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Vertical Vessel lower part replacement

Vertical Vessel lower part replacement

Vertical Vessel lower part replacement

(OP)
In our plant I have to replace a lower third part of a 90´ x 50" vertical vessel during 12 days plant turnaround.

The Vendors sent two different proposals for the replacement:
1) To cut the third lower part. Installing the new third and make it perpendicular with shims on the concrete base and after the upper part is assembled to the lower, guided with six  steel angles welded to the lower part (3´ length).

2) To lift all the vessel then transported to their workshop then cut it and welded in a horizontal position then Lifting and make perpendicular on site. Total weight is 24 metric tons and the radial horizontal distance to the crane is 40´.

Can you tell me the experience in this type of job and what do you think will be the best quality job?  
 
 

RE: Vertical Vessel lower part replacement

Can't tell.  What does your site look like around the tank?  How much interferences?  

What crane do you already have rented for the outage, and what (more expensive) crane will you need for these two lifts?  What is your potential laydown area for the tank on-site?  Movement of tank between laydown area and plant exit?  

Movement fees in their estimate?  Movement permitting and extra taxes between your site and the vender?  

How many connections on the tank and where are they?  Who and how will you do NDE and certs (x-ray ?) if working on site compared to the vender's facility?

Hint:  90 ft x 50" can't fit on most truck routes in congested areas.  

RE: Vertical Vessel lower part replacement

Have done, and prefer option #1.  Prefabricate the lower section, including the skirt.  Just use a crane to raise the vessel slightly, rapidly cut out the lower in sections, then slide in the new lower.

After 1/3 to 1/2 the thickness of the round splice seam weld is complete, the crane can be released.  You can get to the "release the crane" stage in one long day.

RE: Vertical Vessel lower part replacement

(OP)
That is true
Option #1 is 20% cheaper.
One of the advantadges that I see for option #2 is to work in the workshop in front of option #1 in the field and Job can be stopped by wind or rain. July is a cold season and  windy in south southamerica.
The other advantadges  for #2 is a better alignment in horizontal position.
I agree that almost all the jobs that involve a replacement of part of a tower is like option #1,but that is a normal replacement when you replace the upper part.
Regards

 
 

RE: Vertical Vessel lower part replacement

What is the material?

What isd the wall thickness?

What are the  NDT requirements?

RE: Vertical Vessel lower part replacement

(OP)
What is the material,thickness,NDT?

Upper sector is 285 C t=10 mm

The prefabricated lower part is 516 70 cladded with 3mm 316L, there is a transition ring in CS just to weld P1 to P1 with t=12mm

NDT: PT, MT-100% X-ray for the joint of both sectors

Added herein is a pdf files with the prefabricated lower part
 

RE: Vertical Vessel lower part replacement

Similar to others noted... I've done both on the same turnaround.  Option 1 for a similar vessel size that you noted and Option 2 with a smaller vessel (30' x 30" diameter).  

The same questions apply to those noted (when, where etc.).  Now as far as quality... depending on the contractor, location, etc. etc. you can get the same quality as far as vessel construction is concerned on site or within a shop.

 

RE: Vertical Vessel lower part replacement

bernoullies123 is exactly right on the quality of welding.  Good ones are good, indoors or out.  Unless you enjoy repairs, and sometimes repairs of repairs - R/2's, do not choose your welding/boilermaker contractor by price alone.

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