Presentation on theme: "Redundant control system (RCS)"— Presentation transcript:
1 Redundant control system (RCS) Name: Thierry BakkerProject Pursuit manager
2 What is Redundancy? Definitions: Common definition: Surplus to requirements; unnecessary or superfluousEngineering definitions“A device that will provide its intended function upon loss of power.” (2007 NFPA-80)An operation which ensures that a failure of equipment, process, or system does not propagate beyond the immediate environs of the failing entity.
3 Redundant Control System Safety Instrumented SystemsProcess ReliabilityProcess Valve DiagnosticsCERTIFIEDCAPABLESIL 3
4 Redundancy with solenoid valves ++ Safety- - Reliability (production)1oo2One out of two2312312312oo2Two out of two++ Reliability (production)- - Safety
5 Redundancy with solenoid valves 2oo2D231- Safety++ Reliability (production)
6 Reasons for RCS designRedundant SOV commonly used in continuous run processes to prevent spurious trip (Nuisance trip) due to coil failure.Typical Redundant SOV installations:-Do not provide indication of SOV safe failure.Do not provide online maintenance facilities.Do not provide the ability to automatically test for “stuck” SOVs or plugged vents.Do not provide ability to automatically partial stroke test the process valveHave difficulty meeting SIL requirements.
7 Typical 2oo2 SOV Installation RCS Product EvolutionTypical 2oo2 SOV Installation3 way – Normally closed - EnergizedSOV1SAir Supply2oo2 installationSOV2SventIssue: Cannot easily detect failure or its locationBlock Valve
8 Addition of pressure Switches – Status Indication RCS Product EvolutionAddition of pressure Switches – Status IndicationSOV1PS1Air SupplySventBlock ValveSOV2PS2Limit Switches could have been used but they would only indicate that the valve shifted, Could not confirm that the valve ventedIssue: How do you repair the problem without shutting down the process ?
9 Addition of maintenance bypass RCS Product EvolutionAddition of maintenance bypassIsolation ValvesSOV1PS1SAir SupplySOV2PS2SventBlock ValveBy-Pass valveIssue: 1) How do you know when you are in by-pass ?2) How do you know when repair is complete ?
10 Addition of maintenance bypass PS indication RCS Product EvolutionAddition of maintenance bypass PS indicationSOV1PS1SAir SupplySOV2PS2SventPS3Block Valve
11 RCS Product Evolution The ASCO RCS Product SOV1 S Air Supply SOV2 PS2 RCS Product EvolutionThe ASCO RCS ProductAir SupplySventBlock ValveSOV1SOV2PS1PS2PS3
12 RCS Concept ASCO’S RCS package consolidates many of the components using known technology to create a morecomplete package with unique features to meet today's needs…
13 RCS Product Features Ground Din Mounted Terminal Accommodates up to 14 AWG wiringKeyed Maintenance BypassPermits user to service unit withoutdisturbing the processISO-3 Low Power Solenoids (2)4 bolts permit quick replacement1.4 watts (24vdc)Class 1, Div 2 solenoids (non incendive)Pressure Switches (3)Monitors solenoid valve position(diagnostics)Class 1, Div 2Stainless SteelAir-operated Bypass Valve(1)Maintains process while main solenoidvalves are serviced during bypassEnclosure304 or 316 Stainless Steel or FiberglassUL Type 4, 4XBreather ventLimits condensation build-upPneumatic connections
16 Normally Closed Version Normally Closed RCS operates like a 3 way Normally Closed valveIn the de-energized state the unit is venting the process valve actuatorAs long as one solenoid valve is energized air is supplied to the process valve.When both solenoid valves are de-energized the process is vented.Typical application: “ESD systems” (Emergency Shut-down valve) – Fail SafeSOV1 and SOV2 are de-energized. The process shutoff valve is in the closed position. The contact for PS1 is closed indicating that SOV1 is in the de-energized state and the contact for PS2 is closed indicating that SOV2 is in the de-energized state. The contact for PS3 is closed indicating that the bypass valve is not in the bypass state.Normally Closed VersionOperation: The normally closed 2oo2D-SOV operates like a standard normally closed three way solenoid operated valve, where, in the de-energized state, the solenoid is venting the process valve actuator. Both solenoid operated valves must be de-energized to vent the process valve actuator. As long as one of the two solenoid operated valves is in the energized state, the process valve actuator will not be vented and the process valve will remain in the normal position (typically open).Application: The majority of ESD valves are required to close in order to achieve the specified safe state for the process under control (i.e. shut off flow) and they are specified “fail safe” (spring to the safe state) which requires that the solenoid operated valve vent the process valve actuator allowing the process valve move specified safe state on loss of power.Status:SOV1 & SOV2 de-energized
