Allowable stress for B8M bolting

[Lucaclz]

Hi,

I am designing a valve closure bolting considering to use B8M bolts.

According ASME II, D maximum allowable stress at 38°C should be 130 MPa, but I am pretty sure that I can go till 138 MPa (done in past project, but I cannot find anymore the reference).
Does anyone have any reference on how to increase maximum allowable stress for B8M bolting in accordance to ASME code (B16.34)?

Thanks in advance.

 

[IdanPV]

For bolting materials the allowable stress is size dependent, and for size below 24, the allowable stress is 138MPa.

 

[Lucaclz]

In fact I am looking to a 2" bolt. So, no way to increase allowable stress above 130 MPa using B8M?