Safety Testing of Medical Electrical Equipment

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Safety Testing of Medical Electrical Equipment
Soojoud al rujoub hadeel ArAr To Nezar amro
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1 Hazards of Medical Electrical Equipment

• 1.1 Mechanical Hazards
• 1.2 Risk of fire or explos
• 1.3 Absence of Functionion
• 1.4 Excessive or insufficient output
• 1.5 Infection
• 1.6 Misuse
• 1.7 Risk of exposure to spurious electric
  currents

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2 Physiological effects of electricity

• 2.1 Electrolysis
• 2.2 Burns
• 2.3 Muscle cramps
• 2.4 Respiratory arrest
• 2.5- cardiac arrest
• 2.6- ventricular fibrillation

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2.7- effect of frecqency on neuro-muscular
stimulation
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3 Classes and types of medical electrical
equipment

• 4.1- class I equipment

Figure 6. Symbols seen on earthed equipment
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3.2 class IIequipment

• Figure 7. Symbol for class II equipment.

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3.3 Class III equipment

• SELV (Safety Extra Low Voltage )
• SELV is defined in turn in the relevant standard
  as a voltage not exceeding 25V ac or 60V dc.

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4.4 Equipment types
Type Symbol Definition
B Equipment providing a particular degree of protection against electric shock, particularly regarding allowable leakage currents and reliability of the protective earth connection (if present).
BF As type B but with isolated or floating (F - type) applied part or parts.
CF Equipment providing a higher degree of protection against electric shock than type BF, particularly with regard to allowable leakage currents, and having floating applied parts.
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3 Leakage currents

• 3.1 Causes of leakage currents
• a- the voltage on the conductor.
• b- the capacitive reactance between the
  conductor and earth.
• c- the resistance between the conductor and
  earth

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3.2 Earth leakage currenttypes BF CFALL CLASS
I 500micr A
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4.3 Enclosure leakage currentfor class I,II,
TYPES BBF 100micrA, TYPE CF 10 micr A
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4.4 Patient leakage currenttype B BF
100micrAtype CF10micrA per part of apply part

• Patient leakage current path from equipment
  . Patient leakage current path to
  equipment.

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4.5 Patient auxiliary currentclassIIIfor type
BBFCF 10 micrA
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6.10 Leakage current summary
Leakagecurrent Type B Type BF Type CF
Earth 0.5 1 0.5 1 0.5 1
Earth for fixed equipment 5 10 5 10 5 10
Enclosure 0.1 0.5 0.1 0.5 0.1 0.5
Patient 0.1 0.5 0.1 0.5 0.01 0.05
Mains on applied part - - - 5 - 0.05
Patient auxiliary 0.1 0.5 0.1 0.5 0.01 0.05
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5 Testing regimes and relevant documentation

• 5.1 Type tests and routine tests
• 5.2 HTM 8
• 5.3 BS 5724 or IEC 60601
• 5.4 Hospital Equipment Information 95
• 5.5 DB9801 Supplement 1
• 5.6 Medical Devices Directive
• 5.7 ESCHLE
• 5.8 IEC 61010
• 5.9 Hospital Equipment Information 140

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5.10 When to test

• Medical electrical equipment should be inspected
  and tested on the following occasions.
• a- On newly acquired equipment prior to being
  accepted for use
• b- During routine planned preventative
  maintenance.
• c- After repairs have been carried out on
  equipment.

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• 5.11 Recording test results
• 5.12 Equipment Management Software Packages

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SAFETY ANALYSER
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6 Electrical Safety Tests

• 6.1 Normal condition and single fault conditions
• Normal operation means provided for protection
  against safety hazards are intact
• Single fault is a condition in which signal
  means of protection
• Against safety hazard is defective or external
  abnormal condition is present such as
• 1- interruption of one protective earth
  conductor
• 2-the intrupt of on supply conductor of equipment
• 3 -the short circuiting of either constituent
  part of
• double insulation

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6.2 Protective Earth Continuity
Applicable to Class I, all types
Limit 0.2
DB9801 recommended? Yes, at 1A or less.
HEI 95 recommended? Yes, at 1A or less.
Notes Ensure probe is on a protectively earthed point
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6.3 Insulation Tests
Applicable to Class I, all types
Limits Not less than 50MO
DB9801 recommended? Yes
HEI 95 recommended? Yes
Notes Equipment containing mineral insulated heaters may give values down to 1MO. Check equipment is switched on.
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Applicable to Class II, all types having applied parts
Limits not less than 50MO.
DB9801 recommended? not less than 50MO.
HEI 95 recommended? Yes
Notes Move probe to find worst case
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 6.4 Leakage current measuring device
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6.5 Earth Leakage Current
Applicable to Class I equipment, all types
Limits 0.5mA in NC, 1mA in SFC or 5mA and 10mA respectively for permanently installed equipment.
DB9801 recommended? Yes, in normal condition only.
HEI 95 recommended? Yes, in normal condition only.
Notes Measure with mains normal and reversed. Ensure equipment is switched on.
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6.6 Enclosure leakage current
Applicable to Class I and class II equipment, all types.
Limits 0.1mA in NC, 0.5mA in SFC
DB9801 recommended? Yes, NC only
HEI 95 recommended? Yes, class I SFC earth open circuit, class II NC.
Notes Ensure equipment switched on. Normal and reverse mains. Move probe to find worst case.
Figure 13. Measurement of Enclosure Leakage
Current.  
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6.7 Patient leakage current
Applicable to All classes, type B BF equipment having applied parts.
Limits 0.1mA in NC, 0.5mA in SFC.
DB9801 recommended? No
HEI 95 recommended? Yes, class I SFC earth open circuit, class II normal condition.
Notes Equipment on but outputs inactive. Normal and reverse mains.
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Measurement of patient leakage current for each
applied part in turn
Applicable to Class I and class II, type CF (B BF for DB9801 only) equipment having applied parts.
Limits 0.01mA in NC, 0.05mA in SFC.
DB9801 recommended? Yes, all types, normal condition only.
HEI 95 recommended? Yes, type CF only, class I SFC earth open circuit, class II normal condition.
Notes Equipment on but outputs inactive. Normal and reverse mains. Limits are per electrode.
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6.8 Patient auxiliary current
Applicable to All classes and types of equipment having applied parts.
Limits Type B BF - 0.1mA in NC, 0.5mA in SFC.Type CF - 0.01mA in NC, 0.05mA in SFC.
DB9801 recommended? No.
HEI 95 recommended? No.
Notes Ensure outputs are inactive. Normal and reverse mains
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6.9 Mains on applied parts
Applicable to Class I class II, types BF CF having applied parts.
Limit Type BF - 5mA type CF - 0.05mA per electrode.
DB9801 recommended? No.
HEI 95 recommended? No
Notes Ensure outputs are inactive. Normal and reverse mains. Caution required, especially on physiological measurement equipment.
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