JP2014100745A - Punching device for level gauge of liquefied gas carrier and level gauge installation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately install apparatuses such as a level gauge in a liquefied gas tank, by accurately and easily forming an opening part of a complete round shape in a plan view, at a position separated from the vertical center line of a spherical tank in the vicinity of the apex of the tank.SOLUTION: A punching device 25 for a level gauge of a liquefied gas carrier can punch an opening part 23 of a complete round shape in the plan view at a position separated from the vertical center line of a spherical tank in the vicinity of the apex of the tank, and comprises a base part 27, a plurality of expandable leg parts 28 for fixing this base part 27 to an upper part of an opening part punching position on the tank surface, a reference rotary shaft 30 pivotally supported to the base part 27 and vertically extending from the base part 27, a rotational driving part 31 installed in the base part 27 and rotatingly driving the reference rotary shaft 30 and a cutter holding part 32 installed on the reference rotary shaft 30, rotating around the reference rotary shaft 30, freely sliding a cutter 50 capable of cutting the tank in the vertical direction and adjustably holding a radial distance from the reference rotary shaft 30.

Description

  The present invention relates to a piercing device for a liquid level gauge of a liquefied gas carrier ship that forms an opening in a curved surface of a spherical tank or a cylindrical tank mounted on a liquefied gas carrier ship, and in particular, near the top of the spherical tank and the spherical tank. The present invention relates to a level gauge drilling device and a level gauge installation method for a liquefied gas carrier ship that can drill a hole that is a perfect circle in plan view at a position away from the vertical center line.

  As disclosed in Patent Document 1, many liquefied gas tanks of liquefied gas carriers that transport LNG (liquefied natural gas) or the like have a spherical shape that can withstand high pressure. When installing a level gauge in such a spherical tank, it is desirable to install it at the top of the tank, but an inspection hole (manhole) is provided at a position (vertex) that matches the vertical center line of the tank top. Therefore, the opening is perforated at a position slightly away from the vertical center line while avoiding the inspection hole, and the liquid level gauge is installed. The same applies to devices other than the liquid level gauge (pressure gauge, thermometer, etc.) and through parts of piping.

  As described above, when an opening is formed in a spherical tank, in particular, when a modification is made to add (or replace) a device such as a liquid level gauge to the spherical tank mounted on the LNG ship, In general, after opening the opening using a jigsaw, the inner periphery of the opening is shaved with a grinder and finished in a predetermined shape.

  On the other hand, as disclosed in Patent Documents 1 and 2, inside the liquefied gas tank of the liquefied gas carrier ship, a tubular tower called a pipe tower that connects the top and bottom vertically is installed, Inside this pipe tower, piping for carrying in and out liquefied gas, a measuring pipe extending from the above-mentioned liquid level gauge to the tank bottom, and the like are arranged. In recent years, the diameter of the pipe tower has been reduced for the purpose of reducing material costs, reducing the weight, simplifying the structure, and the like.

JP 7-228289 A Utility Model Registration No. 2597457

  As described above, when forming an opening for installing a level gauge near the top of the spherical tank of the liquefied gas carrier and away from the vertical center line of the spherical tank, the opening is viewed from directly above. In a plan view, it is necessary to form a perfect circle, but a line of sight along the normal line of the spherical surface is elliptical. For this reason, cutting with a jigsaw as in the prior art does not allow accurate processing, and the liquefied gas tank of the liquefied gas carrier ship has a thickness of about 30 mm, so it takes a lot of time to work with the actual product. There was a problem of hanging.

  Although it is conceivable to cut the tank by gas cutting or plasma cutting, etc., because it is a work on a huge tank, it is difficult to hold the torch and control the posture, and nevertheless failure is not allowed, For workers, this is a harsh work with great effort.

  On the other hand, as described above, since the diameter of the pipe tower installed in the spherical tank of the liquefied gas carrier ship is reduced, it is difficult to install the above-described liquid level gauge. That is, in the case of a liquid level gauge, a vertical seat tube on which the liquid level gauge is placed is installed at the top of the spherical tank, while the bottom of the spherical tank and exactly above the seat tube are vertically below. There has been an operation of disposing a measuring tube between the installed laser reflecting portion, and it has been difficult to accurately set the fixed positions of the seat tube and the tank bottom within the pipe tower having a small diameter.

  The present invention has been made in view of the above circumstances, and is intended to install a liquid level gauge near the top of a liquefied gas carrier ship, mainly in a spherical shape, and at a position away from the vertical center line of the liquefied gas tank. The liquid level gauge drilling device and the liquid level gauge can be installed in a liquefied gas carrier that can form a perfect circular opening accurately and easily in a plan view and install the liquid level gauge in the liquefied gas tank with high precision. It aims to provide a method.

In order to solve the above problems, the present invention employs the following means.
That is, the level gauge drilling device for a liquefied gas carrier ship according to the present invention is provided with a level gauge drill for a liquefied gas carrier ship that drills a circular opening for a level gauge at the top of a liquefied gas tank or the like in the liquefied gas carrier ship. An apparatus comprising: a base; a plurality of extendable legs that fix the base above the opening drilling position on the surface of the liquefied gas tank; and a reference that is pivotally supported by the base and extends vertically downward from the base A rotary shaft, a rotary drive unit that is installed on the base and rotationally drives the reference rotary shaft, and a cutting machine that is attached to the reference rotary shaft and pivots about the reference rotary shaft to cut the liquefied gas tank And a cutting machine holding part for holding the radial distance from the reference rotation shaft so as to be slidable in the vertical direction.

According to the piercing device for a level gauge of a liquefied gas carrier ship having the above configuration, the base portion is supported by a plurality of legs and stably fixed on the top surface of the liquefied gas tank, and the length of each leg is reduced. By adjusting the expansion and contraction, the hanging position of the reference rotation shaft extending vertically downward from the base can be easily matched with the center point of the opening to be formed on the surface of the liquefied gas tank.
After that, by rotating the reference rotation shaft by the rotation drive unit, the cutting machine attached to the reference rotation shaft via the cutting machine holding unit turns around the reference rotation shaft like a compass, and this cutting The surface of the liquefied gas tank is cut out by the machine to form an opening. This opening is a perfect circle in plan view (viewed in the axial direction of the reference rotation axis).

