GB/T 15214-1994 Reliability test requirements and methods for medical B-mode ultrasonic diagnostic equipment
Some standard content:
National Standard of the People's Republic of China
Medical B-mode Ultrasonic Diagnostic Equipment
Requirements and methods of reliability test formedical B mode ultrasonic diagnostic equipment1 Subject content and scope of application
GB/T 15214—94
This standard specifies the basic requirements and test methods for reliability test of medical B-mode ultrasonic diagnostic equipment. This standard is applicable to the reliability test of medical B-mode ultrasonic diagnostic equipment whose failure law obeys exponential distribution. 2 Referenced standards
GB3187 Basic terms and definitions of reliability GB5080.1 General requirements for equipment reliability test GB5080.4 Equipment reliability test Point estimation and interval estimation methods for reliability determination test (exponential distribution) GB5080.7 Equipment reliability test Failure rate and mean time between failures verification test plan under constant failure rate assumption 3 Terms, symbols and codes
Terms, symbols and codes not defined in this standard shall be as defined in GB3187. 3.1 Mean Time Between Failures (MTBF)
3.1.1 The lower limit of the MTBF assumption value (m1) ml is an unacceptable MTBF value. When the true MTBF value of the equipment is close to m, the standard test plan will be rejected with a high probability. 3.1.2 The upper limit of the MTBF assumption value (m) m. is an acceptable MTBF value. When the true MTBF value of the equipment is close to m., the standard test plan will be accepted with a high probability. 3.1.3 The predicted value of MTBF (mp)
m is the MTBF value determined by the reliability prediction method according to the design, process and use environment of the equipment. 3.1.4 The point estimate of MTBF (m)
The total cumulative relevant test time of the equipment divided by the total number of relevant failures. 3.2 Judgment risk rate
3.2.1 User risk rate (β)
β is the probability that the equipment will be accepted when the true value of MTBF is equal to m. 3.2.2 Producer risk rate (α)
α is the probability of a device being rejected when the true value of MTBF is equal to m. 3.3 Discrimination ratio (Dm)
Dm is one of the parameters of the standard test plan, which is the ratio of m to m. Dm = mo/mi
Approved by the State Administration of Technical Supervision on September 24, 1994 (1
Implemented on March 1, 1995
3.4 Related test time
GB/T 15214--94
Relevant test time refers to the time related to the number of relevant failures of the equipment under test used to verify the reliability requirements or to calculate the reliability characteristic values. This time does not include the warm-up time, maintenance time and downtime of the equipment under test. The relevant test time includes the scheduled connection time and disconnection time.
4 Reliability test and test plan
4.1 Reliability test types
4.1.1 Reliability determination test
A test to determine the reliability characteristic values of the product. 4.1.2 Reliability verification test
A test to verify whether the reliability characteristic values of the product meet the reliability requirements of their specified values. 4.1.3 Field reliability test
Reliability verification or determination test conducted under field use conditions Field tests can provide more realistic test results while requiring less test facilities and test costs. However, field tests cannot be conducted under strictly controlled conditions, and the reproducibility of field tests is not as good as that of laboratory tests. Whether to use field reliability tests as reliability tests or as Its supplementary tests, test conditions, test requirements, etc. shall be agreed upon by the manufacturer and the user. 4.2 Test scheme
4.2.1 Timed truncation test scheme
The timed test scheme recommended by this standard is shown in Table 1, and the test scheme 5:3 or 5:6 in GB5080.7 is adopted. The judgment criteria for the test regulations are: the relevant test time should be accumulated to exceed the predetermined cut-off time (acceptance), or the predetermined number of truncation failures (rejection) occurs. Table 1 Timed truncation test scheme
Characteristics of the scheme|| tt||Nominal value, %
Truncation sequential test scheme
Truncation time
(multiple of ma)
Number of failures
Actual risk, %
The truncated sequential test scheme recommended by this standard is shown in Table 2. The test scheme 4:3 or 4:6 in GB5080.7 is adopted. The judgment criteria specified in the test scheme are shown in Table 3 and Table 4.
