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--- user:kurser:ham_vt2023_l9 [2023/05/01 17:20] – [Praktiska råd för självbyggaren] user
+++ user:kurser:ham_vt2023_l9 [2024/02/13 18:08] (current) – user
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 ======ETA313-09: Theory Lesson 4: Electrical safety, grounding, isolation, EMC ======
-[[user:kurser:ham_vt2023|Back to course information]]
+[[user:kurser:ham_vt2024|Back to course information]]
 **Recommended reading: KonCEPT page 237-259 (Chapter 10,11,12)**
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 =====Tips for the electronics builder=====
-TO BE TRANSLATED ... EVENTUALLY / SA6JKK 2023-05-01
   * The chassis shall be adapted for the device and not be openable without tools.
   * The chassis shall have ventilation holes to prevent overheating. Observe that live parts shall not be reachable from the ventilation holes.
@@ Line 170: / Line 169: @@
-====Säkerhetsåtgärder====
+====Safety====
-Vid reparation ska utrustningen vara spänningslös. Före arbetet ska du
+During repair the device shall be powered off. Before starting working
-. stänga av utrustningens nätströmbrytare
+) turn off the device power swithch
-. dra ur stickproppen ur vägguttaget (dubbel säkerhet).
+) Unplug the power cable (double safety)
-Om trimning eller felsökning måste ske under spänning ska följande iakttas:
+If trimming or fault finding with live voltage is required follow the following,
-Arbeta inte med anläggningen när du är trött eller omotiverad. Då är du minst vaksam mot olyckor.
+  * Do not work when tired or unmotivated
+  * Make sure to not get electrocuted. If possible work with one hand and keep the other hand away from the device. Preferable in your back pocket!
+  * Don't wear (wired) headphones. Use speaker for trimming by ear.
+  * Don't work alone with live devices. Show the other person where the power switch is located. It is preferable if they know how to assist with electrocution injuries.
-Se till att du inte får ström genom kroppen, arbeta helst bara med höger hand och håll den andra borta från den utrustning som du arbetar med.
-Stoppa gärna den fria handen i fickan!
-Ha inga hörtelefoner på huvudet. Använd högtalare om du trimmar med hörseln.
-Helst bör någon finnas i närheten när du arbetar i apparater under spänning. Visa var nätströmbrytaren sitter. Se gärna till att han/hon kan elolycksfallshjälp.
+====Lead Acid Batteries ====
-**Vid arbete med ackumulatorbatterier:**
+Even though the voltage is low for lead acid batteries they can deliver large short circuit currents. Remove rings, watches and similar when working with them. Use isolated tools when working with battery poles.
-Trots att spänningen är låg kan ackumulatorbatterier lämna mycket höga strömmar vid kortslutning. Tag därför av fingerringar, armbandsur med mera. Använd isolerade verktyg vid arbete med batteripolskor.
+Be aware of the electrolyte in lead acit batteries. It is highly corrosive.
-Akta dig för elektrolyten i ackumulatorbatterierna – den är starkt frätande.
+Be aware of the explosion risk from hydrogen released from charging a battery which can send acid into eyes.
-Varning för explosionsrisk av knallgas och syrastänk i ögonen.
+Modern Lithium (Li<>) batteries are incredibly energy dense. These can catch fire with high temperatures and should be treated carefully. Be careful not to overcharge!
-Moderna litium-polymer (LiPo) batterier är oerhört energirika. Dessa kan börja brinna med hög temperatur, och bör behandlas varsamt samt läggas i därför lämpliga skyddspåsar. Akta för överladdning!
+=====When things go wrong (not part of the test)=====
+Electrical fires have different properties compared to the usual solid/liquid fires we usually see. Also electrical injuries are a bit special as they cause harm through internal burns and interference with the nervous system. This section explains my (klondike's) knowledge in these areas so that you can save lifes. I'm a not a certified trainer in fire safety nor electrical injuries/CPR although I have had formal training in these areas. This is not a replacement of such training and you should attend it if you have the possibility of doing so.
+=====Fire safety=====
+In order to burn, fires usually require three things: combustible (i.e. wood), comburent/oxidizer (i.e. oxygen), and enough energy (i.e. the flame that starts the reaction). Remove one and the fire stops.
+Electrical fires are a bit special compared to "normal" fires. In an electrical fire, an electrical fault, for example a short circuit, is providing a huge amount of energy which helps things that would not combust under normal circumstances catch fire.
+To minimize the risks of a fire, you should make sure that your cable insulation has fire retardants and that cables carrying large currents/voltages are never close to any inflammable substances. Also, all such cabling should include appropriate fuses to ensure current is cut in case a fault happens. Still accidents can happen and shorts were current is not large enough to activate fuses can cause fires, here is how to act if such a thing happens:
+  - Move to safety. Avoid any smoke and fumes and try to walk close to the floor.
+  - Turn off the power if you can. No electricity means no extra energy provided to the fire.
+  - Warn everybody about the fire so they can evacuate.
+  - Call 112 and ask for help. Better to have an unnecessary fire brigade call than death people. Prioritize going somewhere safe to calling. If there is a fire alarm activate it.
+  - Do not fight the fire unless you know how to do so safely. Never use an inadequate fire extinguisher, some extinguishing materials conduct electricity so you risk electrocution or worsening the fault. Prioritize use of extinguishers to clear evacuation paths blocked by fire.
+  - Ensure everybody is out. If anybody may still be trapped in the building warn the firemen and give as clear indications about their location as possible.