  Since the cutting machine held by the cutting machine holding part is slidable in the vertical direction, even if the surface of the liquefied gas tank traced by the cutting machine is spherical, curved, uneven, etc., it follows the surface shape. The cutting machine slides up and down so that it can be cut smoothly. Further, since the cutting machine can adjust the radial distance from the reference rotation shaft, the diameter of the opening formed in the tank can be changed by changing the radial distance.

  According to such a piercing device for a level gauge of a liquefied gas carrier ship, even if it is near the top of the spherical liquefied gas tank and away from the vertical center line of the liquefied gas tank, a perfect circular opening is seen in plan view. The liquid level gauge can be installed with high accuracy in the liquefied gas tank.

  In the above configuration, the cutter holder is provided with a height setting unit capable of maintaining the height of the tip of the cutter relative to the surface of the liquefied gas tank at a predetermined height and adjusting the height. It is preferable.

  By providing this height setting section, the distance between the tip of the cutting machine and the liquefied gas tank surface is always kept within a certain distance range regardless of the curved shape of the liquefied gas tank surface to be cut. A perfect circular opening can be formed easily and accurately. Moreover, since the height of the front-end | tip part of a cutting machine can be adjusted, the setting and change of cutting conditions can be performed easily.

  In the above-described configuration, the height setting unit includes only a rotating shaft provided near the tip of the cutting machine holding unit, and an intermediate part supported by the rotating shaft, and contact portions provided at both ends thereof. A pivot lever that is capable of contacting the surface of the liquefied gas tank and pivoting about the pivot axis so as to move the contact portion in the direction of separating from the surface of the liquefied gas tank. It is preferable that the contact portion is capable of moving smoothly on the surface of the liquefied gas tank.

  According to the above configuration, when the cutting machine traces and cuts the surface of the liquefied gas tank, the contact portions at both ends of the rotating lever pivotally supported in the vicinity of the tip of the cutting machine are in contact with the surface of the liquefied gas tank. Move the tank surface smoothly. For this reason, the cutting machine can be smoothly moved (turned) with the distance between the tip of the cutting machine and the surface of the liquefied gas tank kept constant, and a circular opening can be easily and accurately formed on the surface of the liquefied gas tank. .

  In the above-described configuration, the reference rotation shaft is pivotally supported by a central hole having a tip sufficiently drilled at the opening drilling position on the surface of the liquefied gas tank and having a diameter sufficiently smaller than the diameter of the opening. You may do it.

  According to the above configuration, the tip end portion of the reference rotation shaft is pivotally supported by the center hole formed on the surface of the liquefied gas tank, so that it can rotate stably without shaking. For this reason, it is possible to stabilize the trajectory of the cutting machine that rotates together with the reference rotation shaft and cuts and forms the opening on the surface of the liquefied gas tank, and the center position accuracy and roundness of the formed opening can be significantly increased. it can.

  Further, the liquid level gauge installation method of the liquefied gas carrier ship according to the present invention is a method of additionally installing or replacing a liquid level gauge near the top of the liquefied gas tank of the liquefied gas carrier ship, and one of the bottom part or the top part inside the liquefied gas tank. A first fixed point setting step for setting the first fixed point to the laser beam and projecting a laser beam in the vertical direction from the first fixed point toward the other bottom or top of the liquefied gas tank; A second fixed point setting step for setting as two fixed points, a punching step of drilling an opening centering on a fixed point on the top side of the liquefied gas tank among the first fixed point and the second fixed point; and A measuring tube installation in which a measuring tube of the liquid level gauge is installed in a vertical direction connecting a central axis of the seat tube and a fixed point on the bottom side of the liquefied gas tank, and a seat tube welding process for welding and fixing the seat tube of the liquid level meter Process Characterized in that it comprises Te.

  According to the above liquid level gauge installation method for a liquefied gas carrier, vertical laser light is projected from a fixed point set at one of the bottom or top of the liquefied gas tank, and the projection position is set as the second fixed point. Therefore, the first fixed point and the second fixed point can be accurately arranged on the vertical line. Therefore, even if the diameter of the pipe tower installed inside the liquefied gas tank is small, the first fixed point and the second fixed point, that is, the seat tube of the liquid level gauge and the reference member on the bottom side of the tank can be easily installed, A liquid level gauge can be added or replaced with high accuracy in the gas tank.

  Preferably, in the first fixed point setting step, the first fixed point is set on a bottom side inside the liquefied gas tank, and in the second fixed point setting step, the laser light projected from the first fixed point is set. With the projection point as the second fixed point, in the drilling step, first, a center hole is drilled at the laser beam projection point, and then the opening having a predetermined inner diameter in plan view around the center hole Perforate.

In the above method, vertical laser light is projected from the first fixed point set at the bottom of the liquefied gas tank to the top of the tank, and a central hole is first formed at the projection point of the laser light, that is, the second fixed point. An opening for installing a level gauge is drilled around the hole.
Since the central hole formed earlier has a much smaller diameter than the opening formed later, whether or not the laser light passes through the central hole by projecting the laser light again after the formation of the central hole. The position accuracy of the center hole can be confirmed.
And even if the position of the center hole is misaligned, re-open the center hole within the formation range of the opening, or eccentrically enlarge the inner diameter of the center hole to correct the center position of the center hole Can do. Therefore, a liquid level gauge can be additionally installed or replaced in the liquefied gas tank with high accuracy.

