RAMS of HVAC for Rolling Stock Application

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RAMS of HVAC for Rolling Stock Application

Abhishek Kumar

RAMS & LCC Engineer

Sidwal Refrigeration Industries Pvt. Ltd.

Puneet Sharma

Manager Electrical Design, RAMS & LCC Sidwal Refrigeration Industries Pvt. Ltd.

Amit Agarwal

Vice President Servicing, RAMS & LCC Sidwal Refrigeration Industries Pvt. Ltd.

1 Abstract

Purpose -The purpose of this paper is to provide the detailed calculation of reliability, availability, maintainability, safety of HVAC for a desired mission time (time frame).

Methodology & approach – The complete calculation and detailed methodology is based on the systematic approach followed by the standards ROME LABORATORY RELIABILITY ENGINEERS TOOL KIT, EN-50126 & the practically used techniques in rolling stock industry.

Findings The paper provides information about the reliability critical items in a HVAC, how the series & parallel method of calculation is performed, how they are used in calculation of RAMS.

Research limitations This paper is there to provide the RAMS calculation at HVAC level only but this can also be performed at the train level. The author has taken only the methodology which was there in the standards & practically followed by him. There can be some other approach also for this calculation.

Practical Implications – This paper provide the overview of approach & methodology which can be used for the calculation of RAMS of HVAC (Heating Ventilation Air Conditioning) system and can directly use in the rolling stock application.

Key Words- Life Cycle cost, Reliability, Availability, Maintainability and Safety.

2 INTRODUCTION

    1. RAMS (Reliability Availability Maintainability Safety)

    2. Reliability

      Reliability can be described as a discipline related to the design, development, test, and manufacture of an item, so that it successfully performs a certain task under specified conditions for a certain length of time or number of cycles with a specified probability.

      1. Probability density function f (t) = e- *t

        Where;

        f (t)= probability density function = Failure rate

        t = mission time MTBF = 1/

        e.g. = 3.86 * 10 -6

        MTBF = 1/ = 259067

        Mission time (t) = Time for which the component has to perform its intended function. t = 69000 hours

        The reliability at 69,000 hours is 0.77, as represented by the green shaded area to the right of the 69,000 hour point in the probability density function (pdf) plot shown above. The unreliability or probability of failure is 0.23, as represented by the pink shaded area to the left of the 69,000 hour point in the pdf plot.

      2. Reliability Function R (t) = ()

        = e- *t

        Where;

        R = Reliability = Failure rate t = mission time

        e.g. = 3.86 * 10 -6

        MTBF = 1/ = 259067

        Mission time (t) = Time for which the component has to perform its intended function. For mission time t = 69000 hours

        The reliability at 69,000 hours is 0.77. The unreliability or probability of failure is 0.23

      3. Un-reliability F (t) = 1- R (t)

    1. Availability

      It is defined as the time for which of train is available for revenue service. Availability is defined as the percentage of time a system is considered ready to use when asked. It depends on the availability of all the subsystems of the train including HVAC.

      A = MTBF MTBF+MTTR

      A= /

      / +1/µ

      A = µ

      +µ

      Where;

      MTBF = Mean time between failure = 1/

      MTTR = Mean time to repair

      n ()

      Where;

      MTTR =

      i=1

      i=1

      i=1

      n ()

      MTTRi is the repair time for each Line Replacement Unit (LRU) with a total quantity Qi and i is the failure rate for each LRU.

      Where

      i = the failure rate of the i th repairable unit MTTRi = the repair time of the i th repairable unit Q = the number of units in the system

    2. Maintainability

      The probability that a given maintenance action can be carried out within a stated time interval under stated conditions and using stated procedures and resources.

      Repair rate = µ = 1

      MTTR

      Repair

      Repair

      t = allowable down time

      Repair function =

      µ * µ

      Repair function =

      µ * µ

      t

      t

      Time

      Time

      µ µ = = MTTR

      µ

      Maintainability = M (t) = µ µ = 1 – µ

    3. Safety

      Safety is the state of being "safe", the state of being secure from harm or other non-desirable consequences. Safety can also refer to the control of documented hazards in order to attain a satisfactory level of risk. Capability not to harm persons, the environment, or any properties during a whole life cycle.

      1. Deliverables of safety plan:-

        Risk Analysis. Hazard log

        Interface hazard analysis (IHA)

        Operating & support hazard analysis (O&SHA) Preliminary Hazard Analysis (PHA)

        FMECA Failure mode effect critical analysis FTA Fault tree analysis

      2. Failures in HVAC that are considered in Safety Critical Failures

        1. Fire start or smoke release from the HVAC.

        2. HVAC explosion.

        3. HVAC failures leading to electrocution.

        4. Features leading to refrigerant leak outside the HVAC unit. Hazard Function h (t) = () =

          ()

          Where;

          R (t) = Reliability Function

          f (t) = Probability density function = Failure rate

          e.g. = 3.86 * 10 -6

          MTBF = 1/ = 259067

          Mission time (t) = Time for which the component has to perform its intended function. t = 69000 hours

          The reliability at 69,000 hours is 0.77. The unreliability, or probability of failure, is 0.23.

    4. Factors influencing RAMS in Rolling stock application:-

    5. RAMS for lifecycle phases

      Phase No.

      Phase

      General Task

      RAM Task

      Safety Task

      1

      Conceptual Design

      Investigation done on the basis of scope of supply, application of the system & environment in which it has to perform its intended function.

      Investigation on the following points to be done

      System on which RAM is to be implemented.

      Previous similar projects on which this RAM was applied also validating its performance by cross checking the failure rates & MTTR values.

      Predict the failure rates as per respective standards or from the field data of similar projects undergoing in the similar environment & application.

      Current targets of reliability & how these targets can be achieved i.e. series, parallel combination (redundancy) of the components that are having high failure rates.

      Describe the possibility of the RAM controlling requirements for successive scheme life cycle RAM tasks.

      Prepare Reliability Critical item list.

      Investigation on the following points to be done

      Over-all safety consequences of the system.

      Previous similar projects on which this safety performance was applied also validating its performance by cross checking the hazard rate.

      Current targets of safety & how these targets can be achieved i.e. by using EN45545 compliance used for non-metallic materials. Describe the possibility of the safety conrolling requirements for successive scheme life cycle safety tasks.

      2

      System explanation and operative context

      Define the following System

      Mission period & summary scope of operative requests

      Inaugurate RAM policy RAM plan

      Inaugurate Safety policy Safety plan

      3

      Risk investigation and calculation

      Accomplish Risk Analysis Modernize RAM plan

      Accomplish Risk Analysis. Hazard log

      Interface hazard analysis (IHA) Operating & support hazard analysis (O&SHA)

      Preliminary Hazard Analysis (PHA)

      4

      Description of system requests

      Specify system necessities

      Establish

      RAM necessities description RAM plan

      Validation plan for RAM necessities description

      Establish

      Safety necessities description Safety-related submission circumstances.

      Update Hazard log

      Update Interface hazard analysis (IHA)

      Update Operating & support hazard analysis (O&SHA)

      Update Preliminary Hazard Analysis

      5

      Design and allotment of system necessities

      Define the system design. Identify the necessities for incorporation of pre-existing subsystems/mechanisms. Define acceptance standards and developments for subsystems/mechanisms.

      Assign RAM necessities to subsystems/mechanisms.

      Provide component level failure rates as per respective standard and calculate the system reliability by Reliability Block Diagram.

      Modernize the RAM plan. Modernize validation plan for RAM requirements.

      Accomplish hazard analysis. Assign safety requirements to subsystems/mechanisms. Update safety-related application situations. Update Hazard log

      Update Interface hazard analysis (IHA)

      Update Operating & support hazard analysis (O&SHA)

      6

      Design and execution

      Design subsystems/mechanisms. Prepare O&M module. Define and create engineering process for manufacturing subsystems and mechanisms.

      Define and create system amalgamation process. Prepare installation and contracting processes.

      Strategy of RAM tasks of further phases.

      Accomplish RAM investigation. Modernize the RAM plan. Modernize authentication plan for RAM necessities.

      Update Reliability Block diagram. Update Fault tree analysis.

      Predict the MTTR i.e. time to repair the particular component when the respective failure is arrived.

      Check the accessibility of all the components to ensure the minimum MTTR so that maximum availability of the system can be ensured.

      Strategy of Safety tasks of further phases.

      Accomplish hazard analysis. Update safety-related submission circumstances.

