Applying RCM strategy for productive consideration in rolling stock workshop A case study in RAJA Passenger Train Co. Seyed Mohammad Rezvani Zaniani * Mahmoud Valibeigloo Mehdi Asghari RAJA Passenger Trains Co. & Joint master students of maintenance engineering in Luleå University, Luleå, Sweden and Sharif University, Tehran, Iran

[email protected], [email protected], [email protected] Abstract The proper maintenance strategy is the significant concern for rolling stock companies. Historically, most of the maintenance tasks in rolling stock companies are devoted to Preventive Maintenance which leads to some problems such as erroneous maintenance work, unnecessary and conservative maintenance tasks, etc. Hence, it was essential to develop the new strategies to deal with these problems. While the safety is the significant factor in rolling stock industries, the most well known and widely applied maintenance optimization strategy is Reliability Centered Maintenance (RCM), which has its origins in the aerospace industry. So this paper introduce the RCM strategy which offers the most systematic and efficient process to address an overall programmatic approach to the optimization of plant and equipment maintenance productivity. Moreover, the present paper step by step presents the implementation of RCM methodology in the rolling stock maintenance industry in RAJA Passenger Train Corporation as a case study. In this case study the RCM is performed on wheel set maintenance tasks which is the bottleneck of maintenance works and is the main reason for the high level of passenger coach downtimes in this company. Finally it recommends the new maintenance schedule which improves the maintenance productivity by eliminating the downtimes of passenger coaches. Keywords: rolling stock industry, preventive maintenance, RCM, function failure, failure mode, wheel set

1- Introduction The proper maintenance strategy is the significant concern for rolling stock companies. Up to now, some various strategies have been presented by different companies in this matter, which in general would not be accepted by other companies. This situation arises because rolling stock companies are very conventional and conservative in their procedures and because, historically, rolling stock vehicles and equipments have been designed in order to procure a significant level of safety. Accordingly, some basic maintenance strategies such as Breakdown Maintenance were developed. To

sustain an efficiently operating rolling stock and to elude failure of critical equipments, the concentration has clearly shifted over the years to Preventive Maintenance (PM), devoted to fix the equipment according to planned maintenance schedule. By implementing PM some new problems gradually appeared in rolling stock companies as they had occurred in some other industries, such as insufficient pro-active maintenance, frequent problem repetition, erroneous maintenance work, sound maintenance practices not institutionalized, unnecessary and conservative PM, sketchy rationale for PM actions, lack of traceability/visibility for maintenance program, blind acceptance of OEM inputs, PM variability between like/similar units, ineffective use of predictive maintenance applications [4]. On the other hand, many rolling stock and railway companies have to satisfy rules provided by safety regulation authorities that, in several countries, define maintenance procedures and even the frequencies for PM. However, railway is competing with other forms of transport today, and railway companies are being split to provide transport services on a side and infrastructure services on another. Now, customers want the best quality of service at the lower cost, forcing the rolling stock and railway companies to optimize every stage of the process, including maintenance. The rolling stock and railway companies themselves are starting to outsource some maintenance tasks and services, facing that business without any kind of methodology to be applied to test the correctness of maintenance procedures [6]. Therefore it was essential to develop the new strategies to deal with these problems. The Reliability Centered Maintenance (RCM) offers the most systematic and efficient process to address an overall programmatic approach to the optimization of plant and equipment maintenance [2]. RCM basically combines several well-known risk management techniques and tools, such as failure mode and effect analysis and logical tree analysis, in a systematic approach, to support effective and efficient maintenance decisions. Papers on RCM applications treat subjects such as gas compression system in the offshore oil industry, aviation, ships, boiler and turbine auxiliaries in the nuclear industry, and robots in automobile manufacturing [2, 6, 7, 8, 9, 10]. Some attempts have done in railways to use RCM such as REMAIN project, the Norway railways and RAIL project which has been founded by the European Union [6, 11, 12]. However, most of the attempts to implement RCM in railway industries have been done on infrastructures, tracks and signaling. In this paper, we outline the scenario to apply this strategy in the rolling stock company with a case study of RAJA Passenger coaches Co. in Iran. Moreover, the authors intend to display the RCM can increase the productivity of maintenance by increasing the efficiency and effectiveness due to downtime reduction. Hence, a brief description about the RCM methodology and its history has been reported in section 2. Afterwards, the current maintenance strategy, which is already implemented in RAJA rolling stock workshop, has been described in section 3. In section 4 the four stages of RCM methodology and fulfilling the RCM tables are presented step by step, adapted to the case study of wheel set maintenance works in RAJA Co. The result of this strategy and its impact on the coach s downtimes and also maintenance productivity are presented in section 5. We attempt to illustrate each part of this paper by using of photos, tables and diagrams to describe the situation and the concept of this study clearly.

