Applied Part Classification for Mattress for Radiant Heat Warmer

[keen_reader_RA]

Hi all,
I am confused on how to classify the applied part for a mattress in radiant heat warmer.And the skin sensor used for in the same equipment.Will the sensor be Type B o Type BF?

 

[Peter Selvey]

Obviously the surface of a mattress in a infant radiant warmer is isolated from any electrical circuits, so the classification is really just a marking / manual issue.

Most warmers will be Type BF for the temperature and SpO2 sensors. For temperature there are no restrictions in the standard (IEC 60601-1, or IEC 60601-2-21), but it is industry standard to use Type BF. For Sp02 the standard ISO 9919 does require Type BF or CF.

For the 2nd edition, it is OK to have a single Type BF mark (e.g. on the rating label) which covers the whole device.

For the 3rd edition, it is necessary to put the Type BF mark next to the connector, or if there is no connector "on the applied part". I think second part is a mistake and will be amended in the future. It makes little sense to mark the mattress with a Type BF symbol!

 

[Roland chung]

For the 3rd edition, it is necessary to put the Type BF mark next to the connector, or if there is no connector "on the applied part". I think second part is a mistake and will be amended in the future. It makes little sense to mark the mattress with a Type BF symbol!

The 60601-1:2005/A1 (62A/748/CDV) does not modify the position of applied part symbol. I rather think that it is fine since neither location is satisfactory in all cases. The rationale does make sense.

Where a conductor that is not separated from PATIENT CONNECTIONS extends up to the point inside ME EQUIPMENT where an isolation barrier exists, a TYPE BF or TYPE CF marking on the APPLIED PART itself could mislead the RESPONSIBLE ORGANIZATION or the OPERATOR into believing that isolation is built into the APPLIED PART itself. If, on the other hand, the classification depends on the particular APPLIED PART in use, a single marking on the connection point would be inaccurate and multiple marking would be confusing

Furthermore, "marked on APPLIED PARTS" is not new. It is actually a statement in 2nd edition.

 

[Peter Selvey]

Hi Roland:

Marking on individual applied parts is required under the 2nd edition only if there are different classifications on the same equipment (for example, a patient monitor with many applied parts, some are Type BF, some CF, some defib proof, some not).

Most infant radiant warmers have a single Type BF classification for the whole device, meaning a single Type BF symbol on the rating label is sufficient. It is fairly common to have a single symbol on the rating label covering the whole device.

Under the 3rd edition, this option to have a single mark for the whole device seems to have been removed. But the wording looks suspiciously like they meant it to be the same as the 2nd edition but just got mixed up in the rewording process.

This issue first came to light when I was was doing an 2nd -3rd upgrade check for an ophthalmic device where the only applied part was a chin rest. Under 2nd ed, the Type B symbol on the rating label was OK, under the 3rd edition it looks like the Type B symbol has to go on the chin rest, which doesn't make much sense.

I know draft Am1 does not cover this point, but I think that is because everyone is blindsided by risk management & essential performance. The simple technical errors (which so far are actually not that many) will become clear after a couple of years of real use.

Have a look again at the 2nd / 3rd edition, see if you agree with this analysis.

 

[Roland chung]

Yes, I know the precondition for "marked on applied parts" in the 2nd edition is equipment has more than one APPLIED PART with different degrees of protection. Actually, 2nd edition is "silent" pertaining to the precise location of symbol in other cases. This is just our wishful thinking to mark the symbol on the label.

For the symbol on the applied part (there is no connector), I would think this makes more sense than the symbol on the label. This obviously shows the user/patient where the location of applied part and what protection degree is.

 

[keen_reader_RA]

Can you help me as to how a temperature sensor is classified as a Type BF Applied Part. Our temp. sensor is a PT100 Class A sensor.

Can you also explain in simple language what is a Type B and a Type BF Applied Part because we were under an impression that our temp. sensor is a Type B Applied Part.

 

[Peter Selvey]

There is some history here.

Many (many) years ago the first ECG devices used to be non-isolated, and they grounded the patient directly through the ECG electrode.

It was known back then that the probability of death from an electric shock depended on the impedance of the return path. For example, a person touching bare 230V and also standing on a wet cement floor was at much greater risk than a person standing on a carpet with normal shoes. So, imagine a patient in hospital, lying in bed with an ECG connected, leans across to adjust the arial on the TV and gets a full electric shock: if the ECG grounds him, he will likely die; if the ECG is floating then it is likely he will survive, just a bit shaken.

