ASME B16.48 Steel Line Blanks

[BCG1]

For hydrotesting pipe, I am using blanks (or skillets, pancakes, paddels, etc)to seal off at the flanges. Our company has standard tables in place for determining the wall thickness of the blank; however the numbers aren't jiving with the equation in ASME B31-3.

Some supplementary ASME material I found says that "blanks used for test purposes are not subject to these design standards.....often people test to 90% of SMYS"

Okay, so I plugged in 90% of SMYS and still can't confirm the values.

Anyone know what the excepted design standard (or equation) is for "test" blanks?

 

[rzrbk]

The thickness for blanks per the formula in 31.3 would be calculated for the design pressure of the system. (using allowable stress at design temperature from table A-1)

In general, a blank designed this way would be good for at least 1.5x the design pressure during hydrotest, provided the yield stress is not exceeded. (hydro pressure = design pressure x 1.5 x allowable stress at test temp / allowable stress at design temp)

 

[MJCronin]

BCG1...

Give us some specific examples from your tablec and we can take a look at them.

Consider posting this question in the "Boiler and Pessure Vessel" forum..

ASME B31.1 has slightly difrenet requirements for these blanks and the allowable stress values have changed over the years.

-MJC

 

[BigInch]

time machine?

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[jp1989]

Somewhat related....

Is there a difference between Spectacle Blinds and paddle blinds?

 

[MatieMan]

jp1989,
Paddle blind is a half spectacle, the full ring part. Advantages: less weight to handle and less space needed to install (so for the bigger sizes).

For calculation of thicknesses I also refer to formula in ASME B31.3.
Remark: corrosion allowance can be added on one or two sides of spectacle.