CN102590216A - Measurement method for positioning of defects of tank bottom of vertical steel oil tank - Google Patents

Abstract

The invention discloses a measurement method for the positioning of defects of tank bottom of a vertical steel oil tank. The method comprises the following steps of: determining a horizontal circumference at a position higher than a bottom plate of an oil tank along a circumferential inner wall of the steel oil tank, sequentially arranging No. 1, No. 2, No. 3 and No. 4 targets which equally divide a circumference at equal intervals anticlockwise, and establishing a global coordinate system of the bottom plate of the oil tank by taking a connecting line of the No. 1 and No. 3 targets as an X axis and a connecting line of the No. 2 and No. 4 targets as a Y axis; putting a laser range finder on a defect of the bottom plate of the oil tank, and measuring distances Li between the defect and the four targets by using the laser range finder; according to the distances Li between the defect and the four targets, calculating an X value and a Y value of a coordinate point of the defect in the global coordinate system of the bottom plate of the oil tank according to a formula, and determining the position of the defect; and drawing an accurate coordinate position map of the defect in the global coordinate system of the bottom plate of the oil tank according to recorded values, and forming a detection report of the defect of the tank bottom of the oil tank. The method is simple and quick; the positions of the defects on the tank bottom can be accurately determined; and the measurement cost of accurate positioning of the defects of the tank bottom of the oil tank is reduced.

Description

The measuring method of defect location at the bottom of the vertical steel oil tank jar

Technical field

The present invention relates to the localization method of defective at the bottom of the large oil tank jar, the measuring method of defect location at the bottom of particularly a kind of vertical steel oil tank jar that adopts the range measurement and positioning.

Background technology

The vertical steel of oil depot is between tank life, because of a variety of causes can produce the damage defective, after defective appears in oil tank, needs to confirm defective locations, forms defects detection report at the bottom of the oil tank jar, as oil tank is repaired, the foundation of shaping.At the bottom of occurring in the oil tank jar like defective, the exact position of measuring the place is just difficult, and defect location mainly contains two kinds of methods at the bottom of the present vertical steel oil tank jar:

The one, the method for artificial sign is promptly carried out mark with traces such as slate pencils to defective through manual pick, and is simple and easy to do, and it is clear lastingly that shortcoming is that mark is difficult to, and is prone to polluted and cover by dirt, causes the mark defective to disappear.

The 2nd, applied modern computer technology adopts based on descriptive geometry conversion to set up the mathematical model of defect location, uses the automatic growth algorithm of window to realize the identification in defect distribution zone again.This method automaticity is high, and shortcoming is the equipment sophisticated, expensive.

And above two kinds of methods all need be carried out piecemeal position No. and the physical dimension of confirming each plate to tank bottom; Especially for the bigger jar end (as shown in Figure 1) that the arcuate edge listrium is arranged of capacity more than 2000 cubes; When the physical dimension process of record piecemeal position No. and definite each plate; Be prone to data recording and repeat and entanglement, greatly reduce the defect location precision.

How to improve the precision of defect location at the bottom of the vertical steel oil tank jar and can expensive expense reduce, be the problem that POL management is longed for solution always.

Summary of the invention

The objective of the invention is the deficiency that exists to prior art, the measuring method of defect location at the bottom of a kind of vertical steel oil tank jar is provided.It is through confirming a horizontal circumference at the steel oil tank circumferential inner wall; And at four targets that circumference in equal parts is set on this horizontal circumference; And be that initial point is set up the oil tank bottom plate global coordinate system with the oil tank bottom plate center; A laser range finder is placed on the defective of oil tank bottom plate, measure this defective distance L of four targets of distance respectively through laser range finder _i, adopt

$X=\&PlusMinus;\frac{L_2{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}{2R}\mathrm{Sin}\left(\mathrm{Arccos}\frac{{{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}^2+{{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}^2-{2\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{2L_2{L}_4}\right),$ $Y=\&PlusMinus;\frac{L_1{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_3}{2R}\mathrm{Sin}\left(\mathrm{Arccos}\frac{{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA0000129072380000022.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">L</figure-callout>}}_1}^2+{{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_3}^2-{2\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{2L_1{L}_3}\right)$ Computing formula, according to defective apart from the distance L of four targets _iCalculate the X value and the Y value of this defective coordinate points in the oil tank bottom plate global coordinate system; Confirm defective locations, can draw out the coordinate position figure of this defective in the oil tank bottom plate global coordinate system, its method is simple, quick; Can accurately locate the position of defective at the bottom of jar, greatly reduce the pinpoint measurement expense of defective at the bottom of the oil tank jar.

