Safety Question - Page 1
Forum section: electronics / beginners

author: DigitalSignalNewb-cessing
author_rank: Newbie
timestamp: December 15, 2021, 06:04:15 pm
content: Hello,I work in a university and have started being responsible for monthly safety inspections. Mostly these are supposed to cover WHMIS, tripping hazards, fire safety, making sure everyone has appropriate training, equipment is maintained, etc. I have some electronics background but not a lot. I found the following piece of equipment shown in the attached photo. It is a power cord that has been cut and made to go into banana cable jacks. My understanding its original purpose may have been to use with a variac (variable transformer) to allow various meters to be plugged into AC circuits...but I have a strong suspicion it is currently being used to plug directly into a wall outlet.Is this safe? Are there better options? I know in research often custom equipment is needed, and maybe this type of adapter is common practice? This is not a teaching lab, but undergraduate researchers are still hired and work in this space in the summer. I am worried that they might not know dangers of using something like this. I am out of my depth and wanted to get some advice on what best practices are for these types of adapters. Should it at least have a warning sign?I am in Canada if it makes a difference. Any advice any of you can give me would be appreciated. Thank you in advance.

author: BrokenYugo
author_rank: Super Contributor
timestamp: December 15, 2021, 06:11:03 pm
content: I wouldn't call that safe, I believe the technical term is "suicide cord".Even if it is kept from people who are unfamiliar with the hazards it's a super sketchy implementation. Like at least use a box and shrouded jacks...

author: m k
author_rank: Super Contributor
timestamp: December 15, 2021, 06:14:01 pm
content: Variac must be isolated.It's generally unsafe all the time, no matter what.It's not who uses it and how, it's who *can* use it.I've seen direct AC to battery radio in electronics class.

author: bob91343
author_rank: Super Contributor
timestamp: December 15, 2021, 06:16:44 pm
content: That is a useful item, but only for those who understand its purpose and hazards. I have a few of them and use them occasionally. They are used to supply power to units while on the electronics or electric work bench. For instance, testing motors, and such. Yes they can be plugged into a variac and often are. Still they pose a substantial safety hazard from shock and fire and should be used with care.

author: Benta
author_rank: Super Contributor
timestamp: December 15, 2021, 06:21:33 pm
content: Such a cord can make sense, but should not be freely available in the lab. It should only be used under supervision.Lock it up and put it on the list of "available cables/equipment".

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 15, 2021, 06:26:28 pm
content: First, there is no such thing as safe. There are only varying degrees of risk.This cord is certainly high enough in risk potential to not be suitable for sale to the general public.I would also rate it as a bit riskier than I would like for open use in a general lab. But this needs to be broken down a bit. The insulation over potential electrical hazards is not good. Loose electrical tape. And it depends on the nut for the banana jack being screwed down to prevent contact at the base. If those problems were corrected, and an attached warning tag permanently fixed near to banana jack were affixed it would meet my personal standards for such an application. But would still avoid having the device in the lab if it there wasn't a specific use for it. Perhaps in a tool crib requiring checkout and only to persons believed capable of managing the risk.I would have no problems having this in my personal lab, though if it was going to get more than brief use for a seldom or never repeated task I would take the time to make upgrades in the area mentioned above.Since all of the above seems slightly negative towards the creators of this assembly, I do want to point out that this is a lower risk way of doing the task than several options. For example putting banana plugs on the end of the cable which would have fully exposed power when plugged in to the wall but not into the observation instrument. You should also compare this in your thought process to a power cable terminated in ring terminals which is quite common. Protection of the joint is performed by the equipment that the cord is semi-permanently attached to.Another way to manage the risk presented here would be to eliminate this cable and create an adapter box which connects to whatever instruments are being used with the cable. Then a standard IEC cable could be used.Finally, you would be well served in your assignment as safety inspector to do some research on risk management and then have conversation with the university management about risk management goals. There are approaches to deal with this in a somewhat quantitative manner and it is best if all parties involved agree on goals.

author: tunk
author_rank: Super Contributor
timestamp: December 15, 2021, 06:36:52 pm
content: Heat shrink tube instead of electrical tape? Covering all exposed metal.Or something like a Cliff tester for banana plugs (does it exist?).

author: Terry Bites
author_rank: Super Contributor
timestamp: December 15, 2021, 06:40:10 pm
content: Get yourself one of these-https://www.cliffusa.com/products/tools/quicktestx3.pdfIt will keep you one step further from death.

