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Frames Separation Technologies
Mechanical Challenges when Designing a Separator
D ynaflow Lecture 11
Presentation Frames Separation Technologies 2
Outline
– Introduction to Separation
– Oil/Gas/Water Separation basics
– Challenges and impact Separation on vessel design
– R&D and Testing trajectories, CFD
– Conclusion
Outline
Presentation Frames Separation Technologies 3
Outline
Outline
– Introduction to Separation
– Oil/Gas/Water Separation basics
– Challenges and impact Separation on vessel design
– R&D and Testing trajectories, CFD
– Conclusion
Presentation Frames Separation Technologies 4
The act of separating, or the state of being separated, or separate.
Introduction to Separation
Definition of Separating:
- Overboard water (separated to Environmental Specifications)
- Load on compressors/pumps (besides capacity also avoiding damage solids/liquids)
- Pipe line and downstream equipment capacity (sizing)
- Local energy utilization supporting Process (local)
• Why Separation in Upstream Oil and Gas Industry?
Separating main components, gas, oil and water to specification at the source
to minimize transportation efforts and loading on downstream systems
Presentation Frames Separation Technologies 5
• Frames has designed and fabricated upstream Process Separators for the Oil and Gas Industry for over 20 years.
Primary target process design criteria
1. Maximise separation efficiency
2. Minimize pressure loss during separation process
3. Maximize online availability equipment (robustness)
Secondary target design criteria
1. Minimize size (plot space)
2. Minimize weight (related to costs equipment and foundation)
3. Minimize investment costs (maximizing revenue on investment)
4. Minimize delivery time (minimizing time revenue on investment)
Introduction to Separation
Presentation Frames Separation Technologies 6
Separation of the flammable content takes place under elevated pressure
- Law requirements for pressurized equipment (PED/CE/ATEX/….)
- Design code requirements (ASME/BS5500/Rtod/AD/EN13445/….)
- Client Pressure vessel specifications
Separating enhancers (Process Internals)
- Designed for separating purpose
- Mechanically considered Non-pressurized (pressure drop few mbar)
- Installed/removable trough man way (generally 24” ~ 600mm)
Introduction to Separation
Mechanical impact a process design has on the separating equipment
Presentation Frames Separation Technologies 7
Outline
Outline
– Introduction to Separation
– Oil/Gas/Water Separation basics
– Challenges and impact Separation on vessel design
– R&D and Testing trajectories, CFD
– Conclusion
Presentation Frames Separation Technologies 8
Separation principles of FST are based on physical properties of process flow
Separation principles
Oil/Gas/Water Separation basics
Stokes-Law small partials
1. Gravity (Δρ, µ)
2. Centrifugal force (m, arot)
3. Particle Size Difference (µ)
Presentation Frames Separation Technologies 9
Gas/Liquid Separation
Separation of liquid components out of gas stream
– Vessel Inlet
Pipe
Deflector
Inlet device
Vane type
Cyclonic inlet device
Dyn
amic
pre
ssure
Vessel Inlet
Oil/Gas/Water Separation basics
– Between Inlet and Outlet
Knock out from gas flow
Gas Flow Baffles
Between Inlet and Outlet
– Vessel Gas Outlet
Pipe
Outlet Deflector
Wire Mesh Pad
Vane type mist eliminator
Cyclonic outlet device
Dyn
amic
pre
ssure
Vessel Gas Outlet
Presentation Frames Separation Technologies 10
Liquid/Liquid Separation
Separating of different liquids from each other
Dyn
amic
pre
ssure
– Vessel Inlet
Cyclonic inlet device
Vessel Inlet
Oil/Gas/Water Separation basics
– Separation Compartment
Open Settling (Stokes)
Flow Baffles
Coalescence enhancers
Separation Compartment
Dyn
amic
pre
ssure
Droplet Growing
Coalescing filters
Coalescing plate packs
Wire mesh agglomerator
Coalescence Internals
Presentation Frames Separation Technologies 11
Outline
Outline
– Introduction to Separation
– Oil/Gas/Water Separation basics
– Challenges and impact Separation on vessel design
– R&D and Testing trajectories, CFD
– Conclusion
Presentation Frames Separation Technologies 12
• After process design, interaction with the mechanical design takes place
