USE OF EQUIPMENT TROLLEYS FOR MEDICAL ELECTRICAL EQUIPMENT The use of equipment trolleys to mobilise stacks of medical equipment is common practice. Sometimes non-medical electrical equipment (e.g. computers) is used in combination with medical equipment on the equipment trolley. These practices require the equipment trolley to be appropriately constructed so that an acceptable level of patient safety is maintained.

REFERENCES This guidance document references the following standards. IEC 60601 -1:1988 IEC 601-1-1:1992 AS/NZS 2500:2004 AS/NZS 3003:2003 AS/NZS 3200.1.0:1998 AS/NZS 3200.1.1:1995

AS/NZS 3551:2004

Medical electrical equipment, Part 1: General requirements for safety Medical electrical equipment Part 1.1: General requirements for safety—Collateral Standard—Safety requirements for medical electrical systems Guide to the safe use of electricity in patient care Electrical installations—Patient treatment areas of hospitals and medical dental practices and dialyzing locations Medical electrical equipment Part 1.0 General requirements for safety—Parent Standard Approval and test specification—Medical electrical equipment Part 1.1: General requirements for safety—Collateral Standard: Safety requirements for medical electrical systems Technical management programs for medical devices

Some definitions of terms used in this document have been listed in Appendix 1.

REQUIREMENTS The “IEC 60601-1:1988, Medical electrical equipment, Part 1: General requirements for safety” standard and its equivalent Australian standard AS/NZS 3200.1.0:1998 are the root standards for a group of standards that specify the safety requirements for medical electrical equipment. The “IEC 601-1-1:1992 Medical electrical equipment Part 1.1: General requirements for safety—Collateral Standard—Safety requirements for medical electrical systems” standard covers the use of equipment trolleys for medical electrical equipment. The equivalent Australian standard is AS/NZS 3200.1.1:1995. The combination of an equipment trolley and the equipment on it is a medical electrical system. AS/NZS 3200.1.1:1995 specifies the following general requirements for a medical electrical system. A SYSTEM after installation or subsequent modification shall not cause a SAFETY HAZARD for the PATIENT, the OPERATOR or surroundings. A SYSTEM as a whole shall provide: within the PATIENT ENVIRONMENT the same level of safety as MEDICAL ELECTRICAL EQUIPMENT complying with IEC 601-1, and Medical Electrical Equipment Trolleys - Guidance Document

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outside the PATIENT ENVIRONMENT the level of safety appropriate for non-medical electrical equipment complying with other IEC or ISO safety standards.

To satisfy these general requirements for electrical safety, the equipment trolley and the equipment it carries, are required to: (i) provide the same level of protective earthing required by IEC601-1 for medical electrical equipment. (ii) limit the leakage currents to those permissible for one medical electrical device.

Protective Earthing A socket -outlet for the electrical supply has three connections - two live connections (active and neutral) supplying power to the electrical equipment and a third connection for the protective earth conductor. This protective earth conductor acts as an alternate path to earth for any fault currents or leakage currents that may be present. The protective earth is an essential safety requirement for electrical equipment that has a conductive casing or conductive parts that are externally exposed. AS/NZS 3200.1.1:1995 specifies the following protective earth requirements. The PROTECTIVE EARTH CONDUCTOR connection shall be made in such a way that the removal of any single item of equipment in the SYSTEM will not interrupt the PROTECTIVE EARTH CONDUCTOR connection to any part of the SYSTEM, without at the same time disconnecting the supply of electric energy from that part. Outside the equipment the PROTECTIVE EARTH CONDUCTOR shall be routed together with the mains supply conductor.

Leakage Current Limits Small leakage currents flow from the electrically live parts of electrical equipment to its conductive case or parts. As quoted above, AS/NZS 3200.1.1:1995 requires the system as a whole to provide the same level of safety as medical electrical equipment complying with IEC 601-1 within the patient environment. Table 1 lists the maximum permissible earth leakage currents specified in AS/NZS 3551:2004. TABLE 1:

MAXIMUM PERMISSIBLE EARTH L EAKAGE C URRENT Test

Class I equipment with flexible supply cord

Cord connected Class I mobile X-ray equipment

No fault

500 µA

2.5 mA

Neutral Interrupted

1.0 mA

5.0 mA

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If the system as a whole exceeds the maximum permissible leakage current then electrical separation using a separation device must be used to reduce the leakage currents. A separating transformer would be a suitable separation device for an equipment trolley. Appendix ZZ of AS/NZS 3200.1.1:1995 states that Annex EEE is not relevant to Australian and New Zealand requirements. However, Note 5 in Annex EEE does explain that isolation monitoring of the separating transformer is not necessary because a single fault condition can be detected during routine maintenance and a double fault condition is of no concern. A separating transformer will be hereinafter referred to as an isolation transformer.

