As its full name implies, IEC 62353 Medical Electrical Equipment - recurrent test and test after repair of ME equipment, defines the requirements for electrical safety testing of medical electrical (ME) equipment and systems during routine intervals.

Following the need for a unified approach to routine testing, the first edition of IEC 62353 brought together a set number of tests to allow its users to test the MOOP and MOPP dielectric integrity via two distinct leakage current tests:

EQUIPMENT LEAKAGE
Testing the total leakage generated from the incoming mains to the rest of the equipment (confirming integrity of the MOOP).

APPLIED PART LEAKAGE
Testing that floating applied parts (BF&CF) remain at an acceptable floating level (confirming integrity of the MOPP).

In meeting this requirement the IEC 62353 incorporates tests beyond those of type testing. Specifically, it seeks to provide a uniformed and unambiguous means of assessing the safety of medical equipment, whilst maintaining the relevance to IEC 60601-1 and minimizing the risks to the person conducting the assessment.

Importantly, the IEC 62353 standard recognizes that the laboratory conditions described in the IEC 60601, such as elevated mains, isolated TN (Terre Neutral) supply, temperature and humidity conditions cannot always be guaranteed when in-service testing of medical devices is undertaken. More commonly, secondary ground connections caused by data cables and systems, provided measurement errors that can now be overcome by IEC 62353. Another factor raised is that equipment could potentially be damaged by applying type tests (IEC 60601) during in service testing and could therefore represent a potential danger to users.

One of the most significant changes to the 2014 edition is the recommendation to test according to IEC 62353 at the final production line stage and also before equipment goes into service. This will allow recurrent testing to be directly comparable with factory tests, providing for easier greater observation of any variations in leakage measurement. New in the IEC 62353:2014 edition are a number of suggested leakage tests that would isolate the touch leakage current or patient leakage current. Both tests form part of the equipment leakage current.

However, if a manufacturer wants to provide a specific measurement, the IEC 62353:2014 now provides guidance for these tests to be conducted in the informative section of the standard – these might be considered when the equipment leakage values have changed from previous measurements. The 500V DC insulation tests in the 2014 edition have also been supplied with recommended pass/fail limits, taken from internationally accepted practices for insulation testing of electrical equipment. While insulation tests are optional, it’s always recommended to check with the equipment manufacturer if this can be conducted without damaging the equipment under test.

The strength of IEC 62353 enables those who carry out testing to conduct a summary of tests on the input of medical devices (equipment leakage) and on the output of the medical equipment (applied part leakage). As will become evident from the following chapters, the time saving associated with IEC 62353 will also allow for more time to be spent on visual and functional testing.

How does IEC 62353 compare with IEC 60601?

Although IEC 60601 is a type test standard governing the safety of the design and manufacture of ME equipment, for decades biomed and clinical engineers have used the IEC60601 as the basis for regular testing or after service / repair of medical devices. Local variants of IEC 60601 have also been adopted and used as a basis for routine testing.

It is clear that most commonly used electrical safety analysers will only provide means of testing to a subset of tests described in IEC60601 and often exclude destructive tests such as high voltage dielectric testing, constant current 25A testing, SIP / SOP fault condition testing to aid portability and safety of the operator.

So what are the main implications of testing to IEC 62353 and how does it differ from the very well established and widely understood requirements of IEC 60601?

Technical Considerations

The aim of IEC 62353 is to provide a uniform standard that ensures safe practices and reduces the complexity of the current IEC60601-1 standard. All tests are based on leakage testing to IEC 60601, but a number of aspects to improve safety and practicality have been removed.

The most significant changes are:

• No pre-conditioning of equipment under test
• No elevated mains
• No destructive testing
• Testing under single fault condition only
• Summarizing leakage into input and output safety
• Testing at applied part level rather than at patient connection
• Different methods for conducting leakage tests subject to practicality
• Many IEC 62353 tests are directly related to IEC60601 tests, which is shown in figure 6 below.

Figure 6: Comparing IEC 60601 with IEC 62353

Test Frequency

To ensure safety and performance is managed throughout the lifecycle of medical electrical equipment, manufacturers must specify the intervals for testing and inspecting their devices. The basis for this is risk  assessment: the likelihood of occurrence and severity of incorrect operation. Consideration has to also be given to the application of the product, frequency of use, the operational environment and operator competency. IEC 62353:2014 recommends following the manufacturer’s instructions on test intervals.  If this is not available, a test interval between of between six to 36 months is suggested depending on risk assessment.

Vital Preparation

Although  IEC 62353 was first published  in May 2007, many companies  and organizations  are still in the process of making changes to their approach to electrical safety testing. To incorporate the IEC 62353 test philosophy into any organization requires necessary preparation. Options  for choosing  the correct set of tests, requires an understanding  of the purpose and benefits of using the different tests available. Although the onus will inevitably fall on the manufacturers of medical devices to advise on appropriate  in-service test procedures for their own equipment, IEC 62353 clearly has an impact on medical service companies, biomed’s, medical  physics,  clinical engineering and other technical departments. To help  all  those likely  to  be affected by the introduction of IEC 62353 tests, a summary of the test requirements is provided within this guidance booklet.

This IEC 62353 guidance booklet is intended for general information only and cannot be considered a substitute for the full version of the standard.