Crude storage tank w/ internal floating roof, radar stilling well design issue

[stewbaby]

We have a crude storage tank with internal floating roof that was recently constructed with a stilling well for the radar. The stilling well was installed without slots along its length like a gauge pole has (it is just open near bottom of the tank and has a small vent hole near where it meets the roof). Needless to say, without the ability for the crude to enter and exit the stilling well along the length of the well, as the level in the tank rises and falls with crude existing and new crude coming in, the gravity variations between what is in the stilling well and what is in the rest of the tank are starting to cause significant variations between true tank level and what is read by the radar in the stilling well (up to 1' difference). Simple solution might be to move the radar to another nozzle and just shoot the internal floating roof (but it is a cable suspended roof and this also wouldn't allow us to verify / alarm if the level goes below the IFR low leg position). Thinking the only option to correct the stilling well is take the tank back out of service, clean and cut slots in the stilling well. Anyone dealt with this before? Any off the wall ideas?

 

[bimr]

1. If you install an observation port on the roof manhole, you can shoot down through the manhole. The observation port should include a valve so that the glass can be cleaned.

2. You can install the radar unit to shoot the roof surface.

3. You can also install a pressure transmitter on the side of the tank.

 

[IFRs]

You might be able to pull the pole out depending on the support connection under the IFR, then slid a new slotted pole in. Might be tough to hit that small hole though. You can shoot the deck but even if that were good, can you do custody transfer without hand dipping?

 

[stewbaby]

All movement is intercompany so custody transfer accuracy isn't needed. The stilling well support legs (2x2 angle) are welded to the tank floor so even if we could wash off the roof weld, we'd still be attached their. Shooting the roof till the tank is later cleaned and the well replaced looks to be the only option.

Brain storming...wonder if there is some way to 'hot tap' or slice the sides of the pipe in place??? Hydrocutting? Fill it full of water and freeze / burst it open? (ok, I'm getting silly now).

 

[IFRs]

Typically, I don't connect anything to both the floor and roof of a tank because of settlement issues. The lower mount allows movement. Apparently this was not done?

 

[stewbaby]

Right, repad on floor with angle welded directly to it and angle welded to stilling well. Stilling well also seal welded where it goes thru the roof. See your point on differential settlement / uplift.

 

[IFRs]

You may be able to do this:
Get a small dual acting hydraulic cylinder - think Enerpac
Put tapered pointy things on the cylinder and the piston.
Lower it down
Energize it and let it poke holes on both ends
Reverse the pressure and hope the pointy end things do not get stuck
Lower and repeat
The holes will flare outward, must not bind up on the IFR seal plate
Try it first!

 

[stewbaby]

I see where your going...not a bad idea to try in the maint shop and see.

 

[JStephen]

Note that if you have a water bottom in the tank, then you can wind up with nothing but water in the gauge pole while the tank is mostly full of oil with that arrangement.