2- Current Maintenance strategy in Raja RAJA Passenger Trains Corporation has been established in 1996 and presently this company has undertaken the utilization of more than 1300 coaches of different types including passenger, power generator, steam generator, and post and luggage coaches which most of them are passenger coaches. As mentioned previously, maintenance of the passenger coaches composed one of the principal parts of company. Since the passenger coaches existing in RAJA are of higher diversity, maintenance of these coaches requires suitable strategies in conformity with the type of coaches. The general maintenance policy or strategy concerning the passenger coaches, which is already being practiced, is based on the Preventive Maintenances. Generally, we may divide such maintenance activities into three main groups as follows: a. Routine Maintenances: The slight maintenance activities which are performed immediately after the end of the train service to discover and solve the probable faults occurred along the way.

b. Annual maintenance: This kind of maintenance is practiced only on the sub chassis coach equipments such as Bogie, Brake System, Wheel Sets, Couplings, and Buffer in annual fashion. In such maintenances, every part is repaired or replaced based on the related maintenance instructions. c. Overhaul maintenance: Such repairs are done in 4-year periods on coaches. In this series of repairs besides the collection of annual repairs, which are practiced on the sub-chassis equipments, the coach s frame, air condition equipments, electrical components and passenger decoration collections inside the train are overhauled completely after practicing the required inspections and determining the occurred faults. d. Special Maintenances: This kind of maintenance activities is done prematurely, like Emergency Maintenance, exclusively in special occasions such as incidence or improper coach s equipments performances before the maturity date of the annual repairs to comply its function. Maintenance based on a fixed time may not provide the required flexibility. Since the goal of the companies is to increase the productivity, the required review shall be conducted to modify the type and schedule of the maintenance tasks. Some of the drawbacks of the existing strategy are as follows: 1- Disparities in the performance of coaches or coaches can not be taken into account. 2- Since the nature of some repairing is generally dictated by experience, longer safety margins must be allowed. 3- Low cost-effectiveness, especially when the coaches are used infrequently. 4- If the coaches are used to the full, the minimum permissible overall condition may be reached prematurely [20]. As it was mentioned before to avoid these problems the new strategy should be developed. We should consider that, each maintenance strategy offers particular advantages and disadvantages. The best solution for a given situation can only be confirmed by careful consideration of the particular operating environment and required performance outputs. While the safety is the significant factor in rolling stock industries, the most well known and widely applied maintenance optimization strategy is Reliability Centered Maintenance (RCM), which has its origins in the aerospace industry. A full RCM review of a rolling stock fleet is a detailed and structured analysis of each aspect of the vehicles safety and performance and has been shown to offer significant benefit in improving rolling stock reliability and availability which can alert the productivity by reducing the coach s downtimes [23]. Accordingly, we select this strategy to implement in RAJA Corporation. Here, a brief history of RCM for a better background and some vital RCM terminologies for more familiarization by RCM terms are presented.

3- History of RCM RCM has its origins in the findings of the Maintenance Steering Groups (MSG), that were formed in the aviation industry to develop a maintenance program for the Boeing 747 and Lockheed L1011 [14]. Having considered the size, passengers carrying capacity and technological advances of these aircraft, it was initially recommended that a maintenance program was so extensive that it would have made the aircraft a commercial failure. 3-1 what does RCM mean? What does RCM mean? There are considerable definitions of RCM in the literatures [1, 2, 3, 4]. As brief, RCM can be defined as a systematic approach to systems functionality, failures of that functionality, causes and effects of failures, and infrastructure affected by failures. When the failures are realized, the consequences of them must be taken into account. Consequences are classified in: safety and environmental, operational (delays), non-operational and hidden failure consequences. Afterwards, those categories are used as the basis of a strategic framework for maintenance decisionmaking. The decision-making process is utilized in order to select the most appropriate task to maintain a system filtering the proposed classification of consequences through a logic decision tree. Since 1970s until now, RCM was a major challenge in many industries because it changed the focus of PM from bringing back the systems to a reliable condition to maintaining the system only by some

