API 653 Bottom plate patching with square shaped patch

[Metallurgistrbi]

Greetings,

We have a tank where a patch is required near 3 plate junction in bottom. I was planning for a 600mm diagonal square tilted at 45 degree so look like a rhombus. I have 2 queries regarding this

1. The edge of Square patch(rounded to 2" at corner) tilted at 45degree sits directly on all 3 lap joints. Is that prohibited?. I searched in 653 but i could not find any prohibition!!!. So any inputs/reference could be helpful.

2. The corroded area is well covered by the patch. However, is there any minimum distance from corroded area edge to plate patch toe that should be maintained?. According to fig 9.13, there is a minimum 2 inch to be maintained, but it is given for plain plate patch and not for overlapping locations. And again any reference would be helpful

Thanks in advance for your replies

Regards

 

[HTURKAK]

Short answer,

1- It is not prohibited to use Square patch(rounded to 2" at corner) as long as the patch over three-plate laps extends a minimum of 12 in. in all directions .

2- The minimum distance from corroded area edge to plate patch toe 2- inch shall be maintained.




Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[Louisiana Inspector]

Take a look at API 653 Figure 9.13. This will answer your questions.

 

[Dhurjati Sen]

It seems you are going for a temporary repair.
When would you get a chance to carry out internal inspection of the tank again?
Is the corrosion in the product side or in the soil side?


DHURJATI SEN
Kolkata, India