CN103699141A - Method for adjusting and positioning thermal imager for use in thermal imaging monitoring of liquefied natural gas (LNG) storage tank - Google Patents

Abstract

The invention discloses a method for adjusting and positioning a thermal imager for use in thermal imaging monitoring of a liquefied natural gas (LNG) storage tank. The method comprises the following steps: (1) determining the mounting distance of the thermal imager according to the field angle of the thermal imager; (2) setting the mounting height of the thermal imager according to site requirements; (3) arranging a point heat source at a position accounting for a half of the height of the storage tank, and starting the infrared thermal imager, wherein the thermograph shooting center of the infrared thermal imager is coincided with the set point heat source; (4) converting the coordinate of an upper height boundary point and a lower height boundary point on the middle axis of a thermograph shot by the infrared thermal imager along a vertical direction into height coordinates on the outer wall of the storage tank; (5) keeping the inclination angle of the infrared thermal imager invariable, and moving the infrared thermal imager by a preset distance along the vertical direction to allow the thermal infrared image to shoot an image in the height direction of the storage tank at one time. By adopting the method, all heights of LNG storage tanks can be detected, and the temperature field change of the outer wall of the storage tank is found in time.

Description

LNG tank thermal imaging is thermal imaging system adjustment and localization method for monitoring

Technical field

The present invention relates to a kind of thermal infrared imager locating device, relate in particular to the adjustment of thermal imaging system attitude and the localization method of LNG storage tank monitoring.

Background technology

Liquefied natural gas (LNG) (LNG) storage tank is liquefied natural gas transport and stores requisite air container, and the development of LNG storage tank is in recent years to large capacity future development.LNG storage tank is by the steel inner canister of splendid attire low temperature LNG liquid and the compound facility that provides the concrete outer tank of normal running environment and defencive function to form.Once breaking appears in steel inner canister part, heat-insulation layer lost efficacy, storage tank outer wall concrete destruction, all can cause tank temperature field to change, and storage tank sidewall local temperature is reduced, and jeopardized storage tank safety.Thermal infrared imager can show body surface temperature in thermal map mode, be applicable to industry monitoring.Because Large LNG flask volume is huge, the temperature monitoring that utilizes thermal infrared imager to carry out full-height to it need to be adjusted the installation location of instrument, and installation site need to repeatedly be installed mostly at present, constantly adjusts modification summary and obtains.

Summary of the invention

The object of the invention is to overcome the shortcoming of prior art, providing a kind of can all monitor height side wall temperatures fields storage tank, increases work efficiency, and the LNG tank thermal imaging of finding in time dangerous matter sources is thermal imaging system adjustment and localization method for monitoring.

LNG tank thermal imaging of the present invention is thermal imaging system adjustment and localization method for monitoring, and it comprises the following steps:

(1) according to the field angle of thermal infrared imager, determine the mounting distance of thermal infrared imager, the computing formula of mounting distance is:

$\begin{array}{cc}{L}_{\min }=\frac{\frac{H}{2}}{\tan \frac{\mathrm{\α}}{2}}& L\≥L_{\min }\end{array}$

In formula, L is the horizontal range of thermal infrared imager installation site and storage tank outer wall, and α is the field angle of thermal infrared imager, and H is the height of storage tank;

(2) according to site requirements, set the setting height(from bottom) of thermal infrared imager, get 3-4 rice;

(3) at storage tank mid-height place, a heat point source is set, opens thermal infrared imager, make thermal infrared imager take thermal map center and overlap with the heat point source setting, the mounted angle θ of thermal imaging system is: the mounted angle that in formula, θ is thermal imaging system, the setting height(from bottom) that h is thermal infrared imager;

(4) thermal map of thermal infrared imager being taken the vertically upper height frontier point on axis and the coordinate of lower height frontier point is transformed to respectively the imaginary plane height coordinate on the imaginary plane in thermal imaging system shooting process, then the storage tank altitude range that imaginary plane coordinate transform can be photographed to determine thermal infrared imager for the height coordinate on storage tank outer wall;

(5) keep the inclination angle of thermal infrared imager constant, by thermal infrared imager vertically mobile preset distance make thermal infrared imager can once photograph storage tank short transverse image.

