On 2011-10-11, David Billington wrote:
Gunner Asch wrote:
On Tue, 11 Oct 2011 06:09:12 -0700, Larry Jaques
wrote:


Why black pipe? We're not doing nat. gas here. I used all 3/4"
galv steel for my main and 3/4 x 3/4 x 1/2 tee's UP, then two 90 deg
street el's and 1/2" down to my outlet, ball valve and Q/C.

Galv flakes a lot. I hope you use a FLR on each drop, with or without
lube. F'rinstance http://goo.gl/2yi3z .


Indeed. Ive made a point to NEVER use Galvanized pipe in any of the 100
or so air systems Ive designed and installed. This after repeatedly
having to unchoke or replace air solenoids that were
filled/blocked/ruined by flakes..sometimes BIG flakes of Galv.

[ ... ]

Why does the galv flake and is that inside or outside or both. I put
galv pipe handrails at my mothers place over ten years ago and the
external surface, while a bit weathered, is otherwise still perfect, I
tinned the cut ends with solder so no rust there either.

I *think* that it may be a combination of the high pressure air
(more oxygen available), and the cycling of pressure which expands the
pipe and allows it to contract. If it is partially the higher oxygen
partial pressure, I would expect the inside to flake a lot more than the
outside -- but if it is the pressure cycle expansion/contraction, I
would expect it to flake as much on the outside.

Enjoy,
DoN.

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