      Update safety-related application situations. Update Hazard log Update Interface hazard analysis (IHA)

      Update Operating & support hazard analysis (O&SHA).

      Prepare FMECA (Failure Mode Effect Critical Analysis).

      7

      Manufacturing

      Implement and activate industrialized procedure

      Inaugurate RAM declaration arrangements. Modernize the RAM plan. Modernize authentication plan for RAM requirements.

      Check accessibility of all the components to ensure the minimum MTTR so that maximum availability of the system can be ensured.

      If there is any change in component assembly as per manufacturing constraints update the MTTR and system availability report.

      Strategy of Safety tasks of further phases.

      Accomplish hazard analysis. Update safety-related submission circumstances.

      Update safety-related application situations. Update Hazard log Update Interface hazard analysis (IHA)

      Update Operating & support hazard analysis (O&SHA).

      Update FMECA (Failure Mode Effect Critical Analysis).

      8

      Integration

      Incorporate subsystems and mechanisms. Determine system functionality.

      Test and examine scheme. Arrange system provision measures.

      Inaugurate RAM declaration arrangements. Modernize the RAM plan. Modernize authentication plan for RAM requirements.

      Check accessibility of all the components to ensure the minimum MTTR so that maximum availability of the system can be ensured.

      If there is any change in component assembly as per manufacturing constraints update the MTTR and system availability report.

      Strategy of Safety tasks of further phases.

      Accomplish hazard analysis. Update safety-related submission circumstances.

      Update safety-related application situations. Update Hazard log Update Interface hazard analysis (IHA)

      Update Operating & support hazard analysis (O&SHA).

      Update FMECA (Failure Mode Effect Critical Analysis).

      9

      System Authentication

      Establish-

      Authentication report. Procedure for the achievement and estimate of operational and maintenance data.

      Inaugurate RAM declaration arrangements. Modernize the RAM plan.

      Modernize authentication plan for RAM requirements.

      Strategy of Safety tasks of further phases.

      Accomplish hazard analysis. Update safety-related submission circumstances.

      Update safety-related application situations. Update Hazard log Update Interface hazard analysis (IHA)

      Update Operating & support hazard analysis (O&SHA).

      Update FMECA (Failure Mode Effect Critical Analysis).

      10

      System approval

      Record and recognition by signing off all the documents related to RAMS for Safety.

      Verify the approval record.

      Evaluate RAM authentication. Signoff all targets related to failure rates & reliability.

      Inaugurate Self-regulating Safety Assessment Report. Declare validation of safety related documents.

      11

      Operation, maintenance and performance checking

      Provide all statistics essential to express plans/actions for O&M. Implement O&M procedures.

      Implement and retain FRACAS procedure for the acquisition and recording of RAM presentation data. Sustain FRACAS and intermittently

      Implement and preserve procedure for the acquirement and recording of safety performance data.

      Record modifications in the scheme configuration.

      evaluate FRACAS records. Inaugurate records to trace the RAM tasks commenced. Reports of RAM performance investigation and calculation.

      Check all the reliability parameters as per plan and implement all of them in the new project.

      Accomplish hazard analysis. Validate safety-related submission circumstances.

      Validate safety-related application situations. Validate Hazard log Validate Interface hazard analysis (IHA)

      Validate Operating & support hazard analysis (O&SHA).

      Validate FMECA (Failure Mode Effect Critical Analysis).

      Inaugurate reports of safety performance analysis and assessment.

      12

      Decommissioning

      Inaugurate decommissioning plan and linked report.

      Recognize the RAM impact of decommissioning and dumping.

      Recognize the Safety impact of decommissioning and dumping.

    6. Failure categories and classification of failures according to failures

      1. Relevant failures

        A relevant failure of an item is an independent failure which results in a loss of function of that item caused by any of the following:

      2. A fault in an equipment or sub-system while operating within its design and environmental specification limits;

      3. Improper operation, maintenance, or testing of the item as a result of the Contractor supplied documentation.

      4. Failures of transient nature including those with post investigation status as 'No fault found', shall be considered as relevant failure if in the opinion of the Engineer these are attributable to rolling stock. The decision of the Engineer shall be final.

      5. Service failure

        Any relevant failure or combination of relevant failures during revenue service operations, simulated revenue operations or during pre-departure equipment status checkouts to determine availability for revenue service, which results in one of the following:

        • Unavailability of the train to start revenue service after successful completion of pre-departure checkout.

        • Withdrawal of the train from revenue services.

        • A delay equivalent to or exceeding 3 minutes from the Schedule / Time table as noted at the destination station for the one- way trip.

        S. no.

        Top level failure events Train Level Effect

        Effect on operation (passengers, other sub systems,)

        1st line maintenance actions

        Failure classification

        Service Failure

        Relevant Failure

        1

        Loss of ventilation in one car.

        No sufficient air flow for emergency situations more than one cars

        Withdrawal from operation

        X

        2

        Loss of overheating protection 3rd level( Thermal fuse)

        Passenger Safety

        Withdrawal from operation

        X

        3

        Fire inside the Evaporator section of HVAC

        Passenger Safety

        Withdrawal from operation

        X

        4

        Total loss of cooling in one car or more cars

        Passenger discomfort

        Withdrawal from operation

        X

        5

        Failure of Cab Booster

        Driver discomfort

        Withdrawal from operation

        X

        6

        All Service Failure resulting in delay/detention for more than 60 (sixty) minutes or passenger deboard-ment in mid-section

        Train withdrawal / Passenger Deboarding

        Withdrawal from operation

        X

        7

        Loss of ventilation in one HVAC

        No sufficient air flow for emergency situations in one car

        Withdrawal at the end of trip

        X

        8

        Loss of overheating protection 1st level (bimetal thermostat)

        Passenger Safety

        Withdrawal from operation at the end of the trip

        X

        9

        Loss of overheating protection 2nd level (SA sensor)

        Passenger Safety

        Withdrawal from operation at the end of the trip

        X

        10

        Any leakage in piping connections between condenser / evaporator coils

        No passenger discomfort

        Withdrawal from operation at the end of the trip

        X

        11

        Failure of any one HVAC in any car leading to increase in

        Degrade in the temperature control in passenger area

        Withdrawal from operation at the end of the trip

        X

        S. no.

        Top level failure events Train Level Effect

        Effect on operation (passengers, other sub systems,)

        1st line maintenance actions

        Failure classification

        Service Failure

        Relevant Failure

        inside saloon/cab temperature

        28 degree Celsius at the design ambient temperature.

        12

        Water dripping problem

        No effect on the operation but passenger discomfort

        Corrective actions

        X

        13

        Noisy air conditioner due to compressor and condenser fans

        Passenger discomfort

        Withdrawal from operation at the end of the trip

        X

    7. Reliability prediction

      Use recognized standards

      • Model failure of machineries

      • Examine system

      • Compute the system predicted failure of MTBF Evaluate prediction vs. target or required MTBF

      • Evaluate stress or temperature reduction design changes

      • Evaluate practically of design change specially when MTBF is self-inflicted

      1. Methodologies

        Rank

        Method

        Early defects

        Random effects

        Wear out

        Description

        1

        Field Data

        This statistics is provided by service team it is being calculated by RAMS team.

        2

        System reliability assessment

        Combine the calculation method that combines prediction, procedure grading, operative profiles, and software and test data using Bayesian procedures.

        3

        Similar item Data

        Based on investigational reliability field failure data on analogous products functioning in similar atmosphere. Uses generic data from association.

        4

        Translation

        Interprets a reliability prediction based on an experimental value. Indirectly accounts for some factors affecting field reliability that is not unambiguously amounted for in the experimental model.

        5

        Empirical

        Typically relies on experiential failure data to enumerate part-level experimental model variables. Applied is that valid failure rate is appropriate.

        6

        Physics- of- failure

        Representations each failure mechanism for each module life separately. Component reliability is determined by merging the probability density function related with respective failure mechanism.

      2. Common standards

        • MIL-HDBK 217

          Generally associated with military system Provides for many environments Provides multiple quantity levels

        • Bell core (Telcordia) Telecommunication industries standard Models patterned after MIL-HDBK 217 Provides multiple quality level

        • HRD 5

          Telecommunication industries standard Provides multiple quality level

        • NPRD-95

          Non electric parts

          Provides multiple quality level

        • NSWC-07 NAVAL SURFACE WARFARE CENTRE Hand book Reliability Prediction Procedures for Mechanical

      3. Assumptions

        • The components are contnuous failure rates.