17 Normally Open VersionNormally open RCS operate like a 3 –way normally open.In the De-energized state, air is supplied to the process valveAs long as one solenoid valves is energized the process valve will be open toexhaust and remain in the normal position.Typical application: “vent valves”PS1PS2PS3SOV1SOV2B/PExhaustAir SupplySOV1 andSOV2 de-energizedBypass (B/P) valve shownin the normal stateOutletValveOpenpsoutineplugContactClosedSOV1 and SOV2 are de-energized. The process shutoff valve is in the open position. The contact for PS1 is open indicating that SOV1 is in the de-energized state and the contact for PS2 is open indicating that SOV2 is in the de-energized state. The contact for PS3 is closed indicating that the bypass valve is not in the bypass state.Normally Open VersionOperation: The normally open 2oo2D-SOV requires that both solenoid operated valves be de-energized to apply air to the process valve actuator. As long as one of the two solenoid operated valves are in the energized state, the process valve actuator will not have air applied to it and the process valve will remain in the normal position (typically open).Application: The majority of emergency vent valves are required to open in order to achieve the specified safe state for the process under control (i.e. vent off pressure). In order to prevent opening of the process valve due to loss of instrument air, the user may chose to specify the process valve as air to open spring return closed. To move the process valve to the safe state requires the solenoids to apply air to the process valve actuator when they are de-energized. This configuration also fulfills the requirement that the process valve move specified safe state on loss of power.Status: SOV1 & SOV2 de-energized
18 Double Acting VersionSimilar to having one 3 way normally closed valve & 3 way normally openWhen both solenoid valves are de-energized one side of the actuator is venting whilethe opposite side is being pressurizedCustomer must define desired position “Fail close / fail open”If the event of single SOV failureactuator becomes balanced – actuatormaintains last positionAvailable only in 2oo2 operationSOV1 and SOV2 are de-energized. The process shutoff valve is in the closed position. The contact for PS1 is closed indicating that SOV1 is in the de-energized state and the contact for PS2 is closed indicating that SOV2 is in the de-energized state. The contact for PS3 is closed indicating that the bypass valve is not in the bypass state.Double Acting VersionOperation: The double acting 2oo2D-SOV operates similar to a standard normally closed three- way solenoid operated valve and a standard normally open three-way solenoid operated valve with each controlling air pressure to one side of a piston type actuator. In this configuration, when both solenoid operated valves are de-energized, one solenoid operated valve is venting its associated cylinder side of the process valve actuator, while the second solenoid operated valve is applying pressure to its associated cylinder side of the process valve actuator.The user must determine the desired position (open or closed) for the process valve on loss of power (i.e. fail close/fail open). If the desired “fail” state for the valve is open, the normally open solenoid valve of the double acting 2oo2D-SOV will control the air to the side of the process valve actuating cylinder that will drive the process valve shut and the normally closed solenoid operated valve of the double acting 2oo2D-SOV will control the air to the side of the process valve actuating cylinder that will vent and allow the process valve to shut.
