We had an employee last night replacing a finger safe fuse block. When the employee inserted the fuse block, it blew, and resulted in a significant arc. The employee in question is okay, just shaken up.

In trying to figure out the cause and how this could have been prevented, my team tells me that because the fuse blocks were finger safe, the type of work being done did not require any additional PPE or equipment. My understanding is that finger safe reduces risk of exposure to electrical shock due to contact, but does little to address arc flash hazards.

Hoping someone here can provide some insight into best practices when handling "finger safe" fuse blocks. Should the employee be using PPE? Should the control panel have been de-energized to change fuses?

It is based on risk assessment - how likely is it to stick something in there but in general, my (personal) view is it reduces shock exposure but not the arc flash hazard. This is a subject that surfaces in conversations from time to time.

I am glad the person is OK. Was there a fault still on the circuit? i.e. replace blown fuse, insert fuse live with fault and.... Also curious what type of fuse, i.e. current limiting or not.

Sounds like the procedure involved an interaction with a live circuit. Yes, PPE appropriate for the arc flash hazard is required.

It looks to me like worker was troubleshooting....found the issue......and then replaced the fuse without establishing an electrically safe work condition. Had they established an ESWC the incident probably would not have happened. It appears like the worker needs to be retrained on this area for sure.

Have you performed an incident investigation and taken measures to prevent this from happening in the future? See NFPA 70E Article 110.5((J) Incident Investigations: "The electrical safety program shall include elements to investigate electrical incidents.".......and an Informational Note: Electrical incidents include events or occurrences that result in, or could have resulted in, a fatality, an injury, or damage to health. Incidents that do not result in fatality, injury, or damage to health are commonly referred to as a “close call� or “near miss.�

This is surely a "near-miss"

You may be interested in a clipping from my book "the European Arc Flash Guide" taken from the chapter on Myths and Mistakes.

12.11 Finger Safe does not equal Arc Safe.

An industry that has accounted for a fair share of electrical accidents over the years is quarrying. I was contracted by one such operation where an arc flash injury occurred after a cable had been connected into a low voltage form 4 construction switchboard. Whilst I was not involved with the investigation, I visited the substation and got a good idea of what had happened.

The connection had been carried out successfully whilst the switchboard had been isolated and locked out. The switchboard was then re-energised, and a labourer was asked to clear all the debris from the surrounding area. The cable was of steel wire armoured and XLPE (Crossed-linked Polythene) 4 core construction so there was a good deal of stripped insulation and of course armour wires left on the floor. The labourer picked up the armours first and one steel wire went through the “finger safe� ventilation panel which was protecting the live incoming terminations to the switchboard. The worker was badly burnt in the resulting arc flash and was psychologically affected to the point that he did not return to work even when his physical injuries had healed.

I have done forensic investigations on finger safe products, if you can provide me with a part number, I can give you some insights;

First, having a device blow up in your hand because a person doesn't follow the correct procedure is not okay. We had someone injured in a similar situation. He was a very good electrician and making a mistake like your person did, should not result in an injury. It may result in some damage to equipment, but it should not injure or kill. That's the exact reason why manufacturers are forced to do extensive testing before their products are sold. Remember, the Ford Pinto? This was the car that would catch fire if it was hit in the rear. In the end, Ford paid millions of dollars to victims who bought what they thought were safe cars. Same idea applies here. Manufactures must be held to UL standards. If they produce a product that blows up because an electrician makes a mistake, then it's up to them to pay. Blame the victim is not okay. Blame the people who made the device. I attached a photo of the damage. Look at the bottom right side, You will see 4 fuse holders. These were manufactured by Cooper Bussmann. If you want more information, contact me.

So the UL standard and testing includes insertion into a live short circuit?

In an attempt to answer my own question above, I consulted UL4248-1. I found no such requirement or test listed. Wrong standard?