Adopt this method can pass through to adjust installation site and the attitude of thermal infrared imager, make it whole height of Large LNG storage tank can be detected, find in time the change of temperature field of storage tank outer wall, simple to operation, can greatly save the installation positioning time of thermal infrared imager, increase work efficiency, determine in time dangerous matter sources.

Accompanying drawing explanation

Fig. 1 is thermal map coordinate system schematic diagram.

Fig. 2 is perspective view, and wherein 1 is thermal infrared imager, 2 thermal imaging system optical axis, the 3rd, storage tank outer wall, the 4th, imaginary plane S, the 5th, heat point source.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail:

LNG tank thermal imaging of the present invention thermal imaging system adjustment and localization method for monitoring as shown in drawings, it comprises the following steps:

(1) according to the field angle of thermal infrared imager 1, determine the mounting distance of thermal infrared imager, the computing formula of mounting distance is:

$\begin{array}{cc}{L}_{\min }=\frac{\frac{H}{2}}{\tan \frac{\mathrm{\α}}{2}}& L\≥L_{\min }\end{array}$

In formula, L is the horizontal range of thermal infrared imager installation site and storage tank outer wall 3, and α is the field angle of thermal infrared imager, and H is the height of storage tank;

(2) according to site requirements, set the setting height(from bottom) h of thermal infrared imager, get 3-4 rice;

(3) at storage tank mid-height place, a heat point source 5 is set, opens thermal infrared imager, make thermal infrared imager take thermal map center and overlap with the heat point source setting, the mounted angle θ of thermal imaging system is:

the mounted angle that in formula, θ is thermal imaging system, the setting height(from bottom) that h is thermal infrared imager;

(4) thermal map of thermal infrared imager being taken the vertically upper height frontier point on axis and the coordinate of lower height frontier point is transformed to respectively the imaginary plane height coordinate on the imaginary plane in thermal imaging system shooting process, then the storage tank altitude range that imaginary plane coordinate transform can be photographed to determine thermal infrared imager for the height coordinate on storage tank outer wall;

(5) keep the inclination angle of thermal infrared imager constant, by thermal infrared imager vertically mobile preset distance make thermal infrared imager can once photograph storage tank short transverse image.

As one embodiment of the present invention, moving preset distance can determine according to following formula, formula:

$\mathrm{\Δh}=\frac{y_{A2}+y_{B2}}{2}$

In formula Δ h be thermal infrared imager adjustment vertically move down distance; y _a2, y _b2respectively upper height frontier point and the coordinate of lower height frontier point in corresponding to storage tank outer wall coordinate system on axis vertically in the captured thermal map obtaining of thermal infrared imager, storage tank outer wall coordinate system is that to take the heat point source of half At The Height of storage tank be true origin, level is to the right x axle positive dirction, is the rectangular coordinate system that y axle positive dirction is set up straight up.

Certainly coordinate transform formula can also adopt additive method.

The method that in described step (4), the coordinate of upper height frontier point and lower height frontier point is transformed to respectively to the imaginary plane height coordinate on the imaginary plane in thermal imaging system shooting process can be:

At thermal map center, set up rectangular coordinate system, horizontal direction is to the right x axle positive dirction, and vertical direction is upwards y axle positive dirction.The height border of getting respectively on thermal map on the y axle vertical direction that can photograph is respectively A ₀, B ₀.Suppose to exist and pass through storage tank

the heat point source of At The Height, and be parallel to the imaginary plane S of thermal imaging system, as shown in Figure 2.On imaginary plane S4, set up and take the rectangular coordinate system that heat point source is true origin, the horizontal direction of take be to the right x axle positive dirction, by heat point source and be upwards y axle positive dirction perpendicular to x direction of principal axis.A ₀, B ₀correspond on imaginary plane S is respectively A ₁, B ₁.A ₁, B ₁height coordinate definite according to following formula:

If the position coordinates of certain point on thermal map is (x ₀, y ₀), its position coordinates that corresponds on imaginary plane S is (x ₁, y ₁), according to the corresponding relation of optical imagery:

$\frac{F}{f}=\frac{y_1}{y_0}$

In formula, F is the distance of thermal imaging system upper heat point source along thermal imaging system optical axis to empty face S;

F is the focal length of thermal imaging system.

