Eliminating Difficult Start-ups with State Based Controls

Post on 22-Nov-2014

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This presentation explains the benefits of automated start-up.

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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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Education & Training

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Questions ?

www.prosys.comsales@prosys.com