Fuseable resistor color bands

[cybermaus]

I think this is a fuseable resistor.

It makes sense to be one in where it is in the schematic (between 230V Hot en the suppression coil also pictured)
And it nicely did its job, after connecting to a 3-phase with a disconnected, floating neutral, it blew
And after replacing with a normal 3.9 Ohm 1/4 resistor all worked again.

My question is, how do the color bands work, what is the blue color band
I think I can read a normal 3 9 x0.1 10% on the first four bands, but what is the blue band

Or am I completely wrong with the ID

Thanks

[Konkedout]

I don't think you are completely wrong...I forget my lower number multipliers.

Just to say that fusible resistors are not necessarily marked.  Or at least a resistor which blows open easily might not have any marking to indicate.

I have a bunch of unused old stock in 33 ohm and 51 ohm.  For a while I was igniting a small test tube of gunpowder by hitting the resistor with a few hundred volts from a charged up snap in can aluminum electrolytic.  (this for a mole exploder.) The 51 ohm reliably bursts into flames and ignites the gunpowder.  Amazingly some of them are able to be used again but I did not do that.  But the 33 ohm just quietly go open circuit with no flame and no indication of anything adverse.  Nothing about the 33 ohm marking tells me that it is fusible.

[CaptDon]

That looks like a normal carbon resistor and will probably make a nice fireball when burning out. Resistors in line with mains should be ceramic flameproof construction which when severely overloaded make a little pop sound and a tiny little piece of them blows out creating an open circuit without the fire. A carbon resistor is never certified for use as a fusible device!! As for the blue band I think in some cases it indicated 'reliability' like for the military applications and I believe I have also seen it used as a 'temperature drift indicator' measured in parts per million per degree centigrade change but it has been a long time since that extra band was spec'd in our products. We never cared what color it was.

[madires]

Could be Vitrohm BWF series, wirewound, fusible, non-flammable (they look like old carbon resistors).

[armandine2]

...coincidently just watching Richard at Learn Electronics Repair

[cybermaus]

Could be Vitrohm BWF series, wirewound, fusible, non-flammable (they look like old carbon resistors).

Yes, it does look like one of those, including the apparently fixed blue band as "failsafe":
https://www.mouser.com/datasheet/2/447/vitrohm_bwf_wirewound_fusible_resistor_datasheet-2885889.pdf

It also lead me to the existence of IEC 60062 and a document on that, but that does not describe this 'failsafe"
https://cdn.standards.iteh.ai/samples/20940/4ae014b83a7c49adb888d27fd4b35b6b/IEC-60062-2016.pdf

[cybermaus]

That looks like a normal carbon resistor and will probably make a nice fireball when burning out.

Well, as mentioned, it had already "burned out" as result of overvoltage, with absolutely no visible marks.
Also, a hint not shown in the picture, but while admittedly it looks like a very old style carbon, such old resistor absolutely did not fit this rather modern pcb

[CaptDon]

Thank you for that updated information and the blue band explanation. I looked it up in their datasheet. I have not dealt with that style of fusible resistor. All that we used in our locomotive circuit boards were made with the white ceramic base with the resistance element being a spiral band around the body and then having the typical gray colored outer layer and finally the color bands. When they failed from mild overload they would perhaps get somewhat brown colored and fail open circuit. If it were a severe overload a tiny little piece physically would blow out and create the open circuit.

[TimFox]

That looks like a normal carbon resistor and will probably make a nice fireball when burning out. Resistors in line with mains should be ceramic flameproof construction which when severely overloaded make a little pop sound and a tiny little piece of them blows out creating an open circuit without the fire. A carbon resistor is never certified for use as a fusible device!! As for the blue band I think in some cases it indicated 'reliability' like for the military applications and I believe I have also seen it used as a 'temperature drift indicator' measured in parts per million per degree centigrade change but it has been a long time since that extra band was spec'd in our products. We never cared what color it was.

In the early 1980s, when Allen-Bradley carbon composition resistors in brown phenolic packaging were normal, we needed THT fuses on low-voltage lines and thought to save money using 1/8 watt resistors.  Before assembling the prototype, we tried overcurrent through one and found that it overheated and gave off toxic smoke, but did not open up.  We used proper “picofuses” in the same physical size instead.