        • The mechanisms are in their suitable life period.

        • Infant mortalities are detached by element screening.

        • Wear out has not been reached.

        • The mechanisms are considerably standardized with those under which failure rates are dignified.

        • The prediction model uses a simple reliability series system of all mechanisms, in other words, a failure of any module is expected to lead a system failure.

      4. Environments

        • Ground Benign GB = Non mobile temperature & humidity controlled environment.

        • Ground Benign GF = moderately controlled environment such as installation in permanent racks.

        • Space flight SF = Earth orbital. Approaches benign ground condition.

        • Missile, Flight SF = Condition related to powered flight of air breathing missiles, cruise missiles.

        • Missile, Launch ML =Serve condition related to missile launch, space vehicle re-entre and landing by parachute.

        • Cannon, Launch CL = Extreme severe conditions related to cannon launching of 155 mm and 5 inch.

    8. LCC (Life Cycle Cost)

      It is the overall cost which is bared by a stakeholder so that the system can perform its intended function for a particular mission time (time for which the system has to perform its intended function). It Comprise of Labor cost, material cost to perform Corrective, Preventive and overhauling maintenance for the complete life cycle of system.

      1. Three pillars of LCC

        Corrective Maintenance The maintenance activity performed when the failure is happened. Whenever any system or subsystem is produced it cannot be so robust that it will perform its intended function without any failure. Thus when the subsystem fails we replace it or repair it and record the failure rate for the input to RAMS.

        Preventive maintenance- To minimize the failures we have to perform some kind of maintenance so that availability & reliability of our system is increased and the system can perform its intended function for more time.

        Actions that can be performed as preventive task in HVAC-

        • Filter Cleaning (Fresh air)

        • Filter Cleaning (Mixed / Return air)

        • HVAC Inspection & Cleaning (Evaporator & Condenser Coil, Emergency inverter, transformer, FA RA SA & Humidity sensor)

        • HVAC Inspection & Cleaning (Supply fan & condenser fan motor, Compressor, Pressure Transducers, Heater bank, Contactors & circuit breakers, Controller, Fresh air & return air damper, Doors sealing gaskets, Thermal insulation, Sight glass)

        Overhauling- Some of the sub-systems are having less life than the system. So we have to replace the subsystem at the particular interval. So that our system can perform its intended function without any failure. E.g. If the system is having 15 years of life & subsystem is having 7 years of life, we have to replace that subsystem twice during life of the system.

        Note*- If we are not able to meet LCC targets of our customer we can decrease the frequency of overhauling and increase the failure rate.

        2.11 Reliability Critical Item list of HVAC

        Condenser Coil, Compressor, Liquid level indicator , Condenser Fan Assembly, HP Switch, LP Switch, Liquid line solenoid valve

        , Solenoid Valve Coil, Hand shut-off valves, Filter Drier, Supply air Fan Assembly, Evaporator Coil, Expansion Valve, Heater Assembly, Fresh air damper, Emergency Inverter, Emergency Transformer, Temperature probe 1, Temperature probe 2, Temperature probe 3, Humidity sensor, Connector 1, Connector 2, Compressor contactor, Supply Fan Contactor, Condenser Fan Contactor, Heater contactor, Circuit breakers Compressor, Circuit breaker Supply Fan, Circuit Breaker Condenser fan, Circuit Breaker heater, Rotary switch , Controller, Relay, DC-DC Converter, Thermal overheat protector , Bimetal thermostat.

  1. METHODOLOGY & CALCULATION

Description

Formula

Associated RBD

Resultant Failure rate (Series connected)

system = 1 + 2 + . + n

Where

system = Resultant failure rate of the system. 1 = failure rate of component 1

2 = failure rate of component 2

n = failure rate till n no. of components

Resultant Failure rate (Parallel connected)

Where

Where

Resultant Reliability (Series connected)

R system = R 1 + R 2 + . + R n

Where

R system = Resultant reliability of the system. R 1 = reliability of component 1

R 2 = reliability of component 2

R n = reliability till n no. of components

Resultant Reliability (Parallel connected)

R system = 1-((1- R 1) (1- R 2) – .- (1- R n))

Where

R system = Resultant reliability of the system. R 1 = reliability of component 1

R 2 = reliability of component 2

R n = reliability till n no. of components

    1. Reliability

      1. Failure Rate prediction at subsystem level and calculation of failure rate at system level:

        Table provided below defines the operational parameters of train during a mission time.

        Train Mission Profile

        Project: HVAC with 4 refrigeration circuits

        Unit

        No. of trains

        1

        nos.

        No. of cars per train

        6

        nos.

        Train working hours per day

        21

        hours

        HVAC system working hours per day

        21

        hours

        Annual distance

        320000

        Km

        No. of days in year

        365

        days

        Annual hours of operation

        7665

        hours

        Average speed

        46.14

        Km/h

        Mission time (in years)

        2

        years

        Mission time (in hours)

        15330

        hours

        There are two HVAC system installed in one saloon car of a train. So for 6 car train configuration, there are total 12 HVAC system installed on one train.

        Scope of supply

        Equipment

        Qty per car

        Qty per train

        Saloon HVAC unit

        2

        12

        The failure rate for the items (sub system) mentioned in below tables are taken from standard references. The calculation & conversion of failure rate are elaborated in more details below this table:

        Failure Rate Data

        S.No.

        Item Description

        MTBF (hours)

        Failure rate (hour-1)

        MDBF

        (km)

        FPMH

        (10^-6 hours)

        FPMK (10^-6

        km)

        1

        HVAC

        2

        Condenser Coil

        123791

        8.08E-06

        5711717

        8.078

        0.175

        3

        Compressor

        62152

        1.61E-05

        2867693

        16.090

        0.349

        4

        Liquid level indicator

        545791

        1.83E-06

        25182797

        1.832

        0.040

        5

        Condenser Fan Assembly

        83584

        1.20E-05

        3856566

        11.964

        0.259

        6

        HP Switch

        167752

        5.96E-06

        7740077

        5.961

        0.129

        7

        LP Switch

        167752

        5.96E-06

        7740077

        5.961

        0.129

        8

        Liquid line solenoid valve

        167752

        5.96E-06

        7740077

        5.961

        0.129

        9

        Solenoid Valve Coil

        1438021

        6.95E-07

        66350289

        0.695

        0.015

        10

        Hand shut-off valves

        167752

        5.96E-06

        7740077

        5.961

        0.129

        11

        Filter Drier

        3448275

        2.90E-07

        159103409

        0.290

        0.006

        12

        Supply air Fan Assembly

        83584

        1.20E-05

        3856566

        11.964

        0.259

        13

        Evaporator Coil

        123791

        8.08E-06

        5711717

        8.078

        0.175

        14

        TX Valve

        161168

        6.20E-06

        7436292

        6.205

        0.134

        15

        Heater Assembly

        12165450

        8.22E-08

        561313869

        0.082

        0.002

        16

        Fresh air damper

        99006

        1.01E-05

        4568137

        10.100

        0.219

        17

        Emergency Inverter

        9999999

        1.00E-07

        461399954

        0.100

        0.002

        18

        Emergency Transformer

        1669449

        5.99E-07

        77028381

        0.599

        0.013

        19

        Temperature probe 1

        276816

        3.61E-06

        12772290

        3.613

        0.078

        20

        Temperature probe 2

        276816

        3.61E-06

        12772290

        3.613

        0.078

        21

        Temperature probe 3

        276816

        3.61E-06

        12772290

        3.613

        0.078

        22

        Humidity sensor

        276816

        3.61E-06

        12772290

        3.613

        0.078

        23

        Connector 1

        280614108

        3.56E-09

        12947534943

        0.004

        0.000

        24

        Connector 2

        280614108

        3.56E-09

        12947534943

        0.004

        0.000

        25

        Compressor contactor

        4697065

        2.13E-07

        216722579

        0.213

        0.005

        26

        Supply Fan Contactor

        4697065

        2.13E-07

        216722579

        0.213

        0.005

        27

        condenser Fan Contactor

        4697065

        2.13E-07

        216722579

        0.213

        0.005

        28

        Heater contactor

        4697065

        2.13E-07

        216722579

        0.213

        0.005

        29

        Circuit breakers Compressor

        1176470

        8.50E-07

        54282326

        0.850

        0.018

        30

        Circuit breaker Supply Fan

        1176470

        8.50E-07

        54282326

        0.850

        0.018

        31

        Circuit Breaker condenser fan

        1176470

        8.50E-07

        54282326

        0.850

        0.018

        32

        Circuit Breaker heater

        1176470

        8.50E-07

        54282326

        0.850

        0.018

        33

        Rotary switch

        12165450

        8.22E-08

        561313863

        0.082

        0.002

        34

        Controller

        9999999

        1.00E-07

        461399954

        0.100

        0.002

        35

        Relay

        9999999

        1.00E-07

        461399954

        0.100

        0.002

        36

        DC-DC Converter

        498845016

        2.00E-09

        23016709038

        0.002

        0.000

        37

        Thermal Overheat fuse

        15151823

        6.60E-08

        699105113

        0.066

        0.001

        38

        Bimetal thermostat

        15151823

        6.60E-08

        699105113

        0.066

        0.001

        Calculation of the above table

        1. Condenser Coil

          MTBF 123791 (from NPRD 95 Standard)