author: DigitalSignalNewb-cessing
author_rank: Newbie
timestamp: December 15, 2021, 07:25:42 pm
content: Wow, thank you all so much for the quick and helpful responses.My take-away is that a cord like this is useful, but they also pose a big hazard risk and should not be just lying around the lab freely available for anyone. It also seems like this particular implementation is not the best approach. I will recommend that we store these in a locked cupboard with sign-out sheet to limit access to appropriate individuals, add a warning tag to the cord, and also purchase one of the Cliff Quick Test boxes for future use.CatalinaWOW, thank you for the advice on risk management. I think it will be very difficult to get all parties to agree on acceptable levels of risk. I am not sure I understand what you mean about discussing in a "quantitative manner". Are you talking about actuarial tables of liklihood of death? Expectation values of money saved in time/equipment versus money lost in event of injury/death/lawsuit? I just want to make sure no one is needlessly harmed (especially students).Many thanks once again everyone for all your help.

author: Kim Christensen
author_rank: Super Contributor
timestamp: December 15, 2021, 07:28:48 pm
content: As other have mentioned, that cable is poorly made but is not an unreasonable item to have around.Things like this are the reason that all the workbenches where I work have GFI/GFCI outlets as an additional safety feature. (Ground Fault Interrupter)We do have some non-GFCI outlets for special circumstances, but people are trained to use the GFCI protected ones by default. The key to safety is good training and regular reviews of proper procedures for the workers.

author: mansaxel
author_rank: Super Contributor
timestamp: December 15, 2021, 07:34:27 pm
content: I'd like to add a vote on the "Safebloc" / "Quicktest" device. Very useful, and reasonably safe. Not something I let my children use for mains power, but something I feel comfortable with as power source on the bench.I'd also like to add my voice behind rebuilding that device into a having the output end be a box with shrouded banana jacks. That will be something that actually may pass a safety inspection.The cable, as shown, would be confiscated and probably neutered into copper scrap on my watch. Given the alternatives available (among those what I listed above), such bodges have no justification. Unless it is an emergency and power is required to save lives. Research is rarely such emergency.

author: m k
author_rank: Super Contributor
timestamp: December 15, 2021, 07:37:28 pm
content: Nowadays Residual Current Circuit Brakers are so common and cheap that putting the whole area behind these is not really an economical issue.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 15, 2021, 10:02:21 pm
content: Quote from: DigitalSignalNewb-cessing on December 15, 2021, 07:25:42 pmYou are on the right track. And yes, it is nearly impossible to get everyone to agree. Answers to your question show some of that problem.Generally risk assessment involves estimating two quantities. The probability of an adverse event and the consequence of an adverse event. The product of those two is a "measure" of risk. This metric at least passes the first order sanity tests. You want something that is likely to be horrible (costs extreme amounts of money or loss of life) to be extremely unlikely and for something that causes just a momentary inconvenience you are willing to accept a fairly high probability of occurrence.Getting real values for those two probabilities is occasionally easy, but usually difficult and often impossible. But it is usually possible to justify a value to within an order of magnitude or two on the probability of occurrence side, and to classify consequences into a relatively small number of bins. For example you might choose bins like 1-Loss of life, 2-loss of body part or permanent disability, 3-hospitalization with full recovery, 4-medical treatment required, 5-pain or temporary inconvenience and 6-negligable consequences.There is potential for the power cord above to cause any of these five categories, with different probability.The risk value then becomes a tool for balancing investment in controlling various types of risk reduction.There is a lot of literature on this, and some fairly short presentations. It actually can be very helpful in discussing safety with people because the knee jerk reaction is I want everything totally safe. That is not possible and so the problem has to be broken into smaller chunks to achieve better safety.

