YY/T 1837-2022Medical electrical equipment—General requirements for reliability (English PDF)

3.1 Safety

It will not pose an unacceptable risk to persons, property or the environment.

3.2 Part

The main constituent unit module of the equipment. It is composed of more than one component.

3.3 Item

Object of consideration.

3.4 Risk

The combination of the probability of an injury occurring and the severity of that injury.

3.5 Risk analysis

The process of systematically using available information to identify hazards (sources) and estimate risks.

3.6 Risk management

The systematic application of management policies, procedures and practices for risk analysis, evaluation, control and monitoring.

4.1 Goals of reliability work

The goal of carrying out reliability work is to ensure that ME equipment or ME system meets the specified reliability requirements, and to maintain and improve the reliability level of ME equipment or ME system.

4.2 Basic principles of reliability work

The basic principles of reliability work mainly include.

4.3 Coordination of reliability work and other related work

Reliability work needs to be coordinated with other related work, mainly including.

4.4 Classification of reliability work

Reliability work is divided into basic work and optional work. The principles for selecting various types of work for ME equipment or ME system are shown in Table 1.

4.5 Description of reliability work requirements

The ME equipment or ME system manufacturer shall develop a reliability plan for the ME equipment or ME system during the project establishment and demonstration phase of the ME equipment or ME system. Make comprehensive arrangements for the reliability work during the life cycle of ME equipment or ME system. Define the work to be done at each phase. Clarify work requirements. The reliability work list for each phase is shown in Table 2.

5.1 User needs analysis

User needs analysis shall be carried out as early as possible in the early phase of ME equipment or ME system R&D project approval. Provide information for the determination of reliability requirements to meet the actual use needs of ME equipment or ME system.

5.2 Environmental profile analysis

Various environmental factors that may affect the equipment during the equipment life cycle shall be determined according to the characteristics of the ME equipment or ME system. Determine the main environmental parameters by analyzing the collected information. At the same time, the comprehensive effect of various environmental factors is considered, so as to obtain the environmental profile of the ME equipment or ME system. Environmental profile analysis can be used as input for ME equipment or ME system development and design. It can provide reference for reliability test.

5.3 Determination of reliability indicators

Reliability quantitative indicators suitable for ME equipment or ME system characteristics shall be determined, such as mean time between failures (MTBF), mean time to failure (MTTF), failure rate, reliability. The work of determining the reliability indicators of ME equipment or ME system shall pay attention to the following.

6.1 Establishment of reliability models

To carry out reliability allocation, prediction and evaluation, the reliability model of the whole machine equipment or subsystem shall be established. The reliability model includes the reliability diagram and the corresponding mathematical model. Reliability modeling procedures, processes and precautions are as follows.

6.2 Reliability assignment

The reliability indicator of the item shall be decomposed step by step into the reliability indicator of subsystems, components and devices. This is a process of decomposition from whole to part, from top to bottom. After the allocation of reliability indicators is completed, the responsibility for the indicators shall be assigned to the relevant design department. The general workflow and precautions for reliability assignment are as follows.

6.3 Reliability prediction

The reliability indicator of ME equipment or ME system shall be estimated. Whether the proposed design scheme can meet the specified reliability quantitative requirements shall be evaluated. The general procedures, methods and precautions for reliability prediction work are as follows.

6.4 Design failure modes and effects analysis (DFMEA)

Failure mode and effects analysis (FMEA) is a systematic procedure for the systematic analysis of ME equipment or ME system to identify potential failure modes, failure mechanisms, failure causes and their effects on ME equipment or ME system, parts, components. Determine all possible failure modes of ME equipment or ME system, parts or components by systematic analysis, as well as the mechanism, cause, inspection method and effect of each failure mode. Identify potential weaknesses. Propose improvement measures. Design failure modes and effects analysis (DFMEA) refers to the FMEA performed during the design phase. Manufacturers can perform analysis of specific objects based on the characteristics of the ME equipment or ME system.

6.5 Failure tree analysis (FTA)

Failure tree analysis can be carried out as required. Failure tree analysis is one of the tools for system reliability analysis. Failure tree analysis can provide a complex diagram to help the user visualize possible preventive/corrective actions.

When carrying out the failure tree analysis of the item, it is advisable to refer to the following.

6.8 Selection and control of materials, components and parts

Clearly control the selection and use of materials, components and parts for ME equipment or ME system. Ensure that the materials, components and parts used in ME equipment or ME system have a good and stable quality level and a good reliability level.

6.9 Finite element analysis

Analyze and evaluate the mechanical strength and thermal response characteristics of ME equipment or ME system during the design process. Carry out early detection of weak links in load-bearing structures and materials and thermally sensitive points of ME equipment or ME system. Take timely design improvement measures. The following shall be paid attention to in the process of finite element analysis.

6.10 Derating analysis

Reduce the working stress (electrical, thermal, mechanical, etc.) applied to components, so that the stress of the components in use is lower than their rated stress. Achieve the purpose of delaying the degradation of its parameters, thereby reducing the failure rate of components and improving the reliability of use. The following shall be paid attention to when derating analysis.

6.11 Circuit tolerance analysis

Analyze the influence of the parameter deviation and parasitic parameters of the composition of the circuit on the circuit performance tolerance within the specified range of environmental conditions. According to the analysis results, corresponding improvement measures are put forward. The following shall be paid attention to when analyzing circuit tolerance.

6.12 Durability analysis

Identify the parts that may fail prematurely due to wear. Determine the root cause of the failure and possible corrective actions. The following shall be paid attention to in the durability analysis.

6.13 Reliability review

During the design process of ME equipment or ME system, review the reliability work carried out as planned, such as reliability requirements, reliability modeling. Check and supervise the quality of reliability design work, so as to achieve the specified reliability work requirements. The following shall be paid attention to when evaluating reliability.

7.1 Reliability R&D test

Find potential defects in ME equipment or ME system by applying appropriate working loads and environmental stresses to ME equipment or ME system, so as to improve the design to increase the inherent reliability level of ME equipment or ME system.

Mathematical models are used to characterize the level of item reliability growth, so as to meet the requirements of reliability indicators in a more planned way.

Reliability R&D test content and points for attention are as follows.

7.2 Reliability verification and evaluation

Determine whether the ME equipment or ME system meets the specified reliability indicator requirements. Comprehensively evaluate the reliability of ME equipment or ME system under typical working environment conditions. Record and analyze the failures that occur.

8.1 Process failure mode and effects analysis (PFMEA)

The purpose of PFMEA is to identify the potential failure mode of the manufacturing process, analyze and determine its impact on the manufacturing process, ME equipment or ME system, and propose manufacturing process control measures, so as to eliminate or control the weak link of the manufacturing process and improve the ME equipment or ME system reliability.

8.2 Verification of manufacturing process reliability

Through the reliability test evaluation method, verify the part processing technology and the whole machine assembly process that may affect the reliability of ME equipment or ME system, so as to meet the process reliability guarantee capability of ME equipment or ME system.

8.3 Environmental stress screening

Establish and implement screening procedures for ME equipment or ME system, so as to detect and eliminate early failures due to defects introduced by defective components, parts, manufacturing processes and other causes.

The stages, objects and methods of environmental stress screening can refer to the following.