On Sun, 15 Feb 2015 15:49:04 -0600, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

I've dug around for quite a while, and although I find all sorts of
"comforting" diagonal data about fall heights, column separation, etc, I
cannot find a stated vacuum rating for ASTM D2729 pipe (4").

Holey pipe? Por que?


I'm getting ready to re-do a poorly-designed vacuum hold-down system for
a ShopSabre 4896 that has only ONE 2" pipe to each half of the table,
even though the pump has a 4" inlet!(duh!)

The 4" has 4x the area of a single 2", so you're at the halfway point.
What pump is on there now?


4" water pipe (sch 20-40-80) is slightly too large to fit in the space
provided, but 4" ASTM-D2729 sewer pipe will fit. We're only talking 11"
of vacuum (or -5.4psi). But I want some margin of safety, and can't find
a figure anywhere.

Does the ShopSabre have specs on CFM of flow for those? Measure the
holes, add 'em up, and figure the area at 2 pi r2. Finding data for
figuring vacuum by leakage area ought to be tricky, though.


Anyone know?

What type of spoilboard are you using? One with open holes in it, or
one with rubber ringed vacuum switches which apply vacuum only where
they are depressed? A 1hp 5cfm will do ya for the latter, but you'll
need a big multi-horse for the former. Do these come with a regen
blower? (Real efficient, like a compressed air venturi vacuum pump.

--
A sound mind in a sound body is a short but full description
of a happy state in this world.
-- John Locke