determined operational limits in an excellent functional condition. Through this approach, it provides an understanding of how infrastructure works, what it can (or cannot) achieve, and the causes of failures [6]. 3-2- RCM terminology RCM focuses on the maintenance of system rather than equipment operation. In this paper we will encounter with some special terms which we described here. Significant terms in RCM method are listed as follows: 1. Component: a grouping of piece of parts into some identifiable package that will perform at least once significant function as a stand-alone item [4]. 2. System: A logical grouping of components that will perform a series of key functions those are required of a facility [4]. 3. Functional Failure: The inability of a piece of equipment, a system, or a plant to meet its expected function or performance [16]. 4. Failure Mode: The specific manner of failure, leads the circumstances or sequence of events to a particular functional failure [16]. 5. Failure Effect: The immediate physical effects of a functional failure on surrounding items and so on the functional capability of the equipment [16]. 6. Failure Modes and Effects Analysis (FMEA): FMEA is a technique for analysis of a system in terms of its subsystems, assemblies, and so on, down to the part level, to determine failure causes. The analysis addresses issues such as how parts can conceivably fail, the mechanisms producing each failure mode, how the failures are detected, and what can be done to compensate for the failure [17].

4- CASE STUDY: Applying RCM strategy in wheel set maintenance process of Raja Co. RCM as one of the successful maintenance strategies in the modern industries may help us in optimizing the productivity. However, since a coach includes many subordinates such as electric and light equipment, air conditioning system, bogie, wheel set, coupling, and buffer, definition of a RCM system in a comprehensive fashion for rolling stock industries is a difficult task and needs full of efforts and energy, which is out of the patience of this article. Therefore, in this article, we attempted to implement RCM in one of the coach s systems. According to Paper IV [18], about 76% of the coach s downtimes originate from the wheel set breakdown, which causes to detach the coaches during their service. This matter indicates that the wheel set system and its repairing activities are one the main bottlenecks of RAJA Company. Therefore, in this article, this system is chosen as a case study. By considering that the wheel sets are classifies into three main categories this paper presents the RCM implementation all of them by accentuate on their distinctions. Table 1 presents their significant specifications and differences. No I II III

Bogie Brake System MD36 Disk brake MD36 Disk brake MD33 Brake shoe Table 1. The various types of wheel sets

Bearing Spherical Cylindrical Cylindrical

There are four important stages that are used to implement RCM. In some books these stages might be classified into five or more steps; however, the main concept of them are as same: 1- System selection and description and boundary definition 2- System functions and functional failures 3- Failure mode and effect (criticality) analysis 4- Task selection

Stage 1: The first stage of implementing the RCM system includes selection and definition of system and its components and also determination of the system boundaries. Definition of system boundary is so important in the RCM analysis process due to two reasons: 1- There must be a precise knowledge of what has or has not been included in the system so that an accurate list of components can be identified [4]. 2- The boundaries will be the determining factor in establishing what comes in to the system by way of power, signals, flow, heat, etc. As mentioned previously, the wheel set is selected as the studied systems in this article. The main components of wheel set have been described as follows. Moreover for better comprehension of wheel set s components they illustrates in Figure 1. 1- Disk wheel body and wheel tyre: This collection is composed of one disk wheel and separate tyre. Disk wheel body composes the main frame which is fixed to the axle and tyre surrounds it similar like a ring and it is rubbed to the rail. The external level of the tyre holds a special profile and due to having contact with the rail, this profile is gradually eroded. One of the repairing activities that are performed in case of the wheel is to turn the tyre for the reimplementation of the standard profile. Approximately after three times of tyre turning, its diameter is mitigated and when it reaches 42mm according to the instruction, the tyre must be replaced by a new one. Tyre is connected to the wheel body by shrink fitting method.

Figure 1. the wheels the components

2- Axle: it is made of a steel axle and its diameter is different in points that it connects to the wheel body, brake disk, and at the axle s top that is connected to the roll bearing is different. Co.#

Component

Qty.

