I'm hoping someone may have some in

[Ibeam]

I'm hoping someone may have some insight as to the code ramifications on altering an existing fuel storage tank (steel plate construction).

My question is: If the tank is altered, such as installing anchors to a previously unanchored tank, does that open the door to new code requirements for the tank and nozzles.?

The client suspects that the tank (41' ht. x 40.5' dia.) was not originally designed to the applicable code for seismic overturning (Zone 3), drawings are dated 1980. I'm in the middle of determining that, and if it proves true then will look to see if it's feasible to retrofit an anchoring system. The ringwall foundation is 12" wide x 4' deep. The tank bottom rests on oil saturated 6" sand base, with compacted granular fill below that, reaching down to bottom of ringwall. The Tank bottom is 1/4" plate, and the bottom course of shell is 5/16" with the rest being 1/4" plate.

 

[KRSServices]

I am not sure about your codes, but I do know that here, tanks are manufactured and then "baked" to de-stress them, for lack of a better term. They are then stamped and placed into operation. Once these tanks are stamped, they cannot be welded on without being baked again.

KRS Services

http://www.krs-services.com

 

[BobPE]

I have put new chairs and hold downs on older tanks for siesmic, but unfortunately not in the oil industry. I did not design improvements to conform the tanks to new codes since the anchors were specifically for siesmic and were not impacting the function or performance of the tank in the process.

Its a fine line and with all the regulators itching to get at people in the oil industry I wouldnt be a bit surprised if a regulator took it upon themselves to require you to do a code upgrade of the tank. It does warrent having the CLIENT invistage that further for you making it his risk if other improvements are required and not your risk for letting the cat out of the bag. If you were to do the asking of regulators I would think your client could get upset if the directive came back to upgrade to code. If the client tells you to ignore asking, then you default to doing the original task of modifying the tank for siesmic noting in the file that you asked the question whether other code improvements were required and the clients said NO...

BobPE

 

[RDK]

To let the client determine what the code requirement is would be, in my opinion, a failure of an engineer to exercise proper professional judgment and discretion.

It would be completely unethical and would expose you to all the risk associated with that tank, now and forever. The client would simply say that you did not fully advise him of the risk by not doing a full code compliance upgrade. This would work even if the client was another professional engineer. He could say that the reason you were hired was that he did not have the knowledge or time to do this work and research fully all issues and that he was relying on your professional judgment and expertise in advising him of how to proceed.

Having a note in the file would not be much help. The client could simply deny that he issued these instructions or that you advised him that that was the way to go. A direct letter signed by the client might help in avoiding financial liability but would do nothing for your professional liability and your ability to keep your engineering license.

One would never design a floor with less than the Code floor loading if the client told you to do so. Why would one design fuel tank supports that were not to code? If adding the supports triggers a full fuel tank upgrade, then that’s the code requirement. If it’s a discretionary call on the part of the authority having jurisdiction then only that authority can exercise that discretion.

If the client wants you to go ahead without fully determining what the code requirement is then you have two choices. You can refuse to do the work or contact the authority having jurisdiction against your clients direction. If you refuse and someone else does the work, and you have a reason to believe that the code upgrade is not being done than your only choice is to go to your association and/or the code authority.

A lot of the code requirements are fully at the authority’s discretion. The response you get is often a function of how you approach the authority. One way that I use is to say (slightly more diplomatically than this of course) , “I know that this is close to triggering a complete upgrade but if a complete upgrade is required then nothing will be done and what we are proposing is safer than the status quo.” This way you satisfy the code authority that he is working with you to improve safety rather than forcing you to maintain the unsafe current conditions.



Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[BobPE]

RDK:

I hear what you are saying, but this is the real world. Here in the USA the industry exempt engineer has changed the playing field in private industry for us engineers. They take the responsibility of detrmining the scopes of work for projects private professional engineers bid on. We take the approach of doing what the client asks. The cleint gives a scope of work and us engineers do it, correctly I might add.

Your flooring example was off the mark. Looking at your flooring scenairo. If the floor was designed in 1980 and the client wants a chemical resistant coating put on in 2000, should the floor then be brought up to 2000 structural code because you modified it with a paint system?

I understand what you are saying, but the question was if by adding anchors (designed to code of course) does he then have to say....replace the ladder since its not up to code, or change the fenial vent becuase its not up to code, or add containment because its not up to code. This is the slippery slope I was talking about that is really...up to the client to determine, its his facility.....

I didn't imply that engineers should design anything wrong (on purpose of course), but they do have to know their role. Engaging the state regulators for a project to determine what, if any, additional work should be performed outside of the clients scope of work is ethically wrong and non professional. We should only serve to instruct the client of how we would recommend they proceed and let them make the choice. If you are comfortable with a not to the file, which I am, then so be it, if you are comfortable with a notarized sworn statement, go right ahead (although that may be the last time you are working for that client here in the US).

take care

BobPE

 

[Ibeam]

Thanks for the replies..all are interesting and actually better than the answer I was looking for, in that they open up new ways to think about the situation. Bob and RDK appear to be butting heads, but really you both are getting round to the same middle ground, just from opposite extremes.

