Lifting Lug / Trunnion safety factor

[florence12345]

Dear all,

I am currently in gernmany and working with garman code and regulation.
My question is : How you deside the safty factor for the lifting lug when you desing the lifting lug / trunnion acc, to EN code and german regulation. Do you have any reference where is it written that we have to take safty factor of 1.5 or 1.3 or 1.25??

Thanks.
regards,
Neel

 

[Haralt]

Hello!

In the codes for calculating the lifting lugs or trunnions there should be indicated which safety factor to be used.
See DIN 28085 (lifting lugs trunnions heavier vessel)
DIN 28086 (eyelets)
DIN 28087 (top head lifting lugs)

Please look at

http://www.stdsm.cn/Knowledge/ShowPDF?fileName=DE-DIN&docName=DIN 28086-1994.PDF

http://www.stdsm.cn/Knowledge/ShowPDF?fileName=DE-DIN&docName=DIN 28087-1994.PDF

In DIN 28087 there are several different safety factors(or push factors) indicated.


best regards

Haralt

 

[florence12345]

Hello Haralt,

Thanks for the information.
My problem is my vendor design lifting trunnion with safety factor 1.5.

Can i ask him to reduce this safety factor to 1.35? Is it possible by german law?
With saftey factor 1.35 of couse all lifting lug will work as safe. There is no requirement of Client. Client only ask to follow DIN 28085.

Thnaks and regards,
Neel shah

 

[Haralt]

Hello Neel!

Please see for DIN 28085, but only the 3 first pages out of 10 pages, and in German.
It exist also an english version, but not on this link.

http://www.spsp.gov.cn/DataCenter/Standard/PDFView.aspx?ca=/UyKo13ApqA=&Token=$Token$&First=First

I do not want to discuse German laws I am not that experienced. Perhaps other enginers in this forum can give you input.

Best regards
Haralt

 

[dhengr]

Florence12345:
If you are going to be designing lifting lugs and lifting trunnions on pressure vessels, you should certainly know what code you are designing to, and should be pretty darn familiar with that code. Why are you so intent to skinny down the design FoS (factor of safety)? Is it just one part of the whole detail which is giving you problems, or what? Remember, those FoS are there to cover our butts when our design missed a slight overstress, some less than top quality fabrication and welding was done, or the lifting/rigging process doesn’t go quite perfectly, etc. And, on some of these things we really don’t have final control. The general philosophy on FoS and the rigging process has always been the more use and abuse a component can experience (shackles, slings, hooks, and the like) the higher their FoS should be to tolerate this usage and abuse. A lifting lug or trunnion will probably only be used a few times during the life of the vessel, so the reuse and abuse factor can at least be cut back. This doesn’t mean you can skimp on the design, because the one certain thing your client and boss do insist on, is that you don’t drop it. I’ve always felt that top quality detailing, fabricating and welding were more important than the exact material strength or FoS. If something is going to fail (start to fail) it will likely start as some stress raiser, weld imperfection, etc., at a stress/load less than the max. allowable stress. Something that your detailing has caused, not at a high gross average stress. Pay attention to the highly stressed and critical details and welds on the lug or trunnion design them to spec. and detail them cleanly and the rest just falls into place.

 

[MrPDes]

Remember the stresses in the pressure vessel shell that are the result of loading from the lugs shall be limited to the pressure vessel code allowable stresses and associated design margins (Not the Lifting Lug Code allowable stresses). This also applies to the the doubler pad weld or lug welded directly to the pressure envelope.