The objective of the invention is to realize like this:

(1) confirms a horizontal circumference in the position that is higher than oil tank bottom plate along the steel oil tank circumferential inner wall; On this horizontal circumference from the turnover oil tank inlet below; Along counterclockwise No. 1, No. 2, No. 3, No. 4 four targets of spaced set circumference in equal parts successively, be initial point with the oil tank bottom plate center, be the X axle with the line of No. 1, No. 3 target crossing initial point; Line with No. 2, No. 4 targets crossing initial point is the Y axle, sets up the oil tank bottom plate global coordinate system;

(2) laser range finder is placed on the defective of oil tank bottom plate, measure this defective distance L of four targets of distance respectively through laser range finder _i, wherein i is the target sequence number, and with measured each apart from corresponding record in table;

(3) according to the distance L of defective apart from four targets _i, calculate the X value and the Y value of this defective coordinate points in the oil tank bottom plate global coordinate system by following formula, confirm defective locations;

$X=\&PlusMinus;\frac{L_2{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}{2R}\sin \left(\mathrm{<figure-callout\; id="2"\; label="arccos\; L"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">arccos</figure-callout>}\frac{{L_{}}^{}}{}\frac{{{}_2}^2+{{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}^2-{2\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{2L_2{L}_4}\right)$

$Y=\&PlusMinus;\frac{L_1{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_3}{2R}\sin \left(\mathrm{<figure-callout\; id="1"\; label="arccos\; L"\; filenames="HDA0000129072380000022.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">arccos</figure-callout>}\frac{{L_{}}^{}}{}\frac{{{}_1}^2+{{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_3}^2-{2\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{2L_1{L}_3}\right)$

In the formula, L ₁Be No. 1 target distance, L ₂Be No. 2 target distances, L ₃Be No. 3 target distances, L ₄Be No. 4 target distances;

Work as L ₁＜L ₃, X get on the occasion of; L ₁＞L ₃, X gets negative value; L ₁=L ₃, X gets 0;

Work as L ₂＜L ₄, Y get on the occasion of; L ₂＞L ₄, Y gets negative value; L ₂=L ₄, Y gets 0;

(4), draw out the accurate coordinates location drawing of this defective in the oil tank bottom plate global coordinate system, defects detection report at the bottom of the formation oil tank jar according to institute's numerical values recorded.

Said horizontal circumference is higher than the position >=100mm of oil tank bottom plate.

Said target adopts magnetic disk, and the diameter of four magnetic disk is identical with thickness, and the one side of magnetic disk is provided with the central point that is coated with fluorescer or fluorescent powder, and the another side of magnetic disk is adsorbed in inner wall of oil tank.

The central point of each target is positioned at same horizontal line.

Adopt above-mentioned measuring method location tank bottom defective to have the following advantages:

1. through confirming a horizontal circumference in the position that is higher than oil tank bottom plate along the steel oil tank circumferential inner wall; On this horizontal circumference from the turnover oil tank inlet below; Along counterclockwise No. 1, No. 2, No. 3, No. 4 four targets of spaced set circumference in equal parts successively, be initial point with the oil tank bottom plate center, be the X axle with the line of No. 1, No. 3 target crossing initial point; Line with No. 2, No. 4 targets crossing initial point is the Y axle, sets up the oil tank bottom plate global coordinate system.Set up the oil tank bottom plate global coordinate system in this way, both simple and convenient, to accomplish easily again, general survey crew can both be accomplished on request.And the foundation of this coordinate system is laid a good foundation for accurately measuring a jar end defective locations.

2. it is low to measure required expense; Only need a laser range finder and four targets; Laser range finder is the conventional laser stadimeter that market is bought, the target self-control, and its expense is well below adopting the applied modern computer technology; Employing based on descriptive geometry conversion set up the mathematical model of defect location, use the automatic growth algorithm of window to realize the expense of the identification in defect distribution zone again.And the measurement and positioning degree of accuracy is higher than the mode of the tank bottom piece being carried out piecemeal position No. and the physical dimension of confirming each plate.