  The method of installing the liquid level gauge of the liquefied gas carrier according to the present invention is a method of installing a liquid level gauge near the top of the tank when the liquefied gas tank of the liquefied gas carrier is newly constructed. A first fixed point setting step for setting a point, a drilling step for drilling an opening around the first fixed point, a seat tube welding step for welding and fixing a seat tube of the liquid level gauge to the opening, A second fixed point setting step of projecting a laser beam vertically from the central axis of the seat tube toward the bottom of the liquefied gas tank, and setting the projection position as a second fixed point; the central axis of the seat tube and the first A measuring tube installation step of installing a measuring tube of the liquid level gauge at a position connecting two fixed points.

  According to the liquid level gauge installation method of the above liquefied gas carrier ship, the opening is drilled around the first fixed point set at the top inside the liquefied gas tank, and the seat of the liquid level gauge is fixed by welding to this opening. Since the projection position of the laser beam projected from the central axis of the seat tube toward the bottom of the liquefied gas tank is set as the second fixed point, the first fixed point and the second fixed point are accurately arranged on the vertical line. can do. Therefore, even if the diameter of the pipe tower installed inside the liquefied gas tank is thin, the first fixed point and the second fixed point, that is, the seat tube of the equipment and the reference member on the tank bottom side can be easily installed, and the liquefied gas tank The liquid level gauge can be installed with high accuracy during the new construction.

As described above, according to the liquid level gauge drilling device for a liquefied gas carrier according to the present invention, the liquid level can be obtained even near the top of the spherical liquefied gas tank and at a position away from the vertical center line of the liquefied gas tank. It is possible to accurately and easily form a perfectly circular opening in plan view for installing the gauge, and to install the liquid level gauge in the liquefied gas tank with high accuracy.
In addition, according to the liquid level gauge installation method for a liquefied gas carrier according to the present invention, a liquid level gauge can be additionally installed or replaced with high accuracy in an existing liquefied gas tank.
Furthermore, according to the liquid level gauge installation method for a liquefied gas carrier according to the present invention, the liquid level gauge can be accurately installed when a liquefied gas tank is newly constructed.

It is a side view which shows an example of the liquefied gas carrier ship which can apply this invention. It is a longitudinal cross-sectional view of the liquefied gas tank single-piece | unit of the liquefied gas carrier ship shown in FIG. It is a longitudinal cross-sectional view of the tank top part which expanded the III part of FIG. It is a side view which shows one Embodiment of the punching apparatus for liquid level gauges which concerns on this invention. It is a figure which expands the V section of FIG. 4 and shows the lower side fixing | fixed part and height setting part of a cutting machine holding | maintenance part. It is a top view of the lower side fixing | fixed part and height setting part by VI arrow view of FIG. It is a side view of the lower side fixing | fixed part and height setting part by the VII arrow view of FIG. It is a fragmentary longitudinal cross-sectional view of the tank top part which shows the state which set the 2nd fixed point by the projection of the laser beam from a tank bottom part. It is a longitudinal cross-sectional view which shows the state by which the center hole was drilled in the 2nd fixed point. It is a longitudinal cross-sectional view which shows the state which has confirmed the position accuracy of the center hole. It is a longitudinal cross-sectional view which shows the state which has pierced the opening part centering on a center hole. It is a longitudinal cross-sectional view which shows the state by which chamfering was given to the inner peripheral part of the opening part. It is a longitudinal cross-sectional view which shows the state by which the seat tube was temporarily fixed by the opening part. It is a longitudinal cross-sectional view which shows the state by which the seat tube was welded to the opening part. It is a longitudinal cross-sectional view of the liquefied gas tank which shows the 1st fixed point setting process at the time of liquid level meter addition installation. It is a longitudinal cross-sectional view of the liquefied gas tank which shows the 2nd fixed point setting process at the time of liquid level meter addition installation. It is a longitudinal cross-sectional view of the liquefied gas tank which shows the perforation process at the time of liquid level gauge addition installation. It is a longitudinal cross-sectional view of the liquefied gas tank which shows the seat tube welding process at the time of liquid level meter addition installation. It is a flowchart which shows each process of the installation method which additionally installs a liquid level gauge in the existing liquefied gas tank. It is a longitudinal cross-sectional view of the liquefied gas tank which shows the 1st fixed point setting process at the time of new construction of a liquefied gas tank. It is a longitudinal cross-sectional view of the liquefied gas tank which shows the drilling process at the time of new construction of a liquefied gas tank. It is a longitudinal cross-sectional view of the liquefied gas tank which shows the seat tube welding process at the time of new construction of a liquefied gas tank. It is a longitudinal cross-sectional view of the liquefied gas tank which shows the 2nd fixed point setting process at the time of new construction of a liquefied gas tank. It is a longitudinal cross-sectional view which shows the state by which the reference member of the tank bottom part side was installed in the 2nd fixed point at the time of the new construction of a liquefied gas tank. It is a flowchart which shows each process of the installation method which installs a liquid level meter at the time of new construction of a liquefied gas tank.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Configuration of liquefied gas carrier and liquefied gas tank]
FIG. 1 is a side view showing an example of a liquefied gas carrier ship to which the present invention can be applied. This liquefied gas carrier 1 is a so-called MOSS type ship that carries liquefied gas such as LNG, and its hull 2 is partitioned into a bow, a hold, and a stern in order from the front in the traveling direction.

  A plurality of spherical liquefied gas tanks 3 are installed along the longitudinal direction in the hold, and the main facilities such as a living area 5 consisting of a wheelhouse (bridge) and a passenger room on the stern and an engine 6 necessary for navigation. An engine room 7 is provided. In addition, a tank top portion 8 protruding in a dome shape is provided at the top of each liquefied gas tank 3, and a flying passage 9 extending in the front-rear direction of the hull 2 is installed along the tank top portion 8. The flying passage 9 is a passage for crew members and workers, and supports piping and electric wires (not shown) connected to each tank top portion 8.

FIG. 2 is a longitudinal sectional view of the liquefied gas tank 3 alone.
The liquefied gas tank 3 includes a spherical tank body 11 and a pipe tower 12 provided so as to vertically connect the top and bottom of the tank body 11 along the vertical center line C of the tank body 11. It is configured. The bottom of the pipe tower 12 is a pump chamber 13 having a large diameter in which a feed pump (not shown) that feeds liquefied gas to the outside is accommodated, and the top of the pipe tower 12 is connected to the tank top 8.

