SPARE PARTS

APPLICATION OF A DISCRETE PROBABILITY DISTRIBUTION,  POISON DISTRIBUTION,IN CREATING CRITICAL AND OPTIMAL SPARE PARTS LIST ON OCEAN GOING VESSEL.

Note:

This article is made by modifying parts of       “INVENTORY MANAGEMENT OF CRITICAL SPARE PARTS AND ITS RELATION TO PMS”  - by Aleksandar Pudar The complete paper can be found on https://www.academia.edu/37334387/INVENTORY_MANAGEMENT_OF_CRITICAL_SPARE_PARTS_AND_ITS_RELATION_TO_PMS

The ocean-going vessel provides transportation service, and the spare parts inventory reliability is crucial.

Spare parts inventory is necessary to provide emergency services in getting the vessels back to work in the shortest time possible.

Over the years, on the older vessels, the companies accumulate an extensive inventory and the formal procedure to manage it that is due for improvement. The improvement may result in funds savings that can be used elsewhere in the company.

Existing inventory policy is being refined, and its implementation and use followed up/enforced to assist in this task.

For the calculation that resulted in the Critical or Optimal Spare Parts List for each vessel, first required variable is estimated off-hire cost ( using current rates or past 12-month average ), the failure frequency, and the machinery lifetime where it will be used.

Vessel being off-hire for any reason, whether it is for inspection, maintenance, or malfunction, costs money. The precise cost aids managers in decision making as to when to arrange vessel for dry docking, or in the case of repairs, how much to spend on getting the vessel running again.

For accurate cost projection, it is required to know what is being affected by off-hire. Vessel unemployment and income reduction may look like the most a significant part of off-hire costs, any actual cost of the off-hire, an estimate should include the value of the opportunities that were lost when the spares were not available.

To calculate the total off-hire cost, we need to sum up the following values.

• Labour cost, direct and indirect, of the off-hire.

‘To find the direct labour costs, we took the length of the possible off-hire and multiplied it by the hourly costs of the vessel operators. Calculated indirect labour costs by determining how much of a share of the supervisory and support workload the vessel takes, then multiplied that by the costs of the support staff and managers.’ (Source Unknown)

• The cost of direct value loss due to off-hire. The loss = to the worth of the service that would have been produced during the off-hire.
• The start-up costs are related to restarting the vessel, including any additional workers needed energy surges, and inspection costs.
• The costs are related to the actual repair, either temporarily or permanently.

Because of the cost of off-hire will usually exceed the value of the part, all items are valuable on the same level to the operations of the company, to distinguish items of interest from other items, more data needs to be collected rather than just the price of the parts.

We defined a Critical Spare Parts Calculator that took into account:

• Off-hire cost per hour if the part is unavailable
• Off-hire if the spare part is available in stock
• Off-hire if the spare part is not available in stock
• An expected remaining lifetime of the machinery
• Estimated failure frequency
• Inventory interest (including the cost of storeroom, depreciation)
• Cost of the spare part

The calculator resulted in financial value:

• Extra cost per breakdown without the spare part in stock (C)
• ‘Probability that the spare part will be used (P)’ (Olofsson, 2018)
• Expected downtime cost without the spare part (=C*P)
• ‘Expected holding cost of the spare part (H)’ (Olofsson, 2018)
• Expected obsolescence cost if the spare part never will be used (O)
• Total spare part costs (=H+O)
• Expected impact cost

Table 1. Critical Spare Parts Calculator - Modified by Author - ©2009 Oskar Olofsson - www.wcm.nu 

The form is used to calculate the costs if a company buys and keeps the critical spares, or not. The calculation is based on statistical methods and is used to optimise maintenance stores. Filling in figures and estimations, and will result in a critical spare part or non-critical spare part (a buy, or not buy,) recommendation.

For the calculation: estimate downtime costs, the failure frequency, and the lifetime of the machinery where it will be used

Example (modified from- J.Fukuda Feb.2008) :

Identify a required spare parts quantity to achieve a confidence level of 90%. Following data were needed:

Units in need of spares per vessel:  4 units A = 4 EA for two vessels N = 2 vsl.

