Another newbie question

[Woolsocks]

This is an easy one (I think):

I'm going to crash a 15bbl conical from 70 down to 32, all in one shot, and wonder how much CO2 to add to the fermenter to keep it from having negative pressure inside as it cools.

As a side note, is that kind of a crash enough to crumple my fermenter if I don't add the CO2?

[BelgianBrewer]

It is always good to check your under and over pressure valves every time you clean your fermenter.
Do not worry about your tank imploding. For a 15bbl tank from 70F to 32F your change in volume is going to be just under half a gallon. On a 15bbl volume it can be ignored.

BelgianBrewer
www.sbmbrew.com

[Woolsocks]

Cool. I was going to just close the blowoff/CIP arm, crash it, and when it reaches 32, add CO2 until I have + pressure. Is that more-or-less the standard procedure?

[RobZamites]

For a crash to 32°F, I'd usually cap, add .5 psi to the tank and relax

[Sir Brewsalot]

<Maybe Rob just said this>

It's okay to add the pressure to the tank BEFORE cooling, so you have a bit of play to work with... or even cap the fermenters before the FG is reached, saving some of the natural carbonation and pressure.

Cheers,
Scott