Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: Voting Logic in Safety Instrumented System (SIS)
Share
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Safety Instrumented System (SIS) > Voting Logic in Safety Instrumented System (SIS)

Voting Logic in Safety Instrumented System (SIS)

Last updated: July 26, 2020 11:16 am
Editorial Staff
Safety Instrumented System (SIS)
1 Comment
Share
3 Min Read
SHARE

There are 1oo1, 1oo2, 2oo2, 2oo3 etc voting logic in the safety instrumented system architecture.

The voting logic architecture usually used in the field instrument and or final control elements to reach certain Safety Integrity Level (SIL)  or to reach certain cost reduction due to platform shutdown. In general when we must use 1oo1, 1oo2, 2oo2, or 2oo3 voting logic architecture?

Voting Logic

Voting Logic in Safety Instrumented System (SIS)

As mentioned above, there are two purposes why certain voting logic architecture were chosen, first is to reach certain SIL and secondly to reach certain cost reduction due to spurious platform shutdown.

In order to determine a certain SIL requirement, a risk or process hazard analysis is used to identify all process, safety and environmental hazards, estimate their risks, and decide if that risk is tolerable. Where risk reduction is required an appropriate SIL is assigned.

The individual components (sensor , logic solver , final elements, etc.) that are working together to implement the individual safety loops must comply with the constraints of the required SIL.

In essence, this means that all components within that loop must meet a certain Probability of Failure on Demand (PFD), Safe Failure Fraction (SFF) and Hardware Fault Tolerance (HFT) requirement for the intended SIL.

Readers are encouraged to see further detail regarding this PFDavg, SFF, and HFT in the IEC 61508 & IEC 61511.

As general rule, first of all the SIL requirement for any particular condition or application will be determined using a risk or process analysis.

After the SIL was determined then the architecture of the sensor, logic solver, and final control element is studied to investigate which architecture will fulfill the SIL requirement.

For example, if the SIL requirement for a high pressure incoming pipe line is SIL 3, then the architecture of the pressure sensor and final element will be investigated.

If 1oo1 sensor, 1oo1 logic solver, and 1oo1 shutdown valve can fulfill the SIL 3 requirement, then this architecture is chosen. If not, then any other voting logic architecture is investigated.

Let’s say after several investigations the voting logic 1oo2 sensor, 1oo2 logic solver, and 1oo2 shutdown valve can fulfill the requirement of SIL 3, then this voting logic is chosen. If the cost reduction study need to minimize spurious trip due to one of the sensor failed, then may be the sensor voting logic architecture must be upgraded to become 2oo3 architecture.

This architecture may be chosen since if one sensor failed, then the overall architecture is still fulfilling SIL 3 requirement with 1oo2 sensor configuration. Thus it doesn’t need to have a platform shutdown when one sensor failed.

Articles You May Like :

SIS Module Failure

SIS, PLC or BPCS ?

Questions on SIS

Shutdown Logic

ESDV Advantages

Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

What is a Logic Solver? – Safety PLC
Automated Block Valve (ABV)
SIS Design – Safety Instrumented System
Difference between Availability, Reliability & SIL
High Reliability of Safety Instrumented Systems
SIS Logic Solver
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
1 Comment
  • Vivek M says:
    May 21, 2019 at 12:12 pm

    ESD transmitters serving critical shutdown level in Safety Instrumented System are recommended to have voting logic configuration.

    Voting logic is applied to minimize the occurrence of complete loss of production caused by single transmitter fault or spurious trip shutdown. The voting configuration can be 2oo3 or 1oo2D based on SIL assessment and verification.

    There are some consideration when applying voting logic in the process:

    > Transmitters not to have common tapping to the process line/equipment.
    > The transmitters forming the same voting logic shall not be assigned on the same I/O module of Safety Instrumented System.
    > Each instrument cable is routed diversely.
    > Transmitters are set with the same calibration range.
    > It is also recommended to have transmitters from different manufacturer to avoid manufacturing defect causing common mode failure.

    Also on this voting logic configuration, SIS needs to compare the transmitters value and initiate alarm on Human Machine Interface (HMI) for any deviations on measurement among the transmitters.

    Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Safety Integrity Level (SIL)
S84 / IEC 61511 Standard for Safety Instrumented Systems
Direct-actuated Safety and Relief Valves
SIS Final Control Elements
SIS Sensors
What is Safety Instrumented Functions ?
Understanding Emergency Shutdown Button Installation (ESD)
What is Safety Control System ?

Keep Learning

energized-to-safe-loop

Energize to Safe Loop philosophy

Difference between SIS, PLC and BPCS Systems

Difference between SIS, PLC and BPCS Systems

Emergency Shutdown System Philosophy

Shutdown Philosophy

SIS Application Program - Safety Instrumented System

SIS Application Program – Safety Instrumented System

Basic Terms used in SIL Verification

Basic Terms used in SIL Verification

Intrinsic Safe Calculation

Intrinsic Safe Calculation

level of liquid inside a vessel

Concept of Redundancy in Control Systems

pressurized water reactor

SIS Example : Nuclear Reactor Controls

Learn More

Manometer Measures Differential Pressure

How Manometer Measures Differential Pressure for Different Fluids?

Displacement Transducers Objective Questions

Displacement Transducers Objective Questions

Safety Relief Valve

Safety Relief Valve Quiz: Test Your Knowledge

Bonding and Grounding Electrical Systems

Testing and Inspection of Bonding and Grounding Systems

Connecting Faceplates to PLC Project

Connecting Faceplate to PLC Project – HMI Tutorial

Time Response Analysis

State Variable Analysis – Part I

0 to 10 mA Current Loop

What is Live Zero in 4-20 mA Current Loop?

Instrument Process Datasheet

Instrument Process Datasheet (IPDS)

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?