          Failure Rate () = 1

          = 1

          123791

          = 8.08E-06 hour-1

          MDBF (Mean Distance between failure) = MTBF * Average speed of train = 123791 * 46.14

          = 5711717 km

          FPMH (Failure per million hour) = Failure Rate () * 106 = 8.08E-06 * 106

          = 8.08

          FPMK (Failure per million kilometer) = FPMH

          = 8.08

          46.14

          = 0.175

          Note* – Same calculation is followed for the complete table.

          Intrinsic Reliability Calculation Cooling function

          S.no.

          Item Description

          MTBF (hours)

          Component Failure rate (/hour)

          Quantity per HVAC

          Total failure Rate (/hour) (HVAC Level)

          1

          Hand shut-off valves

          167752

          5.96E-06

          8

          4.77E-05

          2

          Solenoid coil

          1438021

          6.95E-07

          4

          2.78E-06

          3

          LP SWITCH

          167752

          5.96E-06

          4

          2.38E-05

          4

          Liquid level indicator

          545791

          1.83E-06

          4

          7.33E-06

          5

          Compressor Circuit breaker

          1176470

          8.50E-07

          4

          3.40E-06

          6

          Compressor Contactor

          4697065

          2.13E-07

          4

          8.52E-07

          7

          Expansion valve

          161168

          6.20E-06

          4

          2.48E-05

          8

          Filter Drier

          3448275

          2.90E-07

          4

          1.16E-06

          9

          HP Switch

          167752

          5.96E-06

          4

          2.38E-05

          10

          Liquid line solenoid Valve

          167752

          5.96E-06

          4

          2.38E-05

          11

          Compressor

          62152

          1.61E-05

          4

          6.44E-05

          12

          Evaporator coil

          123791

          8.08E-06

          2

          1.62E-05

          13

          Condenser coil

          123791

          8.08E-06

          2

          1.62E-05

          14

          Condenser fan circuit breaker

          1176470

          8.50E-07

          2

          1.70E-06

          15

          Condenser fan contactor

          4697065

          2.13E-07

          2

          4.26E-07

          16

          Condenser fan

          83584

          1.20E-05

          2

          2.39E-05

          17

          Supply fan circuit breaker

          1176470

          8.50E-07

          2

          1.70E-06

          18

          Supply Fan

          83584

          1.20E-05

          2

          2.39E-05

          19

          Supply fan contactor

          4697065

          2.13E-07

          2

          4.26E-07

          Total failure rate HVAC level (/hour)

          3.08E-04

          Intrinsic failure rate FPMH HVAC level (/Million hour)

          308.34

          Intrinsic failure rate FPMK HVAC level (/Million km)

          6.68

          Intrinsic failure rate FPMK Train level (/Million km)

          80.19

          Total failure rate HVAC level (/hour) = Summation of all failure rates = 3.08E-04

          Total MTTF HVAC level (hour) = 1

          = 3246 hours

          = 1

          .

          Intrinsic failure rate FPMH HVAC level (/Million hour) = Total failure rate HVAC level (/hour) * 106

          = 308.34

          Intrinsic failure rate FPMK HVAC level (/Million km) =Intrinsic failure rate FPMH HVAC level (/Million hour)

          Average Speed

          = 308.34

          .

          = 6.68

          Intrinsic failure rate FPMK Train level (/Million km) = Intrinsic failure rate FPMK HVAC level * No. Of

          HVAC in 1 Train

          = 6.68 * 12

          = 80.19

          Relevant Failure – Reliability Calculation for Cooling function

          S.no.

          Item Description

          Quantity per HVAC

          MTBF (hours

          )

          Failure rate (/hour)

          Duty cycle

          Component MTBF with duty cycle

          Total failure rate (HVAC level) with duty cycle

          1

          Connector 2

          1

          280614108

          3.56E-09

          1

          280614108

          3.56E-09

          2

          DC-DC convertor

          2

          498845016

          2.00E-09

          1

          498845016

          2.00E-09

          3

          Rotary switch

          1

          12165450

          8.22E-08

          1

          12165450

          8.22E-08

          4

          Controller

          1

          9999999

          1.00E-07

          1

          9999999

          1.00E-07

          5

          Connector 1

          1

          280614108

          3.56E-09

          1

          280614108

          3.56E-09

          8.08E-06

          Failure rate of electrical components

          1.91E-07

          6

          Temperature probe 1

          1

          276816

          3.61E-06

          1

          276816

          3.61E-06

          7

          Temperature probe 2

          1

          276816

          3.61E-06

          1

          276816

          3.61E-06

          Failure rate of sensors

          2.00E-07

          8

          Hand shutoff valve

          8

          167752

          5.96E-06

          0.6

          279587

          3.57671E-06

          9

          Solenoid coil

          4

          1438021

          6.95E-07

          0.6

          2396702

          4.17E-07

          10

          LP

          4

          167752

          5.96E-06

          0.6

          279587

          3.58E-06

          11

          Liquid level indicator

          4

          545791

          1.83E-06

          0.6

          909652

          1.10E-06

          12

          Compressor circuit breaker

          4

          1176470

          8.50E-07

          0.6

          1960783

          5.10E-07

          13

          Compressor Contactor

          4

          4697065

          2.13E-07

          0.6

          7828442

          1.28E-07

          14

          Compressor

          4

          62152

          1.61E-05

          0.6

          103587

          9.65E-06

          15

          Liquid line solenoid valve

          4

          167752

          5.96E-06

          0.6

          279587

          3.58E-06

          16

          HP

          4

          167752

          5.96E-06

          0.6

          279587

          3.58E-06

          17

          Filter drier

          4

          3448275

          2.90E-07

          0.6

          5747125

          1.74E-07

          18

          Expansion valve

          4

          161168

          6.20E-06

          0.6

          268613

          3.72E-06

          19

          Evaporator coil

          2

          123791

          0.6

          206318

          4.85E-06

          20

          Condenser coil

          2

          123791

          8.08E-06

          0.6

          206318

          4.85E-06

          Failure rate of one cooling branch

          3.97E-05

          MTBF of one cooling branch

          25185

          Failure rate of two parallel cooling branch

          2.42E-05

          21

          Condenser fan circuit breaker

          2

          1176470

          8.50E-07

          1

          1176470

          8.50E-07

          22

          Condenser fan contactor

          2

          4697065

          2.13E-07

          1

          4697065

          2.13E-07

          23

          Condenser fan

          2

          83584

          1.20E-05

          1

          83584

          1.20E-05

          Failure rate of one condenser fan branch

          1.30E-05

          Failure rate of one complete cooling circuits

          3.72E-05

          MTBF of one complete cooling circuits

          26885

          Failure rate of all cooling circuits

          2.12E-05

          24

          Supply fan circuit breaker

          2

          1176470

          8.50E-07

          1

          1176470

          8.50E-07

          25

          Supply fan contactor

          2

          4697065

          2.13E-07

          1

          4697065

          2.13E-07

          26

          Supply fan

          2

          83584

          1.20E-05

          1

          83584

          1.20E-05

          Failure rate of one supply fan branch

          1.30E-05

          MTBF of one supply fan branch

          76764

          Failure rate of two supply fan branches

          2.60E-06

          Total failure rate HVAC level (/hour)

          2.42.E-05

          Total failure rate FPMH HVAC level (/Million hour)

          24.20

          Total failure rate FPMK HVAC level (/Million km)

          0.52

          Total failure rate FPMK Train level (/Million km)

          6.29

          Resultant Failure rate (Series connected) = system = 1 + 2 + . + n

          Resultant Failure rate (Parallel connected) =

          = 1

          (())/)

