Shop-Assembled Storage Tanks

[WarFT]

Dear members,

Can we have a sump for a shop-assembled storage tank?
My case is 3.5m diameter vertical tank of 5m high.
The bottom is flat and my client has requested to have a sump.
Should i tell him that this not allowed by API? for this is not mentioned any where in appendix J and also in the design section under sump.

i am wondering whether it won't be a problem foundation wise...

Thanks

 

[MJCronin]

One of the largest sources of engineering errors is client questions, requests,hopes, wishes, last minute changes and general confusion.

I have been and always will be a strong advocate for client drug testing before accepting any work .....

A tiny sump will be a lot of work and expense .... ....Why not suggest a sloped (wedge shaped) bottom for this small tank ?

If the client has reconsidered and the tank has a lot of solids that need to be collected, suggest a cone bottomed tank ???

MJCronin
Sr. Process Engineer

 

[LittleInch]

Can you have a sump - I can't see why not, but at what cost will be up to the vendor.

should be relatively easy to cast a foundation with a sump in it the place the tank on top, cut a hole in the floor where the sump is and lower in a pre-made box and then weld the box to the floor plates.

A bit unusual and maybe they'll back off when the additional cost is advised, but if the client wants it and understands the impact then why not, it's his tank and his money.

Adding it on site will be a lot easier than in the shop with all the issues of transport, lifting the floor off the floor of the shop and getting the foundation to match the sump location.

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

 

[JStephen]

I don't see that it's prohibited, but it would turn into kind of a mess on the detailing.
Note that Annex J assumes "complete shop assembly". If you do some of that work in the field, you'd need to coordinate how and when testing gets done.
Ask them if a 3.5m diameter sump would be okay, that would be simpler.

 

[WarFT]

Guys, the tank will be fully assembled/welded in workshop including the sump (if i include it). it will then be lifted and laid on its foundation on site.
hotworks on site is not allowed; this is why we are fully assembling in workshop.
the foundation is planned to be there already waiting for the tank.

MJ Cronin - Appendix J talks about flat bottom for fully assembled tanks. this is why i am not going for bottom cone as i understand that it will be a problem for a cone bottom with a risk that the foundation might not exactly match the exact tank slope and the bottom might not then be fully supported by the base underneath it.

if i include a sump, i'll have to add it in workshop; and the foundation/tank base will have hole waiting for the tank.
i am wondering whether it will be a problem as i cannot see how the hole made in the tank base will exactly match the recesse required by the sump, hence the sump bottom and side walls might not be completely held by the compacted or concrete foundation while in operation.

 

[LittleInch]

OK, so still feasible.
It would need some fairly tight dimensional control over the sump placement and the concrete base, but it's only a 3.5m diam tank so can't be that hard.

A margin of say 10-15mm all round shouldn't make it an issue in terms of the sump essentially free hanging.
If there is a concern then lay into the base say a 1" grout injection and vent line into the sump opening and then carefully pump in some very liquid grout once you've placed the tank on top of the concrete.

All seems a bit excessive for such a small tank....

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

 

[IFRs]

The no welding in the field complicates things. The sump needs to be properly supported and an air gap may promote corrosion. You could make the sump hole 2" larger all around and install threaded couplings in the sump flange to pump grout or perhaps epoxy into after the tank is put on place. You may have to bring in a large weight to keep the sump from floating while the filler hardens. It may be possible to include in the foundation pour 2 or 3 PVC pipes leading to the sump cavity which you would use to pump grout into the sump area and then backfill to the outer edge.