A method for detecting the manufacturing precision of a ship pipeline

Abstract

A method for inspecting the fabrication accuracy of ship piping requires an inspection fixture. The main body of the fixture has a groove, and a sliding ruler is slidably connected to the groove. A laser projector is fixed on the sliding ruler. The laser line projected by the laser projector is equivalent to the string of a plumb bob, and the dot formed by the laser projection on the bottom surface is equivalent to the tip of the plumb bob. The theoretical distance S from the pipe end face to the longitudinal baseline is used to measure the distance S' from the laser point to the transverse baseline using a ruler or tape measure. The result of S' - S is the deviation value. A positive result indicates a long pipe end, and a negative result indicates a short pipe end. This invention features a simple design, reduces random deviations during inspection, has low manufacturing cost, is highly practical, and achieves an accuracy of ±1mm.

Description

Technical Field

[0001] This invention belongs to the field of marine shipbuilding and design, and specifically relates to a method for testing the accuracy of ship pipeline manufacturing. Background Technology

[0002] The cryogenic piping system of LNG carriers needs to be prefabricated into pipe units within the factory building. During the fabrication of these units, grid lines need to be drawn in the workshop as a basis for controlling and inspecting the installation accuracy of the piping system. During installation, the pipe ends need to be projected and compared with the ground survey line to calculate the deviation. For inspection, the pipe ends are first fabricated, and a plumb bob is suspended from the pipe as a reference point to the ground. The installation deviation during unit fabrication is calculated based on the deviation between the plumb bob and the ground survey line. The cryogenic piping units use 304L and 316L stainless steel, and the pipe ends have no flanges; the pipes are butt-welded. Accurately confirming the pipe center is difficult, and the alignment accuracy cannot meet the standard requirements, making it difficult to guarantee the pipe installation accuracy.

[0003] During unit fabrication, the center of the pipe on the horizontal projection plane must be accurately located on the pipe to be installed on site. The pipe center is compared with the ground line, and the deviation is measured to judge the pipe installation accuracy. The center of the pipe can be accurately measured at the pipe opening and projected onto the ground, reducing pipe installation deviation.

[0004] On LNG carriers, cryogenic pipes are first assembled into units and then hoisted onto the ship for installation. During the hoisting of these units, a total station is used to inspect the pipe openings. When positioning the units, precision measurement personnel use the pipe's center coordinates as a reference. Since the cryogenic pipe openings lack flanges, the total station inspection requires aiming directly at the opening and measuring its center coordinates. Because the opening's interior is a space, using a total station to inspect the opening coordinates presents two challenges: 1. Difficulty in accurately determining the pipe's center point; 2. How to set a reflective target at the center of the pipe's end face. Summary of the Invention

[0005] To address the above problems, this invention provides a method for detecting the manufacturing accuracy of ship pipelines, the technical solution of which is as follows: A method for testing the manufacturing precision of ship pipelines requires the use of a testing fixture. The fixture includes a T-shaped fixture body with a groove at the center line of the web plate of the fixture body. A sliding ruler plate is nested in the groove and slides up and down in the groove. Rollers with machined shaft threads are provided at both ends of the flange of the fixture body, and the rollers contact the outer wall of the pipe opening.

[0006] A long water bubble is horizontally set at the top of the chute, and a clamping pin is set on the back of the bottom of the tooling body, which is clamped to the pipe wall.

[0007] The main body of the sliding ruler is a square plate. A laser projector is fixed on the main body of the sliding ruler. An insertion plate is provided on the back of the sliding ruler. The insertion plate passes through the slide groove and cooperates with the pulley. Turn on the laser projector. The projected laser line is equivalent to the line that hangs the plumb bob. The dot formed by the laser projection on the bottom surface is equivalent to the tip of the plumb bob. Measure the distance from the dot to the baseline to determine the positioning deviation of the pipe opening.

[0008] Clamp the fixture at the pipe opening, with the roller tangent to the outer wall of the pipe opening, and inspect the pipe opening. The theoretical distance S from the pipe opening end face to the longitudinal baseline is S1 + S2. During inspection, use a ruler or tape measure to measure the actual distance S' from the laser beam projection point to the transverse baseline. The result of S' - S is the deviation value. When the result is positive, it indicates that the pipe opening is |S' - S| mm long. When the result is negative, it indicates that the pipe opening is |S' - S| mm short.

[0009] Where S1 is the web thickness of the tooling body, and S2 is the distance from the bottom of the tooling body to the laser line.

[0010] Furthermore, in the aforementioned method for testing the manufacturing precision of ship pipelines, the groove width is 6mm.

[0011] Furthermore, in the aforementioned method for testing the manufacturing precision of ship pipelines, the diameter of the roller is 20-30mm, and the diameter of the threaded shaft is 6-8mm.

[0012] Furthermore, in the aforementioned method for testing the manufacturing precision of ship pipelines, the sliding ruler plate is seamlessly embedded in the sliding groove.

[0013] Furthermore, in the aforementioned method for testing the manufacturing precision of ship piping, the pulley is fixed to the insertion plate via bearings.