Table 2 Truncation sequential test scheme
Characteristics of the scheme
Nominal value, %
n= m
Expected time to make a judgment
(multiples of n)
Maximum cumulative relevant
Multiples of test time (mo)
|tt||The rejection and acceptance decision tables for test schemes 4:3 and 4:6 are shown in Tables 3 and 4. 42
Actual risk, %
Number of process-related failures
GB/T 15214-94
Table 3 Rejection and acceptance decision table for test scheme 4:3 Cumulative relevant test time (m. Multiples)
(equal to or less than)
Note: If the number of relevant failures is greater than or equal to 7, they will be rejected. Table 4 Test plan 4:6 Rejection and acceptance judgment table
(equal to or greater than)
Cumulative relevant test time (multiples of m.) Related failure number
(equal to or less than)
Note: If the number of related failures is greater than or equal to 8, all will be rejected. 5 Test requirements
5.1 Reliability prediction
(equal to or greater than)
Before the reliability identification test, the product should be predicted for reliability, and the product's mean failure-free time prediction value m is equal to or greater than mo, so as to ensure that the reliability test plan accepts the product with a high probability. 5.2 Pretreatment
Before the test, the product shall not be subjected to aging and other pretreatment different from the equipment delivered for use. Before the test, the product is allowed to undergo preventive maintenance treatment consistent with the site. 5.3 Determination of test samples
5.3.1 The test samples shall be randomly selected from qualified products. 5.3.2 The size of the test sample is recommended by Table 5. Table 5 Sample size recommendation table
97-200
Benchmark size
Maximum sample size
10% of the total number (not exceeding 50)
5.4 Test time
GB/T 15214--94
5.4.1 The expected test time is the selected scheme’s truncation time divided by the sample size when the timed truncation test plan is adopted; when the sequential test is adopted, it is the selected scheme’s maximum cumulative relevant test time divided by the sample size. When calculated,moDm·m1
5.4.2 When the timed truncation test plan is adopted, the test is terminated when the test reaches the truncation test time or the number of truncation related failures. 5.4.3 When the sequential test plan is adopted, if a judgment can be made within the maximum cumulative relevant test time, the test is terminated. When the test reaches the maximum cumulative relevant test time, the test must be terminated and a judgment is made on the test according to the judgment standard. 5.5 Test preparation
5.5.1 Inspection and testing of functions and performance
Before reliability testing, the samples shall be inspected and tested for functions and performance characteristics according to product standard requirements, and the inspection results shall be recorded in detail for future reference.
5.5.2 Requirements for test equipment, instruments and meters During the test, the test equipment shall be able to meet the test requirements, and the test instruments and meters used shall comply with the specified measurement cycle. 5.5.3 Formulate a reliability test implementation plan
Before the test, an implementation plan for the reliability test shall be prepared, and its contents shall include: product model and name:
Reliability index of the product;
Selection of reliability test plan;
Determination of sample size;
Regulations on failure criteria;
Requirements for test equipment and test instruments;
Arrangement of test time and regulations on test time; Plan formulation and signature of review and approval personnel. 6 Test stress
6.1 Test stress
6.1.1 Weathering conditions
Ambient temperature
Relative humidity
Atmospheric pressure
6.1.2 Electrical stress
+15+35℃
30%~75%
86-106 kPa
In every 24h, 1/3 of the time the voltage is 198V, 1/3 of the time the voltage is 220V, and 1/3 of the time the voltage is 242V. 6.2 Test timing chart
6.2.1 The equipment test is carried out according to the timing chart below. 6.2.2 In the test, the power is on for 7 hours and off for 1 hour as a working cycle. In each cycle, the panel function is checked for times during the rated working period of the equipment. The rated working period of the equipment shall not be less than 1 hour. 6.2.3 In the test, the specified performance shall be tested according to the requirements of the product standard. At least times shall be tested in every 1/3 of the scheduled test time. The performance characteristics of the sequential test must be tested once before truncation (acceptance). 6.2.4 The cumulative relevant test time of each sample shall not be less than half of the average relevant test time of all samples. 6.2.5 In each 24-hour test cycle, for equipment with multiple probes, each probe shall be tested alternately. 44
Address 220V
Functional inspection
7 Failure classification and judgment
GB/T 15214 ---94
Test timing diagram
7.1 Each observed equipment failure shall be recorded and then classified. 7.1.1 Related failures
All related failures shall be weighted and included in the number of related failures of the equipment. The following failures are related failures:
Failures caused by design defects;
Failures caused by process defects;
Failures caused by manufacturing defects;
Failures caused by component errors;
Failures caused by improper installation and use instructions provided by the manufacturer. Unrelated failures
The following failures are unrelated failures:
Subordinate failures;
Failures caused by misuse;
Failures caused by improper external equipment or measurement;
Failures caused by short-life components specified in the equipment instructions due to failure to be replaced due to the test time exceeding their lifespan;45
GB/T 15214—94
e. Failures occurring during unrelated test time. 7.2 Classification of related failures
7.2.1 Immediate rejection is required
This type of failure is not allowed to occur or exist. Once it occurs or is discovered, a rejection decision should be made immediately. 7.2.1.1 Failure that will cause personal harm or unsafety to the patient or operator when operating according to the instructions for use provided by the manufacturer.