From this they supposed that it's better not to ground the patient directly, and started to have an isolated (floating) circuit for ECG.

This later got adopted as a general concept to have "floating" applied parts. A floating applied part provided protection against a hypothetical situation of the patient being raised to mains voltage (from a double fault in another device).

The 1977 edition then introduced the first requirements, testing this isolation by applying a mains voltage on the applied part and measuring the amount of leakage into the device.

The 1988 edition then added on the full isolation requirements for basic insulation (leakage current test, 2.5/4mm clearance/creepage, 1.5kV isolation).

In principle, the designer of the main device will be responsible to choose the classification (B, BF, CF) and then ensure compliance. Some particular standards also specify a minimum classification, and if there is an electrode type contact, at least BF will be required for 3rd edition.

In many cases, the Type BF insulation will be built into a detachable probe, such as a temperature probe, which is manufactured by another company.

In such as case, although the final responsibility is the manufacturer of the main device, it makes sense to design the temp probe insulation to meet the Type BF requirements in the standard, e.g. a 1.5kVac immersion test, including after sterilization or disinfection as per normal use. You can also declare this in the specifications of your device.

This approach means the main device manufacturer can use your probe and know that Type BF requirements are met.

 

[Roland chung]

This is really a long story. Excellent!!

IEC 60513 actually has the rationale for classification of applied parts. Here are some excerpts as follows:

Except for requiring Type CF applied parts in equipment which is intended for direct cardiac applications, IEC 601 -1 does not contain any requirements regarding the classification necessary for particular types of equipment. The implication is that Type CF, Type BF or Type B applied parts provide an adequate degree of safety.

However, some particular standards disallow Type B applied parts in particular kinds of equipment. The rationale appears to be that Type B applied parts are prohibited where patient connections make particularly low impedance or fixed connections to the patient, (e.g. ECG recording or monitoring electrodes).

For non-intracardiac applications, the significant difference between F-type and Type B applied parts is that, if the patient accidentally contacts mains voltage, an F-type applied part restricts the current flowing through it to a reasonably safe level, while the current flowing in a Type B applied part may only be limited by the impedance of the patient and may present a serious electrocution hazard.

The following considerations should be taken into account during the preparation of product standards, in deciding whether F-type applied parts should be required for particular types of equipment which are not intended for direct cardiac application:

a) whether the patient connections make particularly low impedance or fixed connection with the patient, (e.g. ECG recording or monitoring electrodes); or whether they result in no greater risk than the normal, casual contact to any other item of non-medical electrical equipment.

In the former case, F-type applied parts may offer a significant advantage. In the latter case, Type B applied part may offer an adequate level of safety.

b) whether the equipment is intended for use in isolation, (e.g. in a "consulting room" situation or in the patient's home), where the patient is unlikely to be directly connected to other medical electrical equipment; or in a hospital environment in which a number of items of medical electrical equipment may be used at the same time.

In the former case, Type B applied parts may offer an adequate level of safety. In the latter case, F-type applied parts may offer a significant advantage.

c) whether the equipment is intended for use in areas in which additional protections are provided in the electrical installation, (e.g. residual current devices or isolated mains supplies). Where this is the case, Type B applied parts may offer an adequate level of safety.

d) whether the equipment is of a kind for which F-type applied parts can be provided without technical difficulty or excessive cost.

 

[keen_reader_RA]

Thank you all...That was really informative.We are relatively new here in dealing with Standards,and can be extremely confusing.I will get back, in case I have more doubts!

 

[keen_reader_RA]

8.3 b)An APPLIED PART that includes a PATIENT CONNECTION that is intended to deliver electrical
energy or an electrophysiological signal to or from the PATIENT shall be a TYPE BF APPLIED
PART or TYPE CF APPLIED PART.

F-TYPE ISOLATED (FLOATING) APPLIED PART (herein F-TYPE APPLIED PART)
APPLIED PART in which the PATIENT CONNECTIONS are isolated from other parts of the
ME EQUIPMENT to such a degree that no current higher than the allowable PATIENT LEAKAGE
CURRENT flows if an unintended voltage originating from an external source is connected to the
PATIENT, and thereby applied between the PATIENT CONNECTION and earth
NOTE F-TYPE APPLIED PARTS are either TYPE BF APPLIED PARTS or TYPE CF APPLIED PARTS.

Can you please explain the above two statements.
Our temperature sensor is a PT100 with no separate ground connection to it for isolation.
Can you help what applied part will it be.

The mattress is made of leather and so it is a non-conducting material.
What applied part will it be.