+Fire extinguishers work usually under similar principles although they use different materials and techniques to extinguish the fire. Always make sure you are aware where the two or three closest ones are placed, what kind of fires (A: solid, B: liquid, C: gas, D: metals, E: old classification for electrical, F: fat) it can handle. Never use an extinguisher against a class of fire it cannot handle (for electrical fires always check the label to avoid electrical shock). Never use a fire extinguisher on humans as this may cause larger damage. Never use an extinguisher on a fire if you cannot do so safely. Prioritize extinguishing fires to clear evacuation paths. Prioritize turning off electricity to using an extinguisher in an electric fire.
+To use most extinguishers:
+  - Take the extinguisher as close as safely possible to the fire ensuring a safe distance.
+  - Remove the precinct from the locking ring.
+  - Remove the locking ring.
+  - Point the hose towards the base (lower part) of the flames.
+  - Pull the handle.
+  - Move the hose to cover the whole area in flames.
+Always keep an eye on an "extinguished" fire if it is safe to do so as it might reignite.
+Another useful tool to handle fires is a fire blanket. These can be particularly useful to extinguish fires on humans. Fire blankets work by removing the comburent from the fire. To use a fire blanket do as follows:
+  - Try to get the person on fire to lie on the floor with arms and legs closed and parallel to the body.
+  - Deploy the blanket from head to toes ensuring a bit of slack on the head. Avoid moving the blanket once over the person.
+  - Prepare for a high temperature. If you have work gloves at hand put them quick.
+  - Starting from the top of the head push the blanket as close as possible to the body of the person. Make your way slowly from the head towards the feet.
+  - Call 112 and ask for an ambulance.
+NEVER try to extinguish the fire with a blanket in any direction other than from head to toes. Doing so may cause significantly worse damage on the person.
+=====Electrical shock=====
+During an electrical shock, large currents traverse the body producing burns and/or interfering with the nervous system. The burn damage of an electrical shock is usually below the skin and cannot be easily seen. Also the interference with the nervous system may cause the victim's heart to stop and their muscles to contract and be unable to let the item causing the shock to go.
+In the case a person is electrocuted do the following:
+  - Never touch the person directly or with any conductive material.
+  - Turn off the power immediately.
+  - Call for help.
+  - Try to separate the person from the electrical device/cable using a non conductive element.
+  - Once the person is separated call 112 and ask for an ambulance.
+  - Check the person is conscious and breathes (see CPR section for more info on this).
+  - Note down the body area where electricity came in and, if possible, the area where it came out. If the skin is not too damaged you can also use a pen to mark the surrounding area.
+  - If the person does not breathe, start CPR immediately.
+  - Apply cold water or indirect ice in the burn area until the ambulance arrives.
+  - ALWAYS ensure a person who has been shocked visits a doctor, electrical burns are not always visible and are usually much worse than may appear.
+=====CardioPulmonar Reanimation (CPR/HLR)=====
+If a person is electrocuted or losses consciousness, there is a risk that their heart has stopped beating. Nevertheless, you can still save their life by performing CPR. You should spend a few minutes seeing the videos at https://www.hlr.nu/utbildningsfilmer/ specially the "Vuxen-HLR" one. What follows is a short summary of how to proceed in such a situation:
+  - Ensure it is safe to reach the person, specially if electrical injuries are suspected.
+  - Call for help.
+  - Call the person's name loud to check if they are conscious.
+  - If no response, move your ear close to the mouth and nose to see if the person breathes.
+  - If no breathing call 112 (or ask another person to do so) set the phone on handsfree mode. Report the incident and listen to the operator for support.
+  - If there is a defibrillator close by fetch it (if possible send another person to get it). Closest one to ETA is on the 5th floor close to the stair case.
+  - Place person with the chest up.
+  - CPR: Put both hands one on top of the other on the chest where the center of the imaginary line between both nipples would be. Keep arms stiff and press hard using your body weight. Hands should sink 5 to 6 cm. Remember, a broken rib is better than a dead person. Repeat 30 times in around 15 seconds.
+  - Put your mouth against the other persons mouth, close their nose with a hand and pull their chin down with the other. Give two mouthfuls of air, ensuring the chest of the person rises and holding air for at least a second.
+  - Repeat the CPR procedure until the defibrillator arrives.
+  - When defibrillator arrives press the button to start it.
+  - Place the pads on the chest close to the right shoulder and the other pad on the tummy close to the left elbow.
+  - Follow the instructions, ensure nobody touches the patient before the defibrillator activates. Remember that you might need to press the button defibrillation.
+  - Resume CPR until the defibrillator instructs you to stop doing so.
+The ideal ratio is 30 presses followed by 2 breathes. Presses should be 100 to 120 times per minute.
+CPR is a very tiresome process, if there is more than one person it might be a good idea to take turns between presses and blows.
+Prioritize calling 112 and others close by for help, then getting a defibrillator (if it will take you less than 4 minutes to get it) and then CPR. CPR wins time but does not restart the heart.
+CPR is painful if the person is conscious. If unsure perform CPR and stop if the person complains.
+=====Calling 112=====
+As when answering to an emergency situation, it is important to answer the following questions when calling 112.
+Where? Where is help needed? (Position) Try to give as clear indications as possible
+What? What has happened?
+Who? Who is it distressed? Number of people (if many) and age.
+How? Does the distressed person need help? (ambulance/medicine/fire brigade/police/sea rescue?).
+When? How long ago did the issue happen.