7.2.1.2 Failure of the electrical and mechanical safety indicators of the equipment. 7.2.2 Serious failure
This type of failure seriously affects the equipment's performance of its specified functions and should be counted in the number of related failures of the equipment. 7.2.2.1 The equipment loses or reduces its basic use functions. 7.2.2.2 The functions of various switches and knobs provided for user operation fail. 7.2.2.3 The data processing of the equipment is inaccurate.
7.2.2.4 The main technical performance indicators of the equipment are reduced and do not meet the requirements of the product standards. 7.2.2.5 The same fuse of the equipment is blown three times in the same test cycle due to non-external reasons. 7.2.2.6 Other failures that affect the equipment's ability to complete its main functions. 7.2.3 Minor failures
Although they do not affect the equipment's ability to complete its specified functions, they are indeed caused by the equipment's design, manufacturing, or component failures. Every three minor failures are converted into one and counted as related failures of the equipment. 7.2.3.1 Failure of components with repeated functions. 7.2.3.2 Failure of detection components.
7.2.3.3 Failure of indication components.
7.2.3.4 Failure of auxiliary character display functions. 7.2.3.5 Other failures that do not affect the equipment's ability to complete its main functions. 7.3 Statistics of total related failures
Total related failures minus serious failures = tens (minor failures minus 3). Decimal points are rounded off. 7.4 Judgment of the time of failure
If an exact judgment cannot be made about the time of failure, the failure is judged to have occurred at the time of the last observation and inspection. 7.5 Handling of failures
During the test, if the equipment fails, it should be withdrawn from the test immediately and put back into the test after repair. After the failure repair and before the test is restarted, the performance of the equipment under test can be tested with the test facilities. The failures that occur at this time should not be counted as relevant failures. 7.6 Preventive maintenance
Preventive maintenance during the test process should be specified in the test plan according to the requirements of the product standard. All preventive maintenance carried out according to the plan and regulations shall not be counted as relevant failures.
8 Decision on acceptance and rejection
8.1 Acceptance
If no failures that require an immediate rejection decision have occurred, and the result of the statistical processing is an acceptance decision, the equipment under test should be accepted without taking any further measures. 8.2 Conditional acceptance
If acceptance cannot be made in accordance with Article 8.1, the equipment can be accepted under certain conditions with the consent of both parties. These conditions can be: improving the design or manufacture of the equipment;
b. Improve the prescribed preventive maintenance;
GB/T15214—94
c. Other modifications agreed by both parties, but the reliability index shall not be modified. 8.3 Rejection
If the equipment cannot be accepted according to Article 8.1 and cannot be accepted conditionally according to Article 8.2, it should be rejected. 9 Test data processing
9.1 For data processing when the timed truncation test plan is adopted, see Appendix A (Supplement). 9.2 For data processing when the truncation sequential test plan is adopted, see Appendix B (Supplement). 10 Reliability test report and record
10.1 The test report should provide reliable data for the final judgment of the test results, including: a.
Product model, name and manufacturer;
Selected test plan and test stress;
Failure type and treatment of the test; Processing of test data;
Final conclusion of the test and recommended measures; Person responsible for the test.