Multiple Portable Socket-Outlet A multiple portable socket-outlet has advantages and disadvantages. Appendix AAA of AS/NZS 3200.1.1:1995 provides a summary of both. For equipment trolleys, a multiple portable socket-outlet provides cost-effective commercially available socket-outlets that can be easily mounted on the trolley. Where a multiple portable socket-outlet is used, AS/NZS 3200.1.1:1995 states the following requirements. The MULTIPLE PORTABLE SOCKET-OUTLET, which shall comply with AS/NZS 3105, Approval and test specification—Electrical portable outlet devices, shall be supplied with electricity from a Type 1 residual current device or by an isolated supply of electricity. Unused socket-outlets not required for the system should be protected against inadvertent use by a cover or other effective method of protection.

Additional Requirements In addition to the general requirements already listed, several standards specify additional requirements that equipment trolleys need to meet. A summary of the notable additional requirements follows. AS/NZS 3200.1.1:1995 has the following documentation requirements: 6.8.201 Accompanying documents A SYSTEM (including a modified SYSTEM) shall be accompanied by documents containing all the data necessary for safe and reliable use. NOTE - It is the responsibility of the assembler of a SYSTEM (including a modified SYSTEM), that it is accompanied by documents containing all the data necessary for safe and reliable use. These documents shall include: a) The ACCOMPANYING DOCUMENTS for each item of MEDICAL ELECTRICAL EQUIPMENT(see 6.8 of IEC 601-1). b) The accompanying documents for each item of non-medical electrical equipment. c) The following information: - Instructions for cleaning and, where applicable, sterilizing and disinfecting each item of equipment forming part of the SYSTEM; - additional safely measures which should be applied, during installation of the SYSTEM; - which parts of the SYSTEM are suitable for use within the PATIENT ENVIRONMENT; - additional measures which should be applied during preventive maintenance; Medical Electrical Equipment Trolleys - Guidance Document

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a warning that MULTIPLE PORTABLE SOCKET-OUTLETS should not be placed on the floor; the maximum permitted load for any MULTIPLE PORTABLE SOCKET -OUTLET(S); an instruction that MULTIPLE PORTABLE SOCKET -OUTLETS provided with the SYSTEM shall only be used for powering equipment which forms part of the SYSTEM; an explanation of the risks of connecting a non -medical electrical equipment, which has been supplied as a part of the SYSTEM, directly to the wall outlet when the SYSTEM is supplied via a MULTIPLE PORTABLE SOCKET OUTLET with an isolated supply of electricity or a socket-outlet protected by a Type 1 residual current device; an explanation of the risks of connecting electrical equipment which has not been supplied as a part of the SYSTEM, to the MULTIPLE PORTABLE SOCKET-OUTLET.

AS/NZS 2500:2004 provides the following guidance about medical systems. Use of such a system requires that the total power drawn by the system is limited to that able to be supplied by a single socket -outlet, and is subject to the same overloading considerations as the use of power boards (see Clause 6.8). For such trolley systems, an integral overload circuit-breaker needs to be provided. Trolley-mounted systems need to be powered from a socket-outlet in the same patient area. Systems of this nature used for cardiac-type procedures will need to have earthing assured.

