A straightforward approach using DeltaV SIS for typical BMS systems
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DeltaV SIS can be used to implement burner management systems (BMS) by modeling the system as a state machine with defined states, transitions between states, outputs for each state, and trips that are masked or active in each state. This approach provides a clear and systematic development process that is easy to analyze, implement, operate, verify, and modify. It can improve safety and reduce lifecycle costs compared to traditional implementations.
A straightforward approach using DeltaV SIS for typical BMS systems
- 1. DeltaV SIS for BMS ApplicationsDavid Sheppard, CFSE
- 2. By extending the Emerson digital PlantWeb architecture to safety systems, SmartSISwill provide unprecedented customer value by:enabling safer plantsincreasing availabilitylowering lifecycle costsimplifying regulatory complianceEmerson’s vision
- 3. DEFINITION: SIS(Safety Instrumented System)A SIS Takes a process to a safe state when predetermined (dangerous) conditions are violated (e.g. ESD)Permits a process to move forward in a safe manner when specified conditions allow (e.g. BMS) Takes action to mitigate the consequences of an industrial hazard (e.g. FGS)Related DefinitionsESD - Emergency Shutdown
- 4. ESS - Emergency Shutdown System
- 5. SSD - Safety Shutdown Systems
- 6. BMS - Burner Management System
- 7. FGS – Fire & Gas Systemlogic solvertransmittershutdown valve
- 8. What is the purpose of a BMS?To inhibit startup when unsafe conditions exist.To protect against the unsafe operating conditions and admission of improper quantities of fuel to the furnace.To provide the operator with status information – operator assistanceTo initiate a safe operating condition or shutdown interlock if unsafe condition exists.As per NFPA 85, “the BMS is a control system dedicated to boiler furnace safety and operator assistance……”Why implement BMS in an SIS?Increased safetyIncreased system availabilityRegulatory compliancePotentially lower insurance costs
- 9. Is BMS a SIS?Burners, furnaces and boilers are very critical and complex systems.The fact that accidents and disasters are as few as they are, is due to the long experience has been embodied in various codes and standards. There is evidence that OEMs and end users who wish to comply with standards (IEC/NFPA), or to meet certain insurance requirements, will have to classify burner management systems as safety-instrumented systems, to achieve certification by a third-party agency.In the process industry, a BMS is included in the IEC 61511 definition, although not by direct reference. There is also no exclusionary clause.Burner Management Systems (BMS) are defined as Safety Instrumented Systems (SIS) if they contain sensors, a logic solver and a final control element according to IEC 61511.All safety critical processes must be analyzed and their potential risk determined. By considering a BMS as a SIS, companies can ensure that these systems are designed, maintained, inspected and tested per both the applicable prescriptive standards (API, NFPA, etc.) as well as the latest SIS performance-based standards (ANSI/ISA, and IEC).
- 10. Is a BMS a SIS?Six (6) different codes, standards and / or recommended practices have been, or are currently being developed, that mandate a BMS is a SIS until proven otherwise. The Black Liquor Recovery Boiler Advisory Committee(BLRBAC) has developed several guideline documents regarding design and operation of Recovery Boilers in the Pulp and Paper Industry. These documents invoke SIS requirements on the Recovery Boiler BMS.FM 7605 – Factory Mutual requires that any PLC listed for use in combustion safeguard service meet the SIS requirements contained in IEC 61508. TR84 – The ISA S84 committee has formed a BMS sub-committee to develop a document that clarifies how SIS concepts apply to a BMS. Examples being included in the document for each code or standard are: NFPA 85 – Single burner boilerNFPA 86 – Thermal oxidizerAPI 14C – Process heater with multiple burnersAPI 556 – Glycol ReboilersThe goal of the S84 committee is for industrial users to properly follow the safety lifecycle to define the risk of every BMS to determine if it is a SIS.NFPA 86 Committee is planning to update this standardto reflect their agreement that an industrial BMS is a SIS and that a safety PLC should be used. It also will refer to ANSI/ISA 84.00.01-2004 as acceptable methodology.EN 50156-1 is a European standard covering electrical equipment for furnaces which invokes SIS requirements for a BMS.API 556 document governs design of BMS’s in the petroleum industry. It invokes SIS requirements on BMS’s.