3. according to the distance L of defective apart from four targets _i, utilization

Formula calculates the X value and the Y value of this defective coordinate points in the oil tank bottom plate global coordinate system, confirms defective locations; Work as L ₁＜L ₃, X get on the occasion of; L ₁＞L ₃, X gets negative value; L ₁=L ₃, X gets 0; Work as L ₂＜L ₄, Y get on the occasion of; L ₂＞L ₄, Y gets negative value; L ₂=L ₄, Y gets 0.Calculate simply, quick, and also the defective locations location is accurately, and can save great amount of manpower and material resources.

4. said target adopts magnetic disk, only needs magnetic disk is adsorbed on a horizontal circumference of confirming on the steel oil tank circumferential inner wall, and the target location is simple, fast, and can not cause any damage to the steel oil tank wall, and it is all very convenient to fix or remove.And the diameter of four magnetic disk is identical with thickness, can not influence the accuracy of measurement.

5. especially adopt the inventive method; Do not need again tank bottom to be carried out piecemeal position No. and the physical dimension of confirming each plate; Avoided fully in the physical dimension process of carrying out piecemeal position No. and definite each plate, the phenomenon of record data repetition and entanglement occurring, and saved tank bottom is carried out piecemeal position No. and the required long period of physical dimension of confirming each plate.

The measuring method of defect location is simple, practical at the bottom of the vertical steel oil tank jar of the present invention, especially at the bottom of causing because of accident jar, during defective, adopts the inventive method more can confirm a jar end defect location fast, accurately, for timely reparation oil tank gains time.

Below in conjunction with accompanying drawing and embodiment the present invention is described further.

Description of drawings

Fig. 1 is the synoptic diagram of prior art piecemeal position No. and the physical dimension of confirming each plate;

Fig. 2 sets up the synoptic diagram that the oil tank bottom plate global coordinate system is measured defective locations for the present invention;

Fig. 3 is that the A-A of Fig. 2 is to the section partial view;

Fig. 4 is the enforcement illustration of 1000 cubes oil tank bottom plate location defective A;

Fig. 5 is the enforcement illustration of 1000 cubes oil tank bottom plate location defective B;

Fig. 6 is the enforcement illustration of 1000 cubes oil tank bottom plate location defective C;

Fig. 7 is the enforcement illustration of 1000 cubes oil tank bottom plate location defective D;

Fig. 8 is 1000 cubes the oil tank bottom plate pinpoint report figure of defective everywhere.

In the accompanying drawing, 1,2,3,4 is the target sequence number; 5 are inlet, and 6 is central point, and 7 is base plate, and 8 is oil tank.

Embodiment

Referring to Fig. 1, Fig. 2, the measuring method step of defect location is following at the bottom of the vertical steel oil tank jar of the present invention:

(1) confirms a horizontal circumference in the position that is higher than oil tank bottom plate 7 along steel oil tank 8 circumferential inner walls; On this horizontal circumference from the turnover oil tank inlet 5 below; Along counterclockwise No. 1, No. 2, No. 3, No. 4 four targets of spaced set circumference in equal parts successively, be initial point with the oil tank bottom plate center, be the X axle with the line of No. 1, No. 3 target crossing initial point; Line with No. 2, No. 4 targets crossing initial point is the Y axle, sets up the oil tank bottom plate global coordinate system; Said horizontal circumference is higher than the position >=100mm of oil tank bottom plate 7, and the position that generally is higher than oil tank bottom plate 7 with horizontal circumference is that 100mm is advisable, and makes target can be located at inlet 5 belows of turnover oil tank, is convenient to the laser range finder measuring distance again.Said four targets 1,2,3,4 all adopt magnetic disk, and the diameter of four magnetic disk is identical with thickness, and its diameter and thickness are so that observe to take with hand and be advisable, and generally diameter is 50mm, and thickness is that 5mm gets final product.The one side of magnetic disk is provided with the central point 6 that is coated with fluorescer or fluorescent powder, and the another side of magnetic disk is adsorbed in oil tank 8 inwalls, makes the central point 6 of each target be positioned at same horizontal line.

