API-650 11th Ed, Add 1 - Table 5-1b

[richay]

Paragraph 5.3.5 states that when 6mm plate is specified, then 0.236 inch plate can be used with US Customary units. But does this mean the 1/4 inch values that used to be in Table 5-1b must change to 0.236? All the other values are standard US thicknesses. But 0.236 in this table? Could this be a misprint?



Richard Ay
COADE, Inc.

 

[IFRs]

In the earlier draft versions of this document, it was 1/4". I believe it should be 1/4". My opinion only.

 

[JoeTank]

Dude, It's simply allowing 1/4inch and 6mm plate to be used interchangeably. Ditto for 3/16" and 5mm plate.

Joe Tank

 

[ndeguy]

Actual conversions (1" = 25,4 mm)

1/16" = 1,5875 mm
1/8" = 3,175 mm
3/16" = 4,77 mm
1/4" = 6,35 mm
1/2" = 12,7mm


So the "in-the-head" conversion values (1/16" = 1,5mm thus 1/4" = 6mm and 1/2" = 12 mm) gives less than 6% undershoot - each engineer needs to decide if that is fit for their purpose.

Better is

40 thou = 1 mm
100 thou (1/10") = 2,5 mm
1000 thou (1") = 25 mm

So 1/4" (250 thou) = 2,5 mm * 2,5 = 6,25 mm

as this gives less than 2% undershoot.


Hope I have not clouded the issue!!!


Nigel Armstrong
Lloyds Register
Independent Verification Body Surveyor

 

[JoeTank]

richay,
In my opinion Table 5-1B in API-650, 11th Edition, Addendum 1 is correct as shown. This covers the case where a purchaser allows 6mm plate to be used where 1/4" would normally be shown. Alternatively, it could have stayed at 1/4" and used a footnote similar to that shown in 5.6.1.1 (footnote 3). Both work for me.

Joe Tank