Skid anchorage - overturning 2

[cec17]

For anyone here who has designed the delegated anchorage of a pre-fab mechanical skid:

Do you typically consider overturning as well as shear? I've done numerous skid anchorage designs, but they have always been low enough to the ground where it's a shear concern and wouldn't develop any uplift due to overturning. However I am beginning to wonder about the practice when a skid has a COG that's say 6' or 7' above FFE. Is this usually something you consider?

 

[WARose]

Always. But most of the time, they are so wide, it usually isn't a issue.

 

[dauwerda]

Agree with WARose, always a check.

 

[Aesur]

Yes, technically you should consider overturning/uplift at the same time, unfortunately I often see people design this as separate cases and therefore require less anchorage than should be there.

 

[1503-44]

I often see skid mounted gas treating or vapor recovery systems with small vertical vessels.

You must check OTM stability and anchor bolt tension loads of these skids whenever vessels are tall. They are typically empty or only contain a small amount of liquids and gas doesn't weigh much.

Many skids do not meet sufficient rigidity criteria. Always look at them with an eye for installation at site, sufficient lift and support points, and what equipment will be needed to lifting points, transport and installing in place.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[ads0221]

It's always good to check for tension forces in your anchor bolts. More times than not the empty + wind case will always control on smaller/narrower skids. Extremely heavy and wide skids sometimes won't see any tension most of the time.