ASME B16.48 blank thickness

[auzie5]

I have a NPS 10 line that is purged by a NPS 1 line. The piping configuration is a NPS 10 blind tapped with a NPS 1 nipple valve assembly.

To hydro test the NPS 1 purge piping system, I have installed a line blank between the tapped blind and the adjacent NPS 10 flange.

My question is, according to ASME B16.48 (Table 4) an NPS 10 line blank needs to be 41.1mm thick. However, the blank is only seeing a force equal to the pressure x area of the NPS 1 purge line (which is 10 times less than if I was testing the NPS 10 side of the blank with the same test pressure).

Since I am testing through the NPS 1 line against a NPS 10 blank, can I combine the information in table 4 and size my plate thickness according to the NPS 1 requirements (i.e. 6.4mm thick)?

Here's a simplified overview:

CL900 Line Class
Hydro test at 22,960kPa

(for the sake of simplicity I've avoided using NPS dimensions)

inches mm m area (m^2) Pressure (kPa) Force (kN)
10.00 254.00 0.2540 0.05 22,960.00 1,163.40
1.00 25.40 0.0254 0.0005 22,960.00 11.63

 

[BigInch]

If only 1/1000 of a mm of fluid gets in between the crack, you've got full pressure to deal with.

Independent events are seldomly independent.

 

[auzie5]

Thanks BigInch! Yes you are absolutely correct! I have a NPS 10 spiral wound gasket between the NPS 10 tapped blind and the NPS 10 blank so the blank will actually see pressure over an area equal to the ID of a NPS 10 gasket even though I am feeding the line through a NPS 1 tapped hole through the NPS 10 blind.

Very much appreciate the insight.

K.D.W.