19 RCS Versions Series 5R – No on-board diagnostic processor (AC or DC) Series 5L – with on-board diagnostic processor (DC only)Main Components2 - Solenoid Valves = 2 Digital Output D/O1- Maintenance By-Pass3- Pressure switches = 3 Digital inputs D/IKey function Monitor status of SOV’s & bypassFunctional testing capabilitiesAutomated through PLC or DCSManually initiated testOptional panel mount push button and lightsInitiates program testMain function - Redundant Solenoid valve package with maintenance bypass switch`
20 RCS Versions Series 5L – with on-board diagnostic processor (DC only) Siemens PLC - main Functionreduce programming and total I/O countControls outputs to SOV’sReceives diagnostic input from pressure switchesProvides testing and diagnostic informationPower is supplied to Siemens PLC via the users controllerTesting and diagnostic reporting to any human machine interface (HMI)can be facilitated via MODBUS 485IMPORTANT:Onboard PLC provides testing and diagnostic information only.Siemens PLC is benign to the safety actionPower is supplied to the on-board PLC by users controllerUser’s controller is always responsible for the safety actionSafety action is executed by de-energizing the output power to Siemens PLC
21 RCS Versions Series 5L – with on-board diagnostic processor (DC only) In the event of a PLC failureWatch Dog RelaysWatchdog relays are provided to prevent de-energizing the SOV’s due to a failureOf the on-board PLC outputs.Each SOV receives power through a separate normally closed relay contact onseparate watchdog relays .Watchdog relays are energized by a output from on-board PLCThis keeps normally closed contact in the open positionIf on-board PLC fails the watchdog relay close and SOV 1 & SOV 2 are connected tocontroller allowing the controller to have supervisory control over SOV 1 & SOV2Power to SOVs is maintained avoiding accidental shutdownLoss of PLC will be detected and annunciated``
22 RCS Product – 1oo1 HSIn the 1oo1HS operational mode one SOV is selected as primary and isnormally energized.2. The Hot Standby SOV is normally de-energized and its associated PS verifiesthe vented state. With only one SOV energized position the safety availabilityis increased.0Air SupplyventBlock ValveSOV1PrimarySOV2Hot StandbyPS1PS2PS3SZSO= Closed contact= Open contact
23 RCS Product – 1oo1 HSIf the primary SOV shifts to the vented state (coil failure) its associated PSidentifies the failure and the Hot Standby SOV is energized.2. The Hot Standby prevents the closure of the process valve3 The reliability of the 1oo1HS is the same as 2oo2 operation.Air SupplyventBlock ValveSOV1PrimarySOV2Hot StandbyPS1PS2PS3SZSO= Closed contact= Open contact
25 RCS SIL CertificationCertified SIL 3 Capable by Exida for 1oo1HS, 2oo2DAvailable as an optional feature on configuratorSIL certified units will have a different catalog number than non-SIL unitsIf required, must be identified at the time of part number configurationCurrently SIL certification is only available on units without onboard PLCSupporting documentation for certified units:Exida CertificateFMEDAIEC61508 AssessmentSafety Manual
27 The RCS solution combines the benefits of safety and reliability in a single package. “it’s the only pilot valve system that has no single point of failure that can result in an unwanted closure of the process valve. With the RCS, customers will benefit from higher asset availability, less risk of spurious trips, and safe shut downs of mission critical systems, time after time.”The RCS achieves higher levels of safety by incorporating a redundant, fault-tolerant architecture,high diagnostic coverage, and automated testing. Its self-diagnostic capabilities test both the safetysystem and process valve to ensure continuous proper operating performance.The ASCO RCS was designed to meet the expanding national and international hazardouslocation requirements for safety systems, high reliability, and critical control applications. It allows theend-user to specify a normally closed, normally open or double acting configuration in redundantcontrol “2oo2” (two-out-of-two) or single solenoid with back-up “1oo1” (one-out-of-one)operation.All types of RCS are available with “automatic on-line testing” of the solenoid valves and “partialstroke testing” of the process valve. The RCS also provides users with a maintenance/ by-pass mode,which permits service to the device without taking the process valve off line. This allows the plant tomaintain production without jeopardizing its safety.
28 RCS Information RCS Brochure Available online @ www.ascovalve.com Contains:Product specificationsTechnical details onRCS operationOptional featuresIntroduction to theRCS ConfiguratorAvailable