View Single Post
Old 09-29-17, 10:27 AM   #27
TechShop
FNG
 
Join Date: Jul 2015
Location: Washington
Posts: 71
Thanks: 8
Thanked 19 Times in 13 Posts
Default

Quote:
Originally Posted by ecomodded View Post
I thought it best to double check the psi , the math at 24 sq.in works out to 5750 lbs load at 10 lbs per inch

Im thinking 3/4 inch plywood (again haha) on top of the foam base would work well to spread a 800 lbs or so load from a 80 gal tank

Type I EPS has been tested and found to fall within 10 to 14 ps
i. The resilience of EPS insulation board provides reasonable absorption of building movement without transferring stress to the interior or exterior finish at the joints
XPS foam has far more dimensional stability than EPS foam. The blue stuff at the local stores is usually 15 PSI structural XPS. I special-ordered 25 PSI for use under my concrete slab foundation and used a leftover 2' x 2' square under my water tank.

80 gallons of water is about 667 lbs. Add the weight of the tank and the heat pump and that's the load on your foam when filled.
If your water tank is 24" diameter and only sits on a 2" wide ring / lip around the circumference, the surface loading of the foam would work out like this:

P = M / ((π * R^2) - (π * r^2))

Where P is pressure, M is mass, R is major radius and r is minor radius

P = 750 lbs / ((π * 12 in ^2) - (π * 8 in ^2))
P = 750 lbs / 251.33 in^2
P = 2.98 PSI

So for a large water tank, you may be in the 3 PSI to 5 PSI ballpark.
10 PSI foam is more than enough to handle that load.

I swear I have nothing against plywood...
TechShop is offline   Reply With Quote
The Following User Says Thank You to TechShop For This Useful Post:
ecomodded (09-29-17)