Storage tank implosion 1

[branca1]

Hi, new to this site, which was found whilst searching Google for the above. I am Plant trainer, with no professional qualification, but am ever eager to increase my process knowledge. I am preparing some training on above ground storage tank design and safe operation. I have already covered the fragility of tanks ( tin of beans, 0.3psi),weight viz volume, venting / N2 addition, and the importance of pressure/level alarms.
I was wondering if:-
a) there was anything else that I could add
b) if anybody knows where I may find more info

I hope the above is in-line with the theme of this board.

Thanks Peter

 

[FrancisL]

The most common cause I have heard for tank implosion is not venting properly after steam cleaning.

 

[Leclerc]

Tank vents with pipework down to ground level. If the tank is overfilled, the liquid flow through the vent will syphon out of the tank, lowering its pressure and cause it to collapse.

 

[TheTankman]

Tank venting and other information relating to above ground storage tanks is available online at

http://www.kefco.com/Guidelinesforuseandinstallation.pdf

 

[EGT01]

Depending on your tank size, you may also want to check some of the tank vent manufacturer websites such as

http://www.protectoseal.com/tank_training.html

and

http://www.protectoseal.com/tank_codes.html

Also

http://www.grothcorp.com/dwnload.htm

Look at their Product Selection Guide under LOW PRESSURE SYSTEMS PROTECTION CATALOG

 

[MJCronin]

branca1,

There is another forum about storage tank design that you may want to review.

The site is:

http://www.ast-forum.com

Although may questions are about the details and minutae of design, saftey and protection against vacuum collapse are mentioned.

There are also a couple of books about process plant disasters that you may want to purchase.....they contain details about tank mishaps. All are available from AMAZON

"What Went Wrong?: Case Histories of Process Plant Disasters" by Trevor Kletz

"Learning from Accidents" by Trevor A. Kletz

MJC

 

[SAFTENG]

I have some great photos of tanks that have imploded due to several factors. Two of the most dominat factors are covering up the vent line and then removing product from the tank or as one of the earlier posts mentioned, steam cleaning a tank, closing it up, and letting the steam condense. Several good photos showing both of these events, as well as several other tank failures due to other events. The photos are FREE to use in your in-house training program.

Bryan Haywood

http://www.SAFTENG.net

 

[davefitz]

I have seen photos of tank collapses , generally due to debris plugging the vent. Typically a birdnest, but one case was a piece of plastic tarp from the painting subcontractor covered the tank vent, and it imploded.

In some cases, the tank is restored to original shape simply by refilling with water or whatever fluid it was designed for.

 

[tmc1]

Also make sure your tank can withstand some degree of vacuum and with proper venting system. Pulling of vacuum can cause tank to collapse when content inside is being discharged at high rate. Vacuum breaker is needed.

 

[25362]

It was another thread where I told of having seen a newly constructed tank with vents blocked, adopting the form of a guitar on a cool night, restoring its normal cylindrical shape when the sun shined upon it the next morning.

 

[PYLERH]

If the tank contains water and is in a cold climate, make sure the vent is heat traced, not just the tank. I worked on a water tower that collapsed when the vent froze over in the middle of winter. Big pain in the butt fixing stuff at -40 degrees!!

 

[branca1]

Thanks to all that replied, some useful information

 

[sshep]

Do not forget about draining- a fully open large drain (3"-4&quot to grade or sewer can often far exceed the vacuum breaking basis of pumpout or inbreathing scenarios, and can be overlooked as an inbreathing basis.

Incidently Trevor Kletz cites the proper method of popping out a tank that has been sucked in- attach a stand pipe to the vent nozzle and fill with water until hydrostatic pressure pops the tank back into shape.

 

[MJCronin]

sshep,

This is an interesting method.........which Kletz book did this come from ?

Does anyone else have any website or internet references wher a collapsed tank has been reshaped ?? How about books or texts or case histories ???

Are there any contractors that specialize in this type of work ?

It is my understanding that this can only be done, "on the sly" and it may invalidate any warantee from any tank vendor ?

Comments anyone ????


MJC

 

[EGT01]

No experience with reshaping a tank but just as opinion, seems that you would likely have to exceed the MAWP of the vessel which may make things worse.

 

[EdClymer]

Greetings

You are very correct in your teaching: most vessels are for storage,ie internal pressure and are very unstable under external pressure due to buckling and elastic instability.

The root is that the walls are thin compared with the diameter and as diameter increases the plate approaches a flat plate.

My field is plastics materials and design of vessels manufactured from thermoplastic or thermoplastic/GRP the 'dual construction'

An external loading can develop from, wind pressure (gusts); bending due to wind (buckling); load arm on external bracket; blocked vent or vent of insufficent size or in the very extreme case a low level manhole became
detached and as the top vent was (now) severly undersize - the whole collapsed (and it cost £1 million to clean up the site)

The lesson to be learnt? Ask the right questions before design and consider ALL external loadings.

Regards from Birmingham, England (where plastic's were invented!)






Ed Clymer
Resinfab & Associates
England

 

[CHD01]

Often enough that it should be considered, tanks that have collapsed can be returned to their orignal shape and reused successfully. One simply pressures the tank slowly and safely (not an easy trick for a large tank). One needs to inspect the tank for damage to access potential for recovery and I would again pressure test the tank before returning it to service.

I am NOT an expert at this subject, but I have listened to experts speak on the subject and know that it can and is done at least with API tanks! Not aware of any ASME tanks being done this way.

The more you learn, the less you are certain of.

 

[kbander]

The only times I have seen tanks that have "imploded" is when the vents have been taped up for sandblasting or painting and then someone moves product out of the tank.

I've seen pictures where this happened to a remote tank where it was completely sucked in...to the point that the tank wall ripped off of the floor in one area. The note that came along with the pictures said "Is there anyone that HASN'T done this?"

Yup...a pretty common boo-boo.


Regards,

Bob

 

[sshep]

The above mentioned reference to Kletz and popping out a deformed tank came from "What Went Wrong" 3rd edition, Ch5, storage tanks.

Never try to use pnuematic pressure to blow out a dent- this could be very very dangerous.