Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
ELECTRICAL SAFETY 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 Effects Of Electricity Many people have received an electric shock at some stage or other through carelessness Main effects: – – – – Neuromuscular (stimulation of nerves & muscles) Heating (burns) Electrolysis (decomposition/chemical change) Heart (50 microamps can interfere with cardiac cycle) Cautions It is necessary to respect electricity & it’s hazards 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 And in the second instance due to over familiarity Cautions Electrocution claims the lives of a few hundred people each year, mostly involving domestic electrical equipment The primary variable for determining the severity of electric shock is the electric current which passes through the body. This current is of course dependent upon the voltage and the resistance of the path it follows through the body. An approximate general framework for shock effects is as follows: Electric Current (1 second contact) 1 mA 10-20 mA sustained 100-300 mA Physiological Effect Threshold of feeling, tingling sensation. "Can't let go!" current - onset of muscular contraction Ventricular fibrillation, fatal if continued Shock Physiological Effects Electric Current (1 second contact) 1 mA 5 mA 10-20 mA 100-300 mA 6A Physiological Effect Threshold of feeling, tingling sensation. Accepted as maximum harmless current Beginning of sustained muscular contraction ("Can't let go" current.) Ventricular fibrillation, fatal if continued. Respiratory function continues. Sustained ventricular contraction followed by normal heart rythmn. (defibrillation). Temporary respiratory paralysis and possibly burns. Hospital Safety Electrical equipment is used in Hospitals therefore the same risks are present, but the hazards are greater due to the involvement of sick people 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 Hospital Safety Human susceptibility to electric shock varies from individual to to individual & depends on a number of factors: – – – The patients general state of health The position of any electrodes on the patient The dampness of the patients skin Safety Standards Modern medical equipment is now manufactured in such a way that the risks of electric shock are minimal Shock Micro shock –Effect of current applied to the heart Macro shock- Effect of current applied through the surface contacts Safety Standards Equipment is designed & built to comply with safety standards This lays down constructional guidelines for medical equipment which influence the safety of the equipment Safety Testing To BS EN 60601-1 Medical electrical equipment is divided into two classes – – Class 1 Class 2 And, three types – – – Type B Type BF Type CF Class 1 Is equipment in which protection against electric shock does not rely on basic insulation only, but which includes an additional safety precaution, in that means are provided for the connection of the equipment to the protective earth conductor in the fixed wiring installation in such a way that accessible metal parts cannot become live in the event of a failure of the basic insulation Class 2 Is equipment in which protection against electric shock does not rely on basic insulation only, but in which additional safety precautions such as double insulation or reinforced insulation are provided, there being no provision for protective earthing or reliance on installation conditions Type B Is equipment providing a particular degree of protection against electric shock, particularly regarding: – – Allowable leakage current Reliability of the protective earth connection if present Type BF Is type B equipment with an F type applied part (applied part isolated from all other parts of the equipment to such a degree that the patient leakage current allowable in single fault condition is not exceeded when a voltage equal to 1.1 times the highest rated mains voltage is applied between the applied part & earth) Type CF Is equipment providing a degree of protection higher than that for type BF equipment against electric shock particularly regarding allowable leakage currents, & having a F type applied part Symbols on Medical Devices Class II equipment Type B equipment Type BF equipment Type CF equipment Symbols on Medical Devices Protective Earth Earth (ground) Attention, consult accompanying documents Dangerous voltage Common Safety Test Problems Most problems appear on the mains part (particularly detachable mains leads) Extra vigilance is therefore required by users Electrical Safety Testing Electrical Safety Testing Procedure Visual Inspection Earth Resistance Insulation Leakage Current Earth Leakage Current Touch Current Patient Leakage Current Photos Can you spot the problems? Electrical Safety Testing Leakage Current Test Current Limit Earth Leakage Touch Current Normal Touch Current Patient Leakage Normal Patient Leakage 5 mA 100 μA 500 μA 100 μA B, BF 10 μA CF 500 μA B, BF 50 μA CF Fuses/Circuit Breakers Prevent overloading & fires Stop the electrical current if it exceeds a safe value Fuse rating: – – Power = V I transposing, I=P/V Hazards Water & electricity Overloaded circuits Damaged insulation Misuse of extension cables Exposed wiring Power cords in walkways 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 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 Points To Remember Fuses are the weakest link Avoid touching patients & equipment at the same time, as a conductive path exists Let common sense prevail Safety First Remember do not end up like this person!