Manaway Davit Arm Made From Pipe
Manaway Davit Arm Made From Pipe
(OP)
A vendor of ours is purpose designing some manway davit arms from SA106 Gr.B pipe.
I requested that the -12.5% undertolerance be applied to the pipe - unless of course they do thickness checks to confirm actual pipe thickness.
The davit is for a 24"NB-600# + 5mm Weld Overlay blind flange (circa 570kg / 1250lbs).
Am I being too conservative?
Thanks
I requested that the -12.5% undertolerance be applied to the pipe - unless of course they do thickness checks to confirm actual pipe thickness.
The davit is for a 24"NB-600# + 5mm Weld Overlay blind flange (circa 570kg / 1250lbs).
Am I being too conservative?
Thanks





RE: Manaway Davit Arm Made From Pipe
Regards
r6155
RE: Manaway Davit Arm Made From Pipe
Regards,
Mike
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Manaway Davit Arm Made From Pipe
RE: Manaway Davit Arm Made From Pipe
I jsteng123 says, you can find 'pre-designed' versions of these.
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P.E. Metallurgy, Plymouth Tube
RE: Manaway Davit Arm Made From Pipe
See ASME BTH-1A "Design of Below-the-Hook Lifting Devices" as a guide for davit (standard drawing as PIP or others configurations).
Regards
r6155
RE: Manaway Davit Arm Made From Pipe
RE: Manaway Davit Arm Made From Pipe
My point is, if the design is based on somebody saying "Let's use...uh...18,000 psi!", that's great- but quibbling over the thickness tolerance is pointless, all they have to do is assume appropriately higher stress and they have the same design and you've both wasted some time.
RE: Manaway Davit Arm Made From Pipe
The problem with sloppy work is that the supply FAR EXCEEDS the demand
RE: Manaway Davit Arm Made From Pipe
No calculations is required if all dimensions and materials are as PIP.
PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES
In an effort to minimize the cost of process industry facilities, this Practice has
been prepared from the technical requirements in the existing standards of major
industrial users, contractors, or standards organizations. By harmonizing these technical
requirements into a single set of Practices, administrative, application, and engineering
costs to both the purchaser and the manufacturer should be reduced.
2) @ JStephen:
See PIP VEFV1107 / 18 and 19 “all thickness shown are based on 36 ksi yield strength”
See AISC for allowable stress.
Regards
r6155
RE: Manaway Davit Arm Made From Pipe
Regards
r6155
RE: Manaway Davit Arm Made From Pipe
Note that A106-B is a 35ksi material, not 36 ksi.
I expect the 93% is based on A500 structural tubing.
RE: Manaway Davit Arm Made From Pipe
Regards
r6155
RE: Manaway Davit Arm Made From Pipe
Your statement would not be acceptable to any accomplished AI/AIS or during a Audit/Review. Most davit arms have some sort of welding on the nozzle or flange (Code weld). If it is considered and applies in UG-22 then some sort of design justification is required. This is normally done by calculation but also have accepted tables from the Pressure Vessel Handbook or other engineering standard (JIS,GB BS).
RE: Manaway Davit Arm Made From Pipe
Please, read in full the purpose and use of PIP - www.pip.org
Regards
r6155
RE: Manaway Davit Arm Made From Pipe
A very nice web site but has no bearing on the ASME Requirements. There is nothing more to be said from my side on this issue.
Regards