SpudFiles

Why is the last numbers on a presure gauge color red? will the gauge explode if you go past it?

It depends what the gauge is meant to be mounted on. If you fit a gauge for a cylinder that is rated up to 100 psi on a cylinder that can take 300 psi and fill it to the latter pressure, you'll be perfectly safe in terms of cylinder but probably the gauge will be damaged and not read correctly, though it's unlikely to actually explode.

it wont explode simply wont be trusted anymore accuracy wise.

That is an immediate response though.

There are tonnes of factors you didnt give information on.

-How far past the red
-what brand of gauge
-quality of gauge
-what is the gauge made from
-what does it measure to

only when we have all this can we tell you

EDIT: dammit beat, see what i get for giving lengthy responses

but usually red means bad so yes do not go past it if you value your gauge and its accuracy

They tend to be red as a warning for their intended device in my experience. Usually when people put a gauge of a product, they get one which read higher than the appliance would normally need. Therefore, when the needle goes into the red you've got too much pressure in your appliance.

Take for example, fire extinguishers; A powder extinguisher is tested to 24 bar, but only supposed to be used at 10 bar, so 9-11 are gree on the gauge are green and the rest is red.

The gauge only has a very small volume of air in it, so even if you waaaay overpressurize it, it'll just spring a leak rather than explode

It mostly depends where you got the gage from.
As biopyro said with the fire extinguisher, the gage gets into red where the working pressure of the unit it is mounted on is exceeded.
If you buy an compressor that goes up to 8 bar, the gauge is likely to turn red from 8 bar (or 10 bar)

If you buy a separate pressure gage, the gage will probably not have any red.
A gage will not explode. You can probably go like 3 times around with the needle, but it can be destroyed. If you over-pressurize the gage (that is, over where the markings end) you'll ruin it and it will not return to zero and give wrong readings.

The best way to know for sure is to go the the manufacturer's website and look up the features of that model. By the way, what make and model is it?

it's a gauge i took off a regulator. steel not plastic. last psi number is 160.
back mounted not side mounted.

Then you can use it up to 160 psi. Maybe a bit more, like 180. Ignore the red. The red was just to show the max pressure of that reg.