Gas Blow-by scenario through a liquid dump valve per API 520
sketch2022-09-22nrb
States:
1. Process pressure and temperature
2. Close to state-1
3. Lower pressure than state-2
STATES
1
2
3
4. Lower pressure than state-3 (Fanno flow)
5
4
5. Atmospheric (pressure at elevation above mean sea level)
VTA
"long"
0 PSIG
1 PSIG
Design:
DUMP
A. Piping (ASME B31.8) DP and DT
A
B
C
C
D
E
B. PBV (ASME Sect. VIII Div. 1) MAWP and DT
DESIGN
285 PSIG
1 PSIG
1440 PSIG
285 PSIG
C. Piping, same as design-A
D. Tank (UL 142) DP and DT
E. Vent (API 2000)
EXAMPLE DEMARCATIONS
Notes:
• Use design conditions (not normal operation, not abnormal operation).
• Consider Joule-Thomson effect and gas compressibility factor (automatically
performed by Aspen HYSIS).
• Immediately upstream of state-3 there might be a small orifice restriction.
It's not shown since it's optional.
The design is similar to a tapped spectacle
blind (per ASME B16.48).
• A prior spec. I've used (change X.XXX per results of hydraulic modeling, for
which this is a *square* edged orifice): ORIFICE PLATE, 2 IN. NOM., TO SUIT
ANSI 600 CLASS, OUTSIDE DIA. 4.25 IN., BORE DIA. X.XXX IN., 0.25 IN. THK.,
ASTM A240, GR. 304, SERRATED FINISH PER ASME B16.5 PARA. 6.4.5.3 AND
6.5.6, MFR. DELTA MACHINE, MTRS REQ'D
• A vendor cutsheet with all the lookups:
paddle-blind-thickness-chart-asme-dimensions.pdf