In the coker unit that Ive been involved we have installed this kind of safety valve, they are working properly, I dont know if there are some problem with the minimum temperatura for this type of material (bellow), only for reference
Tag Number
P&ID Dwg. No.
Service
Coke Drum
Line No. / Equip. No.
Full / Semi / Base Nozzle
Semi
Safety or Relief
Relief
Conv. or Bellows
Balanced Bellows
Bonnet Type
Closed
Size: Inlet |Outlet
12 INCH
12 INCH
Flange Rating / Scrwd: In | Out
900#
900#
Flange Facing
RF
RF
Body and Bonnet
5 Cr – 1/2 Mo A217 / 304 SS
Seat and Disc
316 SS
Resilient Seat Seal
N/A
Guide and Rings
ASTM A297 Gr. HE / 316 SS
Spindle
416 SS
Spring
Alloy Steel
Bellows
Inconel 625
Note (**)
Cap: Screwed / Bolted
Screwed
Lever: Plain / Packed
No
Test Gag
No
Vent with Bug Screen
Yes
Bonnet / Spring Coating
Aluminized
Manufacturer
Model No.
12 V 12
Outline Dimensions
Certified Dimension Outline
1.
Two relief valves required for adequate capacity
Code | Stamp
ASME VIII, UV
Fire / P.F. / B.D. / C.W.F.
B.D. During Max Quench
Other
Fluid and State
Hydrocarbon Vapor / Steam
Discharges To
Coker Blowdown Drum
Required Capacity
167747 lbs/hr (Note 1)
Mol. Wt. or Oper. Spec. Grav.
18.02
Press.: Oper. | Set
psig
659660
661662
Temp.: Oper. | Release
F
825
825
Design Press.
psig
Temp
F
681682
890
Constant
707708
Center Center
713714
Center Center
Back Press.
Variable
13 (Note 2)
psig
Built-up
749750
Total
28,0
% Blowdown
779780
% Allowable Overpressure
787788
Overpressure Factor
1.16
Compressibility Factor
1.0
Ratio of Specific Heats
1.28
Oper. Viscosity
cP
0.02
Wt. % Flash | MW of Vapor
Barometric Press.
psia
14.689
915916
Center Center
Calculated Area
in
70.64