author: bob91343
author_rank: Super Contributor
timestamp: December 15, 2021, 10:05:59 pm
content: All this discussion presupposes that bodily contact with mains supply is dangerous. Yes it is, but not as much as presupposed here.I have been connected to the 120V line thousands of times over my 89 year existence and I am still here and healthy as ever. Were I to live in a country using 240 V I probably would have died a long time ago. Susceptible individuals (heart issues, for instance) should be very careful. Wet environments exacerbate the risk.Having said all that, when I use a cord like this, I first connect it to the load carefully (without being plugged in) so as not to risk a clip falling off. Then I inspect my setup. Then I apply power with one hand held behind my back. If the expected result doesn't occur, I unplug and recheck the setup.However the OP was concerned about fulfilling his responsibilities regarding safety, and I agree with the responses for the most part. When at home and not under someone else's responsibility, I am taking all of the risk and am prepared for that. Were I in an industrial environment I would probably be ready to complain about safety issues.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 15, 2021, 10:25:57 pm
content: Quote from: bob91343 on December 15, 2021, 10:05:59 pmI am in total agreement, and your post provides substantial grist for the risk management mill I reference.Your anecdote could be used as a statistic to estimate the probability of a deadly consequence of line contact (less than 1 in 1000, possibly less than 1 in 10,000). But in most organizations the chance of causing a death should be held less than 1 in a million, so your experience is not sufficient by itself to ignore other hazard mitigations.You mention your safety procedures, but in spite of those procedures you believe you have been in contact with line voltage thousands of times. If you knew how often you work with such things (say 10 times per day for seventy of your 89 years) you could infer that your procedures cut your exposure the line contact by something like a factor of 300. A very large improvement.These examples are really mostly for OP.

author: Gregg
author_rank: Super Contributor
timestamp: December 15, 2021, 10:30:55 pm
content: Being a member of the safety police is truly a thankless job. Management thinks of it as a necessary and costly evil and those who get caught think it is unnecessary meddling. But as a member of the safety police it is your job to quietly (if possible) get rid of this suicide cord. Making a fuss over it won’t help your reputation. If it has an ongoing use, you should insist on a safer solution.If someone needs such a cord in the future, they probably will quickly and quietly bodge one together without telling anyone.

author: dietert1
author_rank: Super Contributor
timestamp: December 15, 2021, 10:55:10 pm
content: Working on live equipment with mains voltages exposed on bare metal parts requires training.- Think twice before every move.- Keep your distance, as getting zapped causes strong muscle contractions and you need space for that. Otherwise blood will flow.- Another rule is working with one hand and the other hand stays in the pocket.Better cover up all metal parts that may come live and don't use screwdrivers to peek under those covers..The cable shown is "very special" and was made by an unqualified person. I would keep it as a bad example.Regards, Dieter

author: David Hess
author_rank: Super Contributor
timestamp: December 16, 2021, 02:39:14 am
content: I have the same thing with a 3/4" banana plug on the end.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 16, 2021, 03:57:37 am
content: Back in the day, at the AM Broadcast transmitter site I worked at, we had just such a lead, except that it ended in bare conductors, not banana sockets.It had a serious purpose, which was testing Mains "under-voltage" detectors, which were incorporated in the transmitters.In the event of a "brown out", or other extended low supply voltage, the transmitters shut down to prevent damage to the high power air cooled tubes.One of our regular "routines" was to disconnect the normal supply to these devices, which was connected via a screw type terminal strip, replacing it with the wires of the "suicide lead".The other end of the lead was plugged into a Variac, the voltage was dropped, & we ascertained whether the detector worked correctly.This lead was kept with the various other "useful cables" in a drawer in the workshop.I was a bit paranoid, & if ever I saw it put away with the ends bare, I wrapped them in insulating tape, reasoning that if people had to unwrap the tape they would be reminded of the danger.This was at a station with a small number of staff, all who were Technicians who worked on the "big bities" all the time, so the danger was really minimal.

author: james_s
author_rank: Super Contributor
timestamp: December 16, 2021, 04:02:47 am
content: Quote from: bob91343 on December 15, 2021, 10:05:59 pmI have also been shocked quite a few times by 120V and obviously I'm still here to type this, however at some point it sank in that there are many variables and it only takes once where conditions are just right and you drop dead with no second chance so now I try to be more careful. Now I do own a few cords similar to this one although mine are made with good quality insulated alligator clips rather than electrical tape covered low voltage binding posts. I store them separately and I'm careful not to leave one laying on the bench. More than once I've plugged in the wrong thing when there were multiple similar looking plugs laying around. Given it costs almost nothing to make up a cord that is at least neatly constructed and good habits are free, I can think of no reason to be careless.