(2) laser range finder is placed on the defective P of oil tank bottom plate, measure this defective P distance L of four targets of distance respectively through laser range finder _i, wherein i is a target sequence number 1,2,3,4, and with measured each apart from corresponding record in table;

(3) according to the distance L of defective P apart from four targets _i, calculate the X value and the Y value of this defective P coordinate points in oil tank bottom plate 7 global coordinate systems by following formula, confirm defective locations;

$X=\&PlusMinus;\frac{L_2{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}{2R}\sin \left(\mathrm{<figure-callout\; id="2"\; label="arccos\; L"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">arccos</figure-callout>}\frac{{L_{}}^{}}{}\frac{{{}_2}^2+{{\mathrm{<figure-callout\; id="4"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_4}^2-{2\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{2L_2{L}_4}\right)$

$Y=\&PlusMinus;\frac{L_1{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_3}{2R}\sin \left(\mathrm{<figure-callout\; id="1"\; label="arccos\; L"\; filenames="HDA0000129072380000022.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">arccos</figure-callout>}\frac{{L_{}}^{}}{}\frac{{{}_1}^2+{{\mathrm{<figure-callout\; id="3"\; label="L"\; filenames="HDA0000129072380000011.png,HDA0000129072380000031.png"\; state="\{\{state\}\}">L</figure-callout>}}_3}^2-{2\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA0000129072380000031.png,HDA0000129072380000051.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{2L_1{L}_3}\right)$

In the formula, L ₁Be No. 1 target distance, L ₂Be No. 2 target distances, L ₃Be No. 3 target distances, L ₄Be No. 4 target distances;

Work as L ₁＜L ₃, X get on the occasion of; L ₁＞L ₃, X gets negative value; L ₁=L ₃, X gets 0;

Work as L ₂＜L ₄, Y get on the occasion of; L ₂＞L ₄, Y gets negative value; L ₂=L ₄, Y gets 0;

(4), draw out the accurate coordinates location drawing of this defective P in the oil tank bottom plate global coordinate system, defects detection report at the bottom of the formation oil tank jar according to institute's numerical values recorded.

Be that example specifies with 1000 cubes vertical steel tank bottom defectoscopy below.

1000 cubes vertical steel oil tank bottom plate diameter is 11 meters; Set up the oil tank bottom plate global coordinate system as stated above; Four defective A, B, C, D are arranged respectively in this coordinate system, measure the distance of each defective successively with laser range finder respectively apart from four targets by aforesaid method step.

Shown in Figure 4 is the accurate location synoptic diagram that employing the inventive method records defective A in the oil tank bottom plate global coordinate system, L in the coordinate ₁Distance be 4.39m, L ₂Distance be 3.12m, L ₃Distance be 8.17m, L ₄Distance be 8.63m, bring each distance that records into formula

With

In calculate, obtaining the X value is 2.2, the Y value is 3.05; According to L ₁＜L ₃, X gets on the occasion of, L ₂＜L ₄, Y get on the occasion of principle, X value, Y value be on the occasion of, draw out the accurate coordinates location drawing of this defective A in the oil tank bottom plate global coordinate system.

Shown in Figure 5 is the accurate location synoptic diagram that employing the inventive method records defective B in the oil tank bottom plate global coordinate system, L in the coordinate ₁Distance be 8.0m, L ₂Distance be 1.9m, L ₃Distance be 6.0m, L ₄Distance be 9.6m, bring each distance that records into formula

With

In calculate, obtaining the X value is 0.42, the Y value is 3.97; According to L ₁＞L ₃, X gets negative value, L ₂＜L ₄, Y get on the occasion of principle, the X value is-0.42, the Y value is+3.97, draws out the accurate coordinates location drawing of this defective B in the oil tank bottom plate global coordinate system.

Shown in Figure 6 is the accurate location synoptic diagram that employing the inventive method records defective C in the oil tank bottom plate global coordinate system, L in the coordinate ₁Distance be 7.56m, L ₂Distance be 7.4m, L ₃Distance be 3.9m, L ₄Distance be 3.98m, bring each distance that records into formula With

In calculate, obtaining the X value is 2.64, the Y value is 2.63; According to L ₁＞L ₃, X gets negative value, L ₂＜L ₄, Y get on the occasion of principle, the X value is-2.64, the Y value is-2.63, draws out the accurate coordinates location drawing of this defective C in the oil tank bottom plate global coordinate system.

Shown in Figure 7 is the accurate location synoptic diagram that employing the inventive method records defective D in the oil tank bottom plate global coordinate system, L in the coordinate ₁Distance be 5.2m, L ₂Distance be 9.6m, L ₃Distance be 8.5m, L ₄Distance be 2.43m, bring each distance that records into formula

With

In calculate, obtaining the X value is 1,26, the Y value is 3.61; According to L ₁＞L ₃, X gets negative value, L ₂＜L ₄, Y get on the occasion of principle, the X value is+1.26, the Y value is-3.61, draws out the accurate coordinates location drawing of this defective D in the oil tank bottom plate global coordinate system.