          Failure rate of electrical components (all are in Series)

          = Connector 2 + DC-DC convertor + Rotary switch + Controller + Connector 1

          = 3.56E-09 + 2.00E-09 + 8.22E-08 + 1.00E-07 + 3.56E-09

          = 1.91E-07 Failures/ hour Failure rate of sensors (all are in Parallel) = 1

          (())/)

          Temperature Probe 1 = 3.61E-06 Temperature Probe 2 = 3.61E-06 MTBF = 276816 hours Mission Time = 15330 Hours

          = 1

          ((276816))/15330)

          = 2.00E-07 Failures / hour

          Failure rate of one cooling branch

          = Hand shutoff valve + Solenoid coil + LP + Liquid level indicator + Compressor circuit breaker + Compressor Contactor + Compressor + Liquid line solenoid valve + HP + Filter drier + Expansion valve + Evaporator coil + Condenser coil

          = 3.97E-05 Failures/ hour

          MTBF one cooling branch = 25185 hours

          Failure rate of two parallel cooling branch = 1

          (())/)

          MTBF one cooling branch = 25185 hours Mission Time = 15330 hours

          = 1

          (())/)

          = 1

          ((25185))/15330)

          = 2.42E-05 Failures/ hour

          Failure rate of one condenser fan branch =

          Condenser fan circuit breaker + Condenser fan contactor + Condenser fan

          = 8.50E-07 + 2.13E-07 + 1.20E-05

          = 1.30E-05 Failures/ hour

          Failure rate of one complete cooling circuits =

          Failure rate of two parallel cooling branch + Failure rate of one condenser fan branch

          = 2.42E-05 + 1.30E-05

          = 3.72E-05 Failures/ hour

          Failure rate of all 4 cooling circuits (Parallel)= 1

          (())/)

          MTBF One complete cooling circuit along with condenser fan = 26885 hours Mission Time = 15330 hours

          1

          ((26885))/15330)

          Failure rate of all 4 cooling circuits = 2.12E-05 Failures/hour

          Failure rate of one supply fan branch (all in series)

          = Supply fan circuit breaker + Supply fan contactor+ Supply fan

          = 8.50E-07 + 2.13E-07 + 1.20E-05

          = 1.30E-05 Failures/ Hour

          Failure rate of two supply fan branches (Parallel) = 1

          (())/)

          MTBF one supply fan branch = 76764

          1 ((76764))/15330)

          Failure rate of two supply fan branches = 2.60E-06 Failures/ hour

          Total failure rate HVAC level (Series) = Failure rate of electrical components + Failure rate of sensors + Failure rate of all cooling circuits + Failure rate of two supply fan branches

          = 1.91E-07 + 2.00E-07+ 2.12E-05+ 2.60E-06

          = 2.42.E-05 Failure/Hour

          Total failure rate FPMH HVAC level (/Million hour) = Total failure rate HVAC level * 106

          = 24.20

          Total failure rate FPMK HVAC level (/Million km) = Total failure rate FPMH HVAC level

          = 24.20

          46.14

          = 0.52

          Total failure rate FPMK Train level (/Million km) = Total failure rate FPMK HVAC level * No. Of

          HVAC per train

          = 0.52* 12

          = 6.29

          td>

          3.61E-06

          Relevant Failure – Reliability Calculation for Heating function

          S.no.

          Item Description

          Quantity per HVAC

          MTBF (hours

          )

          Failure rate (hour-1)

          Duty cycle

          Component MTBF with duty cycle

          Total failure rate on HVAC level with duty cycle

          1

          Connector 2

          1

          280614108

          3.56E-09

          1

          280614108

          3.56E-09

          2

          DC-DC convertor

          2

          498845016

          2.00E-09

          1

          498845016

          2.00E-09

          3

          Rotary switch

          1

          12165450

          8.22E-08

          1

          12165450

          8.22E-08

          4

          Controller

          1

          9999999

          1.00E-07

          1

          9999999

          1.00E-07

          5

          Connector 1

          1

          280614108

          3.56E-09

          1

          280614108

          3.56E-09

          Failure rate of electrical components

          1.91E-07

          6

          Temperature probe 1

          1

          276816

          3.61E-06

          1

          276816

          7

          Temperature probe 2

          1

          276816

          3.61E-06

          1

          276816

          3.61E-06

          Failure rate of sensors

          2.00E-07

          8

          Heater circuit breaker

          2

          1176470

          8.50E-07

          1

          1176470

          8.50E-07

          9

          Heater contactor

          2

          4697065

          2.13E-07

          1

          4697065

          2.13E-07

          10

          Bimetal thermostat

          4

          15151823

          6.60E-08

          1

          15151823

          1.32E-07

          11

          Thermal overheat fuse

          2

          15151823

          6.60E-08

          1

          15151823

          6.60E-08

          12

          Heater

          2

          12165450

          8.22E-08

          1

          12165450

          8.22E-08

          Failure rate of SF2 category components

          1.34E-06

          MTBF of one heating branch

          744549

          Failure rate of two heating branches

          2.77E-08

          13

          Supply fan circuit breaker

          2

          1176470

          8.50E-07

          1

          1176470

          8.50E-07

          14

          Supply fan contactor

          2

          1176470

          8.50E-07

          1

          1176470

          8.50E-07

          15

          Supply fan

          2

          83584

          1.20E-05

          1

          83584

          1.20E-05

          Failure rate of one supply fan branch

          1.37E-05

          MTBF of one supply fan branch

          73185

          Failure rate of two supply fan branches

          2.86E-06

          Total failure rate HVAC level (/hour)

          3.28.E-06

          Total failure rate FPMH HVAC level (/Million hour)

          3.28

          Total failure rate FPMK HVAC level (/Million km)

          0.07

          Total failure rate FPMK Train level (/Million km)

          0.85

          Relevant Failure – Reliability Calculation for Ventilation function

          S.no.

          Item Description

          Quantity per HVAC

          MTBF (hours

          )

          Failure rate (hour-1)

          Duty cycle

          Component MTBF with duty cycle

          Total failure rate on HVAC level with duty cycle

          1

          Connector 2

          1

          280614108

          3.56E-09

          1

          280614108

          3.56E-09

          2

          DC-DC converter

          2

          498845016

          2.00E-09

          1

          498845016

          2.00E-09

          3

          Rotary switch

          1

          12165450

          8.22E-08

          1

          12165450

          8.22E-08

          4

          Controller

          1

          9999999

          1.00E-07

          1

          9999999

          1.00E-07

          5

          Connector 1

          1

          280614108

          3.56E-09

          1

          280614108

          3.56E-09

          Failure rate of electrical components

          1.91E-07

          6

          Temperature probe 1

          1

          276816

          3.61E-06

          1

          276816

          3.61E-06

          7

          Temperature probe 2

          1

          276816

          3.61E-06

          1

          276816

          3.61E-06

          Failure rate of sensors

          2.00E-07

          8

          Supply fan circuit breaker

          2

          280614108

          3.56E-09

          1

          280614108

          3.56E-09

          9

          Supply fan contactor

          2

          280614108

          3.56E-09

          1

          280614108

          3.56E-09

          10

          Supply fan

          2

          83584

          1.20E-05

          1

          83584

          1.20E-05

          Failure rate of one supply fan branch

          1.20E-05

          MTBF of one supply fan branch

          83534

          Failure rate of two supply fan branches

          2.20E-06

          Total failure rate HVAC level (/hour)

          2.59.E-06

          Total failure rate FPMH HVAC level (/Million hour)

          2.59

          Total failure rate FPMK HVAC level (/Million km)

          0.06

          Total failure rate FPMK Train level (/Million km)

          0.67

          Service Failure – Reliability Calculation for Heating

          S.no.

          Item Description

          Quantity per HVAC

          MTBF

          (hours )

          Failure rate (hour-1)

          Duty cycle

          Component MTBF with duty cycle

          Total failure rate (HVAC level) with duty cycle

          1

          Thermal Overheat fuse

          2

          15151823

          6.60E-08

          0.5

          30303646

          3.30E-08

          MTBF Fuse

          3.03E+07

          Parallel FAILURE RATE Fuse

          2.29E-14

          2

          Supply fan circuit breaker

          2

          1176470

          8.50E-07

          1

          1176470

          8.50E-07

          3

          Supply fan contactor

          2

          4697065

          2.13E-07

          1

          4697065

          2.13E-07

          4

          Supply fan

          2

          83584

          1.20E-05

          1

          83584

          1.20E-05

          Failure Rate Series

          1.30E-05

          MTBF

          7.68E+04

          Parallel FAILURE RATE Of supply fan

          2.60E-06

          Failure rate of SF2 category components

          2.60E-06

          Total failure rate FPMH HVAC level (/Million hour)

          2.60E+00

          Total failure rate FPMK HVAC level (/Million km)

          0.0564

          Total failure rate FPMK Train level (/Million km)

          0.677

          Service Failure – Reliability Calculation for Emergency Ventilation function

          S.no.

