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BENEFITS OF VARIABLE SPEED DRIVES FOR SUBSEA … · benefits of variable speed drives for subsea...
Transcript of BENEFITS OF VARIABLE SPEED DRIVES FOR SUBSEA … · benefits of variable speed drives for subsea...
BENEFITS OF VARIABLE SPEED DRIVES FOR SUBSEA PRODUCTION AND WELLHEAD HYDRAULIC POWER UNITS
METHODS OF SUBSEA HYDRAULIC SUPPLY PRESSURE CONTROL
Options for pressure control of subsea hydraulic systems:
1. Gap Control – On‐Off Control of Electric Motor Driven pumps
2. Pressure Regulation – pressure reducing valves
3. Gap control with variable speed electric motor driven pumps
TYPICAL SUBSEA LAYOUT
SUBSEA HYDRAULIC SYSTEM
SUBSEA HYD SYSTEM SCHEMATIC
SUBSEA HYD SYSTEM – PHPU SCHEMATIC
SUBSEA HYD SYSTEM – SCM SCHEMATIC
SUBSEA HYD SYSTEM – PHPU, GAP CONTROL
SUBSEA HYD SYSTEM – PHPU, GAP CONTROL
• Simplest, lowest cost• Minimal internal leakage• Higher accumulation• More frequent pump starts
SUBSEA HYD SYSTEM – PRESSURE REGULATION
PRESSURE REGULATION
Sectioned Pressure Regulator‐ Control Spring‐ Sensor (piston)‐ Vent Seat‐ Main Valve Seat
Variable outlet pressureMinimum = Set pointMaximum = Internal relief settingOutlet pressure within the min/max is dependent on relative internal leakage of regulator and downstream components.
PRESSURE REGULATION
• Highest internal Leakage• Higher maintenance• Higher variation in pressure• Allows independent pressure control
SUBSEA HYD SYSTEM – GAP CONTROL WITH VSD
GAP CONTROL WITH VSD –SPEED/FLOW v PRESSURE
GAP CONTROL WITH VSD • Lowest pressure variation• Least pressure cycling system fatigue• Lowest maintenance• Lower accumulation
ACTUAL PRESSURE TRENDS DATA – 3 OPTIONS
BENEFITS OF VSD DRIVEN PUMPS FOR PHPU’S
Criteria Single Speed Electric Motor Driven Pump (Gap control with or without pressure regulation) Variable Speed Electric Motor Driven Pump
Pump starting Motor starts abruptly at maximum speed Soft-start capability.
Pressure spikes on start up High Low
Frequency of Pump Starts High Low
Flow rate Constant at the maximum flow irrespective of demand. Variable to match demand
Accumulator Capacity Required High Low
Pump Starting
BENEFITS OF VSD DRIVEN PUMPS FOR PHPU’S
Criteria Single Speed Electric Motor Driven Pump (Gap control with or without pressure regulation) Variable Speed Electric Motor Driven Pump
Output Pressure Fluctuation(without pressure regulation)
High.1.0 ~ 2.0 MPa
Low. 0.2 ~ 0.5MPa
Output Pressure Fluctuation(with pressure regulation)
High.1.0 ~ 2.0 MPa
Low. 0.2 ~ 0.5MPa
Pressure Variation
BENEFITS OF VSD DRIVEN PUMPS FOR PHPU’S
Criteria Single Speed Electric Motor Driven Pump (Gap control with or without pressure regulation) Variable Speed Electric Motor Driven Pump
Internal Leakage(without pressure regulation)
High Low
Internal Leakage(with pressure regulation)
Very High Low
Component Fatigue High Low
Maintenance High Low
Space envelope High Low
Life cycle cost High Low
Internal Leakage, Maintenance, Space envelope, Life Cycle Cost
VSD SYSTEM DESIGN CONSIDERATIONS
• Motor cooling at slow speed.
• Consider oversizing motor so there is adequate cooling for motor running continuously at slowest speed for worst case ambient conditions.
• Electric motor supplier can provide motor simulation data
• Adequate motor overload and thermal protection – thermistors
• Filters to remove harmonic distortion
• Shielded power supply cables with 3 symmetrical grounding wires from VSD to electric motors to minimise Radio Frequency/Electro Magnetic Interference EMI/RFI
• Parameter set points on VSD will need adjustment for optimum performance and monitoring
Thankyou for your interest.
Questions welcome.