interior of said storing room, the interior sides of said folds which are turned towards to each other being mutually connected by means of a first welding seam as well as one of said folds projecting beyond the other one of said folds and being folded round the terminal edge of the other one of said folds. The background of the invention It has been suggested that stainless thin plates be used to line storing rooms, particularly various types of un¬ derground cavities, used to store i.a. natural gas under a pressure as high as 150 bars. Other possible applications are storage of LPG, other gaseous hydrocarbons, such as ethylene, liquefied petroleum gas etc., other liquefied hydrocarbons, for which a fortified protection is a ne¬ cessity, such as jet fuel, lead-free gas etc., hydrogen gas, hot water, liquid ammonia, as well as various che¬ micals. Another field of application for the invention are thin plate lined, full hole-drilled tunnels designed for hot water distribution, as well as thin plate lined above- ground storing rooms. Stainless linings to be used in the above-mentioned app- lications are very thin, which results in problems as to the joining of the plates. The joints must meet exacting requirements. They must above all be leakproof and resist the pressure of the fluid being stored as well as defor¬ mations to a certain degree due to yieldings of the wall on the exterior side of the lining. Also, a joint which is easy to produce and to test for leaks is required. Al¬ so, it must be easy to make tight possibly detected leaks. Also, it ought to be possible to make tight points of in¬ tersection in a rational manner. Finally, it is desirable that the lining can be applied simultaneously with the production of the joints, i.e. during the same processes. A brief description of the drawings In the following description of a preferred embodiment reference is made to the accompanying drawings, in which: Fig. 1 schematically illustrates the construction of the joint according to the present invention as well as how the lining is fastened to a support; Fig. 2 shows how a welding seam, which is a part of said joint and is leaking, can be repaired; Fig. 3 shows a possible embodiment of a T-joint; and Fig. 4 shows how a joint can be tested for leaks accor¬ ding to the invention. A description of a preferred embodiment In Fig. 1 two thin plates, 1 and 2, are shown and also a joint 3 according to a preferred embodiment of the inven¬ tion. The stainless lining of the preferred embodiment comprises said plates 1 and 2 and is made of a stainless austenitic steel having a thickness of 0.4 mm. On the ex- terior side of said stainless steel lining a concrete wall 4 is provided. A flat bar 5, used to fasten thin plates 1,2 to wall 4, is provided below joint 3 according to this embodiment, extends along the length of joint 3 and is fastened to concrete wall 4 by means of curved steel nails 6. Flat bar 5 can of course be fastened to concrete wall 4 in other ways, e.g. by means of glueing, casting etc . Joint 3 is designed as an upright joint directed towards said storing room. It comprises a first standing fold 7 on first plate 1 and a second standing fold 8 on second plate 2. Between said two folds 7 and 8 one leg 9 of an L-profile 14, thickness 0.15 mm, is positioned, the other leg 10 being welded to flat bar 5. The outer edge of said second fold 8 is designated 11. First fold 7 ex- tends beyond said outer edge 11 about 5 mm and is then folded 180°. The folded fold portion is designated 12. First and second folds 7 and 8 are joined by means of a first welding seam 13. The joint and standing leg 9 of L-profile 14 are also joined by means of this welding seam. Folded fold portion 12 and the exterior side of second fold 8 are joined by means of a second welding seam 16. Welding seams 13 and 16 are produced in the same process step. Welding seams 13,16 will not be loaded, when pressure is exerted on joint 3 by said fluid in said storing room, since said plates are folded inwards and the gas pressure compresses folds 7,8 against each other. Outside welding seams 13 and 16, between first fold 7 and its folded portion 12, a duct 17 is formed, designed for leak-testing by means of a detection fluid, preferab¬ ly for helium leak-testing. When a leak-testing is performed, helium gas or another leak-testing fluid is introduced into duct 17. This tes¬ ting is performed in connection with the construction. The simplest method of detecting leaks is "sniffing", according to already known methods. This technique is illustrated in Fig. 4. When performing the method of testing for leaks, which is directly adapted to the joint according to the invention and vice versa, an injection needle 30 is introduced into one end of said duct 17. In advance duct 17 has been tho- roughly cleaned. In particular, fat or oil films must not be present in the gap, which is formed below said welding seam. Such films are removed by means of suitable solvents. Possible moisture in said gap and/or duct 17 is removed by blowing dry compressed air, possibly warm air, prior to the leak-testing» When said duct has been cleaned in this way, injection needle 30 is introduced into duct 17. The outer diameter of the injection needle suitably is 1-1.5 mm. Said