1 2 3 4 5 6 7 8 9 10 11 12 13

Disk wheel body Wheel tyre Tyre clip Wheel set axle Roller axle bearing Collar Distance sleeve Bush Bearing housing O-ring Axle guide at fulcrum Flare screw & nut Anti-skid

2 2 2 1 4 2 2 4 2 2 4 4 1

14

Axle-mounted brake disk

2

Type I 770mm 920×770×27 770mm 160mm Spherical 2. P. I 35mm Doesn t exist 220mm 500×120×8mm M 24×1.5 MWX3 610mm

Component Description Type II 770mm 920×770×27 770mm 160mm Cylindrical mono 35mm Doesn t exist 240mm 500×120×8mm M 24×1.5 M3 610mm

Table 2. The list of system components and their quantity

Type III 830mm 980×830×27 830mm 150mm Cylindrical 2. P. II Doesn t exist 150mm 240mm 500×120×8mm M 24×1.5 M3 Doesn t exist (Brake shoe)

3- Bearing: the bearing collection is composed of different parts such as roller bearing, collar, distance sleeve, bush, O-ring and bearing housing which whole internal space is full of grease. The bearing collection is connected to the bogie through two axle guide at fulcrums and flare screws. 4- Brake components: each wheel set include an anti-skid which control the air pressure of braking to avoid wheel locking during brake acts. Moreover the wheel sets type I & II possess two brake disks which are connected through special screws to the axle. At the time of braking, the brake pads reduce the speed or stop the wheel through creating friction. It must be noted that the wheel set is supposed to provide the suitable speed for the movement and leading of the coach in the determined direction especially over junctions, supplying the required safety, providing a comfort along the course, and suitable braking when required. Table 2 presents the specification of the parts existing in the system along with the details and their number in the system.

Stage 2: We will now use the information developed in the system description and boundary definition to formulate the specific function and functional failure statements. Much of our effort to this point has been directed toward the ability to accurately list functions and functional failures in order to properly guide the eventual selection of the PM tasks. Importance of this stage lies in the fact that the entire performances of the selected system should be considered in it. Each of these performances is known under the category of Function and if does not operate, the phenomenon is called a Function Failure. Generally, 4 Functions are defined for the wheel set, and for each of them, concerning their performance, 2 or 3 Function Failures are defined. We record the function and functional failure information on the table shown in Table 3. Function#

Function Failure#

1

Function Description

Function Failure Description

Providing the suitable speed 120Km/h 1.1 1.2 1.3

2

Improper wheel rolling on the rail Breakdown on tyre surface profile Improper bearing rotating (jammed) Supplying the required safety Thin & fragile flange of wheel tyre Axle cutting Axle guide of fulcrum cutting

2.1 2.2 2.3 3

Providing a comfort along the course Over noise and friction of rail and tyre Exceeding Vibration & trembling Non harmonic hunting

3.1 3.2 3.3 4

Suitable braking 4.1 4.2

Wheel locking due to jam on the brakes Disk brake cutting Table 3. Function/Function failure description

Stage 3: This step is one of the most important parts to implement RCM. This step brings us to the question of which component failures have the potential to defeat our principal objective to preserve function. This will be the first time in the systems analysis process that we directly connect the system functions and the system components by identifying specific hardware failure modes that could potentially produce unwanted functional failures [5, 15]. This stage has two main sections 3-1 and 3-2; in the first section, which is represented in Table 4, the relation style between every part with the considered damages is presented in the format of a matrix. This matrix is one of the innovative additions that the authors contributed to the systems analysis process, and we often refer to it as the connecting tissue between function and hardware.

3.3

1.2

1.2

1.3

X 1.3

4.2

3.2

X

1.1

4.1

3.1

2.3

2.2

X

2.1

X X X

1.3

Disk wheel body Wheel tyre Tyre clip Wheel set axle Roller axle bearing Collar Distance sleeve Bush Bearing housing O-ring Axle guide at fulcrum Flare screw & nut Anti-skid Axle-mounted brake disk

1.2

1 2 3 4 5 6 7 8 9 10 11 12 13 14

1.1

Component Description

Function Failure

Comp.#

The vertical and the horizontal elements of the matrix are the component list from step 1 and the functional failure list from step 2, respectively. The analyst s task at this point is to identify those components which have the potential to create one or more of the functional failures, and to so indicate this by placing a X in each appropriate intersection box [5].