According to defective A, B, C, D accurate coordinates position and the data that measure in the oil tank bottom plate global coordinate system, be recorded in the consolidated statement and (see the following form),

1000 cubes of each defect coordinate records of oil tank bottom plate

Defective	The coordinate points position	L 1	L 2	L 3	L 4
						A	(2.2，3.05)	4.39	3.12	8.17	8.63
B	(-0.42，3.97)	8.0	1.9	6.0	9.6
						C	(-2.64，-2.63)	7.56	7.4	3.9	3.98
D	(1.26，-3.61)	5.2	9.6	8.5	2.43

Comprehensively draw out defective A, B, C, the D accurate coordinates location drawing (as shown in Figure 8) in 1000 cubes oil tank bottom plate global coordinate system according to this table; Form at the bottom of the oil tank jar four defective A, B, C, D examining report, for repair, shaping tank bottom defective provides foundation.

The measuring method of defect location at the bottom of the vertical steel oil tank jar of the present invention; The jar end defect location that not only is applicable to above-mentioned 1000 cubes large-scale vertical steel oil tank is measured, and is applicable to that also the jar end defect location of all large-scale vertical steel oil tanks is measured, no matter be that tank bottom is band arcuate edge base plate or does not have the arcuate edge base plate; Adopt this measuring method; Can both realize the accurate location survey of one or more defectives at the bottom of the large-scale vertical steel oil tank jar simply, fast, compared with prior art, both improve the accuracy of measuring; Defect location is more accurate, has reduced the expense of measuring again.

Claims (4)

1. the measuring method of defect location at the bottom of the vertical steel oil tank jar is characterized in that the measuring method step of defect location is following at the bottom of this oil tank jar:

(1) confirms a horizontal circumference in the position that is higher than oil tank bottom plate along the steel oil tank circumferential inner wall; On this horizontal circumference from the turnover oil tank inlet below; Along counterclockwise No. 1, No. 2, No. 3, No. 4 four targets of spaced set circumference in equal parts successively, be initial point with the oil tank bottom plate center, be the X axle with the line of No. 1, No. 3 target crossing initial point; Line with No. 2, No. 4 targets crossing initial point is the Y axle, sets up the oil tank bottom plate global coordinate system;

(2) laser range finder is placed on the defective of oil tank bottom plate, measure this defective distance L of four targets of distance respectively through laser range finder _i, wherein i is the target sequence number, and with measured each apart from corresponding record in table;

(3) according to the distance L of defective apart from four targets _i, calculate the X value and the Y value of this defective coordinate points in the oil tank bottom plate global coordinate system by following formula, confirm defective locations;

$X=\&PlusMinus;\frac{L_2{L}_4}{2R}\sin \left(\arccos \frac{{L_2}^2+{L_4}^2-{2R}^2}{2L_2{L}_4}\right)$

$Y=\&PlusMinus;\frac{L_1{L}_3}{2R}\sin \left(\arccos \frac{{L_1}^2+{L_3}^2-{2R}^2}{2L_1{L}_3}\right)$

In the formula, L ₁Be No. 1 target distance, L ₂Be No. 2 target distances, L ₃Be No. 3 target distances, L ₄Be No. 4 target distances;

Work as L ₁＜L ₃, X get on the occasion of; L ₁＞L ₃, X gets negative value; L ₁=L ₃, X gets 0;

Work as L ₂＜L ₄, Y get on the occasion of; L ₂＞L ₄, Y gets negative value; L ₂=L ₄, Y gets 0;

(4), draw out the accurate coordinates location drawing of this defective in the oil tank bottom plate global coordinate system, defects detection report at the bottom of the formation oil tank jar according to institute's numerical values recorded.

2. the measuring method of defect location at the bottom of the vertical steel oil tank jar according to claim 1, it is characterized in that: said horizontal circumference is higher than the position >=100mm of oil tank bottom plate.

3. the measuring method of defect location at the bottom of the vertical steel oil tank jar according to claim 1; It is characterized in that: said target adopts magnetic disk; The diameter of four magnetic disk is identical with thickness; The one side of magnetic disk is provided with the central point that is coated with fluorescer or fluorescent powder, and the another side of magnetic disk is adsorbed in inner wall of oil tank.

4. according to the measuring method of defect location at the bottom of claim 1 or the 3 described vertical steel oil tank jars, it is characterized in that: the central point of each target is positioned at same horizontal line.

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