GB/T 37128-2018Technical requirements for X-ray computed tomography security inspection systems (English PDF)

3.1 X-ray computed tomography; computed tomography

An image of an internal cross-sectional image of an object obtained by computer operation using a series of X-ray fluoroscopic images of different angles method.

3.2 X-ray computed tomography security inspection system

A product for imaging luggage and articles by using an X-ray computed tomography method, the product being obtained by acquiring different objects The projection under the viewing angle is reconstructed to obtain a tomographic image of the object to be inspected, thereby identifying the attenuation coefficient, density and equivalent atomic order of the substance. A number of information, and give a contraband warning message.

3.3 Line pair

A plurality of aluminum plates of the same size and parallel, the distance between the two plates is the same as the plate thickness, and the plate thickness is expressed by the plate thickness (mm).

3.4 Spatial resolution

The ability of the system to identify and distinguish small details of an object.

Note: expressed in terms of the maximum line pair (lp/cm) within the unit distance that the system can recognize.

3.5 Density resolution

The system is capable of distinguishing the ability of substances of similar density.

Note: The absolute value of the density difference between the two substances is expressed as a percentage of the density value of the low density material.

3.6 Atomic number measurement difference

deltaZ

The difference in the atomic number measurements of the same material for different sizes. See formula (1).

In the formula: Z1, Z2---The average of the atomic numbers on a tomogram obtained by scanning two substances of different sizes.

3.7 Relative deviation of measured value

A technical indicator that measures the stability of a system's measurements, expressed in terms of measured values under several conditions and their relative differences.

3.8 Test body

A test object used to test and evaluate image performance metrics.

3.9 Test box

It is used to hold the test body and can pass through the system to complete the special suitcase for checking the performance index of the system.

3.10 Pass rate

Check the amount of baggage in the system unit time.

Note: It is expressed in the number of pieces of checked baggage per hour (pieces/h).

3.11 Leakage radiation dose rate

The intensity of ionizing radiation leaking to the specified location outside the system through the system radiation shielding protection per unit time.

Note: The unit is µGy/h.

3.12 Contraband

Explosive, flammable, corrosive and other dangerous goods that endanger the safety of various public places, and other non-user-identified Items that should be passed.

3.13 Dangerous goods image injection; TIP

A dangerous goods image is randomly inserted into the scanned baggage image. Used to assess the ability of the judger to make manual judgments.

3.14 Secondary power supply

A power supply for a secondary circuit generated by power conversion of a system main input power source.

5.1 Appearance and structure

5.1.1 The appearance of the system should be intact, the surface should be smooth and smooth, the color should be uniform, no obvious mechanical damage, the metal parts should be free of rust, and the plastic parts should not rise. Bubble, cracking.

5.1.2 The logo and characters on the system surface and display panel should be legible.

5.1.3 The system frame has sufficient strength and rigidity to be free from deformation and damage during normal handling.

5.1.4 The degree of protection of the enclosure shall not be lower than the requirements of IP20 in GB/T 4208-2017.

5.2 Performance Specifications

5.2.1 Spatial resolution

The spatial resolution measurement of the system should be greater than or equal to 2.00 lp/cm.

5.2.2 Density resolution

The density resolution of the system should be less than or equal to 3%.

5.2.3 Atomic number measurement difference (not applicable to single energy system)

The difference in atomic number measurements of the same material of different sizes should be less than or equal to 15%.

5.2.4 Relative deviation of measured values

The measured relative deviation of the water column test body placed at the geometric center and edge of the bottom of the system channel shall be.

a) without interference, under the same size conditions, the relative deviation of the measured values does not exceed 1.5%;

b) The relative deviation of the measured values shall not exceed 3% in the presence of interferences and the same size;

c) The relative deviation of the measured values shall not exceed 3% without interference or under different conditions.

5.2.5 Pass rate

The pass rates of different categories of systems shall comply with the requirements of Table 1.

5.2.6 Equipment noise

The device noise value should be less than or equal to 85 dB at any point 1 m from the outer surface of the system body (ie, without the roller table).

5.2.7 Load capacity

The system conveyor belt load capacity should be greater than or equal to 100kg.

5.3 Functional requirements

5.3.1 Image Processing Function

The system should have a grayscale conversion function, a color function, an image inversion function, and an image enlargement function of the CT image.

5.3.2 Three-dimensional image display

The system should have a three-dimensional display function of CT images and an operation function for three-dimensional images.

5.3.3 Image Storage Function

The system should have the following storage features.

a) Image storage function. The image is automatically stored and selected by the operator to select the storage. Time and first-come first when image storage overflows The principle of ordering deletes stored images in order. The stored image includes the device identification number (device ID) and the operator identification number (operator ID). And image generation time.

b) Image retrieval function. The stored image is retrieved based on parameters such as operator ID and image generation time.

c) Image storage security function. to ensure the security of the stored images, only authorized personnel can delete the stored images.

d) Image dump function. It has the functions of USB or CD burning and network dump image data.

e) Image storage capacity. Stores CT images of not less than 10,000 regular items.