1.1

X X X X X X X X

1.3 X 3.3

2.3 X X X

Table 4. Function Failure Matrix

However, the most important section in the implementing of the RCM program which is known as RCM heart as well is stage 3-2. In this section, a complete FMEA Process is performed for the selected system. According to Table 4, against every function failure, those components marked with X are selected, and they are put in the first and second columns of Table 8. Afterwards the component descriptions column, according table 2, are filled out. In the two next columns, Failure Modes and numbers related to the same Function Failures and components that may include one or several Failure Modes are written. The Failure Mode number consist of two number which the first one represents the component number and the second one represents the respective mode of that component. Criteria Remote probability that the failure remains undetected. Such a defect would almost certainly be detected during inspection or test. Low probability that the defect remains undetected Moderate probability that the defect remains undetected High probability that the defect remains undetected

Rating

Probability%

1

86-100

2 3 4 5 6 7 8 9

76-85 66-75 56-65 46-55 36-45 26-35 16-25 6-15

Very high probability that the defect remains undetected until the system performance degrades to the extent that the task will not be 10 completed. Table 5 Example of categorization of detection number [15]

0-5

A Detection number is attributed to every failure mode, which represents the identification scale of that special mode of damage. For determining this number, many tables have been adjusted since now; table 5 represents a sample of such tables which is practiced based on the probable damage identification during the test. After filling the columns related to the Failure Mode, it is the turn of completing the Failure Cause column. In this column, different reasons of establishing every special

model of damage is stated and in the column adjacent to it, the related Occurrence number is attributed to it which is the representative of probable damage. For finding Occurrence number, we may use the former data on the wheel set damages as well as the tables such as Table 6 that based on the damage Occurrence probability, a number between 1 up to 10 is granted to it. The next column is the Failure Effect column that presents the impacts resulted from damage. Such impacts may concern only the wheel set while some of them may has the extended effect and influence the whole coach performance and even it can threat the passengers security. Therefore, in suit with the importance of each Failure Effect, the Severity number is attributed to it that represents the intensity of the damage related to the performance of the passenger coach. Criteria Remote probability of occurrence. It would be very unlikely for these failures to be observed even once. Low probability. Likely to occur once, but unlikely to occur more frequently.

Rating

Possible failure rate%

1

0

2 3 4 Moderate probability. Likely to occur more than once. 5 6 7 High probability. Near certain to occur at least once. 8 9 Very high probability Near certain to occur several times. 10 Table 6 Example of categories of likelihood of occurrence [15]

1:20000 1:10000 1:2000 1:1000 1:200 1:100 1:20 1:10 1:2

This is a completely qualitative technique and commonly used industry to extend the idea of categorization to all other measures that are being considered, as well as Severity. Table 7 defines 10 categories of failure Severity based on industrial used when doing FMEA on a manufacturing process. Criteria Minor. A failure that has no effect on the system performance and the operators can ignore it Low. S failure that would cause slight deterioration to the coach but that would no annoyance to the passengers. Moderate. A failure that would cause a high deterioration in system performance, but slight dissatisfaction of passengers. High. A failure that causes significant deterioration in system performance, but that does not affect safety. Very High. A failure that would seriously affect the ability to complete the task or which could cause damage, serious injury, or death. Table 7 Example of categorization of severity

Rating 1 2 3 4 5 6 7 8 9 10

In practice these three numbers were multiplied together to produce the Risk Priority Number (RPN). In fact, RPN represents the priority of failures in every system and plays much the same role as criticality [15]. Since these three numbers are all digits from 1 up to 10, the RPN will be a number between 1 and 1000. The important point here is that no border parameter has been presented in case of RPN number. According to the practical form of RCM in various industries we encounter with different border numbers; however, for this case study we use the 133 as a border line for RPN number which was used in most of similar industries of rolling stock. The importance of RPN border is that demonstrates we can not run the component up to it failure. Use of RPN number has one advantage and that is the possibility of arranging damages based on the priority in suit with one number and avoids from establishing discriminative comments. Considering the fact we may not present the entire details

related to different stage of RCM, however, it is tried to include the above-mentioned sections in Table 8. It must also be noted that stage 3-2 is done for each 3 types of the wheel sets which are described formerly. However, due to the limited space, Table 4 is only filled according to the data achieved from the wheel set type II.