AS/NZS 3003:2003 has the following requirements about socket-outlets and equipotential earthing. Please note that “LPD” is an abbreviation for “Leakage Protection Device”. 2 GENERAL REQUIREMENTS FOR BODY-PROTECTED AND CARDIAC-PROTECTED ELECTRICAL AREAS … 2.6.4 Type of socket-outlet Socket-outlets shall be switched in all active conductors. NOTE – All supply conductors in TRANSFORMER -ISOLATED SUPPLIES are active conductors. 4 ADDITIONAL REQUIREMENTS FOR CARDIAC-PROTECTED ELECTRICAL AREAS ... 4.4.2.4 Earthing of LPD protected points The following points shall be connected to the EP JUNCTION via individual or shared conductors with a maximum of 0.1Ω between each point and the EP JUNCTION: a) The earthing terminal of all socket-outlets specified in 2.3.2 as requiring LPD protection; b) All EP TERMINALS associated with the socket-outlets specified in (a); c) The earthing terminal of permanently connected CLASS I EQUIPMENT with metal parts that are accessible in the PATIENT ENVIRONMENT and are not in contact with structural metal. … NOTE – CLASS II and CLASS III EQUIPMENT that is not in contact with structural metal does not require earthing. d)

The earthing point in electrically conductive wiring enclosures that are accessible in the PATIENT ENVIRONMENT provided all supply wiring is protected by LPDs and the enclosure is not in contact with structural metal. NOTE – Connections may be made by fixed wiring to the EQUIPOTENTIAL earthing system or by flexible cable connected to an EP TERMINAL.

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RECOMMENDATIONS Annex BBB of AS/NZS 3200.1.1:1995 provides examples of combinations of medical electrical equipment and non-medical electrical equipment. Where the equipment on the equipment trolley is combined with equipment off the trolley, the solutions provided in Annex BBB section need to be considered. Table 2 provides a summary of the requirements for an equipment trolley that is being used in a body-protected electrical area. Table 3 provides a summary of the requirements for an equipment trolley that is being used in a cardiac-protected electrical area.

Switching of Active /Neutral Required

Equipotential Earthing Required

Combined Equipment Earth Leakage more than allowable

Unused SocketOutlets Protected from Inadvertent Use

Accompanying Documentation Required

Type 1 RCD supplying Multiple SocketOutlet(s) Isolation Transformer supplying Multiple SocketOutlet(s)

Protective Earthing for Class 1 Electrical Devices Required

Type of Power Supply on the Equipment Trolley

Integral Overload Circuit-Breaker Recommended

Table 2: Requirements for an equipment trolley used in a body-protected electrical area

Yes

Yes

Active

No

Isolation Transformer required

Yes

Yes

Yes

Yes

Both

No

Needs to be investigated

Yes

Yes

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Combined Equipment Earth Leakage more than allowable

Unused Socket Outlets Protected from Inadvertent Use

Accompanying Documentation Required

Isolation Transformer supplying Multiple Socket-Outlet(s)

Equipotential Earthing Required

Type 1 RCD supplying Multiple Socket-Outlet(s)

Switching of Active /Neutral Required

Type of Power Supply on Equipment Trolley

Protective Earthing for Class 1 Electrical Devices Required

Requirements for an equipment trolley used in a cardiac-protected electrical area

Integral Overload Circuit-Breaker Recommended

TABLE 3:

Yes

Yes

Active

Yes

Isolation Transformer required

Yes

Yes

Yes

Yes

Both

Yes

Needs to be investigated

Yes

Yes

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APPENDIX 1:

Definitions

The origin of the following definitions is quoted after the defined term.

MEDICAL ELECTRICAL EQUIPMENT (definition from AS/NZS 3200.1.0:1998) Electrical EQUIPMENT, provided with not more than one connection to a particular SUPPLY MAINS and intended to diagnose, treat, or monitor the PATIENT under medical supervision and which makes physical or electrical contact with the PATIENT and/or transfers energy to or from the PATIENT and/or detects such energy transfer to or from the PATIENT. The EQUIPMENT includes those ACCESSORIES as defined by the manufacturer which are necessary to enable the NORMAL USE of the EQUIPMENT. MEDICAL ELECTRICAL SYSTEM

(definition from AS/NZS 3200.1.1:1995)

Combination of either more than one item of MEDICAL ELECTRICAL EQUIPMENT or MEDICAL ELECTRICAL EQUIPMENT and other non-medical electrical equipment having a specified function and inter-connected by: - COUPLING, and/or - a MULTIPLE PORTABLE SOCKET -OUTLET. NOTE - The SYSTEM includes those accessories which are needed for operating the SYSTEM and are to be specified by the manufacturer. LEAKAGE CURRENT

(definition from AS/NZS 3200.1.0:1998)

