Blowdown - Baker Hughes Consolidated 19000 Series Instruction Manual

XVI. Setting and Testing (Contd.)
Table 11: SetPressureMultipliersforColdDifferentialTestPressureatAmbientTemperature
Operating Temp.
°F
250
300
350
400
450
500
550
600
650
700
750
800
850
Table 12: Set Pressure Multipliers for Cold
DifferentialTestPressure
Degrees of Superheat Temperature
°F
100
200
300
400
500
600
700
800
Table 12 lists the multiplier to be used based on temperature
above the saturated temperature (degrees of superheat).
ColdDifferentialTestPressureForBackPressure
Compensation
When a conventional Series 19000 valve is to operate with a
constant back pressure, the cold differential test pressure is
the set pressure minus the constant back pressure.
Sample Calculations For Series 19000 safety relief
valves (refer to Tables 11 and 12)
Set pressure 2500 psig (172.37 barg), temperature
500º F (260.0ºC), backpressure atmospheric
Set Pressure .................................. 2500 psig (172.37 barg)
Multiplier (see Table 11) ............................................ X1.019
Cold Differential Set Pressure ....... 2548 psig (175.68 barg)
Set pressure 2500 psig(172.37 barg), temperature 500º
F(260ºC), constant backpressure 150 psig(10.34 barg).
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Multiplier
°C
121 1.003
149 1.006
177 1.009
204 1.013
232 1.016
260 1.019
288 1.022
316 1.025
343 1.028
371 1.031
399 1.034
427 1.038
454 1.041
Multiplier
°C
38 1.006
93 1.013
149 1.019
204 1.025
260 1.031
316 1.038
371 1.044
427 1.050
Operating Temp.
°F
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
Set Pressure ................................ 2500 psig (172.37 barg)
Minus Constant Back Pressure ............-150 psig(-10.34 barg)
Differential Pressure ...................... 2350 psig (165.13 barg)
Multiplier (see Table 11) ............................................ X1.019
Cold Differential Set Pressure ............ .2395 psig(165.13 barg)
Set pressure 2500 psig (172.37), temperature
100ºF (37.8ºC), constant backpressure 150 psig (10.34
barg).
Set Pressure .................................. 2500 psig (172.37 barg)
Minus Constant Back Pressure ............ -150 psig (-10.34 barg)
Cold Differential Set Pressure ...... 2350 psig (162.03 barg)
Set pressure 400 psig (27.58 barg) on superheated
steam, temperature 650ºF
(343.3ºC), backpressure atmospheric
Operating Temperature ............................. 650º F (343.3ºC)
Minus Temperature of
Saturated Steam at
400 psig (27.58 barg) ............................. -448º F(-266.7ºC)
Degrees of Superheat ................................. 202º F(94.4ºC)
Set Pressure .................................... 400 psig (27.58 barg)
Multiplier (see Table 12) ........................................... X1.013
Cold Differential Set Pressure .......... 405 psig (27.92 barg)
F. Blowdown
The blowdown for all Series 19000 valves is fixed. Do not
attempt to adjust the blowdown on these valves. Typical
blowdown is less than 10 percent. The blowdown under the
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Multiplier
°C
482 1.044
510 1.047
538 1.050
566 1.053
593 1.056
621 1.059
649 1.063
677 1.066
704 1.069
732 1.072
760 1.075
788 1.078
816 1.081