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RAMS and Operation Requirements for a Resilient Tunnel Ventilation System

Ibrahima Khalil Mbaye, EUR INGParsons Corporation, Senior Tunnel

Ventilation EngineerDoha, Qatar

Toronto, 26 June 2019


Key Presentation Take-Aways

• Purpose of the Presentation

• What about TVS ?

• What about RAMS?

• What about Operation Requirements?

• How does RAMS Consideration allow to design a resilient TVS?

• Conclusion


Purpose

Aiming to Define a comprehensive strategy for the Delivery of a Resilient Tunnel Ventilation System for Railways Project relying on the RAMS process.


What is Tunnel Ventilation System (TVS) about?

TVS is a System involved in a wide range of underground infrastructure projects:

• Road Tunnels

• Underground Railways, metro, light rail, high speed

• Electrical High Voltage Cables Tunnels

• Mining Tunnels

• Sewage Tunnels


What is TVS about? Railways Metro Major Functions

1. Comfort Management by ensuring:

• Air quality,

• Acceptable Air temperature for Passenger and Equipment in tunnel,

• Acceptable level of induced pressure due to train piston effect,

• Acceptable levels of air velocity,

• Acceptable level of noise,

• Operator’s comfort during Maintenance activities in tunnel.


2. Safety Management by ensuring:

• Tenable conditions for passenger’s evacuation whenever required,

• Achieving critical velocity (Kennedy formula)

• Tenable conditions for passenger inside the train under congestion

• Proper and safe access to each TVS equipment

What is TVS about? Railways Metro Major Functions


What is Tunnel Ventilation System (TVS) about? Typical Equipment

• Axial Fans• Jet Fans• Motorized Smoke and Fire Dampers• AHUs, depending on the region, cooling in the tunnel may be required• Temperature, airflow, humidity sensors in tunnel• Electrical Distribution Boards,• Variable Speed Drives• Soft-Starters• Control Panel with Human Machine Interface (HMI) screen and

Programmable Logic Controller (PLC)• Control Panel with Push-Button for Emergency


What is RAMS about?

• Reliability, quantified by the Mean Time Between Failure (MTBF) of single core equipment

MTBF is provided by the Manufacturer based on the lessons learnt from previous projects.

• Availability, quantified by the ratio A

𝐴 =𝑀𝑇𝐵𝐹

𝑀𝑇𝐵𝐹 +𝑀𝐷𝑇

MDT is the Mean Down Time, most of the time, it is considered as the Mean Time To Restore (MTTR).


What is RAMS about?

• Maintainability, quantified by the Mean Time To Restore (MTTR)

𝑀𝑇𝑇𝑅 = 𝐼𝐷𝑇 + 𝐼𝑅𝑇 + 𝐴𝑅𝑇

IDT is the Incident Detection Time, IRT is the Incident Response Time and ART is the Active Repair Time

• Safety, quantified by the Safety Integrity Level (SIL) for any System Safety Function, defined in IEC 61508.

THR (Tolerable Hazard Rate) per

hour

SIL level

10-9 THR 10-8 SIL 4

10-8 THR 10-7 SIL 3

10-7 THR 10-6 SIL 2

10-6 THR 10-5 SIL 1


What is RAMS about?EN 50126

Current Presentation Area of Focus


What is RAMS about?EN 50126 Design Deliverables

• Concept Design Functional Analysis, • to describe the System Functions along with their involved core equipment. • Core equipment is broken down into Line Replaceable Units (LRU).

• FMECA (Failure Modes Effects and Criticality Analysis), • to assess the Criticality of any Core Equipment failure. • Safety related and Non Safety related Failures are identified. • Safety Related Failures are Service Affecting Failures and are expected to be reflected in the

Hazard Log.

• RAM Prediction Report, • to assess the Reliability of the System by performing Reliability Block Diagram (RBD)

considering dependencies and redundancies.


What is RAMS about?EN 50126 Design Deliverables

• Hazard Analysis, identification of all credible Hazards involving the System.