Current that is not functional. The following LEAKAGE CURRENTS are defined: EARTH LEAKAGE CURRENT, ENCLOSURE LEAKAGE CURRENT and PATIENT LEAKAGE CURRENT. EARTH LEAKAGE CURRENT Current flowing from the MAINS PART through or across the insulation into the PROTECTIVE EARTH CONDUCTOR. ENCLOSURE LEAKAGE CURRENT Current flowing from the ENCLOSURE or from parts thereof, excluding APPLIED PARTS, accessible to the OPERATOR or PATIENT IN NORMAL USE, through an external CONDUCTIVE CONNECTION other than the PROTECTIVE EARTH CONDUCTOR to earth or to another part of the ENCLOSURE. PATIENT LEAKAGE CURRENT Current flowing from the APPLIED PART via the PATIENT to earth or flowing from the PATIENT via an F-TYPE APPLIED PART to earth originating from the unintended appearance of a voltage from an external source on the PATIENT. NORMAL CONDITION

(definition from AS/NZS 3200.1.0:1998)

Condition in which all means provided for protection against SAFETY HAZARDS are intact. SINGLE FAULT CONDITION

(definition from AS/NZS 3200.1.0:1998)

Condition in which a single means for protection against a SAFETY HAZARD in EQUIPMENT is defective or a single external abnormal condition is present. SEPARATION DEVICE

(definition from AS/NZS 3200.1.1:1995)

A component or arrangement of components with a SIGNAL INPUT PART and SIGNAL OUTPUT PART that prevents for safety reasons a transfer of unwanted voltage or current between parts of a SYSTEM.

LEAKAGE PROTECTION DEVICE(LPD)

(definition from AS/NZS 3003:2003)

The following devices are known as LPDs: a) Low-voltage isolation transformers complying with AS/NZS 4510; Medical Electrical Equipment Trolleys - Guidance Document

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b)

Type I low-voltage residual current devices (RCDs) complying with AS/NZS 3175, AS/NZS 3190 or AS/NZS 61009.1. NOTES – (1) Type I RCDs have a maximum rated residual current not exceeding 10 mA and a maximum tripping time of 40 m/S. (2) The Type I RCD may be part of a residual current circuit breaker (RCCB).

BODY-PROTECTED ELECTRICAL AREA

(explanation from AS/NZS 2500:2004)

Where parts of medical electrical equipment are fastened to parts of a patient other than the heart, the use of a residual current device (RCD) or an isolation transformer with line isolation monitor (LIM) will ensure, that if any contact is made between a live conductor and earth (either directly or as a function of leakage currents), ‘macroshock electrocution’ is very unlikely. A patient area with such wiring is specified in AS/NZS 3003 as a body-protected electrical area and is required to be marked with an appropriate sign 200 mm × 90 mm.

CARDIAC-PROTECTED ELECTRICAL AREA

(explanation from AS/NZS 2500:2004)

Where the procedure involves direct connection to the heart, RCD or isolation transformer protection, similar to that required for a body-protected electrical area, is supplemented with special earthing facilities to also provide protection against ‘microshock electrocution’. Such a system not only protects against any fault or leakage currents posing a macroshock hazard, but also reduces the potential difference appearing between any conducting surfaces in the vicinity of the patient (electrically -operated equipment, plumbing and similar) to a level well below that which would produce microshock electrocution. A patient area with such wiring is specified in AS/NZS 3003 as a cardiac-protected electrical area and is required to be marked with an appropriate sign.

EQUIPOTENTIAL (EP) JUNCTION (EPJ)

(definition from AS/NZS 3003:2003)

The junction of an EQUIPOTENTIAL earthing system and the RETURN EARTH(S) in a CARDIACPROTECTED ELECTRICAL AREA. NOTE – The EP JUNCTION also provides a reference point for resistance and voltage measurements during pre-commissioning testing and routine testing.

EQUIPOTENTIAL EARTHING SYSTEM

(rationale from AS/NZS 3003:2003)

Requirements for the EQUIPOTENTIAL earthing system are based on the assumption that: a) Up to 1 A a.c. leakage current will flow to earth via the EPJ from all the LPD protected points listed in 4.4.2.4; and b) Up to 1 A a.c. leakage current will also flow to earth via the EPJ from any of the non-LPD protected points listed in 4.4.2.5. Under these conditions a maximum of 0.1 volts a.c. will appear between any of these points and the EPJ.

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