IEC Standards for the Safety and. Efficacy of Medical Electrical Equipment . Introduction. It might, perhaps, be a little too self-evident to say that there is no. The new IEC standard for the in-service and post repair testing of electromedical devices introduces new requirements. These and their. STANDARD. IEC. CEI. NORME. INTERNATIONALE. First edition. Première édition. Medical electrical equipment –. Recurrent test and test after.
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While the first day of the U. Published on September 7, The requirement for safety testing medical electronic ME equipment is regarded as essential to ensure that apparatus does not pose any danger to users or patients.
To meet this need, many different standards have been published to describe what is considered safe for the patients and operators of ME equipment.
The most widely used standard is IEC Clearly, safety testing at the design 662353 and at the end of the production line are vitally important, but 26353 about when the equipment enters service? This was the basis for the introduction of IECthe newly published 63253 standard for medical electrical equipment—recurrent test and test after repair of ME equipment. Each part of the medical device market has different electrical safety testing requirements.
The motivation for most test requirements is the need to comply with statutory legislation and meet public liability considerations.
An Introduction to IEC 62353
But even when the need for safety testing is recognized, other factors come into play. One example is the culture of organizations, which can affect the type of test equipment used and the frequency of testing.
Another factor can be the environment in which testing is undertaken, which can vary from the production line, the laboratory, an operating theater, to the patient ward. The introduction of IEC is intended to streamline this position and harmonize all standards that aim to control the safety of electromedical EM devices used in the treatment, care, and diagnosis of patients.
IEC Medical Electrical Equipment—recurrent test and test after repair of medical electrical equipment—defines the requirements of ensuring the in-service electrical safety of EM equipment and systems. As far as possible, it is an attempt at standardizing the safe operation and testing of ME equipment, while respecting specific local requirements and meeting increasing demands for risk management.
In meeting these aims, IEC incorporates tests beyond those of type testing. Specifically, it seeks to provide a uniform and unambiguous means of assessing the safety of medical equipment, while maintaining the relation to IECand minimizing the risks to the person conducting the assessment.
Importantly, the new standard recognizes that the laboratory conditions described in IEC cannot always be guaranteed when in-service testing of idc devices is undertaken. As a type-testing standard, the current IEC does not provide any guidance to standardizing test requirements once an item of ME equipment has passed the design phase. Once a medical device enters into service, a number of potential test scenarios arise, including:.
Although visual inspection is not clearly defined in IECits inclusion is a fundamental requirement of all routine test and maintenance procedures. Three different insulation test methods are recommended for different types of ME equipment. The test methods are:. The ground bond test proves the integrity of the low-resistance connection between the ground conductor and any metal conductive parts, which may become live in fault situations with Class I medical devices.
Although many Class I medical devices are supplied with an equipotential point, most, if not all, medical devices require multiple ground bond tests to validate the connections of additional metal accessible parts on the enclosure.
IEC requires a minimum test current of mA, either AC or DC, but when using a DC test current, the resistance must be tested in both polarities of the test current. The open circuit voltage of the current source should not exceed 24V. The highest test reading will determine the pass or fail result of this test in comparison with different test limits included in IEC for different types of equipment.
For example, the test limit for a Class I device including a power cable not exceeding 3 meters is mV. Higher test currents of 25A or 10A have been traditionally favored, based largely on IEC requirements. The assumption was made that higher currents could best detect any damaged conductors present. In addition, when analog instruments were widely used for low-resistance measurement, it was often necessary to use high-test currents to produce sufficient voltage drop across the sample to generate the necessary needle deflection.
However, higher test currents—of 10A or more—might potentially be destructive to parts of the device under test, which are connected to the protective ground but have a functional purpose, such as screening. As such, consideration should be given to the test current.
With modern electronics and digital technology, the use of higher test currents is regarded as no longer necessary—a fact recognized by IEC with its mA minimum current. On the other hand, low-test currents—of less than 8A—may not always overcome problems associated with contact resistance caused by constriction, pressure, or film resistance factors, and may therefore show a relatively higher reading than there is and indicate unnecessary failures.
Recently, new test technology has been pioneered in the form of a new low-energy, high-current test that overcomes the previous contact-resistance problems that inhibited the wider application of protective ground testing using 1A or mA test currents.
Importantly, the new low-current test technology enables valid ground continuity tests to be carried out using battery-powered testers, significantly increasing the portability and versatility of handheld safety analyzers used in in-service safety testing routines, significantly speeding up the testing process. Research has shown that it is current rather than voltage that is the source of electricity-related injuries and deaths.
As a result, there are stringent rules on the design of medical equipment to ensure that the patient and operator are not exposed to those currents that do not form part of the functional operation of the device.
These are called leakage currents. In the interests of helping to guarantee safer practice and the repeatability of test measurements, IEC defines different types of leakage current tests—one for total equipment leakage and another for applied parts leakage currents. IEC specifies three methods— direct, differential, and alternative—that can be used to determine the leakage of EM equipment.
The direct leakage method included in IEC is the same as that in IECmeasuring the true leakage through a body model measuring device to ground. Another disadvantage is that secondary ground connections will produce a lower reading, thus potentially allowing faulty equipment to pass the test. The direct method does therefore require a fully isolated device under test and must be performed on a terre neutral supply and in each polarity of the incoming mains supply to guarantee measurements are taken at the maximum potential leakage current.