  As shown in FIG. 3 in an enlarged manner, the upper surface of the tank top portion 8 is spherical in order to ensure pressure resistance, and an inspection hole (vertex) passes through the central portion, that is, the position (vertex) through which the vertical center line C passes. Manhole) 15 is provided. A liquid level gauge 16 and other devices (not shown) are installed at a position slightly away from the vertical center line C while avoiding the inspection hole 15. The level gauge 16 is installed on a vertical seat tube 17 fixed so as to penetrate the upper surface of the tank top portion 8, and a plurality of measuring tubes 19, 20 extending vertically downward from the level gauge 16 are pumped. The chamber 13 is connected to a measurement reference member 21 installed on the tank bottom surface. The seat tube 17 is inserted and welded into a level gauge installation hole 23 (opening portion) drilled at a position away from the vertical center line C on the upper surface of the tank top portion 8.

  The liquid level gauge 16 measures the liquid level, temperature, and pressure of the liquefied gas stored in each liquefied gas tank 3, and the data is input to a computer system (not shown) so that the liquefied gas carrier 1 The total amount of liquefied gas loaded is calculated. This system is called CTS (Custody Transfer System), and since tariffs at the time of customs clearance are assessed based on the amount of liquefied gas loaded calculated by this CTS, high accuracy and reliability are required. Accordingly, the installation accuracy of the liquid level gauge 16 is considerably severe.

  The liquid level gauge installation hole 23 for installing the liquid level gauge 16 (seat tube 17) must be a perfect circle in plan view, but at a position deviated from the top of the tank top part 8 formed in a spherical shape. Since it is formed, it is elliptical except in plan view. For this reason, accurate machining is difficult if an incision is made using a jigsaw or the like. In addition, in the actual matching method in which a small hole is first formed and the inner diameter of the hole is gradually enlarged to match the outer diameter of the seat tube 17, the tank top portion 8 is thick, so that the It takes time.

[Configuration of perforating device for level gauge]
FIG. 4 is a side view showing an embodiment of the level gauge punching device 25 according to the present invention. The level gauge perforating apparatus 25 is an apparatus configured to easily form a perfect circular opening in a plan view in a spherical portion such as the upper surface of the tank top portion 8.

  The level gauge punching device 25 fixes a thick flat base plate 27 (base) having a rectangular shape in plan view, and fixes the base plate 27 above the drilling position of the level gauge installation hole 23 of the tank top portion 8. A plurality of extendable legs 28 and a base rotation shaft 30 that is pivotally supported through the central portion of the base plate 27 and extends vertically downward from the base plate 27, and is installed on the base plate 27 to rotate the reference rotation shaft 30. And an air motor 31 (rotation drive unit), and a cutting machine holding unit 32 that is attached to the reference rotation shaft 30 and rotates about the reference rotation shaft 30.

  For example, the base plate 27 may be a duralumin plate having a thickness of about 10 mm and a side of 40 cm. However, the size, thickness, material, and the like are not limited thereto, and may be changed as long as necessary rigidity can be secured. it can.

  Four legs 28 are rotatably connected to four corners of one surface of the base plate 27 via pillow ball joints 34 (spherical joints). It is essential that the number of the leg portions 28 is three or more, but four is preferable for stably supporting the base plate 27. The leg portion 28 can be expanded and contracted to an arbitrary length by an expansion / contraction portion 28 a provided in the middle portion thereof, and an ON / OFF type suction cup 36 is provided at each tip portion via a pillow ball joint 35. ing.

  The expansion / contraction range of each leg part 28 can illustrate the range of less than 1 m at the shortest and about 1.5 m at the longest, for example. Further, the suction cup 36 is turned off when the lever 36a is raised to lose its adsorptivity, and is turned on when the lever 36a is tilted to be sucked onto the spherical tank surface. In this embodiment, the level gauge punching device 25 is used. Can be fixed in a standing posture on the surface of the tank top portion 8.

  By providing such an ON / OFF type suction cup 36 at the tip of the leg 28, the leg 28 can be easily attached to, detached from, fixed to, or adjusted in position with respect to the surface of the tank top 8, and the level gauge is used. The installation workability of the entire punching device 25 can be improved. The same applies to the removal. In addition, if moderate rotation resistance is given to the pillow ball joints 34 and 35, the wobbling of the leg part 28 and the suction cup 36 can be suppressed, and the manageability of the perforating apparatus 25 for level gauges can be improved.

  On the other hand, the reference rotation shaft 30 is rotatably supported at its upper end portion by a bearing 38 provided at the center portion of the base plate 27, and a front end portion (lower end portion) is a center hole drilled in advance in the tank top portion 8. 40 is pivotally supported. A detachable pivot shaft 41 is rotatably attached to the tip of the reference rotation shaft 30, and the tip of the pivot shaft 41 is inserted into the center hole 40, so that the tip of the reference rotation shaft 30 is pivoted. It is pivotally supported by the center hole 40 through 41. Therefore, the reference rotating shaft 30 is supported at high rigidity as a both-end support shaft that is pivotally supported by the base plate 27 (bearing 38) and the tank top portion 8 (center hole 40). It is desirable that the inner diameter of the center hole 40 be formed sufficiently smaller than the inner diameter of the level gauge installation hole 23. Specifically, it may be about 10 mm. Further, it is preferable that there is no unnecessary play between the center hole 40 and the pivot shaft 41.

  The air motor 31 is fixed to the lower surface side of the base plate 27 and rotates by receiving air pressure from an air hose 43 connected to the upper surface side of the base plate 27. Since the pinion gear 44 provided on the main shaft of the air motor 31 meshes with the driven gear 45 provided integrally with the intermediate portion of the reference rotation shaft 30, the number of teeth of the pinion gear 44 is significantly smaller than the number of teeth of the driven gear 45. The rotation of the air motor 31 is greatly decelerated and transmitted to the reference rotation shaft 30. On the lower surface of the base plate 27, a controller 46 for performing ON / OFF operation of the air motor 31 and adjusting the rotation speed is provided. The air motor 31 can be replaced with an electric motor.