• Hazard Log, list of all Hazards recognized as “non tolerable” based on the EN 50126 Risk Matrix and as required by the Project:

• SIL Assessment Report, through Fault Tree Analysis (FTA)to check the final design is achieving the required THR (Tolerable Hazard Rate).

Risk Ratings R1, R2, R3 and R4 to be defined by the Client


• Availability Target, percentage of availability of the System

• MTTR Target• Non Service Affecting Failures MTTR, generally, comparable to the Engineering Hours. Only

for Preventive Maintenance and Corrective Maintenance when it is a non Service Affecting Failure

• Service Affecting Failures MTTR, generally a shortest time, allowable for a specific operation duration, can be one year duration (13 Operational Periods)

• System Failure Rates, an explicit target to minimize the System Service Affecting Failures depending on its MTTR.

For instance, for Tunnel Ventilation System, it will take time to fix a faulty equipment (fans of 10 tons weight, motor, dampers, Distribution Panel, etc.), therefore the TVS allocated Failure Rate is as low as practicable to achieve the MTTR.

Operation Requirements and RAMS (Key Performance Requirements KPR)


How Does RAMS Process allow to design a Resilient TVS?

Concept Design

Functional Analysis

Safety Functions

Non Safety

Functions

FMECA

Non Safety

Related Failures

Safety Related Failures

Hazard Analysis

Hazard Log

TVS Core Mitigation Measures

TVS Dependencies

/Interfaces Mitigation Measures

TVS Operation Mitigation Measures

Space Proofing, Power Supply, SCADA, Dynamic Signage,

Platform Screen Doors, Rolling Stock, Signaling, MEP, EMC,

etc.

Mitigation Measures

RAM Calculations

FTA

RAM and SIL

targets Achieved

TVS Implementation

of mitigation measures

ManufactureInstallation T&C Phase and O&M Manuals

Spare Parts List

RBD

TVS Design with

mitigation measures

SIL Calculations


TVS Intrinsic Mitigation Measures outcome of Hazard Log

• TVS shall be compliant with NFPA 130

• TVS shall ensure tenable conditions for the Passenger’s evacuation

• TVS shall prevent passenger from eardrum discomfort

• Each Safety Critical equipment shall have a Duty and Stand by

• Both Duty and Stand by Equipment shall have independent power supply

• The TVS Control System shall be SIL 2


TVS Interface Mitigation Measures outcome of Hazard Log

• Power Supply and SCADA availability shall be 99.999%.

• Power Supply and SCADA networks shall be redundant.

• SCADA commands to TVS shall be SIL 2.

• TVS equipment in tunnel shall not infringe the Rolling Stock gauge.

• TVS to achieve the critical velocity based on the Rolling Stock fire heat release rate.

• TVS to maintain the air temperature to ensure the Rolling Stock Air Conditioning Operating.


TVS Interface Mitigation Measures outcome of Hazard Log

• TVS response and Dynamic Signage to be consistent with the evacuation route.

• The TVS design to define the level of Pressure to be withstood by the Platform Screen Doors and the exposed Structural Walls.

• Appropriate TVS response to be triggered for congested trains.

• Signaling to ensure the max number of trains within a Tunnel Ventilation Zone.

• Each TVS Equipment to be provided with proper and safe access.

• Each TVS equipment to be provided with clear delivery/replacement route.


TVS Operator Mitigation Measures outcome of Hazard Log

• The Operator shall follow the TVS O&M Manuals.

• The Operator shall follow the TVS Asset Maintenance Strategy.

• Yearly Proof test shall be conducted for TVS control equipment.

• The Operator shall select the appropriate TVS mode in case of train fire.

• The Operator shall ensure the Minimum Operation Conditions.

• The Operator shall be aware of the TVS Service Affecting Failures.


CONCLUSION

A TVS Design through RAMS process allows to achieve the Operation Requirements by considering the implementation of the appropriate mitigations measures, outcome of the Hazard Log:

• TVS intrinsic mitigation measures, to be implemented in the TVS design,

• TVS mitigation measures transferred by Other Parties,

• Other Parties mitigation measures transferred by TVS,

• Operation and Maintenance TVS related mitigation measures.


RAMS and Operation Requirements for a Resilient Tunnel Ventilation System

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