10.2 Reliability test failure analysis report
Each failure should have a report. The content of the report should include the description of the failure and the judgment of the failure; the analysis and corrective measures of the failure; the opinions signed by the test operator, maintenance personnel, test leader and technical leader on the failure handling. 10.3 Test record
The observation and operation of the test should be recorded in detail. The test record includes the reliability test log, function and performance characteristic test record. 47
GB/T 15214—94
Appendix A
Data processing of timed truncation test plan
(Supplement)
A1Calculation of the mean time between failures point estimate (m). Divide the cumulative total relevant test time T by the total cumulative number of relevant failures, that is: m=T/
A2Estimation of the bilateral confidence interval of the mean time between failures. The medical B-type ultrasound equipment adopts a confidence level of (1-2β)%. A2.1 When the test makes an acceptance decision, the estimation method is as follows: A2.1.1 Calculate the point estimate of the mean time between failures (m) according to A1. A2.1.2 According to the corresponding cumulative number of related failures and the specified confidence level, read the corresponding lower limit factor and upper limit factor from Table A1. (A1)
A2.1.3 Multiply the point estimate of the mean time between failures (m) by the lower limit factor and the upper limit factor respectively to obtain the lower limit value (mz) and upper limit value (mu) of the mean confidence interval between failures (m). A2.1.4 Express the above calculation results in the following form: m =XX %(ml,mu)
where: ××%
is the confidence level of the interval estimate.
Table A1 Confidence limit factors for MTBF verification values of the timed truncation test scheme (for acceptance) Cumulative related
Number of failures
80% lower limit
80% upper limit
90% lower limit
90% upper limit
GB/T 15214--94
A2.1.5 For values not listed in the table, the lower and upper limits are calculated according to the following formula: Lower limit of MTBF =
x\((1 +C)/2.2Y+ 2)
Upper limit of MTBF:
Where. T—
Total cumulative related test time;
Cumulative number of related failures,
Confidence level of interval estimate;
—lower quantile value of the x distribution.
xr(1- C)/2,2)bzxZ.net
·(A4)
A2.2 When the test makes a rejection decision, the estimation method is the same as A2.1, where table A1 is changed to table A2. For the calculation of values not given in the table, the lower limit is calculated using formula (A3), and the degree of freedom 2+2 in the formula is changed to 2%, and the upper limit is still calculated using formula (A4). Table A2 Confidence limit factors for MTBF verification values of the timed truncation test scheme (used when rejecting) Cumulative correlation
Number of failures
80% lower limit
80% upper limit
Appendix B
Data processing for truncated sequential test scheme
(Supplement)
B1 When the test makes an acceptance decision, the estimation method is as follows: Average
90% lower limit
90% upper limit
US 478
81.1 Table B1 gives a conservative mean failure-free 19 for the truncated sequential test scheme 4:3, and Table B2 gives a conservative mean failure-free 19 for the truncated sequential test scheme 4:6. 15214-—94
80% and 90% standard lower confidence limit factor 6 and 80% and 90% standard upper confidence limit factor 6(0)B1.2 Multiply the lower limit value m of the mean time between failures determined in the test plan by 6t(1) and u(i) to obtain the actual confidence limit and confidence interval:
my m O,(i)
mu m du(i)
Express the above calculation results in the following form:mr XX %(mi,mu)
Where: ××%—confidence level of interval estimate. Table B1
Cumulative correlation
Number of failures
Cumulative correlation
Number of failures
Sequential test scheme 4 with truncation on the acceptance boundary: 3Confidence limit factors for MTBF verification valueTotal test time:
(multiples of m)
80% lower limit
80% upper limit
90% lower limit
Sequential test scheme 4 with truncation on the acceptance boundary: 6Confidence limit factors for MTBF verification valueTotal test time t|| tt||(multiple of mi)
80% lower limit
When the test makes a rejection decision, the estimation method is as follows; B2
80% upper limit
90% lower limit
（B3)
90% upper limit
90% upper limit
When a truncated sequential test plan is used, once the rejection condition is met, the test can be terminated at any time t due to a rejection decision. Therefore, it is impossible for Tables B3 and B4 to list the confidence factors of all possible results. Linear interpolation is used to calculate the standard time value that cannot be listed (equal to the quotient of the actual total cumulative relevant test time T divided by the lower limit value of the mean time between failures m, determined by the test plan), or in special cases, the distribution is used to calculate the exact confidence factor. After the total cumulative relevant test time reaches t·m, a rejection decision is made. B2.1 If t is greater than the minimum value listed in Table B3 or Table B4, the 80% or 90% confidence lower limit factor is calculated as follows: B2.1.1 Look up (it) and (i, t) in the table. Then tt
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