[0014] Furthermore, in the aforementioned method for testing the manufacturing precision of ship pipelines, a support plate is horizontally fixed on the back side of the bottom end of the web plate of the tooling body, a round bubble is fixed on the support plate, and a reinforcing plate is provided below the support plate.

[0015] This invention features a simple design. By replacing the traditional plumb bob method with laser projection, it firstly avoids measurement deviations caused by plumb bob oscillation, reducing the probability of random deviations during detection. Secondly, using a laser beam as a reference to detect positional deviations results in high detection efficiency and strong tooling practicality. Thirdly, the new tooling achieves a measurement accuracy of ±1mm. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of tooling measurement; Figure 2 yes Figure 1 Schematic diagram of the structure from the perspective of AA; Figure 3 yes Figure 1 Schematic diagram of the structure from the perspective of a mid-BB (Browser-Based Array) Figure 4 yes Figure 1 Schematic diagram of the structure from the perspective of DD; Figure 5 This is a schematic diagram of the clamping pin structure; Among them, 1-tool body, 2-roller, 3-long bubble, 4-slide groove, 5-pipe, 6-laser projector, 7-sliding ruler, 9-clamping pin, 9-1-pin, 9-2-spring, 9-3-limiting plate, 9-4-sleeve, 9-5-base plate, 9-6-flat head screw, 9-7-wear-resistant end, 13-support plate, 14-reinforcing plate, 15-round bubble, 16-laser line. Detailed Implementation

[0017] The invention will be further described with reference to the accompanying drawings.

[0018] like Figures 1-4 The method for inspecting the manufacturing precision of ship piping, as shown, requires an inspection fixture. The fixture includes a T-shaped main body 1, with a groove 4 located at the center line of the web plate. A sliding ruler 7 is nested within the groove, sliding up and down within it. At both ends of the flange, rollers 2 with machined threads on their shaft diameters are provided. The diameter of the rollers is 20-30 mm, and the diameter of the threaded shaft is 6-8 mm.

[0019] After screwing two equal-diameter rollers onto the horizontal part of the ruler plate, two small rollers and a ruler plate with a sliding groove are formed on the main body of the ruler plate. When the two small rollers are placed at the pipe opening, the small rollers are tangent to the pipe wall. The tooling described above is such that when two small circles of equal diameter are tangent to a large circle, the perpendicular bisector of the line connecting the centers of the two small circles must pass through the center of the large circle (pipe hole).

[0020] Based on the above components, a 6mm wide groove is machined along the center line of the vertical part of the ruler plate. A movable sliding ruler plate is nested in the groove without gaps. The thickness of the web of the sliding ruler plate is equal to the width of the groove. The web is embedded in the groove without gaps and moves radially along the groove, and also exhibits a lateral swing phenomenon.

[0021] The sliding ruler plate consists of a face plate and a web plate. The face plate and the web plate are perpendicular to each other. The face plate is processed to be a smooth surface. After the web plate of the sliding ruler plate is embedded in the sliding groove, the lower surface of the face plate of the sliding ruler plate is in contact with the vertical part of the plate. The friction between the two smooth surfaces is small, which allows it to move smoothly up and down.

[0022] Holes are drilled at the top and bottom ends of the web plate, and bearings are embedded in the round holes. Long shafts are installed in the inner holes of the bearings, and fixed wheels are set at both ends of the shafts. Elastic rubber is installed on the wheels. A total of 4 wheels are installed on the web plate. The wheels are in contact with the surface of the vertical ruler plate. When the sliding ruler plate moves up and down along the slide groove, the wheels on the web plate can roll to reduce friction.

[0023] Based on the fact that the center of the tooling main slide groove passes through the center of the circle, a long water bubble 3 is installed on the ruler plate. The long side of the long water bubble is parallel to the line connecting the centers of the tooling main body. When the long water bubble is in the center, the projection of the center of the tooling main slide groove coincides with the projection of the center line of the pipe 5 on the ground.

[0024] On the lower back of the ruler plate, a support plate 13 is installed. The support plate is semi-circular, and the diameter of the ruler plate is the same as its width. The support plate 13 is perpendicular to the surface of the fixture body 1, and its surface is parallel to the line connecting the centers of the two original rollers. Below the support plate 13, a right-angled triangular reinforcing plate 14 is installed, with its right-angled sides glued to the ruler plate and the support plate. A round bubble 15 is glued to the face of the support plate 13. If the bubble is perfectly centered, it indicates that the center line on the plate surface is a plumb line.

[0025] With the center line of the tooling body in a plumb line in space, a laser projector is installed on the sliding ruler plate. A laser projector 6 is installed on the sliding ruler plate. The laser projector projects a laser line 16, which is also in a plumb line state. The projected laser line is equivalent to the line that hangs the plumb line. The point formed by the laser projection on the bottom surface is equivalent to the tip of the plumb line. The point where the tip of the plumb line points to the ground is completely coincident with the laser beam projection point.

