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Coating for storage tank bottom plate

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Adilmk

Mechanical
Apr 18, 2016
1
RO
Dear Experts,

Here by request your valuable suggestion for my queries.

We have an upcoming Crude oil storage tank to be Coated. The diameter is 37 meter and it has an height of 12 meter. client has requested us to to sand blasting first to remove coating from the blast, then we undergo NDT tests. Now it took two months for this process and all the NDT and repair work has been accomplished now its turn to blast again and coat the bottom plate. This is storage tank with floating roof and legs. Client requested to do complete bottom plate painting with only one coat paint up to a shell level height of 30 cm. we are using HEMPEL 85671. Now there are few suggestions required from the experts regarding the coating procedure for this tank as follows.

1. As this did is quiet big, we have available only two sets of blasting machine and we start blasting around 7Am to 1PM. after 1PM client representative visit for blast profile check.
2. How to blast and paint this area on the same day. One of coating engineer when discussed through phone , he said to blast possible area on the day, blow the used grit to non blasted area. then before painting mask the edges of the blasted area for coating and do coating inside the blasted area.
3. then the next day, remove the masking tape of 2" and start continue with the same area and before coating sand down the edges to merge with the new coating. in this case, again when we paint the area does at the end the DFT going to be higher? how to protect the area at the edges from dry spray falling over the old painted area. if we put some cover, does this going to create a line on the painted area at the edges??
4. regarding floating roof legs, suggestion was to jack up and do blasting and painting. how to cover the area completely when the jacks are inside the tanks.

can somebody explain clearly the procedure for bottom plate, especially we have problem with the dft at the roof leg area. as we need to paint the leg, the dry spray falls near the area and create more dft.

thank u
 
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Dear Adilmk,

At first I have certain points or queries to you.

1. What is the required DFT? For Eg, if 300 microns, in how many coats is it applied?
2. It is not a good practice to blow out the dust and abrasive inside a tank. So use some vacuum cleaning methods.
3. What is the maximum permissible DFT stated by the manufacturer?
4. Do you need a holiday test after completion?
5. Are you an inspector or supervisor?

CocoE
 
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