  The cutting machine holding unit 32 holds the cutting machine 50 capable of cutting the tank top portion 8 so as to be slidable in the vertical direction and to adjust the radial distance from the reference rotation shaft 30. A clamp part 52 fixed to the middle part so that the position can be adjusted up and down, a holding arm 53 extending horizontally from the clamp part 52, and a slide shaft 54 slidably held vertically at the tip of the holding arm 53 The upper fixing portion 55 and the lower fixing portion 56 are respectively fixed to the upper and lower portions of the slide shaft 54 with the holding arm 53 interposed therebetween.

  As the cutting machine 50, a type capable of cutting the tank top part 8 without touching the surface of the tank top part 8, such as a plasma cutting machine or a gas cutting machine, is recommended. As a result, no reaction force is generated from the cutting machine 50 at the time of cutting, and such a reaction force does not act on the level gauge punching device 25 side, and therefore, the base plate 27 of the level gauge drilling device 25. In addition, it is possible to improve the accuracy of the level gauge installation hole 23 by preventing the positional deviation of the reference rotation shaft 30 and the like.

  The torch shape of the cutting machine 50 is vertically long, and its upper part is clamped and fixed by a clamp-like upper fixing part 55, and the lower part (tip part) is a ring-like lower side fixing also shown in FIGS. It is inserted into the part 56 from above and fixed with a fixing screw 57. Note that the torch shape of the cutting machine 50 in this embodiment is merely an example, and other shapes are not denied. However, since the cutting machine 50 turns around the reference rotation shaft 30, the torch shape is vertically long. Is preferable in that the probability of interference with the leg portion 28 and the like is small.

  The holding arm 53 can change the amount of protrusion from the clamp part 52 by the action of the built-in rack and pinion mechanism by rotating a dial 59 provided in the clamp part 52, thereby The turning radius around the reference rotation shaft 30, that is, the diameter of the level gauge installation hole 23 to be drilled can be changed.

  A height setting unit 61 is provided in the lower fixing unit 56 of the cutting machine holding unit 32. The height setting unit 61 keeps the height of the tip of the cutting machine 50 with respect to the surface of the tank top 8 at a predetermined height and allows the height to be adjusted. 5-7 is a figure which shows the lower side fixing | fixed part 56 and the height setting part 61. As shown in FIG.

  The height setting unit 61 has a horizontal rotation shaft 62 provided on the side surface of the lower fixing portion 56 located at the distal end portion of the cutting machine holding unit 32, and an intermediate portion is pivotally supported by the rotation shaft 62. The rotating lever 63 includes ball sliders 64 (contact portions) provided at both ends of the rotating lever 63. The ball slider 64 rolls the steel ball 64 a so that it can slide smoothly on a flat surface. Height adjusting screws 64 b protruding from the top surface are provided at both ends of the rotating lever 63. It is screwed to the horizontal height adjustment plate 63a. By changing the screwing amount, the height of the lower fixing portion 56 relative to the surface of the tank top portion 8, that is, the height of the tip portion of the cutting machine 50 can be changed.

  Only the ball slider 64 at both ends of the rotating lever 63 can contact the surface of the tank top portion 8, and each ball slider 64 is moved to the surface of the tank top portion 8 around the rotating shaft 62. Turn to move in the direction of separation. Each ball slider 64 can move smoothly on the surface of the tank top portion 8. As shown in FIG. 6, an extension of a line connecting the two ball sliders 64 in a plan view passes through the central portion (center hole 40) of the level gauge installation hole 23, and the two ball sliders 64 are level gauges. It is preferable to determine the direction of the rotation lever 63 so as to straddle the outline of the installation hole 23.

  When the cutting machine 50 is installed in the cutting machine holding part 32, the weights of the cutting machine 50 and the slide shaft 54, the upper fixing part 55, the lower fixing part 56, etc. pass through the rotary shaft 62 and the central part of the rotary lever 63. In addition, the ball sliders 64 (steel balls 64 a) at both ends of the rotation lever 63 are pressed against the surface of the tank top portion 8. At this time, the tip of the cutting machine 50 is separated from the surface of the tank top portion 8, and its height is easily adjusted by changing the screwing amount of the ball slider 64 to the height adjusting plate 63a of the rotating lever 63. it can.

[Drilling procedure for level gauge installation hole]
8 to 11 show a procedure in the case of drilling a completely circular level gauge installation hole 23 in a plan view on the upper surface of the tank top portion 8 using the level gauge drilling apparatus 25 configured as described above. Show.

  First, as shown in FIG. 8, vertical laser light L is projected from a first fixed point P1 (see FIG. 15) provided at the bottom of the liquefied gas tank 3 as will be described later. A point projected on the lower surface of the liquid level gauge is set as a second fixed point P <b> 2 that becomes the center point of the level gauge installation hole 23.

  Next, as shown in FIG. 9, the center hole 40 is vertically drilled according to the second fixed point P2. Since the center hole 40 is a small hole of about 10 mm as described above, it can be easily formed by a drill or the like.

  Next, as shown in FIG. 10, the vertical laser light L is projected again from the first fixed point P1 at the bottom of the liquefied gas tank 3, and whether or not the laser light L passes through the center hole 40 (second fixed point P2). The position accuracy of the center hole 40 is confirmed by looking at the above. When the laser beam L does not pass through the center hole 40, the position accuracy of the center hole 40 is poor. Therefore, the laser beam L is measured again and the center hole 40 is reopened within the formation range of the level gauge installation hole 23, or The center position of the center hole 40 is corrected by eccentrically expanding the inner diameter.

