thank you. it is small (ok miniscule). but those few millimeter is sometimes a killer if you're going to slip a test blind in a big cooler or reboiler in terms of spreading those flanges. we learn our lesson last turnaround. i can still remember the cursing of our riggers and pipefitters because of those few millimeter. The hydro itself is not a problem. once you filled it with water (ok with chloride not exceeding 50 ppm), it does not make a difference whether we test at 1.5 or 1.3.
oops sorry. i have forgoten to mention, our plant is in the middle of the desert (wehre it take as long as 3 months to have those b16.5 flanges delivered). im from saudi arabia ( imean the place whre the complex is located). by the way, for the benifit of the other, the flange facing Everett has pointed out is normally serrated with 125 rms surface. this matches with the spiral wound gasket.
thanks again. by the way nichols maybe you can help settle the issue between our chief machinist and me. He says that a smooth surface (mirror polished) is better than a serrated one (phonograph finish) in sealing the flange face. Is he correct? and ... have you come across a criteria in determining damage sustain by a flange face (how many scratrches or goucges or nicks) before you start refacing (we're using Climax machine). damn those pipefitters and millwright.
-----Original Message-----
From: EVERETT W. NICHOLS [mailto:enichols@bbtel.com]
Sent: 28 May, 2001 4:41 PM
To: PipingDesign@yahoogroups.com
Subject: Re: [PipingDesign] Hydro Test Pressure
Go with the 1.5 value. If you use the ASME B31.3 equation to size your line blind requirements you will find that by using the 1.5 x the PSIG design value and then use the 1.3 x the same value the material minimum thickness between the two is miniscule. Try it. You could also consider this 1.5 as an added safety factor. I would opt for going with off the shelf blinds versus homemade. Most manufactures of these blinds design them for full B16.5 pressure ratings. If someone was to forget or had a need for a permanent blind, then they would hold up to the working pressures. This saves from having to sketch, procure and fabricate. Plus the manufactured blinds also come with a gasket facing on the blinds. In the USA - Mack Iron Works is a very good supplier. Everett Nichols
> i can understand that Christopher. I don't have a copy of the latest
B31.3,
> but if you do - has there been a change in the b31.3 code allowables? Im
> trying to save on the fabrication of blinds during the coming turnaround.
I
> just want to have a blind that i can use either for piping, tanks,
exchagers
> or vessels using the 1.3 factor.
>
> -----Original Message-----
> From: Christopher Wright [mailto:chrisw@skypoint.com]
> Sent: 26 May, 2001 9:08 PM
> To: ?
> Subject: Re: [PipingDesign] Hydro Test Pressure
>
>
> >Has there been any changed to the
> >latest edition of the process piping code with regarrds to the material
> >design factor and the hydro test rquirement ?.
> The change was made to the ASME Code as a result of the increased
> allowable stress made a couple of yous ago. The proof factor was
> decreased from 1.5 to 1.3 to maintain the same margin against yielding
> during the hydrotest. If the piping code allowables didn't change, then
> the proof factor wouldn't change.
>
> Christopher Wright P.E. |"They couldn't hit an elephant from
> chrisw@skypoint.com | this distance" (last words of Gen.
> ___________________________| John Sedgwick, Spotsylvania 1864)
> http://www.skypoint.com/~chrisw
>
>
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Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Received on Tue May 29 01:03:00 2001
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