Presentation on theme: "1. 2 Electrical safety Content Physiological Effects of Electricity Basic Electrical Theory Human susceptibility to electric shock Codes and Standards."— Presentation transcript:
2 Electrical safety Content Physiological Effects of Electricity Basic Electrical Theory Human susceptibility to electric shock Codes and Standards. Equipment Design Electrical Safety Testing Procedure Specific Hazards & Personal Safety
3 Introduction Everyone should have some knowledge of the every day source of energy known as electricity Everyone should also know about the potential hazards & how to avoid them
4 Are you aware Electrocutions are the 5th leading cause of Accidental death in the U.S. More than 700 people lose their lives every year because of accidents associated with electricity and electrical products 40,000 residential electrical fires occur annually. More than $2 billion is lost on property damage.
5 Our main objectives are to understand the possible electrical hazards and fault scenarios and learn how to improve deigns of medical instruments.
6 Cautions It would appear that the young & old are more prone to electric shock Perhaps this is due in the first instance due to a lack of appreciation of the dangers
7 Electricity in the body Muscles –Muscles control all the body movements Including & importantly those that keep us alive - Breathing and Heart –The brain controls voluntary muscles using Current pulses along nerves
8 External current through the body Many people have received an electric shock at some stage or other through carelessness Main effects: –Neuromuscular (stimulation of nerves & muscles) -- Loss of muscle control –Spasms & Involuntary movement –Inability to let go –Burns
9 External current through the body external & internal Muscle cramps Respiratory arrest Ventricular fibrillation (50 microamps can interfere with cardiac cycle) Electrolysis
10 Basic Electrical Theory Voltage [driving force] causes current [e - ] to flow AC / DC - from safety perspective - negligible difference Single Phase / Three Phase. Circuit / loop is necessary for current to flow a start point - a route - an end point
11 Voltage, Current and Resistance Voltage increases => Current increases Resistance decreases => Current increases Voltage = Current / Resistance - Ohms Law
12 The complete circuit A complete Circuit or loop is necessary for current to flow
13 A complete circuit complete Circuit or loop is necessary for current to flow Current takes the path of least resistance
15 Hospital Safety Now days the patient environment contains a large amount of medical equipment providing various functions to aid the care of patients Many items of medical equipment may be connected to the patient at the same time The hazards are greater due to the involvement of sick people
16 Human susceptibility to electric shock Current Ferequency Body and skin Resistances Duration Body weight Point- of- entry
17 Physiological Response to Electricity Threshold of Perception 1 mA Let - go – Current 5 mA Muscles Contraction 10 mA Pain and respiratoryParalysis 50 mA Ventricular Fibrilation 100-300 mA Burns 1 A
19 Current vs. Frequency Difference in DC vs AC shocks Very high threshold/low sensitivity at high frequencies used in many medical applications Diathermy F = 27,12 MHz T = 10 -6 s Nerve communication T =10 -5
21 Duration/Body Weight Susceptibility Strength- duration curve is a very important plot, applicable to shocks, pacemaker/defib rillator type devices, etc.
23 Micro- vs. Macroshock Hazards Points of Entry
26 Safety Standards Modern medical equipment is now manufactured in such a way that the risks of electric shock are minimal
29 The Liverpool Safety Tester 1973
33 Hazards Water & electricity Overloaded circuits Damaged insulation Misuse of extension cables Exposed wiring Power cords in walkways
34 Precautions If equipment gets wet, get it checked If cabling damaged /exposed, get it checked Do not replace fuses on medical equipment If equipment damaged, get it checked
35 Fuses/Circuit Breakers –The Fuse is very thin piece of wire. The wire has a quite low melting point. As current flows through the wire it heats up. If too large a current flows it melts, thus breaking the circuit Use appropriate fuse size/rating
36 How Can Users Assist? Do NOT carry out any repairs yourself Check equipment for damage before use Ensure there is no damage to mains plug Ensure there is no damage to mains cable Do understand how to use the equipment safely
37 Electrical cables & plugs Mains cable –Brown Live - power –Blue Neutral –Green/yellow Earth
38 Electrical cables & plugs Mains cable –Brown Live power –Blue Neutral –Green/yellow Earth L N
39 Can you spot the problems?
41 Whats the problem?
46 Summary Your responsibility to take care of yourself and others