5.3.4 Dangerous Goods Image Injection (TIP) Function

The system should have the following dangerous goods image injection function.

a) Dangerous goods image injection function can be set to manual injection or the system automatically injects according to preset rules. System support injection The whole package image or individual dangerous goods image is recognized by the operator and gives a clear indication of the correctness of the identification result.

b) Administrators and maintenance personnel can update the TIP-enabled Dangerous Goods Image Database, including adding or subtracting images.

c) The system supports centralized TIP management through the network.

5.3.5 Network communication function

The system should have a computer-wide interface and have the function of information exchange and linkage control with other related systems.

5.3.6 Remote Reading Function

The system should support remote viewing capabilities to view images in a non-local control center.

5.3.7 Dangerous goods automatic alarm function

When the system detects dangerous goods, it should be able to automatically prompt and assist with sound and light alarms.

5.3.8 Timing and counting function

The system should have system operation timing, ray emission timing, baggage count and count reset function.

The above timing and counting should be fully preserved after replacement of the source and other components.

5.3.9 Dangerous Goods Database Expansion

The system should have a dangerous goods database extension.

5.4 Safety requirements

The system should meet the following safety requirements.

a) There is obvious system power and ray emission display device (indicator), the system power-on indicator is green, and the ray emission indicator is red.

b) An emergency stop switch shall be fitted at a location accessible to the operator. In the event of an emergency, the operator can pass it immediately The power supply of the system X-ray emitting device and the moving device is cut off. The emergency stop switch is red.

c) The system is equipped with a key switch and a secondary power switch. The position of the key switch "on" and "off" is clearly identifiable.

d) Safety protection interlocking devices shall be installed at the hood of the X-ray emitting area and the rotating area with rotating parts, once the hood is hit On, the interlock device is disconnected, and the power supply of the X-ray transmitting device and the moving device should be disconnected immediately.

e) X-ray leakage agent at any distance 5 cm from the outer surface of the system body (excluding the roller table) (including the inlet and outlet of the equipment) The rate is less than or equal to 5 µGy/h.

5.5 Power Supply Adaptability Requirements

When the power supply voltage is within 85%~110% of the nominal voltage and the nominal frequency is within ±3Hz, the system should work normally.

5.6 Electrical safety requirements

5.6.1 Protective grounding

The system should meet the following protective grounding requirements.

a) The system has a protective earthing terminal for connecting the protective earthing conductor and has an obvious marking;

b) The resistance between the metal surface of the system and the ground terminal is less than or equal to 0.1ohm.

5.6.2 Insulation resistance

The insulation resistance between the system power supply terminal and the exposed metal parts of the casing shall be greater than or equal to 100 Mohm under normal environmental conditions.

It should be greater than or equal to 2Mohm under hot and humid conditions.

5.6.3 Electric strength

The clearance and creepage distance shall be designed to meet the requirements of 6.7 of GB 4793.1-2007.

Between the phase line and the neutral wire of the system power supply and the bare metal parts of the casing, it shall be able to withstand the AC voltage of 45Hz~65Hz specified in Table 2 or The DC voltage equivalent to the AC peak has a 1 min anti-electricity test. There should be no breakdown or arcing during the test.

5.6.4 Accessible parts allowable limits

Distance between all accessible parts of the system and the reference test site, or 1.8 m (along the surface or through the air) on the same system The allowable current limits between any two accessible parts within the range are as follows.

a) Normal condition. RMS value is 0.5mA for sine wave, 0.7mA or DC value for non-sinusoidal or mixed frequency current 2mA;

b) Single fault condition. RMS value is 3.5mA for sine wave, peak current is 5mA for non-sinusoidal or mixed frequency current or straight Flow 15mA.

5.7 Electromagnetic compatibility

5.7.1 Immunity requirements

The immunity of the system shall comply with the requirements specified in Tables 1, 2 and 4 of GB/T 17799.2-2003.

5.7.2 Launch requirements

The emission limits of the system shall comply with the requirements specified in Tables 1, 2 and 3 of GB 17799.4-2012.

5.8 Environmental adaptability

5.8.1 Overview

The system should meet the following environmental adaptability requirements.

a) The system is a large-scale electromechanical product, and it is allowed to carry out the ring of electrical components with independent functions when the whole machine is not tested in the environment. Adaptability test

b) electrical components with independent functions, after the environmental adaptability test, the performance parameters shall comply with the technical requirements of the electrical components;

c) After the climatic environment and mechanical environment test, the system does not appear rust and mechanical damage;

d) After the constant damp heat environment test is completed, the insulation resistance test is carried out immediately, and the test result meets the requirements of 5.6.2.

5.8.2 Climate environment adaptability requirements

The climate environment adaptability requirements are shown in Table 3.

5.8.3 Mechanical environment requirements

5.8.3.1 Mechanical requirements of the whole machine

The mechanical environment requirements of the whole machine are shown in Table 4.