In the meantime, I've been given a new twist on the calcs by being asked about money figures. Bob, you mentioned that you've installed anchor chairs in the past. Do you have a ball park idea on a per chair and a-bolt assembly (installed)? I'm not to that point yet, and right now I'm wondering about the geometry of the chair because I have 6"(or less)from shell face to outside of ringwall face, probably not enough cover. Also, I'll probably have to add concrete to facilitate the overturning forces in the foundation.

 

[cvg]

RDK, BobPE

I understand where both of you are coming from. I happen to work for a Canadian firm, but live and work in the US...

I have observed over the past few years that the liability or the responsibility to protect the Owner is different between the two countries. Partly a difference between the more socialistic versus capitalistic government/societies.

Being from the US, I tend to side with BobPE and his more pragmatic approach. We are continually asked to conform to a myriad of government regulations especially involving public safety and environmental protection, but yet trying to use common sense and spend the public money in a responsible way and also try to avoid the attorneys.
I certainly wouldn't advise an unethical approach, however, upgrading the safety of a tank for seismic loading does not sound unethical. And I agree that it is certainly outside of the scope of work to investigate the entire tank or even other infrastructure connected to the tank to see if it meets all government regulations. Where would you stop?

 

[BobPE]

IBEAM:

RDK and I don't butt heads too often, I wouldn't worry. Things are just very different there in Canada, and I may add, maybe for the better.

The chair and anchor construction could be a lot of money if looked at as a unit price. As you eluded too, the foundation will need a lot of work and will most likely be the driving expense. Adding to the foundation makes installing the chairs easier as you can embed the bolts. But the foundation design is tricky as you have to attach to the old foundation. Putting a price on that is beyond the realm of free advice here....but you knew that!!!

I think you are on the right track. Your calcs will be pretty much black and white with no wiggle room except for the factor of safety you put on them. These calcs will drive the price of the project along with your site conditions and soil. There are a lot of people out there doing this type of retrofit for tanks, so you should get a competative price for construction.

Sorry, I just don't know enough about the project to feel good giving you a ball park price....My hourly rate is 150$ if you need to hire me as a consultant LOL!!!!
BobPE

 

[Ibeam]

No worries Bob, I figured out some rough (extremely rough) dollar figures for the chairs and talked with someone from Chance about helical piles. That'll be enough to initially get a budget estimate rolling. (due today).

What I need to do now is look at the concrete pull out capacity for the anchor. If I can expoxy grout the a-bolt (probably 1" dia.)into the existing ringwall, then maybe I can use Pilasters/bumpouts/pilecaps (2'x2' square) to secure the head of the pile to the ringwall.

One thing that's bothering me about casting the anchors into new concrete is the large eccentricity I'm creating between the shell face and the bolt axis. I'd like to keep the anchor as close to the shell as possible, but again, I only have 6" or less space between the shell and edge of ringwall. Then there's the existing reinforcement to contend with if drilling into it.

What's so frustrating is that I suspect this process has been done a thousand times over, but I can't find literature or go-by's to reference.

Any thoughts on whether or not the extra force from the eccentricity would be a large impact on design?

 

[BobPE]

IBEAM:

From what you are saying it sounds like you have to make an engineering judgement, with you being the primary support for the decision with calculations and no back-up with similar projects. That is a tough position to be in, but you have to remember, you are the only one qualified to make the decision. I would think that epoxy into the existing ringwall won't due since there just isnt enough room to drill the hole without damaging the concrete. Your structural calcs will probably show it is insufficient too, making you go to anchors in the new concrete. The chair design should be able to be made strong enough to handle placing the anchors an extended distance from the shell and not a hugh amount of extra money.

Good luck, I hate deadlines too by the way!!!

BobPE

 

[chicopee]

ARE YOU SURE THE ANCHOR SYSTEM IS FOR SEISMIC REASON AND NOT FOR BUOYANCY CONCERN THE LADDER OF WHICH IS THE PREVALENT REASON TO ANCHOR A U.S.T.?

 

[Ron]

I would suggest you check the provisions of API 653 for the tank. Further, most codes allow for "maintenance" functions to be performed without upgrading to current code. There is typically no mandate to upgrade unless the the cost to repair or maintain exceeds a threshold (usually 25% of replacement value in a single activity).

 

[jgillikin]

Look at using API 653 as a cod repair for pressure vessels. We use this type of code repair for all vessels (pressure or atmospheric) in the pulp and paper industry. It is a very good code for all tank repair/modifications. You can get a copy of API 653 for a small fee.