[0026] After marking the position of the laser projection dot on the ground, use a measuring tape to measure the distance from the projection point to the horizontal and vertical baselines respectively. Determine if the projected center of the pipe opening deviates from the ground line from the tolerance. If the deviation exceeds the tolerance, it needs to be corrected in time. Positioning can only be performed after the tolerance requirements are met. See the appendix for details. Figure 4 .

[0027] The main body of the fixture is equipped with a clamping pin at the top. The clamping pin is a finished device composed of a pin 9-1, a spring 9-2, a limiting plate 9-3, a sleeve 9-4, a base plate 9-5, a flat-head screw 9-6, and a wear-resistant end 9-7. It has a spring clamping function and is used to clamp the pipe wall and stabilize the fixture. After the main body of the fixture is adjusted to a state where it can be measured, the limiting plate 9-3 connected to the sliding sleeve 9-4 is pulled up by hand. There is a protruding limiting tongue at the lower end of the limiting plate. The limiting tongue is embedded in the sliding groove in the center of the base plate 9-5. A shaft 9-1 is set between the fixed end and the limiting plate. The spring 9-2 is fitted on the shaft. The spring is set between the two limiting plates and is set along the shaft 9-1. It has pressure and pushes the lower limiting plate to squeeze the sliding sleeve 9-4 downward. The wear-resistant end 9-7 clamps the pipe wall and fixes the main body of the fixture to the pipe, so that it has the conditions for stable measurement.

[0028] To ensure that the spring compression force does not completely squeeze the sliding sleeve 9-4 out of the shaft 9-1 range, a groove is set in the center of the base plate 9-5. The tongue tip of the lower end of the limiting plate 9-3 is embedded in the groove in the center of the base plate 9-5. The length of the groove limits the stroke of the sliding sleeve 9-4 and will not exceed the length range of the shaft 9-1.

[0029] The left and right deviations of the pipe opening can be obtained directly through measurement, while the deviations of the front and rear end faces of the pipe opening need to be calculated. The calculation process is as follows: Assume the thickness of the fixture body is S1, the distance from the bottom surface of the sliding ruler plate to the laser line is S2, and the distance from the end face of the pipe opening to the laser line is S. The theoretical distance from the end face of the pipe opening to the longitudinal baseline is S = S1 + S2. During inspection, the distance from the center of the laser point to the transverse baseline is measured using a ruler or tape measure as S'. The result of S' - S is the deviation value. A positive result indicates that the pipe opening is |S' - S| mm long, and a negative result indicates that the pipe opening is |S' - S| mm short.

Claims

1. A method for testing the manufacturing precision of ship piping, characterized in that, The inspection fixture is required. The fixture includes a T-shaped fixture body. A groove is opened at the center line of the web of the fixture body. A sliding ruler is nested in the groove and slides up and down in the groove. At both ends of the flange of the fixture body, rollers with shaft diameter machining threads are set. The rollers contact the outer wall of the pipe opening. A long water bubble is horizontally set at the top of the chute, and a clamping pin is set on the back of the bottom of the tooling body. The clamping pin is clamped to the pipe wall. The main body of the sliding ruler is a square plate. A laser projector is fixed on the main body of the sliding ruler. An insertion plate is provided on the back of the sliding ruler. The insertion plate passes through the slide groove and cooperates with the pulley. Turn on the laser projector. The projected laser line is equivalent to the line that hangs the plumb bob. The point formed by the laser projection on the bottom surface is equivalent to the tip of the plumb bob. Measure the distance from the point to the baseline to determine the positioning deviation of the pipe opening. Clamp the fixture at the pipe opening, with the roller tangent to the outer wall of the pipe opening, and inspect the pipe opening. The theoretical distance from the pipe opening end face to the longitudinal baseline is S = S1 + S2. During inspection, use a ruler or tape measure to measure the actual distance S' from the laser beam projection point to the transverse baseline. The result of S' - S is the deviation value. When the result is positive, it indicates that the pipe opening is |S' - S| mm. When the result is negative, it indicates that the pipe opening is |S' - S| mm. Where S1 is the web thickness of the tooling body, and S2 is the distance from the bottom of the tooling body to the laser line.

2. The method for detecting the manufacturing precision of ship pipelines according to claim 1, characterized in that, The groove is 6mm wide.

3. The method for detecting the manufacturing precision of ship pipelines according to claim 1, characterized in that, The diameter of the roller is 20-30mm, and the diameter of the threaded shaft is 6-8mm.

4. The method for detecting the manufacturing precision of ship pipelines according to claim 1, characterized in that, The sliding ruler plate is seamlessly embedded in the sliding groove.

5. The method for detecting the manufacturing precision of ship pipelines according to claim 1, characterized in that, The pulley is fixed to the insertion plate by bearings.

6. The method for detecting the manufacturing precision of ship pipelines according to claim 1, characterized in that, On the back of the bottom of the web of the main body of the tooling, a support plate is fixed horizontally, a round water bubble is fixed on the support plate, and a reinforcing plate is set below the support plate.

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