author: james_s
author_rank: Super Contributor
timestamp: December 16, 2021, 04:05:10 am
content: Quote from: dietert1 on December 15, 2021, 10:55:10 pmI've heard that advice a lot and I'm not sure I agree in all cases. Working one-handed can be awkward and may lead to risky behavior like balancing something that could fall over.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 16, 2021, 04:13:48 am
content: Quote from: bob91343 on December 15, 2021, 10:05:59 pmExactly!This how we always did things in my various jobs.It must have worked, because, although, as happens in life, I lost workmates in accidents, only one was during working hours, & that was a fall from a height.Others were one other fall, & three air crashes.Two of the latterwereto people working, but not for my employer, the others were leisure time deaths.Nary a one from Electrocution!Quote

author: dietert1
author_rank: Super Contributor
timestamp: December 16, 2021, 05:01:23 am
content: Quote from: james_s on December 16, 2021, 04:05:10 amAnyway, the advice is not to work on live equipment with mains voltages exposed. You turn it on, test/probe something and turn it off a minute later.If you need to hold a live device with your left hand in order to probe with your right hand, you can wear insulating gloves. The 230 V AC we have in Germany kills if you let it flow from one hand to the other. If it flows from one finger to the other (of your right hand) there will be a strong movement and some smell, but nothing serious.Regards, Dieter

author: rsjsouza
author_rank: Super Contributor
timestamp: December 16, 2021, 11:49:14 am
content: As others have hinted, the risk can only be mitigated and it seems you have much more responsibilities under your belt than only electrocution.Among the excellent suggestions on what to do with the cable (I also have a similar prop for my variac connections, BTW) there are many more depending on the nature of the work being done, such as establishing a buddy system (no one working on High Voltage can be alone in a lab, although this might be hard in a research environment), large shutoff buttons, GFI/GFCI, transparent blast shields in specific benches, hanging power cords above head height, etc.Among the scenarios that I have seen and I have heard in various workplaces are blowing supply cords on benches (due to shorted rectifiers), blowing mains power supply capacitors (where a blast shield was critical to contain the flying parts), falls due to long exposure to shocks (no GFCI on the benches we used, nor shutoff buttons), tripping in cords across two adjacent benches (someone was taking a shortcut, despite the warning labels), finger cuts in fans without grilles (especially older equipment) and so on. The list of imaginative scenarios can be quite long - thus the word "mitigate".Good luck in your endeavour.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: December 16, 2021, 04:20:32 pm
content: That looks familiar. I have one that was dedicated to connection from my variac to a battery powered bench meter for voltage monitoring. The meter is long gone, but the cord makes an occasional appearance. I have a number of suicide cords and similar to above have been bitten many times, but have never had an incident with the cords. Nonetheless, be a cool safety nazi and quietly get rid of it.

author: Shock
author_rank: Super Contributor
timestamp: December 16, 2021, 06:57:05 pm
content: Get someone with electronics knowledge to make a proper fitting. The main problem is it's exposed and instead could be electrically insulated. Open exposed connectors on mains leads have a way of ending up on the floor or someones lap or moving around on the bench, so it's better to have an fitting or proper insulated connectors. Even if it had a couple of insulated banana sockets it's still a hazard so should be tagged.A warning tag similar to the linked one should be attached at the exposed end. You should add to the tag that it is for authorized or supervised use only, not to be removed and presents an electrocution, shorting and reverse wiring hazard. This will hopefully avoid someone unfamilar with mains wiring grabbing it. Don't forget to tag the other device as well. If you make a fitting it needs to be labelled clearly there as well.As mentioned they shouldn't be left out in the open in an environment that has public access. In the case where you have exposed mains equipment on the bench, the bench should be clearly signed.https://www.lockouttag.com/2-sided-electrical-hazard-danger-tag/sku-tg-0880This is the minimum you should do but it doesn't replace legal obligations. In an office setting or a factory floor that cable would be removed.

author: dmills
author_rank: Super Contributor
timestamp: December 17, 2021, 05:48:58 pm
content: I second the Cliff quick test, excellent bit of kit, and I have one permanently mounted on the output side of my variac (Together with an ordinary mains socket), quite useful.That said, I ALSO have various permutations of suicide cord in a draw, including some really odd ones (domestic plug to 63/3 socket (Used for insulation testing heavy three phase gear) and the like!They are occasionally necessary, but there is usually a better way.

author: dietert1
author_rank: Super Contributor
timestamp: December 17, 2021, 09:07:27 pm
content: Happened to find this demonstration of suicide cable, action starts at 3:30Regards, Dieter