5.8.3.2 Mechanical environment requirements for components

See Table 5 for the mechanical environment requirements for electrical components with independent functions.

6.1 Test conditions

Unless otherwise specified, all test environmental conditions are normal atmospheric conditions.

--- Ambient temperature. 15 ° C ~ 35 ° C;

---Relative humidity. 45%~75%;

--- Atmospheric pressure. 86kPa~106kPa.

6.2 Main instruments and tools for testing

Test box. used to hold the test body, the specific requirements are shown in Appendix A, A.1, A.2, A.3;

Scattering body. See Appendix B of GB 15208.2-2018 for specific requirements;

Dosimeter. meet the requirements of 6.2 of GB 15208.1-2018;

Grounding resistance tester. milliohm (mohm) level, the measurement error does not exceed ± 3% (± 5 words);

Insulation resistance meter (Megohmmeter). 1000V, measurement error does not exceed ±10%;

Leakage current meter. accuracy 0.01mA;

Withstand voltage tester. range 0kV~5kV.

6.3 Appearance and structure inspection

6.3.1 Visual inspection

Check by visual inspection and manual methods.

6.3.2 Shell protection level test

Test the degree of protection of the enclosure according to the requirements of Chapter 12 of GB/T 4208-2017.

6.4 Performance test

6.4.1 Spatial resolution test

Run the system, place the test box 1 at the geometric center of the bottom of the detection area, and test the length of the test box along the direction of the conveyor belt, scanning Test box, visually measure the tomographic image of the two test bodies 1 in the test box 1, with the smallest line pair that can be identified, the space corresponding to the space in Table A.1 The resolution value is the spatial resolution value of the system.

6.4.2 Density resolution test

Run the system, place the test box 1 at the geometric center of the bottom of the detection area, and test the length of the test box along the direction of the conveyor belt, scanning The test box was visually inspected for the tomographic image of the test body 2, and the difference in gray value between the nine sodium chloride solution rods and the substrate water tank was resolved. Distinguishable The density resolution corresponding to the sodium chloride solution rod (any diameter can be used) is the density resolution of the system.

6.4.3 Atomic number measurement difference test

Run the system, place the test box 2 at the geometric center of the bottom of the detection area, and test the length of the test box along the direction of the conveyor belt, scanning Test box, respectively, the atomic number measurements Z1 and Z2 of the test bodies 3 and 4 at different diameters are calculated, and the atomic number is calculated using the formula (1). The measured value difference is deltaZ.

6.4.4 Relative deviation test of measured values

Running the system, the test box 3 is placed in the center of the belt, the length direction of the test box is along the direction of movement of the conveyor belt, and the test bodies 5, 6, and 7 are sequentially scanned. 8. Obtain 4 sets of measured values µ0, µ1, µ2, and µ3; place the test box 3 on the belt at a position 10 cm from the edge, and sequentially scan the test bodies 5, 6, 7,8, obtain another 4 sets of measured values µ4, µ5, µ6, µ7; compare µ1, µ2, µ3, µ4, µ5, µ6, µ7 with µ0, and calculate between them in turn The relative difference | µn - µ0 |/µ 0 × 100%, n = 1 ~ 7. The measured value µ4 should meet the requirements of 5.2.4a), and the measured values µ2, µ3, µ6, µ7 should be To meet the requirements of 5.2.4b), the measured values µ1, µ5 shall meet the requirements of 5.2.4c).

When measuring the measured values, for the test bodies 5, 6, and 8, select a fault in the middle third of the section, draw a cross section with the test body The circular inscribed square area, the average value of the reconstructed values in the area is counted as the measured value; for the test body 7, the middle three points are selected Part of a certain fault, draw a square area inscribed with the circular cross section of the test body, and then draw a stainless steel rod outside the test body In the square area connected, the measured value of the test body 7 is calculated using the formula (2).

In the formula: M1, N1---the average value of the reconstructed values in the above-mentioned inscribed square region and the number of pixels;

M2, N2 - the average value of the reconstructed values in the above-mentioned circumscribed square region and the number of pixels.

For each reconstructed image, the relative deviation of the measured values should be tested and recorded as a set of statistical results.

A set of statistical results with the smallest relative deviation is used as the basis for standard evaluation.

6.4.5 Pass rate test

When the belt is running stably, the package is continuously scanned and timed according to the standard of each package length plus a total gap of 1m, in continuous scanning When the time reaches 1h, the statistical processing is completed and the number of packages of the image is displayed as the system pass rate.

6.4.6 Equipment noise test

In the area where the ambient noise floor is less than or equal to 50dB(A), when the system is in no-load operation, at any point 1m away from the system, The sound level meter measures and records the measured noise value.

6.4.7 Load test

Uniformly placing a load of 100 kg or more in the conveying conveyor belt along the conveying direction within 1 m, measuring the conveying of the conveyor belt The speed should be no less than 90% of the rated speed.

6.5 Function check