# RAMS of HVAC for Rolling Stock Application

DOI : 10.17577/IJERTV10IS080073

Text Only Version

#### 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/Âµ

A = Âµ

+Âµ

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 = Âµ = 1

MTTR

Repair

Repair

t = allowable down time

Repair function =

Âµ * Âµ

Repair function =

Âµ * Âµ

t

t

Time

Time

Âµ Âµ = = MTTR

Âµ

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

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 99.995 Connector 2 1 280614108 2 7300 14600 1 99.995 Compressor contactor 4 4697065 2 7300 14600 0.997 99.69 Supply Fan Contactor 2 4697065 2 7300 14600 0.997 99.69 Condenser Fan Contactor 2 4697065 2 7300 14600 0.997 99.69 Heater contactor 2 4697065 2 7300 14600 0.997 99.69 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 99.88 Controller 1 200401 2 7300 14600 0.93 92.974 Relay 25 9999999 2 7300 14600 0.999 99.854 DC-DC Converter 2 498845016 2 7300 14600 1 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) QiÃ—i QiÃ—iÃ—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 = Âµ = 1

MTTR

= 1

.

= 0.23809

t = allowable down time

= 2 hours

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

= 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.