Challenges and impact Separation on vessel design
Process Design Mechanical Design Vessel
Separation length Tan-Tan Length Vessel
Inner Diameter Vessel Outer Diameter Vessel
Inner Diameter Nozzles Nozzle Sizes
Location and type of Internals Internal design Vessel
Process Internals Design
Segment sizes due to access
Installation sequence
Fastening principle
Weight limitation (<25kg)
Presentation Frames Separation Technologies 13
• Some limitations due to Mechanical requirements
Challenges and impact Separation on vessel design
Locations and size of nozzles
Weld to weld distance (space)
Needed reinforcement due to pressure
Code limitations (opening : shell : head)
Location external piping connection
Other Mechanical considerations
Loading external piping
Heat Treatment (stress relieving)
Mechanical loading in internals
Choice of materials
Presentation Frames Separation Technologies 14
• Weld to weld distance (space)
Challenges and impact Separation on vessel design
- Lowest level nozzles (small size vertical separators)
- Lowest man way (short vertical separators)
- Series of level nozzles in separation compartment (3 phase separator)
Presentation Frames Separation Technologies 15
• Needed reinforcement due to pressure
Challenges and impact Separation on vessel design
Due to flow velocity and dynamic pressure process determines Inside Diameter nozzles
- Standard schedule pipes reinforce to the inside
- Higher pressure -> smaller ID pipe
- Self reinforced, with fixed ID reinforce to outside
- More weld pace needed
- Possible problems with discontinuity connecting piping
Presentation Frames Separation Technologies 16
• Code limitations (opening : shell : head)
Challenges and impact Separation on vessel design
Difference in design codes pressure vessels limiting large nozzles in heads and shells
- Possible nozzle location in knuckle zone of a formed head
-Way to calculate nozzles loads (FEA analyses)
Presentation Frames Separation Technologies 17
• Loading external piping
Challenges and impact Separation on vessel design
Nozzle loadings external piping transferred to support vessel
- Large nozzle loadings can impact saddle design and vessel supporting
- Transfer all loadings onto saddle supporting
Presentation Frames Separation Technologies 18
• Heat Treatment (stress relieving)
Challenges and impact Separation on vessel design
Fabrication sequence
- Stress relieving according to code requirements can impact the fabrication
schedule when it comes to welded internals
Possible problems with Heat Treatment ferrite internals
- Temperature to 650 °C can cause buckling of thin SS 316L internals
1. Dimensional unreliability
2. Cracking of weld due to deformation stress
Sigma Phase
- The delta ferrite can transform to a very brittle phase “sigma
phase”, if heated above 550°C for very prolonged periods.
Presentation Frames Separation Technologies 19
• Mechanical loading in internals
Challenges and impact Separation on vessel design
- Internals designed as non-pressure parts.
- Flow impact can have great effect on the internals design and it’s supporting
σyield >> σmat flow
fnat > fflow
The natural frequencies cyclone assembly including supporting calculated.
Max rotating frequency fflow = 2,567 Hz
Total Liquid Flow 1050 MB/d (7000 m³/h)
Gas flow 95 MMSCFD (2.5 MMNm³/d)
Presentation Frames Separation Technologies 20
Challenges and impact Separation on vessel design
Max. Displacement:
7 mm
Max. Stress:
164 MPa
Max. Stress:
64 MPa
Max. Displacement:
2 mm
Several supporting studies
Presentation Frames Separation Technologies 21
Norm
alM
ode
1
Norm
alM
ode
2
4.89 Hz 8.86 Hz
7.4 Hz 11.6 Hz
Norm
alM
ode
2
Norm
alM
ode
1
Challenges and impact Separation on vessel design
Normal system modes calculation
Presentation Frames Separation Technologies 22
Norm
alM
ode
1
10,61 Hz
Eventual design based on studies
Challenges and impact Separation on vessel design
Presentation Frames Separation Technologies 23
• Choice of materials
When designing a separator and selecting the appropriate materials of construction, there is always
a balance between
Challenges and impact Separation on vessel design
Allowance/Austenitic-Ferritic/Alloys/ (HIC, NACE,SSC..)