Occurrence

Severity

RPN

5

1.1.1

Coach detachment

5

150

2

1.1.2

Coach detachment

5

60

5

1.1.3

Coach detachment

5

150

3 2

1.1.4 1.1.5

Coach detachment Coach detachment

5 5

90 60

7 7 8 4

1 .1.1 Improper wheel body milling 1 .2.1 Fragments between tyre and wheel body 2.1.1 Improper adjustment of wheel into the tyre 2.1.2 Improper tyre milling 3.1.1 Improper tyre clip press 2.2.1 Improper braking 2.2.2 Rail faults 2.3.1 Overuse 5.1.1 Fragments

7 4 5 8

1.2.1 1.2.1 1.2.2 1.3.1

Coach vibration Coach vibration Derailment Coach Breakdown

6 6 9 8

294 168 360 256

Bearing heat

4

5.1.2 Lack of grease

4

1.3.1

Coach Breakdown

8

128

5.1

Bearing heat

4

5.1.3 Improper installment

3

1.3.1

Coach Breakdown

8

96

6.1 7.1 8.1 9.1 9.2 9.3 10.1 2.4 2.4 2.4

Grease leakage Sleeve broken Bush broken Heat Clearance Grease leakage Grease leakage Sd<22mm Sd<22mm Sd<22mm

3 2 2 4 5 3 3 4 5 7

1.3.2 1.3.3 1.3.3 1.3.1 1.3.4 1.3.2 1.3.2 2.1.1 2.4.2 2.4.2

Bearing heat Roller failing Roller failing Coach Breakdown Derailment Bearing heat Bearing heat Derailment Derailment Derailment

7 6 6 8 9 7 7 9 9 9

63 96 96 128 315 63 63 288 360 504

Wheel set axle Wheel set axle Axle guide fulcrum Axle guide fulcrum Wheel tyre Wheel set axle

4.1 4.1 11.1

Crack Crack Crack

3 6.1.1 Improper installment 8 7.1.1 Improper installment 8 8.1.1 Improper installment 4 9.1.1 Improper washing 7 9.2.1 Abrasion surface 3 9.3.1 Incorrect sealing 3 10.1.1 O-ring failure 8 2.4.1 Bogie deformation 8 2.4.2 Bent axle 8 2.4.3 Tyre overuse on the same curve track 9 4.1.1 Fatigue 9 4.1.2 Collision 9 11.1.1 Fatigue

7 2 2

2.2.1 2.2.1 2.3.1

Derailment Derailment Derailment

9 9 9

567 162 162

11.1

Crack

9 11.1.2 Collision

2

2.3.1

Derailment

9

162

2.5 4.2

3 3

2.5.1 Profile erosion 4.2.1 Bent axle

8 5

3.1.1 3.2.1

192 120

12.1 13.1 14.1

1 12.1.1 Less than 500Nm 7 13.1.1 Lack of air pressure 4 14.1.1 Improper material of disk & pad brake

3 8 5

3.3.1 4.1.1 4.2.1

Unsatisfied pass. Loose passenger comfort Tyre abrasion Coach vibration High collision probability

8 8

Flare screw & nut Anti-skid Axle-mounted brake disk

Tyre noise Coach trembling Loose screw Tyre erasure Disk broken

5 6 7

15 336 140

Detection

F.E.#

Comp.#

F.F.#

Stage 4: The main goal of this stage is to determine the maintenance tasks and time schedule for each breakdown. Therefore RPN is the main factor to determine it. In this stage, according to Table 8¸ the columns included Function Failure, Failure Mode & Failure Cause, are fulfilled and then according to Component Description

