Question About Vacuum Valves

[german]

Hi guys, I'm planing to built my vacuum hold down this weekend, and I'm in the middle of a situation: I have a 17 hp blower which I get for a very good price, this blower has a 2 3/4" outlet, so I'm gonna run a 3" schedule 40 pipe, which I got from Home Depot; the problem is that they don't carry 3" valves, 2" is the bigest size they had, mi question is, could I use 2" valves without compromising the vacuum performance?.

Any responce will be apreciated.

German.

[stevem]

By reducing the volume of air moving through the pipe, you will be reducing the ability of the system to cope with vacuum leaks.

[thewoodcrafter]

You mean the blower has a 2 3/4" inlet.

If you tee to several valves for several zones (and step down to 2" PVC) 2" valves should be fine.

That is the way mine is piped. I have 5 zones.

[german]

I'm planing to run 6 zones( a valve per zone ), and yes the inlet is 2 3/4", I got the idea for the pipeing size from this post http://www.talkshopbot.com/forum/messages/15719/20766.html, I just want to save some money, the 3" valves are very expensive ( $ 87 dollars a piece )

German.

[german]

Steve, I was thinking in that situation too; thank you.

German.

[Gary Campbell]

German...
Looks like the blower has a 2 1/2" NPT inlet, which is fairly common for the 350CFM and up sizes. 2 1/2" is available, but not everywhere.

You should pipe from the blower to the filter with 2 1/2, use a 2 1/2 to 3 adapter to go into the manifold. To insure full flow to all zones when needed, use a 3" manifold. Then branch off the manifold with 3 by 2 tees. Each zone can then be valved with a 2" valve.

I am of the opinion that, especially when large blowers with 300+ CFM are used, that you can restrict the flow and lower your hold down capabilities with inefficient or undersized plumbing. (2") I will defer to the grater knowledge of the good men like Harold, that know how to use the formulas. This is the result of real world, not scientific, testing.

Another note: Do not use a regen blower without a filter and a relief valve.
Gary

[german]

Gary, thankyou very much for take the time and answer to my question, I'm going to buy those valves and reductions from home depot early in the morning, and spent the weekend doing the manifold.

German.