above ground tank erection

I can only tell you what I would use and this may not be the same for you. We would use a FCAW(flux core MIG) 70 series wire with a 75% argon/25% co2 back up gas and manually weld the verts and automatic weld the the circumferential seams. I would not start welding out the first circ. seam until I had the next shell section completely fit up. You can start the verts as soon as you get a few shell sections ahead on the fitting. The tank bottom is probably lap joints and it is going to draw some but you can limit this by getting it fit up completely before welding out and then by welding opposite areas to keep the pull in line. The thing about tank bottoms is that when you fill the tank the weight of its contents will flatten the bottom out if it has some warpage. All weld seam will warp somewhat and this is why you should have plenty of what I cal pull dogs (fit up brackets) and wedges to make the steel go where it should. Now the third question is very elementary. I would use scaffolding clips welded to the tank and then insert angle iron brackets made to fit into these clips. The brackets should have posts with eyes on them to allow a steel cable to run through them for a hand rail and a place to tie off to. Once I got the clips and brackets up I would then cover them with approved 2" x 12" scaffolding boards 2 boards wide. You should have enough scaffolding materials to make at least make three rounds of scaffolding around the tank (I would prefer to have enough to scaffold every weld seam) This stuff is pretty standard in the USA and most all tankies do it this way because it has proven to work fast and well. I have to say for you to be asking these elementary questions that I wonder if you should be trying to build a tank at all. I say this because tank building in the USA at least is a very competitive buisness and only the companies that really know tank construction are able to compete well. I assume this is the case in other countries as well.

I don't know what welding method you gonna use but I used to work on tanks and we always used stick process.

On a 1/4" (6mm) plate we used cellulose rod 3.15mm then:

1. During welding on both sides should use Key-Plates fixed to the shell plates with some ball pins through some nuts welded to the shell plates. Then use some more ball pins wedged between the key-plates and the shell plates either to push out or pull in the shell plates as required. These key-plates should be placed @ a foot from each other on the inside.

2. Use 2 off 6mm or thicker 2"x4" run-out plates on top and bottom edges of shell plates to tack them together (set 4mm gap between them and no bevelling) use 3 vertical down runs. Adjust the welding current to give you better than half way through penetration during the first run. Use the flicking method with the tip of the rod for the first two run and do a nice smooth draw down for your last (third) run. (Always make sure remove slag properly before the next run!) Then clean the back by electric gauge or can use angle grinder and repeat the same process 3 runs again. As long as the final run has a surface protrusion > 1mm is OK.

3. We used cranes because the shell plates were pre-bent in workshop and delivered to site and they were too heavy to lift by hand as they weighed close to a tonne each, and used self loading grip clamps on top edge for lifting.

The aforementioned key-plates were always on the inside to keep the pre-bent plates together prior to setting the gaps between them (using the run-out plates to tack them together).

The horizontal runs between the rings were done by LH (low-hydrogen) rod inside and outside however, may be the rutile rod is acceptable but it has almost half the tensile strength of LH. The gap again should be set to about 4mm and sometimes you can make the first run with cellulose to fill up the gaps, especially if it's not even.

I think the 9mm thickness is an over kill for the bottom plate if it is lying on the ground. What I saw was 1/4" would do just fine if it is welded on both inside and outside, for that we used the iron based flux rod (5.6mm) that I do not know the name of.

Remember - this is rated as a coded-welding job!!!

Make sure you know what you're doing because our welds were randomly x-rayed.

What do you wanna store in it, nuke waste? It won't be good for that!

I have not explained the Key-plates adequately but if you insist some other times. It is well after midnight here in the UK now.

Dear Sir,

The first two above referred to: answers, obviously come from reliable and knowledgeable boiler-makers/welders. Definitely abide by their skills and experience.

What I will add is that very often tanks are built in remote areas, where craneage and other safety issues are hard to come by.

In my past engineering experience the safest method of tank erection (short of the new techniques of : on-ground welding , and hydraulic lifting of the whole strake at a time ) is the water borne system.

This consists of welding the : bottom plates, then the first strake of the shell . In this partly built tank, all shell fittings and valves are fitted. Therafter either the roof trusses (if the tank does not have one , then a series of light frames are made secure onto empty steel drums inside the tank ). The floatation capacity of this frame is such that it can even use a short inverted V mast , to which an air winch is adapted.The whole thing is made to have the winching system exactly at the right lifting point ( see below). Where winds are strong it allows to be in the exact position at the most opportune moment.

Water is then pumped into the tank and the wheel spoke type of structure is then floating. When it nearly reaches the top of the first strake, and at the point where it will be doing the lifting of the individual (next) shell plate, it is temporarily anchored ( internally :to the shell plate) by means of blank " nuts " , "wedges " and "carrots ". This enables it to make the first lift. The lifted shell plate will be anchored temporarily and as described by others above with the use of "shims" and " wedges". These items are typical " true boiler -makers " tools of trade. The method is continued right around until closure of that strake.

Once all the strake has been secured with the "key plates", "carrots " "shims " and "wedges " Simple but safe "chairs " ( made from steel round rebars , and angles prepared on the ground are lifted , and simply hooked onto the external side of the shell plates . These are designed so that at the very least three levels of good timber planks scaffoldings can be made secure between each chair so that the "verts"or vertical welding as well as the external horizontal welding can be performed accurately and in all safety by the external welding crews . The chairs have open large washers welded externally so that two rows of safety ropes can be properly secured on the circumference of this temporary external scaffolding . If this is done properly it is almost entirely fool or accident proof.

As the previous , and obviously : boiler-maker/welder experts , have warned you : Do not play around . Go by the API Rules and more importantly get the best professional advice you can get on site.

NB The above water system is very safe IF you, or your Foreman , know what you are doing and do not have a crane. It is cooler in hot climates.In fact it checks out the reliability/integrity of the foundations . As well and at the same time fulfills the : hydraulic tests that are a necessity for any code be they : API,Lloyds, or Veritas.

One feature I found most compelling besides the safety of erection is that : in tropical hurricane zones , it eliminates the worry and concerns of partly finished shells that collapse with hurricane : winds if the retaining guys have been insufficient. That risk I have always avoided.

Labor Omnia Vincit

More questions than answers:

• What is to be contained in the <...storage tank...> and its temperature?
• What does the "for construction" issue drawing (which cannot be seen from here) say about it?
• How are the various components to be supported while the <...welding procedure...> is carried out?
• If <...welding...> is to be carried out on the inside, then what is the escape plan for those working inside it?
• How have similar tanks been erected at the facility and elsewhere?
• Etc.