1.1

1

Disk wheel body

1.1

Tyre clearance

6

1.1

1

Disk wheel body

1.1

Tyre clearance

6

1.1

2

Wheel tyre

2.1

Tyre clearance

6

1.1 1.1

2 3

Wheel tyre Tyre clip

2.1 3.1

Tyre clearance Tyre clearance

6 6

1.2 1.2 1.2 1.3

2 2 2 5

2.2 2.2 2.3 5.1

Flat detection Flat detection Profile erosion Bearing heat

1.3

5

5.1

1.3

5

1.3 1.3 1.3 1.3 1.3 1.3 1.3 2.1 2.1 2.1

6 7 8 9 9 9

Wheel tyre Wheel tyre Wheel tyre Roller axle bearing Roller axle bearing Roller axle bearing Collar Distance sleeve Bush Bearing housing Bearing housing Bearing housing O-ring Wheel tyre Wheel tyre Wheel tyre

10

2 2 2

2.2 2.2 2.3

4 4 11

2.3

11

3.1 3.2

2 4

3.3 4.1 4.2

12 13 14

F.M.#

Failure Mode

F.C. #

Failure Cause

Failure Effect

Table 8 FMEA process for wheel set type II.

the flowchart of Figure 2, columns 1 up to 7 are answered by considering the RPN which obtained from previous stage for each failure or breakdown. Task selection in the RCM process requires that each task meet the applicable and effective test, which is defined as follows: Applicable: the task will prevent or mitigate failure, detect onset of failure, or discover a hidden failure such as PM tasks and periodical tests.

Effective: the task is the most cost effective option among the competing candidates. The said flowchart has been designed in a way that the safety has first priority. If failures have direct impact on health and safety, it will not important whether it can influence on quality and expense or not, so flowchart is conducted in a direction to be able to predict failures by using Predictive Maintenance methods such as Condition Monitoring, and if the PdM is not exist or justifiable the flowchart as far as possible determines the PM tasks or Periodical Tests to prevent the failures. If the failures does not affect on the coach safety, some other priorities such as quality and expense shall be considered to determine the maintenance tasks. In the case of all these factors does not have any importance the flowchart makes a deliberate decision to allow an equipment to operate until it fails, which is called Run-to-Failure (RTF). Rather, the maintenance action occurs only after the failure has occurred. There are some limited cases where such a strategy makes common sense. The RPN is the very important criterion to reply the flowchart questions and at last determine the PM tasks. Whereas in some failures, a Failure Mode is identified due to different Failure Causes the various RPN can be obtained. In this case, the Failure Cause which possesses the greatest RPN is considered to take the maintenance task. The high value of RPN can also have some other importance in maintenance tasks. In this situation, if the predictive equipments are available, using them shall be recommended in spite of their financial expenses. This is done to reduce the detection number because the severity is difficult to reduce. For instance, in the FM# (5.1) the thermal sensors have been recommended because of high value of RPN256, while for the FM# (7.1) no maintenance task of any kind is ever performed. 1-Will failure has direct and destructive impact on health & safety? Yes

No

2-Can redesign cost effectively solve problem? No 3-Will failure has direct impact on quality? Yes No 5-Is there any method which can predict the failures? Yes No

Yes

4-Will failure has a lot of damage? No

6-Is predictive method cost justifiable? Yes No

7-Is there any preventive method to decrease or eliminate the failures? No Yes

Condition monitoring

Define PM

Run to failure

Redesign

Figure 2. The task selection flowchart

The other important application of the flowchart is to identify the maintenance schedule. As mentioned previously, the wheel sets are divided into three main types which are different in some technical specifications. The reliability of each type of wheel set has been assessed in paper IV [18], so the schedule of PM tasks will be different for these three types with a same reliability. Here, these diversities are determined by I, II and III as a symbol of each wheel set type and the recommended time schedule introduced in front of them.

5-Conclusion

As mentioned at the beginning of this article, the general maintenance strategy for the wheel set in RAJA Company based on the time- and used- base issues. Although this matter makes a simple maintenance scheduling, considering the disparities of passenger coaches and their different uses, it can not assure the higher productivity in the field of maintenance. In other words, each failure function in a coach depends on its impact on the whole system, will need a particular maintenance task. In the meantime, considering the extension of the equipment and different passenger coaches as well as different repairs that are supposed to be applied on them seems difficult. Purpose of this report is to present in practice one of the successful maintenance strategies in Rolling Stock Industry and in RAJA Company. Moreover, instead of expanding RCM to the entire maintenance and repair units and complexity of works, it is tried to make use of it in the most fundamental section of offering services by coaches, i.e. wheel set that compose 76.34% of the coaches detachment reasons [18]. F.F# Co.# Comp. Desc.