According to above-mentioned formula, can obtain successively the some A on thermal map ₀, B ₀correspond to the upper A of imaginary plane S ₁, B ₁position coordinates.

The method that is the storage tank height coordinate on storage tank outer wall by imaginary plane coordinate transform in described step (4) is:

The heat point source of take on storage tank outer wall is set up rectangular coordinate system as true origin, and the horizontal direction of take is to the right x axle positive dirction, and vertical direction is upwards y axle positive dirction, the A on imaginary plane S ₁, B ₁point corresponds on storage tank outer wall and is respectively A ₂, B ₂.

A ₂, B ₂height coordinate definite according to following formula:

$y_{A2}=L\tan (\arctan \frac{y_{A1}}{F}+\mathrm{\θ})+h-\frac{H}{2}$

$y_{B2}=L\tan (\arctan \frac{y_{B1}}{F}-\mathrm{\θ})+h-\frac{H}{2}$

According to above-mentioned formula, can obtain successively the some A on thermal map ₁, B ₁correspond to A on storage tank outer wall ₂, B ₂height coordinate y _a2, y _b2.

In order to make thermal imaging system can photograph whole height of storage tank, must adjust thermal imaging system position.Keep the inclination angle of thermal imaging system constant, it is vertically upper mobile.If thermal map point A ₀, B ₀the height coordinate corresponding on storage tank outer wall is respectively y _a2, y _b2, mobile height distance Δ h is positive moving direction straight down, mobile height distance is determined according to following formula:

${\mathrm{\Δ}}_1=y_{A2}-\frac{H}{2}$

${\mathrm{\Δ}}_2=y_{B2}+\frac{H}{2}$

$\mathrm{\Δh}={\mathrm{\Δ}}_2+\frac{{\mathrm{\Δ}}_1-{\mathrm{\Δ}}_2}{2}=\frac{y_{A2}+y_{B2}}{2}$

In formula, Δ ₁, Δ ₂it is respectively the distance between the thermal infrared imager visual field height that can photograph and actual tank roof height, bottom of storage tank height; Δ h is that thermal infrared imager is adjusted the distance on the vertical direction of the required movement in position, is positive moving direction straight down.

By above-mentioned formula, can calculate thermal infrared imager along needing mobile distance, delta h in short transverse.

Claims (1)

1. thermal imaging system adjustment and localization method for LNG tank thermal imaging monitoring, is characterized in that it comprises the following steps:

(1) according to the field angle of thermal infrared imager, determine the mounting distance of thermal infrared imager, the computing formula of mounting distance is:

$\begin{array}{cc}{L}_{\min }=\frac{\frac{H}{2}}{\tan \frac{\mathrm{\α}}{2}}& L\≥L_{\min }\end{array}$

In formula, L is the horizontal range of thermal infrared imager installation site and storage tank outer wall, and α is the field angle of thermal infrared imager, and H is the height of storage tank;

(2) according to site requirements, set the setting height(from bottom) of thermal infrared imager, get 3-4 rice;

(3) at storage tank mid-height place, a heat point source is set, opens thermal infrared imager, make thermal infrared imager take thermal map center and overlap with the heat point source setting, the mounted angle θ of thermal imaging system is:

the mounted angle that in formula, θ is thermal imaging system, the setting height(from bottom) that h is thermal infrared imager;

(4) thermal map of thermal infrared imager being taken the vertically upper height frontier point on axis and the coordinate of lower height frontier point is transformed to respectively the imaginary plane height coordinate on the imaginary plane in thermal imaging system shooting process, then the storage tank altitude range that imaginary plane coordinate transform can be photographed to determine thermal infrared imager for the height coordinate on storage tank outer wall;

(5) keep the inclination angle of thermal infrared imager constant, by thermal infrared imager vertically mobile preset distance make thermal infrared imager can once photograph storage tank short transverse image.

Images