vesselguy,TGS4
I've been using Visual Vessel Design from OhmTech for more than 4 years now.My experience is that this is the best software for mechanical design of pressure vessels and shell & tube heat exchangers. I especially enjoy to use the new module for flange calculations according to EN...
I think OhmTech VVD is the best buy out there.
At least it is much better than DISASU and Compress.
Try out the demo version and see for yourself
http://www.ohmtech.no
http://www.disasu.com/
http://www.compress.com
http://www.pvelite.com
Regards
Entery