EJMA Section 4.10.2 provides an empirically derived formula for internal sleeve thickness as follows:
tmin = t(based on diameter) x (V/100ft/s)^2 x (L/18")^2 x E300F/Etemp
where:
t is .06" for 26" to 48" diameter (my particular case)
V is fluid velocity if greater than 100 ft/s
L is length if...
TugboatEng,
The problem with burying anodes and/or providing impressed current in the soil adjacent to the 6 foot deep, 60 foot diameter, massive concrete foundation, is the unknown conductive characteristics of the concrete.
Burying anodes in the wet sand under the floor plates would require...
TugboatEng,
I was intending to bury anodes in the wet soil surrounding the concrete foundation and run copper conduits to the tank shell.
Stray currents resulting from electrical potential would be routed from the aluminum tank to the magnesium to the soil rather than from the aluminum tank to...
TugboatEng
Are you suggesting that the gap between the sand bed and aluminum plate is the crevice?
None of the corrosion cavities is located at a floor seam weld or the fillet welded backing bar where you might find a crevice.
Wikipedia states the following:
"For a given crevice type, two...
Ultrasonic floor thickness measurements found 20 sites of galvanic corrosion around the perimeter of the tank.
A typical corrosion site comprises several square inches where thickness dropped abruptly from 0.5" to less than 0.25" with localized pitting thicknesses of approximately 0.125".
The...
TugboatEng,
Unlike most metals, aluminum oxide density is larger (3.96 g/cm^3) than the parent (2.7 g/cm^3), so that should mean that the corroded mass would occupy less volume than the parent.
TugboatEng, LittleInch and itsmoked,
The 4"dia aluminium steam heating coil is u-bolted to 2 foot high pedestal supports welded to the floor plates. 4 inches of sand is what lies beneath 96% of the floor plates - except in the area near the perimeter where it was washed out during the leak...
LittleInch
Sketch is attached as requested.
Heating steam, condensate and Demin supply pipes cannot be disturbed, which is why a 6 foot deep somewhat cylindrical slab or foundation was required to prevent frost heaving...
FacEngPE,
The examination report did not mention any other surface pits, therefore I am inclined to think that these must be dirt particles.
If more detailed UT scans of the perimeter floor plate do not detect pits on the underside I will advise a fillet welded patch per API 653 and...
In the last photo I posted there is a dark area on the aluminium shell directly above the leak, which could be explained by maintenance activity or it could be related to the 'event'.
Kiribanda,
Cathodic protection is not shown on drawings and after 50 years of service I suspect a sacrificial anode may be depleted, so I agree that galvanic corrosion is likely the cause if galvanic corrosion also disabled the grounding cable.
The curious thing about this corrosion pit is its...
Another Picture of the hole is attached.https://files.engineering.com/getfile.aspx?folder=be925516-3a78-4bb8-90fa-df0b29f4c75a&file=Hole_in_Floor_Plate.docx
FacEngrPE
I have attached a photo of the floor plate hole (it seems you can only upload one at a time). It is circular and appears to have straight sides all the way through the thickness. A borescope video and a replica of the hole is planned.
The floor is 1/2" thick ALCAN 5083-H12A, tank...
Ground cable and hole pictures are attached.https://files.engineering.com/getfile.aspx?folder=e951f5c0-4238-43d9-9dad-2b001cc5e449&file=Grounding_Wire_(3).JPG
thread238-153684
A 50 ft dia x 34 ft high aluminum demineralized water storage tank located outdoors began leaking from the floor at a single location on the perimeter in March.
After draining, internal inspection revealed a 1/2"dia hole in the floor plate approximately 6 inches inboard from...
TugboatEng,
During a mock-up I found a problem with the proposed setup.
The CLO cover is flat rather than cone-shaped and the tube fitting protrudes a little allowing air bubbles to accumulate around it.
The negative pressure in these bubbles is equal to the head of oil in the CLO, which is...
TugboatEng,
Actually, the CLO + TRE would automatically maintain the level in the bearing oil reservoir - like a hummingbird feeder.
The TRE would be large enough (3 USGAL) to avoid in-service top-ups and only require re-filling when the motor is off-line for other maintenance.
TugboatEng,
Lubricating oil is constantly being lost from the bearing housing reservoir past shaft seals.
There is no possibility of capturing and recycling as you suggest.