- 11. Burners and boilers are very critical and complex systemsDistance of boiler displacement = 50m
- 12. DeltaV SIS advanced function blocks simplify configurationIEC 61508 certified modules and functionality for BMSCause and Effect Matrix (CEM)Step SequencerState TransitionProvides very efficient configuration and powerful application software.Available dynamos and faceplates make the application very transparent for the operator.
- 13. Example BMS StatesS03S04Shutdown,Not ReadyS02Ignite PilotPre-Purge In progressPurge CompleteShutdown,& ReadyS01S05Startup failurePilot only RunningS06Trips from States5, 6, 7, 8, 9, 10, 12Mixed firing, set low fire positionS12S07S13Cold Start, Set Low fire positionS08Waste Gas OnlyS09S10Ignite Main with PilotMixed GasMain without pilot, not at Temp
- 14. 3 Main Logic Part to a BMS SystemIn order to define a BMS you must know 3 fundamental items. 1. States & Transitions – When to move from one to another 2. Outputs – Valve Positions defined for each State 3. Trips – Including which is active during each StateOnce these are defined, the DeltaV SIS logic can be programmed inAn easy to follow manner.The following Example is a Single Burner-Multi Fuel with 13 states:
- 15. BMS State Transition Diagram1) No Trip condition exists and all trips have been reset1) Operator initiates pilot ignition with hand switch.1) Operator initiates Purge hand switch.S03S04S02Ignite PilotPre-Purge In progress Purge Complete Shutdown,& ReadyS01S051) Total volume flow of nitrogen is confirmed at 200 SCFM for 5 minShutdown,Not ReadyPilot only Running1) Pilot flame detected within 15 secStartup failureS061) At least 15 seconds elapsed2) At least 6 hours of cold restart time is elapsed OR Operator over-rides this timer.3) Operator initiates "Light Main Burner" hand switch.Trips from States5, 6, 7, 8, 9, 10, 121) Flame detectors confirm flame within 15 sec2) Additional 15 sec for flame stabilization1) Low fire positions confirmed1) Operator initiates “Mixed Gas“ hand switchS12S07S13Mixed firing, set low fire positionCold Start, Set Low fire positionS08Waste Gas OnlyS09S10Ignite Main with Pilot1) Operator initiates "Waste Gas Only“ hand switch1) Low fire positions confirmedMixed GasMain without pilot, not at Temp1) Reached min temp2) Operator initiates hand switch to “Mixed Gas"
- 16. State Transitions – Defines What Allows the Logic to move from one State to AnotherFor Example: To move from State 2 – Shutdown and Ready to State 3 – Pre Purge in Progress The Operator Selects Cold RestartThe Built in DeltaV SIS Function Block - State Transition Block - is used to Easily Define the Transition Logic.
- 17. Outputs – Defined Per StateOnce the States are defined, the position of each Output (Valve, ignitor, etc) is defined in each state in a simple tableOutputsStates
- 18. Outputs - Defined per stateOutputsStatesOutputsStatesThe DeltaV SIS logic has a simple matrix that mirrors the table. It drives the outputs blocks
- 19. Trip Matrix / Appropriate MaskingDifferent Trip conditions should be masked during different states. For example, seeing Flame is Required when running, but it must be masked when not running This cause needs to be “masked” in this state!This cause has to be able to trip in this state.
- 20. Trips – Including Masking Defined per StateThis Cause is “masked” in this State!StatesOutputsThe DeltaV SIS logic has a simple matrix that mirrors the table above that masks conditions based on the state the burner is in
- 21. Simple DocumentationState Transition DiagramTripsOutputsTransitions
- 22. BMS Trips Graphics – Normal State
- 23. BMS Trips Graphics – Trip State
- 24. BMS Ring of Fire – Step S02
- 25. BMS Ring of Fire – Step S06
- 26. SummaryThe State Transition Diagram approach is a very clear and systematic development process:Define the states and transitions.Define the outputs in each state.Define the required trip signals.Define per state if a trip is active or masked.Very good for developing functional requirements in an interdisciplinary team.The approach can also be used for other applications.
- 27. Safety lifecycle benefits:Reduced cost and improved safetyAnalysis – a well defined approach and easily understandable.Implementation – can be easily implemented using standard function blocks and dynamosOperation – because failures can easily be located and removed.Verification – each state has clearly defined output signals and trip causes which can easily be tested and verified.Modification – the solution is unambiguous and can easily be modified.