This week's thoughts on tanks and design considerations:

Dear Jim,

I always find your newsletters interesting but sadly have only written to you on a few occasions (and one was a slightly angry response to an article about young engineers! I was a young engineer at the time - sorry for that!)

I don't have any tables regarding steam in pulp addition, but do have some comments regarding design considerations. I've been in the industry for 20 years now, starting out at a mill built in the 1920s, then one in the 1980s and now work in one less than 8 years old. So, in a way have experienced 100 years of design changes in the paper industry!

I've noticed the newer mills have virtually no steam injection into tanks instead relying on heat exchangers (with a a recirc pump) or steam injection before the tank.

Where steam is injected into the tank, it is done in multiple locations through smaller pipes perhaps to minimise the bubbling potential and also to better distribute the heat.

Modern Tanks have large vents at the top as well as large overflows. The vents are curved to prevent rain ingress. Perhaps a design standard should be the vent and the overflow total area should be twice that of the inlet? The tanks always have two level sensors as a fail safe to prevent overflowing - a standard pressure sensor and a prong sensor in the roof of the tank that stops all pumps into the tank and cannot be overridden.

I've found using the haz op process when installing new projects is useful to iron out potential safety hazards.

Kind Regards,
Peter Oughtibridge      

___ 

Any other thoughts on the matter? As always, your help is appreciated.