Bio sludge Tank 2

[zhamal]

Hi dear sir ,

I work in Contractor.

I am responsible for Storage tanks.

We have one tank that keeps inside gas to liquid bio sludge in future.

We have performed hydrotest . But bottom plate went down , buckling came out .

Owner rejected it made Hyundai design company to revise drawing and to put channels all around the bottom.

my question is how this is serious that bio sludge product. Can the tank be safe with this product in near 30 years.

How to convince the Client that everything is ok.

 

[Dhurjati Sen]

The failure during hydrotest could be due to many factors, like poor design, poor welding, poor quality control.

I think the last two had been the culprits.

Submit a repair procedure and carry out the job professionally this time.

DHURJATI SEN

 

[LittleInch]

Well it doesn't look like an awful lot of support to the floor.

Failure of the floor in service could very easily kill people if they were close to the tank.

Also is the sludge heavier than water? If so there is more load than water so how was it tested?

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

 

[JStephen]

The design of a cone bottom with radial supports is not covered by any of the tank standards.
API-650 does include spacing requirements for a "flat" bottom supported on grillage that could be applied here, and it would give fairly close spacing. It is based on just treating the bottom plate as a beam spanning from one support to the next.
To analyze or certify a design with any degree of confidence, I would suggest a finite element approach with a designer experienced with such applications.
Pay attention to the details. For example, if you assume the cone is "fixed" at the shell, is the shell at that point able to resist the resulting loads, and are resulting deflections small enough to justify the "fixed" assumption? Where the plate connects to the radial beams, are the radial forces transferred to the beam (and their eccentricity) also considered in the beam design? Is the cone designed as being axisymmetric when in fact it is not? Does the design approach address the large deflection theory for the plates?

 

[LittleInch]

I wonder if the original design was for a smaller tank and someone has just extended it without actually doing the design calculations / assessment???

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

 

[Geoff13]

As JStephen has noted, these types are tanks are unique, with a complex stress situation.

You should be asking Hyundai (the responsible designers) your questions. They should be the ones asserting that the tank design is good for the product and service life. The erection contractor should only need to show they've followed the drawings provided to them.

There are basically 2 ways the tank bottom can support the liquid weight above it.
[ul][li]Bending. Given the large beam spacing this would require a very thick bottom, even if your product depth is fairly small. I suspect this is what you have since I don't think the alternative matches your photo.[/li]
[li]Tension. It is almost impossible to have a reasonable circumferential tension stress without also rolling the bottom plates to a radius. Due to the large angle between the radial beam there would also be a very large inward radial force on each support beam. Based on the photos I don't think this is your structural system.[/li]
[/ul]

The shell-to-bottom junction is both unstiffened and unsupported in the photo, which is surprising. There is too little info to say more. Once again, Hyundai should be the ones reviewing your hydrotest observations.

It is inevitable that the bottom will deflect when filled with product (or hydrotest), just like how the shell bulges when a tank is filled. This is not a concern, unless the deflections still exist after the tank was emptied. Hydrotest should not cause permanent deformation.

 

[MJCronin]

Can you post more information ? .... More pictures ? ...... Who came up with this design ? ....Was it you the Contractor OR Hyumdai

How deep is the bulge ? Can it be measured ?

Did you hydrotest the tank while it was partially or completely full of sludge ?

Did an MBA force you to perform the Hydrotest while the tank was already in service and full of sludge ?

Can you post excerpts from original design drawings AS WELL AS The recommended channel fix by the client ?

I agree with what has been stated above by Geoff

The shell-to-bottom junction is both unstiffened and unsupported in the photo, which is surprising. There is too little info to say more. Once again, Hyundai should be the ones reviewing your hydrotest observations.

MJCronin
Sr. Process Engineer

 

[MikeG7]

The bulging is due to weight of sludge and pressure, exceeding the original design or due to some manufacturing issues.
The spacing of supports for that diameter looks inadequate, depending on the height of tank.
Now that it is bulged, it can get worse with time as corrosion take place (in 30 years) unless it's stainless or corrosion resisting steel.
It is, as mentioned, non standard design. I usually do FEA to check the flat bottoms as well as the junction stress. You can check with Roarks formulas also the flat bottom and in my opinion add more intermediate bracing between the radial supports (to make the panels into smaller areas).
Then you should be OK for the future. It depends who is responsible for the design, usually the contractor is working to engineers drawings.

 

[bimr]

Hi dear sir ,

I work in Contractor.

I am responsible for Storage tanks.

We have one tank that keeps inside gas to liquid bio sludge in future.

We have performed hydrotest . But bottom plate went down , buckling came out .

Owner rejected it made Hyundai design company to revise drawing and to put channels all around the bottom.

my question is how this is serious that bio sludge product. Can the tank be safe with this product in near 30 years.

How to convince the Client that everything is ok.

Contract with an respected independent third party to review the drawings and calculations.

 

[zhamal]

Bottom thickness 7.5 mm. It is a brand new tank. It is hydrotested with a just simple water without any sludge. Twice.

 

[IFRs]

In my opinion the tank is not safe for use. The bottom needs more support.

 

[LittleInch]

How to convinve your client? Well you need show by design that the tank is not overstressed, but also that you are fitting more supports.

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

 

[saplanti]

It seams there is a (or more, the photo does not cover entire bottom and not clear) frame structure which might be touching/supporting the lower section of the vessel. If this is right I am not sure how effective the frame support(s) is. I guess the important factor is the heigth of the cylindrical section of the vessel.

If the frame does not support the bottom of the vessel I would expect some sort of buckling restrain member(s) at the intersection of the cylinder section and the bottom cone all around with supporting columns attached. Depending on the height of the cylindrical section there might be an additional grid structure supporting the bottom.

The best is to ask the manufacturer to provide the supporting calculation.

 

[goutam_freelance]

It appears that flat bottom has deformed and become conical. As a starting point you can use Sec VIII div 1 'UG-34 UNSTAYED FLAT HEADS AND COVERS' and check the required thickness. The required thickness will be substantial unless stiffners/reinforcements are used.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/