RAMS of HVAC for Rolling Stock Application

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

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.