P&T Rating by ASME Application question 1

[Ltrujillo]

Hi,
I have three ASME Section I Safety Valves, rated for saturated steam service, with an ASME "V" stamping.
- 1st. valve is set 1,128 psi (drum) size 3”-600#RF X 6”-150#RF
- 2nd. Valve is ser 1,163 psi (drum) size 4”-600#RF X 6”-150#RF
- And 3rd. valve is set 934 psi (outlet of super heater) size 3”-900#RF X 6”-150#RF

The rated boiler is 250,000 Kg/h @ 1,040 psig @ temperature saturated steam on the Drum and the outlet of super heater is 880 psig @ 905°F approx.

My doubt is, the P&T rating by ASME select for these valves is the correct? Because this inlet flanged is of 600#RF and not of 900#RF for the 1st and 2nd valves. The base material flanged is WC6 and temperature class B & D how it are indicated.
All valves are Dresser with the follow models;
1st. 3-2745B-1-X-1WSC
2nd. 4-2765B-1X-1WSC
3rd. 3-2746D-1-X-1WSC

I wait for their soon answer
Thanks

 

[jte]

LTrujillo-

A 1 ¼ Cr-1/2 Mo A217 Grade WC6 material CL-600 flange at 600°F is good to 1210 psig and 900 psig at 900°F according to the 2003 edition of B16.5. Seems that the flange ratings are appropriate.

Next time consider posting this to forum794 (more mechanical type issues such as this flange rating question) or forum1203 (more flow / process type issues) to reach a more targeted audience.

jt