          Item Description

          Quantity per HVAC

          MTBF (hours

          )

          Failure rate (hour-1)

          Duty cycle

          Component MTBF with duty cycle

          Total failure rate on HVAC level with duty cycle

          1

          Connector 2

          1

          280614108

          3.56361E-09

          1

          280614108

          3.56E-09

          2

          DC-DC converter

          2

          498845016

          2.00463E-09

          1

          498845016

          2.00E-09

          3

          Rotary switch

          1

          12165450

          8.22E-08

          1

          12165450

          8.22E-08

          4

          Emergency Inverter

          1

          9999999

          1.00E-07

          1

          9999999

          1.00E-07

          5

          Emergency Transformer

          1

          1669449

          5.99E-07

          1

          1669449

          5.99E-07

          Failure rate of electrical components

          7.87E-07

          6

          Supply fan circuit breaker

          2

          1176470

          8.5E-07

          1

          1176470

          8.50E-07

          7

          Supply fan contactor

          2

          4697065

          2.12899E-07

          1

          4697065

          2.13E-07

          8

          Supply fan

          2

          83584

          1.1964E-05

          1

          83584

          1.20E-05

          Failure rate of one supply fan branch

          1.30E-05

          MTBF of one supply fan branch

          76764

          Failure rate of two supply fan branches

          2.60E-06

          Total failure rate HVAC level (/hour)

          3.39.E-06

          Total failure rate FPMH HVAC level (/Million hour)

          3.39

          Total failure rate FPMK HVAC level (/Million km)

          0.07

          Total failure rate FPMK Train level (/Million km)

          0.88

          Reliability Calculation category wise

          S.no.

          Item Description

          Total failure rate (Train level) FPMK

          1

          Relevant Failure Cooling function

          6.294

          2

          Relevant Failure Heating function

          0.853

          3

          Relevant Failure Ventilation

          0.673

          4

          Service Failure Emergency Ventilation

          0.881

          5

          Service Failure Heating

          0.677

    2. Reliability Block Diagram

      Item Description

      Per HVAC

      MTBF

      Life of item in years

      Hour Per year

      Mission Time

      ( Hours )

      Reliability

      Reliability %

      HVAC

      1

      96.804%

      Condenser Coil

      2

      123791

      2

      7300

      14600

      0.889

      88.875

      Compressor

      4

      62152

      2

      7300

      14600

      0.791

      79.064

      Liquid level indicator

      4

      545791

      2

      7300

      14600

      0.974

      97.360

      Condenser Fan Assembly

      2

      83584

      2

      7300

      14600

      0.840

      83.973

      HP Switch

      4

      167752

      2

      7300

      14600

      0.917

      91.665

      LP Switch

      4

      167752

      2

      7300

      14600

      0.917

      91.665

      Liquid line solenoid valve

      4

      167752

      2

      7300

      14600

      0.917

      91.665

      Solenoid Valve Coil

      4

      1438021

      2

      7300

      14600

      0.990

      98.990

      Hand shut-off valves

      8

      167752

      2

      7300

      14600

      0.917

      91.665

      Filter Drier

      4

      3448275

      2

      7300

      14600

      0.996

      99.577

      Supply air Fan Assembly

      2

      83584

      2

      7300

      14600

      0.840

      83.973

      Evaporator Coil

      1

      123791

      2

      7300

      14600

      0.889

      88.875

      TX Valve

      4

      161168

      2

      7300

      14600

      0.913

      91.339

      Heater Assembly

      1

      12165450

      2

      7300

      14600

      0.999

      99.880

      Fresh air damper

      2

      99006

      2

      7300

      14600

      0.863

      86.289

      Emergency Inverter

      1

      9999999

      2

      7300

      14600

      0.999

      99.854

      Emergency Transformer

      1

      1669449

      2

      7300

      14600

      0.991

      99.129

      Temperature probe 1

      1

      276816

      2

      7300

      14600

      0.949

      94.862

      Temperature probe 2

      1

      276816

      2

      7300

      14600

      0.949

      94.862

      Temperature probe 3

      1

      276816

      2

      7300

      14600

      0.949

      94.862

      Humidity sensor

      1

      276816

      2

      7300

      14600

      0.949

      94.862

      Connector 1

      1

      280614108

      2

      7300

      14600

      1.000

      99.995

      Connector 2

      1

      280614108

      2

      7300

      14600

      1.000

      99.995

      Compressor contactor

      4

      4697065

      2

      7300

      14600

      0.997

      99.690

      Supply Fan Contactor

      2

      4697065

      2

      7300

      14600

      0.997

      99.690

      Condenser Fan Contactor

      2

      4697065

      2

      7300

      14600

      0.997

      99.690

      Heater contactor

      2

      4697065

      2

      7300

      14600

      0.997

      99.690

      Circuit breakers Compressor

      4

      1176470

      2

      7300

      14600

      0.988

      98.767

      Circuit breaker Supply Fan

      2

      1176470

      2

      7300

      14600

      0.988

      98.767

      Circuit Breaker Condenser fan

      2

      1176470

      2

      7300

      14600

      0.988

      98.767

      Circuit Breaker heater

      2

      1176470

      2

      7300

      14600

      0.988

      98.767

      Rotary switch

      1

      12165450

      2

      7300

      14600

      0.999

      99.880

      Controller

      1

      200401

      2

      7300

      14600

      0.930

      92.974

      Relay

      25

      9999999

      2

      7300

      14600

      0.999

      99.854

      DC-DC Converter

      2

      498845016

      2

      7300

      14600

      1.000

      99.997

      Thermal Overheat protector

      1

      15151823

      2

      7300

      14600

      0.999

      99.904

      Bimetal thermostat

      1

      15151823

      2

      7300

      14600

      0.999

      99.904

      Reliability Block Diagram for RRTS HVAC unit

      FAT

      Hand shut LP Liquid level Compressor Compressor Compressor HP Hand shut

      0.9486 off valve CB Contactor off valve 0.9166 0.9166 0.9736 0.9877 0.9969 0.7906 0.9166 0.9166

      Connector 2 DC- DC Rotary Controller Connector 1 RAT Converter switch

      0.9999 1.0000 0.9988 0.9297 0.9999 0.9486 0.384422308

      0.998719 SAT

      0.929688257 Filter Expansion Evaporator Condenser

      0.9486 drier valve coil coil

      0.99986439 0.9958 0.9134 0.8887 0.8887

      Complete HVAC Reliability 0.96804

      0.926840275

      Hand shut LP Liquid level Compressor Compressor Compressor HP Hand shut off valve CB Contactor off valve

      0.9166 0.9166 0.9736 0.9877 0.9969 0.7906 0.9166 0.9166 Condenser Cond. Fan Condenser Supply fan Supply fan Supply

      fan CB Contactor fan CB Contactor fan

      0.9877 0.9969 0.8397 0.9877 0.9969 0.8397

      0.384422308 0.826799621

      0.82679962

      Filter Expansion Evaporator Condenser drier valve coil coil 0.9958 0.9134 0.8887 0.8887

      0.621064105 0.51349557

      Hand shut

      LP

      Liquid level

      Compressor

      Compressor

      Compressor

      HP

      Hand shut

      off valve

      CB

      Contactor

      off valve

      0.9166

      0.9166

      0.9736

      0.9877

      0.9969

      0.7906

      0.9166

      0.9166

      0.384422308

      Filter

      Expansion

      Evaporator

      Condenser

      drier

      valve

      coil

      coil

      0.9958

      0.9134

      0.8887

      0.8887

      Hand shut

      LP

      Liquid level

      Compressor

      Compressor

      Compressor

      HP

      Hand shut

      off valve

      CB

      Contactor

      off valve

      0.9166

      0.9166

      0.9736

      0.9877

      0.9969

      0.7906

      0.9166

      0.9166

      Condenser

      Cond. Fan

      Condenser

      Supply fan

      Supply fan

      Supply

      fan CB

      Contactor

      fan

      CB

      Contactor

      fan

      0.9877

      0.9969

      0.8397

      0.9877

      0.9969

      0.8397

      0.384422308

      0.82679962

      0.826799621

      Filter

      Expansion

      Evaporator

      Condenser

      drier

      valve

      coil

      coil

      0.970001629

      0.9958

      0.9134

      0.8887

      0.8887

      0.51349557

      0.621064105

      Heater

      Bimetal

      Thermal Overheat protector

      Heater

      Contactor

      Thermostat

      0.9969

      0.9990

      0.9990

      0.9988

      Heater

      0.993783796

      CB

      0.9877

      0.999961359

      Heater

      Bimetal

      Thermal Overheat protector

      Heater

      Contactor

      Thermostat

      0.987628516

      0.9969

      0.9990

      0.9990

      0.9988

      0.993783796

      0.99707184

      Emergency Emergency

      0.999257 Inverter Transformer

      0.9985 0.9913

      0.989846498

    3. Availability

      1. MTTR (Mean Time to repair) of complete HVAC

        S.no.

