Anchor bolts of storage tanks 2

[Ahmed Habashy]

Hi
We have installed new prefabricated tank api650 d4.5 m h 6m on its foundation on 8 anchor bolts m30
4 bolts from 8 not completely fit with required 2 nuts and washer some cases 1 nut fit due to shortage in required length of anchor bolt by 5 cm in those bolts
So what is the solution for this case and safety of tank regarding current situation

 

[LittleInch]

Why 2 nuts? To avoid loosening or to provide sufficient force?

Safety of tank should be good so long as you have at least one nut fully engaged. IMHO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JStephen]

Took me a while to find these because I didn't know remember what they were called:

https://www.canam.com/en/product/elocone-nuts/#description

I concur that one nut fully-engaged is adequate. The second nut is mainly intended to act as a lock-nut.

Other potential solutions, depending on details:
-Trim a few inches off the anchor, add a coupling nut and stud to extend up through the anchor chair. Note that this may reduce the effective bolt stretch length required for seismic uplift, so not to be done willy-nilly.
-Modify the anchor chair by cutting/welding. This needs to be confirmed in the design and may not be feasible. If the tank is already painted, this is undesirable.

 

[MJCronin]

Agree with Littleinch ...I understand that "Double nutting" is sometimes used to secure fasteners in VIBRATING EQUIPMENT (there is no other reason to do this)

Nothing in API-650 requires double-nutting and .... hopefully your tanks are not vibrating

(It has been my experience that usually some buttt-hole management makes a proclamation that causes these issues)

IMHO, too many MBAs build/repair these process plants with only the "tribal knowledge" of the temporary employees that they hired just this morning

MJCronin
Sr. Process Engineer

 

[IFRs]

API 650 allows and specifically mentions double nutting:

5.12.12 Any anchor bolts shall be uniformly tightened to a snug fit (nuts hand tight in contact with anchor chair top plate plus maximum of 1/8 turn with wrench) and any anchor straps shall be welded while the tank is filled with test water but before any pressure is applied on top of the water. Measures such as peening the threads, or adding locking nuts, or tack welding nuts to chairs, shall be taken to prevent the nuts from backing off the threads.

If you can't double-nut, choose one of the other options. Peening is what I see most commonly if double nuts are not possible. My anchor chair drawings include double nutting.

Elocone nuts - nice solution for short bolts!!

 

[r6155]

Install a new nut (half-way, 15mm) onto the end of the current anchor bolt. Spot weld.
Install a new bolt (with the required length) into this nut. Spot weld.
No changes to the chair are required.

Regards

 

[MJCronin]

Thank you IFRs ... I stand corrected ...

But, clearly ... Chapter and verse of API_650 allows many ways of anchor bolt locking and demands locking, by fiat

However, in my opinion, peening/thread upsetting would be the best choice for short threads

MJCronin
Sr. Process Engineer

 

[r6155]

Any photo?
Regards

 

[Ahmed Habashy]

Photos of case

 

[r6155]

Next time send a photo when you open a post.
The problem does not exist.
I waste my time,

 

[LittleInch]

Agree,

Either use a thinner nut to be your lock nut or just use Loktite or some other way to stop the nut moving if the bolt becomes unstressed.

Two identical nuts look nice, but its the function you need.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.