F.M.#

Failure F.C. # Mode Tyre 1 .1.1 clearance

Failure Cause

RPN 1

1.1

1

Disk wheel body

1.1

1.2

2

Wheel tyre

2.2

Flat detection

2.2.1

1.2

2

Wheel tyre

2.3

2.3.1

1.3

5

Roller axle bearing

5.1

Profile erosion bearing heat

1.3

6

Collar

6.1

6.1.1

1.3

7

7.1

1.3

8

Distance sleeve Bush

1.3

9

Bearing housing

9.2

Grease leakage Sleeve broken Bush broken clearance

1.3 10 2.1 2

O-ring Wheel tyre

10.1 Leakage 10.1.1 2.4 Sd<22mm 2.4.3

O-ring failure tyre overuse on the same curve track

63 N 504 Y

2.2

Wheel set axle

4.1

4.1.1

Fatigue

567 Y

11.1 Crack

11.1.2

Collision

2.5

Tyre noise 2.5.1

4.2

4

2.3 11 3.1

2

Axle guide at fulcrum Wheel tyre

3.2

4

Wheel set axle

3.3 12

Flare screw & nut Anti-skid

4.1 13 4.2 14

Axle-mounted brake disk

8.1

Crack

Coach vibration 12.1 Loose screw 13.1 Flat detection 14.1 Disk broken

5.1.1

7.1.1 8.1.1 9.2.1

Improper wheel 150 N body milling by the operator Improper braking 294 Y

2

3

4 5

6 7

Selective Decision

N Y

- N

- Y

Overuse wear out Fragments

360 Y

-

-

- N

- Y

256 Y

-

-

- Y

Y

-

Improper installment Improper installment Improper installment Abrasion surface

63

N

Y

-

-

-

-

-

1-Peridical test. Visual After each inspection service 2-RTF 1- CM. Laser profile I =1050 hr. check II =810 hr. 2- PM. Repair the III= 640 hr profile on specified time CM. Laser profile after each check service 1-CM. heat sensors -Online 2-Optical thermometer -After each service RTF

96

N

N N N

-

-

-

RTF

96

N

N N N

-

-

-

RTF

- Y

Y

-

1- online 2- every six month

N N N - - - Y

Y

-

1- CM. heat sensors 2- Periodical test. Dimension control of housing RTF 1-CM. Laser profile check 2- PM. Repair the profile on specified time Periodical test. Magnetic axle Test Ultrasonic axle Test Magnetic guide Test

I =1050 hr. II =810 hr. III= 640 hr Annually

315 Y

-

-

- N

- Y

-

- N

- Y

162 N

N Y

- Y

N N

Profile

192 N

N Y

- N

- Y

PM -turn the tyre in specified frequency

4.2.1

Bent axle

120 N

N Y

- N

- N

Bent axle test

12.1.1

less than 500Nm 15

-

13.1.1

Lack of air pressure Improper material of disk & pad brake

1- RTF 2- Visual test 1- PM repairing 2- Test of Anti-skid 1- PM periodic inspection 2- RTF

N

336 Y 140 N

-

-

-

14.1.1

Est. freq.

N N N -

-

-

-

- Y

N Y

N Y

- N

- Y

I =1050 hr. II =810 hr. III= 640 hr

Every three months Annually

After each service Annually

Table 9. Task selection

With a view to the results acquired in stage 4, we may observe the type of the maintenance tasks and its time schedule and omitting erroneous and unnecessary maintenance tasks with regard to the

previous state, which this matter by itself results in the reduction of downtime and increase of productivity within the organization.

Acknowledgment This paper was one of the results of a project that was financially supported by the Raja passenger train corporation, so we would like to thank the Maintenance Department and Documentation Unit staff at this company, and in particular Mr. Mahmoud Ja fary the president of Raja Company, Mr. Amir Taheri the head of maintenance Department and Mr. Majid Mirzabeigi the head of coaches overhaul workshop of Raja Company. Also, we would like to appreciate Professor Uday Kumar of Div. of Operation and Maintenance Engineering in Luleå University of Technology for their direction and supervision on this study.

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