I have a horizontal tank that is not anchored down, simply sitting in two saddles.  I looked through API 650 and found no mention of anchoring or wind uplift for horizontal tanks, only vertical tanks.  What standard do I use to determine if the horizontal tank needs to be anchored down or if it is fine the way it is?

jrh2,
     You need to consider the loadings onto the tank in order to determine whether it need to be anchored down. If all your calcs show that the tank is stable then anchoring may not be required. Will the tank be subject to temperature variation (process or ambient)? If so then without anchoring will it tend to "ratchet" thereby causing problems with the attached piping? There are operational considerations which may dictate that the tank needs to be fixed at least at one end such that you definitely know it's movement during operational cycles. You don't specify the size/weigth of the tank which could be of some help!

jrh2,

You need to use a standard that provides a basis for determining wind loadings - internationally there are a number, but I see references to ASCE 7 in the US. Apart from wind there is seismic. It's a matter of summing up all the loads tending to shift or overturn the tank, and determining whether there is enough inherent stability (when empty for wind, or with liquid for seismic) to see whether you require anchorage or not.

Cheers,
John

The tank is in the southeast US so sesmic should not be a problem.  It is a 7,000 gallon peroxide storage tank.  The dimensions are 9' diameter by 16'6" long.  The weight is 2,150 lbs empty and 72,400 lbs full.  I keep hearing UL 142 come up in conversation about horizontal tanks.  Does anybody know if this code would help with the loading calculations?

JohnGP - Do you happen to work for Georgia Pacific?

I don't see that UL 142 addresses wind loading at all in just looking through it.

Sorry jrh2, I'm in the Pacific, but nowhere near Georgia!

Just use a wind code to calculate the overturning moments - I'm not familiar with ASCE 7, but provided it has the shape factors, then it should be straight forward.

API 650 wont help you much as it is for vertical tanks.

For cylindrical horizontal tanks under wind loading it is really a matter of using your local loading code and determining the overturning/ sliding loads.

I doubt pure uplift is a problem, however you could get uplift on one side of the saddles due to overturning, in which case anchoring would certainly be required.

In general it is good practice to have some nominal anchorage on horizontal tanks.