        Item Description

        Qty per system, Qi

        Individual Failure Rate, i [FPMH]

        Average Time to Perform Corrective Maintenance Tasks, MTTRi

        MTTR

        i

        (h)

        Qi×i

        Qi×i×MT TRi

        Localiz ation

        Isolat ion

        Disasse mbly

        Interch ange

        Reassem ble

        Alignm ent

        Check out

        1

        Condenser Coil

        2

        8.078

        0.16

        0.16

        0.25

        0.25

        0.93

        0.25

        6

        8.00

        16.16

        1.29E+02

        2

        Compressor

        4

        16.090

        0.16

        0.16

        0.25

        0.25

        0.93

        0.25

        6

        8.00

        64.36

        5.15E+02

        3

        Sight glass

        4

        1.8322

        0.0833

        0.083

        0.25

        0.25

        0.93

        0.25

        6

        6.00

        7.33

        4.40E+01

        4

        Condenser Fan Assembly

        2

        11.964

        0.0833

        0.083

        0.06

        0.06

        0.06

        0.06

        0.06

        0.5

        23.92

        11.96

        5

        HP Switch

        4

        5.96118

        0.0833

        0.083

        0.06

        0.06

        0.06

        0.06

        0.06

        0.5

        23.84

        11.92

        6

        LP Switch

        4

        5.96118

        0.0833

        0.083

        0.06

        0.06

        0.06

        0.06

        0.06

        0.5

        23.84

        11.92

        7

        Liquid line solenoid valve

        4

        5.961

        0.0833

        0.083

        0.25

        0.25

        0.93

        0.25

        6

        6

        23.84

        143.07

        8

        Solenoid Valve Coil

        4

        0.695

        0.0833

        0.083

        0.016

        0.017

        0.017

        0.017

        0.017

        0.25

        2.78

        0.695

        9

        Hand shut-off valves

        8

        5.96118

        0.0833

        0.083

        0.25

        0.25

        0.93

        0.25

        6

        6

        47.69

        286.14

        10

        Filter Drier

        4

        0.29

        0.0833

        0.083

        0.166

        0.167

        0.167

        0.167

        0.167

        1

        1.160

        1.160

        11

        Supply air Fan Assembly

        2

        11.964

        0.0833

        0.083

        0.066

        0.067

        0.067

        0.067

        0.067

        0.5

        23.93

        11.96

        12

        Evaporator Coil

        1

        8.078

        0.16

        0.16

        0.25

        0.25

        0.93

        0.25

        6

        8

        8.078

        64.63

        13

        TX Valve

        4

        6.205

        0.0833

        0.083

        0.25

        0.25

        0.93

        0.25

        6

        6

        24.82

        148.912

        14

        Heater Assembly

        1

        0.082

        0.0833

        0.083

        0.06

        0.06

        0.06

        0.06

        0.06

        0.5

        0.082

        2

        0.0411

        15

        Thermal overload fuse

        1

        0.066

        0.0833

        0.083

        0.02

        0.02

        0.02

        0.02

        0.02

        0.25

        0.066

        0.01649

        16

        Thermal fuse

        1

        0.066

        0.0833

        0.083

        0.01

        0.01

        0.01

        0.01

        0.01

        0.1

        0.066

        0.00659

        17

        Bimetal thermostat

        3

        0.066

        0.0833

        0.083

        0.01

        0.01

        0.01

        0.01

        0.01

        0.1

        0.198

        0.01979

        18

        Fresh air damper

        2

        10.1004

        0.0833

        0.083

        0.37

        0.37

        0.37

        0.37

        0.37

        2

        20.20

        40.402

        19

        Emergency Inverter

        1

        0.1

        0.16

        0.16

        0.04

        0.04

        0.04

        0.04

        0.04

        0.5

        0.1

        0.0500

        20

        Emergency Transformer

        1

        0.599

        0.16

        0.16

        0.04

        0.04

        0.04

        0.04

        0.04

        0.5

        0.599

        0.2995

        21

        Temperature probe 1

        1

        3.613

        0.0833

        0.083

        0.02

        0.02

        0.02

        0.02

        0.02

        0.25

        3.613

        0.903

        22

        Temperature probe 2

        1

        3.613

        0.0833

        0.083

        0.17

        0.17

        0.17

        0.17

        0.17

        1

        3.612

        3.613

        23

        Temperature probe 3

        1

        3.613

        0.0833

        0.083

        0.0167

        0.017

        0.017

        0.017

        0.017

        0.25

        3.612

        0.9031

        24

        Humidity sensor

        1

        3.613

        0.0833

        0.083

        0.0167

        0.017

        0.017

        0.017

        0.017

        0.25

        3.612

        0.90312

        25

        Connector 1

        1

        0.00356

        0.0833

        0.083

        0.0667

        0.067

        0.067

        0.067

        0.067

        0.5

        0.003

        0.00178

        26

        Connector 2

        1

        0.00356

        0.0833

        0.083

        0.1667

        0.167

        0.167

        0.167

        0.167

        1

        0.003

        0.0035

        27

        Compressor contactor

        4

        0.2129

        0.0833

        0.083

        0.0167

        0.017

        0.017

        0.017

        0.017

        0.25

        0.851

        0.2128

        28

        Supply Fan, Condenser Fan & Heater contactor

        6

        0.2129

        0.0833

        0.083

        0.0167

        0.017

        0.017

        0.017

        0.017

        0.25

        1.277

        0.31934

        29

        Circuit breakers (all type)

        10

        0.850

        0.0833

        0.083

        0.0167

        0.017

        0.017

        0.017

        0.017

        0.25

        8.500

        2.125001

        30

        Rotary switch

        1

        0.0822

        0.0833

        0.083

        0.0167

        0.017

        0.017

        0.017

        0.017

        0.25

        0.082

        0.02055

        31

        Controller

        1

        0.1

        0.05

        0.05

        0.08

        0.08

        0.08

        0.08

        0.08

        0.5

        0.1

        0.050000

        32

        Relay

        25

        0.1

        0.0833

        0.083

        0.0667

        0.067

        0.067

        0.067

        0.067

        0.5

        2.500

        1.250000

        33

        DC-DC Converter

        2

        0.002

        0.0833

        0.083

        0.0167

        0.017

        0.017

        0.017

        0.017

        0.25

        0.004

        0.001002

        n i=1 n i=1

        ( ) = 1.43E+03

        ( ) = 3.41E+02

        =

        =

        n () 1.43E+03

        MTTR =

        i=1

        i=1

        i=1

        n () 3.41E+02

        MTTR of Complete HVAC = 4.20E+00 hours

      2. MTBF (Mean Time between Failures) of complete HVAC Reliability for 2 years of mission time = 96.80398%

        Mission Time (hours) = 2 years = 2* 7665

        =15330 hours

        R (t) = ()

        = e- *t

        After applying above equation Failure rate () of complete HVAC = 2.121E-06

        MTBF = 1/ Failure rate () =471475

      3. Availability of Complete HVAC

        A =

        +

        Availability of complete HVAC = 99.999109%

    4. Maintainability

      = 471475

      471475+ .

      = 0.99999109

      Repair rate = µ = 1

      MTTR

      = 1

      .

      = 0.23809

      t = allowable down time

      = 2 hours

      Maintainability = M (t) = µ µ = 1 – µ

      = 0.3788

      Maintainability of complete HVAC = 37.88 %

    5. Safety

      Hazard Rate h (t) = ()

      ()

      F (t) = 1- R (t)

      = 1 0.96

      = 0.04

      R (t) = 0.96

      h (t) = 0.04 = 0.04166

      0.96

      Hazard Rate of complete HVAC = 4.166%

  1. RESULTS

    Failure Rate of individual components so that main culprits of failure can be find out and either the components are to be changed or redundancy is provided.

