Eliminating Difficult Start-ups with State Based Controls
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1 Standards Certification Education & Training Publishing Conferences & Exhibits Automated Start- Automated Start- up of a Difficult up of a Difficult Process Process By Dustin Beebe, P.E. By Dustin Beebe, P.E.
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This presentation explains the benefits of automated start-up.
Transcript of Eliminating Difficult Start-ups with State Based Controls
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Standards
Certification
Education & Training
Publishing
Conferences & Exhibits
Automated Start-up of Automated Start-up of a Difficult Processa Difficult Process
By Dustin Beebe, P.E.By Dustin Beebe, P.E.
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Presenter
• Dustin Beebe, P.E.– Graduated from Arkansas with B.S. in Chemical Engineering– Joined ProSys in 1996– Earned Professional Engineer designation in 2001– Became CEO of ProSys in 2009
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Presentation Goals
• Brief Introduction• What makes processes difficult?• How to manage• Q & A
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About ProSys
ProSys is an innovative professional engineering firm specializing in the area of process control
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Engineering Services
Engineering Services include:• Basic Control• Advanced Control• Boundary Management• Alarm Management• Operator Interface • Dynamic Simulation• Many More…
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Issues that Affect Startup
• CSB - $10 B per year lost due to operator error• Aging workforce – experience is retiring• Variability in Operator expertise on shifts• Staffing levels• Prolonged start-up time• Excessive off-spec product• Equipment damage• Greater process complexity
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Total Automation Results
• Quicker startups (1/2 to 2/3 reduction)• Repeatable – like it’s on rails• Reduced errors and overshoots• Positive HSE impact• More Reliable • Less off-spec product• More benefits depending on situation
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Process Stability
• In a chemical process– Stability is increased by adding mass
– More metal (heat sink, spare capacity)– More inventory (spare capacity, time to respond)
– Comes at a cost– More heat loss– More off-spec product– Loss of efficiency / under leveraged asset– Materials / Labor
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What makes processes so difficult?
• Small envelopes• Multitasking• Computational• Running next to the limit• Trip / Interlock logic
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Safety
Process Envelopes
Process Envelopes:• Envelopes represent a
process context which when violated result in consequences
• Consequence represents to which envelope the boundary belongs
OperationalReliability
Environmental
EconomicProduct A
EconomicProduct B
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Safety
Process Envelopes
Process Envelopes:• Small envelopes make
it difficult to maintain operations
Operational
ReliabilityEnviro
nmental
EconomicProduct A
EconomicProduct B
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Examples of small envelopes
• Operational / Controllability– An exothermic reaction requires an exact
stoichiometry – Variability of just 5% off of ratio results in loss of
reaction and requires restart of heater and reduction of feed
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Examples of multitasking/computational
• Operational / Controllability & Economic– A train of separation columns that have limited
inventory within the column to feed the next– A small adjustment to the column could end up with a
dynamic response that starves downstream columns– Operator has to adjust multiple columns to keep from
going on total reflux or slopping product
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Safety
Process Envelopes
Process Envelopes:• Maintaining Boundaries
– Operator Response– Interlocks– Regulatory Controls
– SP– Override
– Automation
Operational
ReliabilityEnviro
nmental
EconomicProduct A
EconomicProduct B
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Operator Response• Pros
– Keeps it running– In-place
• Cons– Keeps it running– Human Reliability– Not Reproducible– Safety Exposure
Safety
Process Envelopes
Operational
ReliabilityEnviro
nmental
EconomicProduct A
EconomicProduct B
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Safety
Process Envelopes
Interlocks• Pros
– Deterministic– Good layer of
protection• Cons
– Moves away from operational and economic envelopes
Operational
ReliabilityEnviro
nmental
EconomicProduct A
EconomicProduct B
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Safety
Process Envelopes
Regulatory Controls• Pros
– Stabilizes– Steers to target
• Cons– Not intelligent of
operational objective– Need to be coordinated
Operational
ReliabilityEnviro
nmental
EconomicProduct A
EconomicProduct B
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Corralling the Process
APCAPC
RegulatoryRegulatory
SequenceSequence
State LogicState Logic
InterlocksInterlocksAlarms issued for
unexpected or
unplanned events
Trips due to interlocks should be rare!
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Manually Operated Plant
• Operator– Follows manual procedure– Coordinates regulatory controls– Coordinates with outside operations– Responds to alarms– Fights interlocks
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Automated Plant
• Automation– Follows procedure– Coordinates regulatory controls– Reduced manual outside operations
• Operator– Responds to alarms– Coordinates with outside operations
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On the Edge
• F-16 Fighter– Is designed for negative static stability (NSS) in
subsonic flight– Literally flies on the verge of going out of control – NSS design enhances the maneuverability of the
aircraft (optimal for fighter jet)
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On the Edge
• Flight Control Computer (FLCC)– Takes input from the pilot and manipulates control
surfaces to achieve desired objective– Maintains a series of limiters that govern orientation of
the aircraft. Prevents conditions which would induce unstable flight
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On the Edge
Process Envelopes:• Economic envelopes
can often fall on the edge of an operational or safety boundary Operational
EconomicProduct A
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On the Edge
Operational
EconomicProduct A
APC
Process Envelopes:• APCs have constraint
control and can be layered with override strategies
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Total Automation on TDC/TPS
State logic
Dynamic Alarming and
Sequence Coordination
Configuration and
Maintenance
Operation
Sequences
SequencesSequences
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State Transitions
• All State Transitions– Controls are coordinated in a repeatable manner– There are at least 2 levels of logic on top of regulatory
or discrete layer– State logic (Macro logic)– Controller / Sequence logic (Micro logic)
– Alarms are dynamically managed
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State Transitions
• Manual or Auto• States are summarized on display for operator• Operator can monitor and request state changes
from high level and drill for detail• Logic is available to operator
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Elements of Good Implementation
• Acquire correct tools• Get trained or use experienced personnel• Target acquisition / Justification• Design• Develop• Simulate• Train• Commission• Maintain / Improve
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Total Automation Results
• Quicker startups (1/2 to 2/3 reduction)• Repeatable – like it’s on rails• Reduced errors and overshoots• Positive HSE impact• More Reliable • Less off-spec product• More benefits depending on situation
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The Modern Automated Plant
• Utilizes process control• Does not require the same skill level and
experience as a manual plant• Resilient to frequent transition of personnel• Profitable
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The Modern Automated Plant
• Reduces training costs versus a manual plant
• Is safer and more efficient to operate
Dow’s “stateful control” systems and safety culture have made the company one of the safest in the petrochemical industry
J.M. “Levi” Leathers – Dow Chemical
Control Magazine, May 2010
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