  Next, as shown in FIG. 11, the level gauge drilling device 25 is installed above the center hole 40, and the reference rotation is performed with the tip of the pivot shaft 41 of the reference rotation shaft 30 inserted into the center hole 40. The length of each leg 28 and the fixing position by the suction cup 36 are adjusted so that the shaft 30 is vertical. Since the reference rotation shaft 30 is supported at an angle perpendicular to the base plate 27, the level of the reference rotation shaft 30 is made to coincide with the center hole 40 with the level plate placed on the upper surface of the base plate 27 and the base plate 27 being horizontal. If it does so, the reference | standard rotating shaft 30 will become vertical naturally.

  Since the base plate 27 is supported by the four leg portions 28 and is stably fixed on the surface of the tank top portion 8 and the length of each leg portion 28 can be adjusted to expand and contract, The hanging position of the reference rotation shaft 30 extending vertically downward from the base plate 27 can be easily matched with the center hole 40.

  Next, as shown in FIG. 4, the cutting machine 50 is set in the cutting machine holding part 32, and the amount of protrusion of the holding arm 53 from the clamp part 52 is adjusted by adjusting the dial 59 provided on the clamp part 52, The turning radius from the reference rotating shaft 30 of the cutting machine 50, that is, the inner diameter of the level gauge installation hole 23 is determined. Further, as shown in FIG. 5, the distance between the tip of the cutting machine 50 and the surface of the tank top portion 8 is adjusted by adjusting the screwing amount of the ball slider 64 to the height adjustment plate 63 a of the rotating lever 63.

  Then, while operating the cutting machine 50, the air motor 31 is activated to rotate the reference rotation shaft 30, and the cutting machine 50 is turned around the reference rotation shaft 30 like a compass to cut off the upper surface of the tank top portion 8 in a round shape. Then, the level gauge installation hole 23 is drilled. At this time, if the cutting machine 50 is rotated once at a time and the inner peripheral portion of the level gauge installation hole 23 is not cut off, it is rotated left and right by half a turn, and a slight uncut is formed. It is possible to prevent the reference rotation shaft 30 from dropping simultaneously with the opening of the installation hole 23.

  Since the cutting machine 50 held by the cutting machine holding part 32 is slidable in the vertical direction, even if the surface of the tank top part 8 traced by the cutting machine 50 is spherical, curved, uneven, etc. The cutting machine 50 slides up and down following the surface shape, thereby enabling smooth cutting. Moreover, since the cutting machine 50 can adjust the radial distance from the reference rotation shaft 30, the diameter of the level gauge installation hole 23 can be easily changed.

  Further, the height setting unit 61 always maintains the height of the tip of the cutting machine 50 with respect to the surface of the tank top 8 regardless of the curved shape of the surface of the tank top 8. In the middle of cutting, the cutting machine 50 is welded to the cutting part, and the cutting machine 50 is prevented from becoming too high and cutting is interrupted. The meter installation hole 23 can be easily and accurately formed. In addition, since the height of the tip of the cutting machine 50 can be adjusted by the height setting unit 61, the cutting conditions can be easily set and changed.

  Further, the cutting is performed in a state in which the tip end portion of the reference rotation shaft 30 is pivotally supported through the pivot shaft 41 in the small-diameter central hole 40 previously drilled in the tank top portion 8. It can rotate stably without shaking. For this reason, the turning trajectory of the cutting machine 50 that turns around the reference rotation shaft 30 to cut the tank top portion 8 can be stabilized, and the center position accuracy and roundness of the formed level gauge installation hole 23 can be stabilized. Can be significantly increased. The pivot shaft 41 is not an essential element. For example, the tip end portion of the reference rotation shaft 30 may be directly inserted into the center hole 40 and supported.

  The level gauge installation hole 23 formed as described above is a perfect circular opening having a high accuracy in a plan view while being near the top of the tank top portion 8 and away from the vertical center line C. Become. For this reason, the installation of the seat tube 17 and the level gauge 16 which will be described next can be performed with high accuracy.

  When the level gauge installation hole 23 is formed, as shown in FIG. 12, a chamfer 67 is applied to the inner periphery of the level gauge installation hole 23 in preparation for groove welding with the seat tube 17. This chamfering operation is performed by a worker using a grinder. For example, a chamfering device (not shown) is attached to the cutting machine holding portion 32 of the leveling device 25 and the chamfering is performed in the same manner as when the leveling hole 23 is drilled. It is also conceivable to perform processing.

  Next, as shown in FIG. 13, the seat tube 17 is temporarily fixed to the level gauge installation hole 23, and the seat tube 17 is welded to the level gauge installation hole 23 as shown in FIG. 14. This welding is performed from both the inside and outside of the tank top portion 8. Further, this welding is performed while shielding the weld from the atmosphere with an inert gas (TIG welding or the like). And the level gauge 16 is attached to the seat tube 17 welded in this way.

  The level gauge drilling device 25 is not limited to drilling the level gauge installation hole 23 in the liquefied gas tank 3 of the liquefied gas carrier 1, but for example, a spherical tank or a dome-shaped tank installed on the land. It can also be applied to the case of drilling.

[Liquid gas tank level gauge installation method 1]
Next, when the CTS-compatible liquid level gauge 16 is additionally installed in the liquefied gas tank of an existing liquefied gas carrier ship that does not have a CTS-compatible liquid level gauge, or the liquid level gauge 16 is moved to another location in the tank. A remodeling method (replacement method) in the case of (replacement) will be described with reference to FIGS. In addition, FIG. 19 is a flowchart which shows each process in this liquid level meter installation method.

  First, as shown in FIG. 15, a first fixed point P <b> 1 positioned below the liquid level gauge 16 is provided at one of the bottom or top, preferably the bottom, inside the liquefied gas tank 3 and inside the pipe tower 12. Set (first fixed point setting step S1).

  Next, as shown in FIG. 16, a vertical laser beam L is projected from the first fixed point P1 toward the top of the liquefied gas tank, that is, the tank top portion 8, and the projection position is set as a second fixed point P2. Set (second fixed point setting step S2). FIG. 8 is an enlarged view at this time.