    Failure rate (per hour)

    0.000018

    0.000016

    0.000014

    0.000012

    0.00001

    0.000008

    0.000006

    0.000004

    0.000002

    Condensor Coil

    Compressor Liquid level indicator Condensor Fan Assembly

    HP Switch LP Switch

    Liquid line solenoid valve Solenoid Valve Coil Hand shut-off valves

    Filter Drier Supply air Fan Assembly

    Evaporator Coil

    TX Valve Heater Assembly Fresh air damper Emergency Inverter

    Emergency Transformer Temperature probe 1

    Temperature probe 2

    Temperature probe 3

    Hygrostate

    Connector 1

    Connector 2 Compressor contactor Supply Fan Contactor Condensor Fan Contactor

    Heater contactor Circuit breakers Compressor Circuit breaker Supply Fan Circuit Breaker Condensor fan Circuit Breaker heater

    Rotary switch Controller

    Relay DC-DC Converter

    Thermal Overheat protector Bimetal thermostate

    Condensor Coil

    Compressor Liquid level indicator Condensor Fan Assembly

    HP Switch LP Switch

    Liquid line solenoid valve Solenoid Valve Coil Hand shut-off valves

    Filter Drier Supply air Fan Assembly

    Evaporator Coil

    TX Valve Heater Assembly Fresh air damper Emergency Inverter

    Emergency Transformer Temperature probe 1

    Temperature probe 2

    Temperature probe 3

    Hygrostate

    Connector 1

    Connector 2 Compressor contactor Supply Fan Contactor Condensor Fan Contactor

    Heater contactor Circuit breakers Compressor Circuit breaker Supply Fan Circuit Breaker Condensor fan Circuit Breaker heater

    Rotary switch Controller

    Relay DC-DC Converter

    Thermal Overheat protector Bimetal thermostate

    0

    Repair of individual components so that main culprits of loss in availability can be find out and either the components are to be changed or redundancy is provided.

    Repair Time (hours)

    Repair Time (hours)

    DC-DC Converter

    Relay Controller Rotary switch

    Circuit breakers (all type) Supply Fan, Condensor Fan & Heater contactor

    Compressor contactor Control Connector P2 Power Connector P1

    Hygrostate Temprature probe 3

    Temprature probe 2

    Temprature probe 1 Emergency Transformer Emergency Inverter Fresh air damper Bimetal thermostat

    Thermal fuse

    ESTI

    Heater Assembly

    TX Valve Evaporator Coil

    Supply air Fan Assembly

    Filter Drier Hand shut-off valves Solenoid Valve Coil Liquid line solenoid valve

    LP Switch HP Switch

    Condensor Fan Assembly

    Sight glass Compressor Condensor Coil

    DC-DC Converter

    Relay Controller Rotary switch

    Circuit breakers (all type) Supply Fan, Condensor Fan & Heater contactor

    Compressor contactor Control Connector P2 Power Connector P1

    Hygrostate Temprature probe 3

    Temprature probe 2

    Temprature probe 1 Emergency Transformer Emergency Inverter Fresh air damper Bimetal thermostat

    Thermal fuse

    ESTI

    Heater Assembly

    TX Valve Evaporator Coil

    Supply air Fan Assembly

    Filter Drier Hand shut-off valves Solenoid Valve Coil Liquid line solenoid valve

    LP Switch HP Switch

    Condensor Fan Assembly

    Sight glass Compressor Condensor Coil

    0

    1

    2

    3

    4

    5

    6

    7

    8

    9

    0

    1

    2

    3

    4

    5

    6

    7

    8

    9

    Reliability of individual components so that main culprits of reliability can be find out and either the components are to be changed or redundancy is provided.

    Reliability %

    120.000

    100.000

    80.000

    60.000

    40.000

    20.000

    0.000

    Condensor Coil

    Compressor Liquid level indicator Condensor Fan Assembly

    HP Switch LP Switch

    Liquid line solenoid valve Solenoid Valve Coil Hand shut-off valves

    Filter Drier

    Supply air Fan Assembly

    Evaporator Coil

    TX Valve Heater Assembly Fresh air damper Emergency Inverter

    Emergency Transformer Temperature probe 1

    Temperature probe 2

    Temperature probe 3

    Hygrostate

    Connector 1

    Connector 2 Compressor contactor Supply Fan Contactor Condensor Fan Contactor

    Heater contactor Circuit breakers Compressor Circuit breaker Supply Fan Circuit Breaker Condensor fan Circuit Breaker heater

    Rotary switch

    Controller

    Relay DC-DC Converter

    Thermal Overheat protector Bimetal thermostate

    Condensor Coil

    Compressor Liquid level indicator Condensor Fan Assembly

    HP Switch LP Switch

    Liquid line solenoid valve Solenoid Valve Coil Hand shut-off valves

    Filter Drier

    Supply air Fan Assembly

    Evaporator Coil

    TX Valve Heater Assembly Fresh air damper Emergency Inverter

    Emergency Transformer Temperature probe 1

    Temperature probe 2

    Temperature probe 3

    Hygrostate

    Connector 1

    Connector 2 Compressor contactor Supply Fan Contactor Condensor Fan Contactor

    Heater contactor Circuit breakers Compressor Circuit breaker Supply Fan Circuit Breaker Condensor fan Circuit Breaker heater

    Rotary switch

    Controller

    Relay DC-DC Converter

    Thermal Overheat protector Bimetal thermostate

    Reliability %

    120.000

    100.000

    80.000

    60.000

    40.000

    20.000

    0.000

    Data

    Results

    Reliability of complete HVAC with 4 Circuits (2 years of mission time)

    96.804%

    MTTR of complete HVAC with 4 Circuits (2 years of mission time)

    4.20E+00 hours

    Availability of complete HVAC with 4 Circuits (2 years of mission time)

    99.99911%

    Maintainability of complete HVAC with 4 Circuits (2 years of mission time)

    37.88 %

    Safety/ Hazard rate of complete HVAC with 4 Circuits (2 years of mission time)

    4.166%

  2. CONCLUSION

    This research was accomplished in assistance with mentor in RAMS & service of HVAC with an approach of quality & reliability enhancement at the system level by taking in consideration of service failure & relevant failures.

    The research work was carried out to find the reliability at system level by using the sub system level approach. To enhance the reliability of the system we provided redundancy at the subsystem level by analyzing the failure rate (taken from respective standards) of reliability critical sub system along with mission time.

    On the basis of reliability & time to restore the system to perform its intended function, we calculated the availability of the system at train level.

    Maintainability analysis of the system is carried out by taking in consideration of the repair rate and allowable down time at train level.

    For safety analysis, we have taken the HVAC failure which leads to fire, HVAC explosion, toxic refrigerant leak, electrocution. We have calculated the Hazard rate by taking inputs from probability density function and reliability function.

    The key objective of the research was to study how the redundancy provided at sub system level will enhance the system level reliability.

    The key objective of this research was the calculation of the availability of HVAC at train level. The benchmark value of availability for HVAC in rolling stock is approx. greater than 95% during normal operation as by the calculation of 4 circuit, we get he value of 99.99 %. This shows the series parallel combination of sub system is perfect as per requirement of rolling stock.

  3. ABBREVIATIONS

    RAMS Reliability, availability, maintainability & safety HVAC Heating ventilation air conditioners

    MTBF – Mean time between failure MDBF Mean distance between failure FPMH – Failure per million hour FPMK – Failure per million kilometers MTTR Mean time to repair

    LCC Life cycle cost

  4. REFERENCES

  1. United States Air Force Rome Laboratory Reliability Engineer's Toolkit (1993).

  2. MIL-HDBK-338, Electronic Reliability Design Handbook.

  3. Klion, Jerome, A Redundancy Notebook, Rome Air Development Center, RADC-TR-77-287, December 1987.

  4. Reliability Modeling and Prediction, MIL-STD-756B, November 1981.

  5. McGregor, Malcolm A., Approximation Formulas for Reliability with Repair, IEEE Transactions on Reliability, Volume R-12, Number 4, December 1963.

  6. Bazovsky, Igor, Reliability Theory and Practice.

  7. O'Connor, Patrick, D. T., Practical Reliability Engineering.

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