Tuesday, February 5, 2008

Thoughts about penstock sizing and PVC.

Sizing penstock pipe is not a very exacting science. The low to high flow can vary by a factor of thousands. In an average season we get 1000 to 1 winter to summer. So picking the 'design' flow I figured out how much water we can draw during the 10 wettest months and still have a reasonable waterfall too. I figured that a couple of months in the summer we would have to reduce water use or shut down. So if you make your pipe big you'll spend more money on pipe but you'll generate more power during winter. If you make the pipe smaller you will not be able to capture additional energy during the winter but you'll have enough for your needs all year long and save money on the pipe purchase.
So in short, look at the pipe prices and spend as much as you can on this.
Up to 50% of your total budget is reasonable.
If you are looking to sell power back to the grid then spend more on bigger pipe.
If you are just looking to cover your own energy needs go for smaller pipe.
I highly recommend steel pipe for penstock, over plastic for heads over 100 feet. Even though 6" schedule 40 PVC pipe can handle 160 PSI, I had a T burst as I was making a minor adjustment to a butterfly valve. The static pressure in the powerhouse was 95 PSI.

Look at the picture.

For powerhouse plumbing I still use plastic because it is so much more available (in smaller sizes 2,4,6 inches at Lowes) and cheaper and easier to glue together. Six inch PVC is not as readily available in schedule 80 as schedule 40. So I wrapped the schedule 40 PVC (after assembly and glue up) with fiberglass tape and coated it with resin to make it as strong (or stronger) as schedule 80 PVC.

This is the place we got our steel pipe. Shipping (Ohio to NY) was $800.

Crestwood Tubulars, Inc.
P.O. Box 6950
St. Louis, MO 63123
(Fax) 314-842-9064

New & Used Steel Pipe Specials

10000’ 3.500” x .254” SRL/LRL Used Bare $1.59/ft Ohio
35000’ 4.500” x .205” LRL/DRL #2 Used $2.30/ft Ohio
16000’ 4.500” x .205” LRL/DRL New Surplus $3.38/ft Ohio
9000’ 4.500” x .224” LRL/DRL New Surplus $3.65/ft Ohio
5000’ 4.500” x .237” DRL #1 Used Cleaned $2.95/ft Okla
4000’ 4.500” x .237” DRL #1 Used XTRU $2.95/ft Ohio
2300’ 5.500” x .244” SRL Used, Bare $3.95/ft Ohio
2200’ 6.625” x .188” SRL New Bare $4.50/ft Ohio
4000’ 6.625” x .250” SRL/DRL #1 Used, Bare $5.95/ft IL
26000’ 6.625” x .250” DRL #1 Used, Bare/FBE $5.75/ft OK
2000’ 6.625” x .344” DRL #1 Used $6.50/ft Okla
2000’ 7.000” x .231/.272” SRL/LRL #2 Used,Bare $4.35/ft Ohio
50000’ 8.625” x .219” DRL Good Used, Bare $5.75/ft Okla
3400’ 8.625” x .219” D/TRL New Surplus FBE $7.85/ft Ohio
7500’ 8.625” x .264” SRL/LRL #2 Used, Bare $4.95/ft Ohio
25000’ 8.625” x .300” 50’ R/L, #1 Used, Good Yield $7.25/ft TX
4000’ 8.625” x .322” Good Used, Bare, DRL $7.75/ft TX
4500’ 10.750” x .250” D/TRL New Surplus FBE $9.95/ft Ohio
1200’ 10.750” x .365” DRL Used Bare $12.95/ft Okla
27000’ 12.750” x .250” DRL #1 Used FBE OD $11.25/ft TX
1800’ 12.750” x .250” D/TRL New Surplus FBE $13.90/ft Ohio
5000’ 14” OD x .312”DRL #2 Used, Bare $14.35/ft Ohio
2000’ 14” OD x .375” #1 Used Srl/DRL $19.50/ft TXs
1000’ 16” OD x .250” DRL New A252-3 $21.00/ft Ohio
2000’ 16” OD x .250” DRL #2 Used $16.00/ft Okla
3500’ 16” OD x .312” DRL New Surplus FBE $20.00/ft Ohio
1700’ 16” OD x .500” DRL Used, Cleaned $24.00/ft Ohio
1000’ 18” OD x .250” DRL New A252-3 $23.50/ft Ohio
400’ 18” OD x .375” SRL/DRL #1 Used $26.50/ft Illinois
2000’ 22” OD x .250” DRL #1 Used Cleaned $22.00/ft Illinois
1000’ 24” OD x .375” DRL New Surplus, Pritec $29.90/ft Ohio
2000’ 30” OD x .312” 20’0” #1 Used Cleaned $45.00/ft Ohio
100’ 36” OD x .330” #1 Used, DRL, Cleaned $59.90/ft Okla.
240’ 48” OD x .375” 40’ New A252 Spiral $88.00/ft Ohio
Prices are for truckload quantities. Please call us at 1-800-238-7473 for more details, processing costs and delivered prices. Many other sizes in stock and much more on the way! Please call for prices on all your pipe requirements.

1 comment:

morgan from maine/NC said...

Thanks for documenting your projects, I've enjoyed your blog enormously!