  Next, in accordance with the position of the second fixed point P2, as shown in FIG. 17, a level gauge installation hole 23 having a predetermined inner diameter in plan view is provided on the upper surface of the tank top portion 8 for the above-described level gauge. Drilling is performed using the punching device 25 (piercing step S3). FIG. 11 is an enlarged view at this time. In this drilling step S3, first, the center hole 40 is drilled at the projection point (second fixed point P2) of the laser beam L (see FIG. 9), and then the liquid level gauge installation hole 23 is centered on this center hole 40. Perforate. It is desirable that the diameter of the center hole 40 is much smaller than the diameter of the level gauge installation hole 23. For example, it is about 10 mm.

  Next, a chamfer 67 for welding is applied to the inner peripheral portion of the level gauge installation hole 23 (see FIG. 12), and as shown in FIG. 18, the measurement reference member 21 is installed at the first fixed point P1, A seat tube 17 serving as the base of the liquid level meter 16 is welded and fixed along the vertical direction in the surface meter installation hole 23 (the seat tube welding step S4). FIGS. 13 and 14 are enlarged views at this time.

  Next, the measuring tubes 19 and 20 of the level gauge 16 shown in FIG. 3 are installed in the vertical direction connecting the central axis of the seat tube 17 and the first fixed point P1 (measurement reference member 21). Finally, the liquid level gauge 16 is installed on the seat tube 17 to complete the installation of the liquid level gauge 16 (measurement pipe installation step S5).

  According to the above-described liquid level gauge installation method, the vertical laser beam L is projected from the first fixed point P1 set at the bottom (or the top) inside the liquefied gas tank 3, and the second fixed point P2 is matched to the projection position. Therefore, the first fixed point P1 and the second fixed point P2 can be accurately arranged on the vertical line. Accordingly, even if the diameter of the pipe tower 12 installed inside the liquefied gas tank 3 is small, the first fixed point P1 and the second fixed point P2, that is, the seat tube 17 of the liquid level gauge 16 and the measurement reference member 21 are installed. It is easy to make a modification to install the level gauge 16 in the liquefied gas tank 3 with high accuracy.

  Further, as described above, the first fixed point P1 is set on the bottom side of the liquefied gas tank 3, the projection point of the laser beam L projected vertically from the first fixed point P1 is set as the second fixed point P2, and the perforation is performed. In step S3, a small-diameter central hole 40 is first drilled at the second fixed point P2, and then the level gauge installation hole 23 is drilled around the central hole 40.

  For this reason, after the small-diameter center hole 40 is drilled, the vertical laser light L can be projected again upward from the first fixed point P1, and the position accuracy of the center hole 40 can be confirmed. Even if there is a deviation, the center hole 40 is reopened within the formation range of the level gauge installation hole 23, or the center position of the center hole 40 is corrected by eccentrically expanding the inner diameter of the center hole 40. be able to. Therefore, equipment such as the level gauge 16 can be installed in the liquefied gas tank with high accuracy.

In the above embodiment, the first fixed point P1 is set on the tank bottom side first, then the second fixed point P2 is set on the tank top side, and the level gauge installation hole 23 is perforated. It is not limited to this procedure.
For example, the first fixed point P1 is set at the top of the liquefied gas tank 3 first, the center hole 40 is drilled here, and the laser beam L is projected vertically from the center hole 40 toward the bottom of the liquefied gas tank 3. The procedure may be such that the second fixed point P2 is set at the bottom of the tank, then the level gauge installation hole 23 is drilled around the center hole 40 and the seat tube 17 is fixed by welding.

[Liquid gas tank level gauge installation method 2]
Next, the installation method of the liquid level gauge 16 at the time of new construction of the liquefied gas tank of the liquefied gas carrier ship will be described with reference to FIGS. In addition, FIG. 25 is a flowchart which shows each process in this liquid level meter installation method.

  First, as shown in FIG. 20, a first fixed point P1 is set near the top of the liquefied gas tank 3, that is, near the top of the pipe tower 12 (tank top 8) (first fixed point setting step S11).

  Next, with the first fixed point P1 as the center, as shown in FIG. 21, a level gauge installation hole 23 having a predetermined diameter in plan view is drilled by using the above-described level gauge drilling device 25 (drilling). Step S12).

  Next, as shown in FIG. 22, the seat tube 17 serving as the base of the level gauge 16 is welded and fixed along the vertical direction in the level gauge installation hole 23 (the seat tube welding process S <b> 13).

  Next, as shown in FIG. 23, a vertical laser beam L is projected from the central axis of the seat tube 17 toward the bottom of the liquefied gas tank 3, and the projection position is determined as a second fixed point P2 (second fixed point setting step). S14).

  Next, as shown in FIG. 24, the measurement reference member 21 is installed at the second fixed point P2, and finally, in the vertical direction connecting the central axis of the seat tube 17 and the second fixed point P2 (measurement reference member 21), The measurement pipes 19 and 20 of the liquid level gauge 16 shown in FIG. 3 are installed to obtain the embodiment shown in FIG. 2 (measurement pipe installation step S15). Finally, the liquid level gauge 16 is installed on the seat pipe 17 and the liquefied gas tank 3 new construction is completed.

  According to the above-described liquid level gauge installation method, the vertical laser beam L is projected from the first fixed point P1 set at the top inside the liquefied gas tank 3, and the second fixed point P2 is applied to the bottom of the liquefied gas tank in accordance with the projection position. Therefore, the first fixed point P1 and the second fixed point P2 can be accurately arranged on the vertical line. Accordingly, even if the diameter of the pipe tower 12 installed inside the liquefied gas tank 3 is small, the first fixed point P1 and the second fixed point P2, that is, the seat tube 17 of the liquid level gauge 16 and the measurement reference member 21 are installed. It is easy to install the liquid level gauge 16 with high accuracy when the liquefied gas tank 3 is newly constructed.

