Page 1 Accumulator Sizing Instructions Discussion The purpose of the accumulator system is to provide closing energy to all members preventer stack. This is usually done with a hydraulic system designed and built power to the equipment in 5 seconds or less to maintain the required pressures as Usable fluid volume is defined as the volume of fluid recoverable from an accumula accumulator operating pressure and 200 psi above the precharge pressure. The accu operating pressure is the pressure to which accumulators are charged with hydrauli to 1000 psi what is the usable fluid volume the accumulator bottle will deliver be of 3000 psi and 1200 psi. In the following spreadsheets cells with BLUE numbers require input, cells with YE and RED numbers are calculated values. In order to calculate usable fluid volumes within accumulators, the ideal gas law For example: Assume the total gas volume of the accumulator bottle is 10 gallons. Solution: Since the gas law formula requires absolute pressures, we must add atmo P3 = 1000 psig + 15 psi (atmospheric) V3 = 10 gal. (gas volume of Koomey 11 gallon nominal accumulator) P1 = 3000 psig (system working pressure) + 15 psi (atmospheric) At a pressure of 3000 psig the gas volume = V2 V1 = P3 * V3 / P1 = 1015 (10) / 3015 = 3.366 gallons (gas) At a pressure of 1200 psig the gas volume = V2 V 1 V 2 V 3 U sable F luid 40 gallons 12.8 gallons F luid level @ 300 psi F luid level @ 1200 psi F luid level @ 1000 psi 40 G allon s U sab le F lu id 3000 p sisystem APEXINDO
Transcript
Page 1
Accumulator Sizing
Instructions
DiscussionThe purpose of the accumulator system is to provide closing energy to all members of the blowoutpreventer stack. This is usually done with a hydraulic system designed and built to provide closing power to the equipment in 5 seconds or less to maintain the required pressures as desired.
Usable fluid volume is defined as the volume of fluid recoverable from an accumulator between theaccumulator operating pressure and 200 psi above the precharge pressure. The accumulator operating pressure is the pressure to which accumulators are charged with hydraulic fluid, usually 3000 psi.
to 1000 psi what is the usable fluid volume the accumulator bottle will deliver betwen the operating pressuresof 3000 psi and 1200 psi.
In the following spreadsheets cells with BLUE numbers require input, cells with YELLOW background and RED numbers are calculated values.
In order to calculate usable fluid volumes within accumulators, the ideal gas law formula P1V1 = P2V2 is applied.For example: Assume the total gas volume of the accumulator bottle is 10 gallons. If the bottle is precharged
Solution: Since the gas law formula requires absolute pressures, we must add atmospheric pressure
Subsea StacksFor sizing subsea mounted accumulator bottles, the addtional precharge pressure required to offsetthe hydrostatic head of the seawater column and the effect of subsea temperature should be considered.
The precharge pressure must be increased to compensate for cold water. The temperature compensatedprecharge pressure is calculated from the follwing equation:
Therefore, the usable fluid volume (per bottle) is = (8.352 - 3.366) = 4.986 or » 5 gallons
Temperature compensated Pprech = Original Pprech * (460 + surface Temp oF) / (460 + seabed Temp oF)
Surface BOP Control System Calculation Sheetfor Control Fluid and Minimum Accumulator Volume Requirements
Control Fluid RequirementsType Size Close (gal) Closing Ratio
API 53BOPS system should have sufficient usable Hydraulic fluid volume (with pump inoperative) to close and open one Annular type preventer and all ram-type preventer from a full-openposition against zero wellbore pressure .After closing and opening one Annular and all ramtype preventers the remaining pressure shall be 200 psi above the minimum recommendedpressure.
API Accumulator requirement
1 times all functions Close and Open
Annular Close/Open 40.99
Ram 1 Close/Open 21.52
Ram 2 Close/Open 21.52
Ram 3 Close/Open 21.52HCR Open/Close 0.78
106.33 GL
Triplex Pump 15HP 3/4 plungger triplex pump Model T
Flow 6.4 GPM
Air Pump Model UA8026-MFlow 4.6 GPM air pump #1
Flow 4.6 GPM air pump #2Total 15.6 GPM
Up to 2000Psi accumulator volume 107 GL
Time 107 / 15.6 = 6.86 mn
Up to 3015 psi (only electric pump) volume 143 GL Volume 143 - 107 = 36 GL to come up to 3015 psi
Additional time 36 / 6.4 = 5.63 mn
Total time 12.48 mn
Surface BOP Control System Calculation Sheetfor Control Fluid and Minimum Accumulator Volume Requirements
Control Fluid RequirementsType Size Close (gal) Closing Ratio
KUFPEC Accumulator requirement Exibit B section 2-5-14
1.5 times the closing of 1 Annular, 1 Ram and Open 1 HCR
Annular Close 23.58 1.5 35.37Ram Close 11 1.5 16.5HCR Open 0.4 1.5 0.6
52.47 GL
Triplex Pump 15HP 3/4 plungger triplex pump Model T
Flow 6.4 GPM
Air Pump Model UA8026-MFlow 4.6 GPM Air pump # 1
Total 11 GPM
Up to 2000Psi accumulator volume 62.5 GL
Time 62.5 / 11 = 5.68 mn
Up to 3015 psi only electric pump volume 83.6 GL
gallons Volume 83.6 - 62.5 = 21.1 GL to come up to 3015 psi
gallonsAdditional time 21.1 / 6.4 = 3.30 mn
Total time 8.98 mn
gallons
gallons
Rig 8 Accumulator remaining pressure after use of 52.47GL requiered by KUFPEC to close BOP
Subsea BOP Control System Calculation Sheetfor Control Fluid and Minimum Accumulator Volume Requirements
Control Fluid RequirementsType Size Close (gal) Open (gal) Closing Ratio
Annular Preventer #1 88 61(Note the opening and closing volumes of one annular only are required for this calculation.)Ram Preventer #1 17 16Ram Preventer #2 17 16Ram Preventer #3 17 16Ram Preventer #4 17 16Ram Preventer #5Other 1.7Total 157.7 125
Available control fluid volume from subsea accumulators
500 feetSurface Temperature ( ° F) 50 degreesTemperature at Seabed ( ° F) 40 degrees
3000 psia (usually 3015 psi)
1000 psia (usually 1015 psi)
11 gallons each
89 AccumulatorsActual surface precharge pressure required to compensate 1020 psiafor temperature (Pprech)
11 -1) ( 1 - 1223 / 3222.5 ) = 6.21
89 * 6.21 = 552
Stack Working Pressure (psia) = 3000 = 275Minimum Ram Preventer closing Ratio 10.90
or: = 1200 psi
11 -1) { 1222.5 - 1222.5 }1423 3222.5
4.80 gallons
89 * 4.80 = 427
Water depth at which control system will operate (Dw)
Closing / Size requirements.* The closing System must be capable of closing each Ram Preventer within 30 Sec`s* Closing time for Annulars must not exceed 45 Sec`s.
Tool PusherSubSea EngineerCo/Man
5"
18 3/4"
* Accumulator Working Pressure must be 3000 psi
* Precharge Pressure must be 1000 psi
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