High yield -> light design
Cracking/Microstructure/Properties change at Temp.
Strength of material
Corrosion/erosion
Weldability
Availability
Cost
Short delivery time
Short period revenue on investment
Exact choice of combination of the above highly depends on the market.
Flexibility is the key to success for a market attractive design
Presentation Frames Separation Technologies 24
Challenges and impact Separation on vessel design
• Using FEA for areas outside Codes
FEA used for situations where the common vessel code calculations do not
provide the confidence in the mechanical integrity.
Definition of the model is the key to the result
Presentation Frames Separation Technologies 25
Outline
Outline
– Introduction to Separation
– Oil/Gas/Water Separation basics
– Challenges and impact Separation on vessel design
– R&D and Testing trajectories, CFD
– Conclusion
Presentation Frames Separation Technologies 26
Improvement demand
R&D
Processdesign rules
Project Operation
• R&D on Separation Principles and Internals satisfying continuous changing demand
R&D and Testing trajectories, CFD
Lab andfield tests
Processdesign rules
CFD
In house software
Field experience Continuous
improvementof products and
systems
Main targets in R&D FST
1. Better separation efficiency
2. Less pressure loss during separation
Presentation Frames Separation Technologies 27
R&D and Testing trajectories, CFD
• Field Testing
Actual conditions at platform in the North SeaLiquid droplets sizes in Gas Stream around Separator
Impact on probe tip Droplet sizes measurement
Upstream/Downstream Probe Grade efficiency internals
Presentation Frames Separation Technologies 28
R&D and Testing trajectories, CFD
• Laboratory Research
Research on Axial Cyclone with university of Delft
– Gas/Liquid Separation
-0,5
0
0,5
1
1,5
2
2,5
3
-1 -0,8 -0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1
Dimensionless radial coordinate (-)
Dim
ensi
onle
ss v
eloc
ity (-
)
Laser Doppler Anemometry Velocity profiles
Phase Doppler Anemometry Droplet size distribution
CFD Modelling
Presentation Frames Separation Technologies 29
R&D and Testing trajectories, CFD
• Laboratory Research
Research on Inlet Cyclone with universities of Edinburgh
Liquid Flow Coalescer effect cyclone
Gas/Liquid Flow Foaming effect
Gas/Liquid Flow Gas/Liquid Separation
CFD Modelling
Presentation Frames Separation Technologies 30
Case 1: Elliptical head.Pressure drop: 7.03e03 (Pa)
Case 2: Conical headPressure drop: 5.55e03 (Pa)
• CFD Analyses Pressure Drop
Impact the type of vessel head has on the pressure drop
– Pressure drop at outlet head gas flow
– Gradient in velocity profile flow
R&D and Testing trajectories, CFD
Presentation Frames Separation Technologies 31
• CFD Analyses Liquid Draining
Maximum drain capacity internal system
– Increase loading on internals
– Gas/Liquid separation limited by draining
R&D and Testing trajectories, CFD
Presentation Frames Separation Technologies 32
R&D and Testing trajectories, CFD
• CFD Analyses
CFD evaluating assembly internals in vessels
– Flow profiles– Loading areas on internals– Optimising assembly
Presentation Frames Separation Technologies 33
Outline
Outline
– Introduction to Separation
– Oil/Gas/Water Separation basics
– Challenges and impact Separation on vessel design
– R&D and Testing trajectories, CFD
– Conclusion
Presentation Frames Separation Technologies 34
Conclusion
• Conclusion
• When designing and fabricating a Process Vessel, Mechanical requirements constantly interact with the Process design
• Constant improvements demanded
• “Lessons Learnt” are essential to be secured
• Conservative industry where application of modern techniques and tools can be challenging to implement
• FEA is used more regularly to analyze the mechanical integrity of the system but mostly beyond the codes
• The criticality of our industrial application do not allow mistakes to be made
• Flexibility in solving at hand issues using al sorts of techniques are crucial
Presentation Frames Separation Technologies 35
Thank you for your attention