Expansion Tanks

Mike Lundstrom

I am putting a heating system together for one of the schools I look after and I am unable to find a consistent way to size expansion tanks. I am hoping to use a plain steel tank with sight glass. Can anybody give me some advice. Thank You

Mike Lundstrom

Alan(CaliforniaRadiant)Forbes

Archive

Here's a previous response from our own, inimitable Robert Bean:



DATE: Jul 10, 2001
SUBJECT: Expansion Tanks - Quick Selection Chart
NAME: Robert Bean

Attached below are sizing selections for Bladder, Diaphragm and Plain Steel Tanks using 15/30 pressures and 40/180 temperatures for a handful of typical volumes using either 50/50 glycol or water.

Plain Steel tanks absorb the air or nitrogen charge.

Bladder tanks contain a rubber bag, which seperates the air charge from the fluid and prevents system fluid from contacting steel walls of
tank.

Diaphragm tanks usually contain a "rubber pancake" separating the air from the fluid however the fluid is in contact with the steel shell.

Some manufactures use non-code diaphragm tanks welded inside an ASME shell to produce ASME Diaphragm tanks which is why they
are lower in cost but are non repairable in comparison to the repairable bladder tank.

But if you've ever had the chance to repair a bladder tank it's a lot like pulling calves.

Maybe the tank gurus on the site can check the numbers...would be happy to make corrections and repost.

If you're looking for an expanded chart let me know...I'll do up to 10 more examples if there is consensus.

RB




To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Jerry Boulanger_2

The sight glasses

on standard cushion tanks are a source of leaks. The top gasket on the glass is above the normal water line, so it dries out and allows the air to leak out of the tank.

Use an airtrol tank fitting - it will allow you to check the water level in the tank. If you do use a sight glass, keep it valved off and only open the valves when you want to check the water level.