injection needle, i.e. the injection needle tip, is inserted in said testing duct to roughly half its length and is fastened by means of several layers of a glue 31, which makes the opening of said duct completely tight around said injection needle. In the opposite end of said duct - the outlet end - a similar injection needle 30' is inserted, which also is tightly glued in end 31' of said duct. A hose 32 for feeding helium gas or another leak-testing fluid and an extension 33 are used and cor¬ responding means 32' and 33' in said outlet end. Prior to testing the air in duct 17 must be removed, which can be done by blowing helium gas or a corresponding leak-tes- ting fluid having a suitable pressure into said duct, un¬ til this gas escapes through said outlet end. A few se¬ conds later said outlet end is closed by means of a hose clamp 34, subsequent to which the testing of the joint can be performed immediately. As an alternative, said outlet end can be closed from the beginning by means of a hose clamp 34. Subsequently the air is removed - by means of a suction pump - through the inlet end, until a predeter¬ mined vacuum has been obtained, and subsequently helium gas or a similar leak-testing fluid having a suitable pres- -sure automatically fills said duct. The testing of the joint can subsequently be performed immediately. One of these two alternatives can be chosen according to the circumstances. The scanning is done continuously along joint 3 by means of a sniffer pistol 35. The tip of said sniffer pistol is held closely to said gap below welding seam 16. The scan¬ ning speed can be varied somewhat due to exterior circum¬ stances, but normally it stays in the interval 10-20 mm/s, A suitable gas pressure is 1 bar. When leaks in joint 3 are detected, they are corrected in the simplest manner by means of a welding seam repair work, a new welding seam 20 being made, according to Fig. 2. Said first and second folds 7 and 8 are joined in the area of said repair work welding seam 20, which makes a sweep inside the leak area without crossing duct 17, a free passage being spared for the leak-testing gas through duct 17 past the repair work area. A T-joint embodiment 24 is shown in Fig. 3. The folded fold portions 12 are in this instance cut off up to a few centimeters from the point of intersection. Welding seams 13 and 16 are turned upwards and make leak-testing duct 17 tight immediately in front of the cutting off-area. These portions of the welding seams are designated 13', 16' . From end points 26,27,28 of welding seams 13,16 and all the way up to said point of intersection 29 standing folds 7 and 8 are joined by means of icroTIG-welds.

Claims: Patent claims 1. A method of testing the joints for leaks in a thin plate lined storing room, particularly an underground storing room, for a fluid, a gas or a liquid, c h a ¬ r a c t e r i z e d in that said joints (3) are welded upright joints having at least one exterior fold portion (12) , which is folded in such a way that a closed duct (17) is-formed in a space between said exterior folded fold portion (12) and longitudinal welding seams (13,16) , which mutually connect all the elements of the joint, and in that a leak-testing fluid is fed into said duct, possible leaks being detected by sensing the leak-tes¬ ting fluid, which passes a welding seam, by means of which said folded fold portion (12) has been welded. 2. A joint between mutually connected plates (1,2) , in a thin plate lined storing room, in particular an under¬ ground storing room, for a fluid, a gas or a liquid, which joint (3) is an upright joint comprising edge folds (7,8) on the edge portions of the mutually connected plates (1, 2) , which folds are standing and extend into the interior of said storing room, the interior sides of said folds, which face each other, being mutually connected by means of a first welding seam (13) and one of said folds (7) projecting past the other fold (8) and being folded around the terminal edge (11) of said other second fold, c h a ¬ r a c t e r i z e d in that the interior side of said folded fold portion is connected to the exterior side of said second fold (8) by means of a second welding seam (16) , and in that said first fold, before it is folded around, projects past the terminal edge (11) of said se¬ cond fold, a closed duct (17) being formed outside said two welding seams (13,16) for a leak-testing fluid bet- ween the folded fold portions. 3. A joint according to claim 1, c h a r a c t e r i z e d in that the forward thin portion (9) of a fastening device (14) is welded in said first welding seam (13) , between said two folds (7,8) , the rear portion (10) of said fas- tening device being directly or indirectly fastened in said wall (5) of said thin plate lined underground sto¬ ring room. 4. A joint according to any of claims 2 and 3, c h a - r a c t e r i z e d in that said plate and folds have a thickness of less than 1 mm. 5. A joint according to claim 4, c h a r a c t e r i z e d in that said thickness is 0.25-0.75 mm.

Inventors: FLODIN BENNY, FREDERIKSSON RUNE, HAHN TORBJOERN, FLODIN, BENNY, FREDERIKSSON, RUNE, HAHN, TORBJOERN
Applicants: AVESTA LINING AB, AVESTA LINING AKTIEBOLAG
Application year: 1989
Main classification: B65G5
IPC codes: G01M3