Earlier volvos had a split crank sheave.  Remove bolts, places
existing spaces before / aft of flange to tighten new belt, and you're
done.

Later ones are very conventional

Or loosen alternator brackets and move it out of the way, swap belts, and
retension alternator.

In article <28c255171e980890903ab94d65f73013
@localhost.talkaboutautos.com>, abucfaninbtown@msn.com says...

It's a conventional replacment, except for the fan shroud.
You loosen the alternator to slacken off the belt, slip the belt off the
pulleys and then you have to feed the the belt over the fan blades and
out of the shroud. Take it one blade at a time, find the slight "loose"
spot in the shroud and feed the belt through there, turning the fan as
you go. Replacement,as they say in all the best workshop manuals, is
the reverse procedure!