How Seismic values affect Lifting lug Calculations Section VIII div.1 1

[Jwesterman]

We recently had a client update their seismic values for a ASME Section VIII div 1 vessel. The new values have caused the lifting lugs to fail. My question is does anyone know how they are related or can point me in the right direction to research. It seems to me that unless the are setting the vessel during an earthquake then the two would not be related. Calculations are done in PV elite. FYI Thanks in advance.




Jake​

 

[SnTMan]

Don't forget, the wind might be blowing as well

EDIT: Seriously, you might check that PVE is increasing allowables for seismic events.

Regards

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[JStephen]

Did the revised values make the vessel heavier? or change center of gravity?
Or, did the plate to which the lugs are attached get thinner?
Were there software updates or code updates in the meantime?
You may have an option to set allowable stresses or stress increase for lifting lugs- did that get changed?

 

[DriveMeNuts]

You state that "unless they are setting the vessel during an earthquake", as though earthquakes are predictable, and that you can just schedule the lift for when an earthquake isn't scheduled to occur.
Many Companies deem that the likelihood of an earthquake occurring during a short duration lift is infinitesimal, and therefore take the corresponding infinitesimal risk to disregard Seismic effects in the design of the lifting lug.
Perhaps, if the lift was for a long duration, or it is known that people will be working under the suspended equipment, then including a seismic factor would be wise.
Perhaps, approach your client with the specification discrepancy, and have a conversation with them about your conundrum. Perhaps, they will be reasonable and allow you to comply with their old spec.

 

[r6155]

More info: PV vertical or horizontal, dimensions, weight ?.
As say DriveMeNuts take a conversation with your client.
Remember: test of lifting lug must be made in the shop.

Regards

 

[GD2]

OP,
Sec VIII Div 1 and 2 don't provide directly the Loads to be considered during erection but API 579-FFS Table 2.C.3 provides the following loads and the allowable stress to be considered during erection .

1. Dead load of component less: insulation,fireproofing, piping, all loose internals, catalyst,packing, etc.
2. Temporary loads and forces caused by erection
3. Full wind or earthquake, whichever is greater.

Allowable membrane stress:: Code of construction design allowable stress.

Hope it helps.

GDD
Canada

 

[r6155]

1) ASME VIII is a code, not a book
2) See
a)PIP VESV1002 january 2019 Design and Fabrication Specification for Vessels ASME Code Section VIII, Divisions 1 and 2
4.2.8.2 Impact Factor
1. A minimum impact factor of 2 shall be applied to the lift weight for the design of lifting devices

b)Pressure Vessel Design Manual 4th Ed. Dennis R. Moss and Michael Basic

Regards

 

[KevinNZ]

Does API 579-FFS really say full EQ design for lifting? That would mean the crane also has to be designed for full EQ loads, including horizontal loads! What is the pint of API579-FFS asking for design considerations that were not in the original design?

What happens when the EQ occurs before the hold-down bolts are in place? Do we need design for the EQ when the vessel is on the fab shop?

EQ design is a statically determined. If full EQ design is for a 1:1000 year event, then design with this value for erection would be a 1: 365000 year event!

 

[jt1234]

I can not imagine how you will theoretically include the EQ during lifting when vessel is in the air by sling. It is the additional impact from the sling due to crane jumping in such extreme you may consider using higher impact factor which to be agreed with client, also increase the allowable stress to 90% or 95% of the yield for a sudden shock force.
In normal lifting, we use 1.5 impact factor for hundreds of vessels purchased. PIP using 2 is too high that I believe it will be marked down in the revised edition.