  In the above-described embodiment, the first fixed point P1 is set on the tank top side first, the level gauge installation hole 23 is drilled, and the seat tube 17 is fixed by welding. Although the vertical laser beam L is projected toward the bottom and the projection position is determined as the second fixed point P2, it is not limited to this procedure. For example, the first fixed point P1 may first be set at the bottom of the liquefied gas tank 3, and then the second fixed point P2 may be set at the top of the tank to make the level gauge installation hole 23.

  It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and can be appropriately modified or improved within a scope not departing from the gist of the present invention. Are also included in the scope of rights of the present invention.

  For example, in the above embodiment, the spherical liquefied gas tank has been described as an example, but the present invention can be similarly applied even when the liquefied gas tank is rectangular. Furthermore, even if the top surface of the liquefied gas tank is a spherical surface, a flat surface, an inclined surface, or a polygonal bent surface, the piercing device for a liquid level gauge and the liquid level meter installation method of the liquefied gas tank carrier according to the present invention are effective.

DESCRIPTION OF SYMBOLS 1 Liquefied gas carrier 3 Liquefied gas tank 12 Pipe tower 15 Inspection hole 16 Level gauge 17 Seat pipe 19,20 Measuring pipe 21 Measurement reference member 23 Level gauge installation hole (opening which becomes a perfect circle by planar view)
25 Punching device for level gauge 27 Base plate (base)
28 Leg 30 Reference Rotation Shaft 31 Air Motor (Rotation Drive Unit)
32 Cutting machine holding part 36 Suction cup 40 Center hole 50 Cutting machine 61 Height setting part 62 Rotating shaft 63 Rotating lever 64 Ball slider (contact part)
C Vertical center line L of tank L Laser light P1 First fixed point P2 Second fixed point S1, S11 First fixed point setting step S2, S14 Second fixed point setting step S3, S12 Drilling step S4, S13 Washing tube welding step S5, S15 Measuring tube installation process

Claims (7)

A piercing device for a liquid level gauge of a liquefied gas carrier ship that pierces a circular opening for a liquid level gauge at the top of a liquefied gas tank or the like in a liquefied gas carrier ship,
The base,
A plurality of extendable legs for fixing the base above the opening drilling position on the surface of the liquefied gas tank;
A reference rotation shaft that is pivotally supported by the base and extends vertically downward from the base;
A rotation drive unit installed at the base for rotating the reference rotation shaft;
A cutting machine that is attached to the reference rotation shaft and pivots about the reference rotation shaft so that the cutting machine capable of cutting the liquefied gas tank can be slid in the vertical direction and the radial distance from the reference rotation shaft can be adjusted. A cutting machine holder,
A piercing device for a liquid level gauge of a liquefied gas carrier, characterized by comprising:   The cutter holder is provided with a height setting unit capable of maintaining the height of the tip of the cutter relative to the surface of the liquefied gas tank at a predetermined height and adjusting the height. The piercing device for a level gauge of a liquefied gas carrier ship according to claim 1 characterized by the above. The height setting unit is
A rotating shaft provided near the tip of the cutting machine holding unit;
An intermediate portion is pivotally supported by the pivot shaft, and only contact portions provided at both ends thereof can contact the surface of the liquefied gas tank, and the contact portion is centered on the pivot shaft and the liquefied gas tank. A rotating lever that rotates so as to move in the direction of separation with respect to the surface of
Configured with
The piercing device for a level gauge of a liquefied gas carrier ship according to claim 2, wherein the contact portion can move smoothly on the surface of the liquefied gas tank.   The reference rotating shaft is pivotally supported by a central hole having a tip sufficiently drilled at the opening drilling position on the surface of the liquefied gas tank and having a diameter sufficiently smaller than the diameter of the opening. The piercing device for a level gauge of a liquefied gas carrier ship according to any one of claims 1 to 3. A method for installing a liquid level gauge of a liquefied gas carrier ship when an additional liquid level gauge is installed or replaced near the top of the liquefied gas tank of the liquefied gas carrier ship,
A first fixed point setting step for setting a first fixed point at one of the bottom or top of the liquefied gas tank;
A second fixed point setting step of projecting laser light in the vertical direction from the first fixed point toward the other of the bottom or the top inside the liquefied gas tank, and setting the projection position as a second fixed point;
Of the first fixed point and the second fixed point, a drilling step of drilling an opening around a fixed point on the top side of the liquefied gas tank;
A seat tube welding step of welding and fixing the seat tube of the liquid level gauge to the opening;
A measuring tube installation step of installing the measuring tube of the liquid level gauge in a vertical direction connecting a central axis of the seat tube and a fixed point on the bottom side of the liquefied gas tank;
A level gauge installation method for a liquefied gas carrier, characterized by comprising: In the first fixed point setting step, the first fixed point is set on the bottom side inside the liquefied gas tank,
In the second fixed point setting step, the projection point of the laser light projected from the first fixed point is the second fixed point,
In the drilling step, a center hole is first drilled at a projection point of the laser beam, and then the opening having a predetermined inner diameter in plan view is drilled around the center hole. Item 6. A liquid level gauge installation method for a liquefied gas carrier according to Item 5. A liquid level gauge installation method for a liquefied gas carrier ship, in which a liquid level gauge is installed near the top of the tank when a liquefied gas tank of a liquefied gas carrier ship is newly constructed,
A first fixed point setting step for setting a first fixed point near the top of the liquefied gas tank;
A perforating step of perforating the opening around the first fixed point;
A seat tube welding step of welding and fixing the seat tube of the liquid level gauge to the opening;
A second fixed point setting step of projecting laser light in the vertical direction from the central axis of the seat tube toward the bottom of the liquefied gas tank, and setting the projection position as a second fixed point;
A measuring tube installation step of installing the measuring tube of the liquid level gauge at a position connecting the central axis of the seat tube and the second fixed point;
A level gauge installation method for a liquefied gas carrier, characterized by comprising:

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