The differential test method measures the leakage current as a result of imbalance in current between the live and neutral conductors. The main advantage of using the differential leakage method is that the ground conductor remains intact during the measurement, thus providing safer working conditions.
Differential measurement of leakage also does not require an isolated device under test because it relies on comparing the difference in current between the live and neutral conductors to measure the complete leakage of the device being tested, including leakage caused by secondary connections.
Measurements can also be influenced by the presence of magnetic fields—the principle of measuring differential current—and measurements must be done in both directions to identify the worst-case scenario.
The differential leakage measurement method is also only able to measure the AC component. The alternative method is similar to a dielectric strength test at mains potential, using a current limited voltage source at mains frequency. The live and neutral conductors are shorted together and the current limited voltage is applied between the mains parts and other parts of the equipment.
The main advantage of using the alternative method included in IEC is that the device under test is not connected to the mains supply and provides the safest possible test conditions for the operator. In addition, this measurement is only taken in a single polarity and is similar to a dielectric test at mains potential using a current limited mains frequency supply.
Leakage measurements achieved using the alternative method are highly repeatable and provide a good indication of deterioration in the dielectrics of the medical device under test.
An Introduction to IEC – 24×7 Magazine
The disadvantages of using the alternative method are that measurements cannot be compared with previous IEC tests, and those active parts of the circuitry that require mains potential between live and neutral cannot be tested for possible leakage. For this reason, the alternative leakage method is only relevant for certain types of EM devices.
IEC defines two iev kinds of leakage current tests for applied parts—equipment leakage current that tests for total leakage deriving from the applied parts, enclosure, and mains parts combined to real ground; and applied part leakage current that checks for total leakage deriving from the combined patient connections within an applied part to ground and any conductive or nonconductive parts on the enclosure.
The IEC equipment leakage can be performed using a direct, differential, or alternative method.
Figures 1, 2, and 3 provide a schematic representation of the equipment leakage test on Class I grounded ME equipment. The applied part leakage test measures the RMS deriving from the combined patient connections within an applied part to ground and any conductive or nonconductive parts on the ie.
All patient connections of a single function within an applied part shall be connected together BF and CF and measured one at a time. The test is conducted by applying a irc limited 3.
Figures 4 and 5 provide a schematic representation of the applied part leakage test on Class I grounded ME equipment. The electrical safety testing of ME equipment is a crucial part of the overall safety validation of medical devices and requires specialized test equipment. Although the onus will remain on the manufacturers of medical devices to advise on appropriate tests for their equipment, the new standard will clearly have a significant impact on medical service companies and clinical engineering, EBME, medical physics, and other technical departments.
In all cases, when choosing a suitable electrical safety analyzer, care should be taken to ensure that it can be used to test in accordance with IEC requirements and that it is capable of performing accurate and repeatable test routines.
For more information, contact. Please provide your name and email to continue. By using this site, you are accepting our terms and conditions. Ultrasound Systems and Probes If the buzz at the recent RSNA annual meeting is any indication of market trends, the ultrasound sector is hotter…. Testing Times Each part of the medical device market has different electrical safety testing requirements.
Enter IEC IEC Medical Electrical Equipment—recurrent test and test after repair of medical electrical equipment—defines the requirements of ensuring the in-service electrical safety of EM equipment and systems. In-Service Test Requirements As a type-testing standard, the current IEC does not provide any guidance to standardizing test requirements once an item of ME equipment has passed the design phase.
Once a medical device enters into service, a number of potential test scenarios arise, including: Acceptance 662353, also referred to as initial or reference testing. This test is carried out before a new medical device is authorized for use, and is undertaken to ensure correct and complete delivery.
Safety testing of medical devices: IEC 62353 explained.
Acceptance testing is often not limited to electrical safety tests, with some basic function tests being applied to verify correct performance. Routine testing, also referred to as PPM, preventive product maintenance. Routine testing is not limited to safety testing and often includes the verification of correct functionality. After service and repair testing—carried out following a repair, adaptation, or product upgrade. It is often part of a service carried out by in-hospital mechanical or clinical engineering teams.
In many cases, more rigorous electrical safety testing is needed after the replacement of components or reconfiguration of medical devices. The following are typical visual checks that should be made: Housing enclosure—look for damage, cracks, etc; Contamination—look for obstruction of moving parts, connector pins, etc; Cabling supply, applied parts, etc —look for cuts, wrong connections, etc; Fuse rating—check correct values after replacement; Markings and labeling—check the integrity of safety markings; and Integrity of mechanical parts—check for any obstructions.
The test methods are: Insulation between mains parts and ground—this test is used to verify that the mains parts are adequately insulated from ground Class I or the enclosure Class II. Insulation between applied parts and ground—this test is used to verify that the applied parts are adequately insulated from ground Class I or the enclosure Class II.
Insulation between applied part and mains—this test is used to verify that the applied parts are adequately insulated from the mains parts and is applicable to Class I and Class II BF and CF equipment only. IEC Ground Bond Test The ground bond test proves the integrity of the low-resistance connection between the ground conductor and any metal conductive parts, which may become live in fault situations with Class I medical devices.
IEC Leakage Testing Research has shown that it is current rather than voltage that is the source of electricity-related injuries and deaths. Direct Leakage Method The direct leakage method included in IEC is the same as that in IECmeasuring the true leakage through a body model measuring device to ground. Keeping It Safe Follow this checklist for safety testing and keep all the bases covered.