tank construction

The standard API 650 will guide you for this job.

we normally construct using API650 or 620, but in this case, it's a tank for common purpose. So, I'd rather not use the more severe API...

Besides the Tank standards, there are environmental codes and local building codes. You will have to look them up in your area. Good practice and most codes require a spill/catch basin be under the tank that can hold all the contents of the tank in case of a leak or rupture.

If the contents are flammable, the tank should be grounded.

Here is a typical guide for home fuel tanks from Nova Scotia. There are many other standards that depend on intended use and contents.

thanks for your reply

you're right about the local rules and codes.

I ought to clarify the matter.

The tank will be installed in a spill bassin of 15000m³, the bassin houses some 18 tanks, and this one (90m³) will be added, so leak etc is covered. The idea is to use a second hand tank for urea solution 40%. The product is considered 'dangerous' and the tank should be constructed following international, european or codes of good practice. By 'good practice' I understand that the tank is checked up on thickness, and material; a calculation note made up covering these items and presented to a 'notified body' for control. Acceptance for use will include a hydraulic test (tank full plus 25mbar).

The question was in fact about getting some hints on calculating the tank.

is contacting the manufacturer out of the question. they won;t know it is 2nd hand.

If this is an atmospheric tank you will not test as full + added pressure. Full + visual inspection is good enough. 15 psi is the ASME threshold to call it a pressure vessel. Do some baseline NDT for the service to establish remaining life. Map the tank if you don't have a drawing available. (create your own drawing) Do visuals and take pictures on some of the "t" intersections internally along the wall, UT floor and walls, nozzles. Pay special attention to the floor to wall joints. Inspect splash guards, fill tubes, etc. Vacuum box the floor joints with soapy water. #1 is do all this safely, do not go in without knowing it is properly prepared for entry, meaning air purged, cleaned and entry procedures in place. Urea is a fertilizer, it is also used for SCR units. Have fun and be safe!!!

Be careful if the tank holds oils it could fall under the SPCC rules for spill prevention, containment and countermeasures. Also flammable liquid tanks could be another one such as PSM. Most companies require following the API standards as a minimum for designing and calculating the required wall thicknesses and such for an atmospheric tank. On many instances one may require extra corrosion allowance to be added to the minimum wall thickness of the tank beyond what the standards dictate as well. I look over the inspection and repair of 635 different tanks where I work and even the ones that are holding water have to be built and or repaired by the API 620/650/653 or ASME codes It is very nice to have the documentation that shows you did the work by the standard when something goes wrong later and a problem occurs. Thier is also the added safety factor of knowing things are up "to snuff" so to speak as far as codes standards and regulations go.

pipewelder

I believe it would be easier to certify the tank for its new intended use rather than apply a code. Reverse engineer the tank...Decide on contents and use i.e. specific gravity, pressure, vacuum, temperature, seismic zone, wind load, etc, etc....Once you have the parameters and minimum design standards, you can certify the tank is suitable according to use. Or rather Is the tank suitable for the application...Be careful when considering for hazardous applications...You do not know the joint efficiencies, weld quality, previous stresses incurred, etc. you may want to do some NDT.