A106 sched 40 hot oil steel pipe potential for warping. 1

[stanking]

These 3 inch pipes (not insulated) supply hot oil to each press platten. oil temp is 410 deg F. These secondary loops have constant oil circulation. If sprayed with fire hose (2 inch) with ambient temp water is there any chance of pipe warpage? This press has 16 plattens 8 ft by 16 ft and warpage could result in mechanical interference between hot oil supply pipes as press is opened and closed.

Thanks, Stan

 

[stanking]

Adding to my thread, If water is sprayed on one side of a hot pipe it will obviously curve in the direction of side that was cooled. The question is at these relatively low temperatures, will any of the curvature be retained once the steel pipe temp is back in equilibrium? I suspect not, but am looking for confirmation somewhere and have not had any luck thus far in my search.

 

[stanweld]

I would expect some mild warpage. I once had a secondary redundant pump that the manufacturer misdesigned. Operating temp was 450 F and only one side of the bearing housing was heated to 450 F while the other side was essentially at ambient. Needless to say the pump would not start up when required - essentially due to the warpage inducing excesive load on the bearings.

 

[stanking]

Thank you Stanweld for the response. If I understand your comment, it would be possible to have some "mild warpage" even after the temp difference from one side of pipe to the other is no loger there? In this case the pipe is vertical, about 15 ft long and supported only at bottom end. Even 1/4 inch of retained warpage at unfixed end of pipe after the temp has equalized could cause problems.

 

[Metalguy]

Your question has many variables-the amb. temp. of the sprayed water, the amount (cooling rate), etc.

Why not set up a simple test-heat a 15' vert. pipe electrically and then spray it.

 

[stanking]

Thanks for the suggestion metalguy, Here is scenario. This 3 inch Sch 40 pipe sitting in mill (ambient air about 100 deg F) with hot oil flowing thru it. Suddenly hit with 2 in fire hose, water at about 80 deg F. So, in probably a fraction of a second the surface temp on one side is reduced to boiling temp of water about 212 deg F here at sea level. My logic keeps saying no permanent distortion cause no plastic flow (metal temp to low).

But, before I tell several maint managers at the mill no way. I keep wondering could the rapid temp change on one side of pipe surface induce some internal stress that would permanently distort the pipe and keep it from going back straight once water is back off this pipe? The experiment would be great except being able to replicate the 400 deg oil circulating thru it.

Thanks again for your time.

 

[Metalguy]

The real problem is the very small amount of permanent warping that you can tolerate. I think there's a real possibility that you could permanently warp it 1/4" or more given the long length.

Something else to keep in mind. The yield strength of carbon steel can be drastically lower at 450 deg. F than at 80 deg. I was involved in a test program to find out how much reduction in YS there was (440 deg F), and as I recall the least amount was ~20-25%, and the highest was ~35%! You wouldn't even need to reach the 0.2% YS (common) to permanently warp your pipe 1/4" in 15'.

 

[stanweld]

I tend to agree with Metalguy. Permanent distortion will occur. Based on your scenario, I think that it will be somewhat smaller than 1/4". Good luck.