Each unit operates average 225 RH per month, M= 225 RH

The period between overhauls is 7500 RH, MTBR = 7500 RH 

The initial period of use is 24 months, T = 24 m.  Using the following formula

By using Poison Distribution [2]equation

0 spare, P = exp (-5.76) = 0.003 = 0.3% < 90%

1 spare, P = 0.003 (1+5.76) = 0.0213 = 2.13% < 90%

2 spares, P = 0.003(6.76+16.6) = 0.0736 = 7.36% < 90%

3 spares, P = 0.003 (23.36+31.85) = 0.1739 = 17.39% < 90%

4 spares, P = 0.003(55.21+45.9) = 0.3185 = 31.85% < 90%

5 spares, P = 0.003 (101.1+52.8) = 0.485 = 48.5% < 90%

6 spares, P = 0.003 (153.91+50.7) = 0.6448 = 64.48% < 90%

7 spares, P = 0.003 (204.6+41.7) = 0.7763 = 77.63% < 90%

8 spares, P = 0.003(246.3+30.1) = 0.8710= 87.10% < 90%

9 spares, P = 0.003(276.4+34.2) = 0.9316 = 93.16% > 90%

By following the above, it is determined that the recommended quantity comes to nine spare parts for 24 months lifespan of the unit in question for two ships to achieve a confidence level of 90%. Of course, to expedite the calculation, an excel spreadsheet is used.

Table 2 – “Vessel Spares Quantity (Poison Distribution) Calculator.” – Created by 3rd Officer Stefan Grozev - 2018©Reederei Nord BV - www.reederei-nord.com

The additional data needed is the lead time on the part and the cost of off-hire of the vessel, rather than just the price or the quantity of a new part. Because the new parts price is less than the cost that would incur while not having it, the cost of off-hire is used, instead, along with the lead time associated with that item.

The spares of interest are those who are not accessible to source in a short period and cause an expensive off-hire loss to the company. It takes some items weeks to receive, while others are readily available at any time. Identification of the lead time is crucial.

Snapshot 1 – Inventory - Snapshot by Author from Danaos Enterprise –Supplies Control Module 

After the downtime cost, lead time and required quantity were determined next step is to do standard RA using a matrix for each critical and optimal spare part and critical and standard equipment, and the result will be a standardised ship specific Critical and Optimal Spare Parts List. RAs has been done to ensure that there are no omissions in the use of Critical Spare Parts calculator and to identify additional risks. The goal is to minimise the losses by providing a risk assessment.

The collected spare parts data is ranked in an RA matrix allowing the technical team to visualise which items are of interest.

As it is seen, this process does not replace technical expertise and the experience or technical personnel; it aids it. 

Table 3 - Extract from “SHIPBOARD MANUAL – DECK / ENGINE PROCEDURES 2.3 – Critical Equipment and System APPENDIX I: RISK ASSESSMENT FOR CRITICAL EQUIPMENT IDENTIFICATION.”

Snapshot 2 - Critical Spare Part List - taken by Author from Danaos Enterprise –Technical module

Effective inventory management is essential and plays a pivotal role in engineering management.

Shipping companies deal with many spares, in inventory and on top we have to cope with unpredictable demand. The standard way of approach cannot be used, but instead, need to be adapted to fit the environment better to assist the company in inventory management.

1. References:

1.       Hmida, J.B, Grant, R & Lee, J. 2013. Research Article Inventory Management and Maintenance in Offshore Vessel Industry. HINDAWI - Journal of Industrial Engineering. [Online]. 2013(Article ID 851092), 1-7. [27 February 2018]. Available from: https://www.hindawi.com/journals/jie/2013/851092/

2.       Robinson, A. 2014. Transportation Management Company | Cerasis. [Online]. [20 February 2018]. Available from: http://cerasis.com/2014/09/03/inventory-control/

3.       Abuhilal, L, Rabadi, G & Sousa-Poza, A. 2006. Supply chain inventory control: a comparison among JIT, MRP, and MRP with information sharing using simulation. Engineering Management Journal. 18(2), pp. 51–57.

4.       Koçaǧa, .Y.L & Şen, A (2006). Spare parts inventory management with demand lead times and rationing. [Online]. (Volume 39, 2007 - Issue 9 Ed.).  Journal IIE Transactions Volume 39. [20 February 2018]. Available from: http://www.tandfonline.com/doi/abs/10.1080/07408170601013646    

5.       Vaughan, T.S. 2005. Failure replacement and preventive maintenance spare parts ordering policy. European Journal of Operational Research. [Online]. 161(1), 183-190. [20 February 2018]. Available from:

6.       Olofsson, O. 2018. World-class-manufacturing com - Spare Parts. [Online]. [20 February 2018]. Available from: https://world-class-manufacturing.com/spare/spare.php

7.       RNBV. 2015. 23 – Critical Equipment and System APPENDIX I: RISK ASSESSMENT FOR CRITICAL EQUIPMENT IDENTIFICATION. In: Reederei Nord BV, R.N.B.V ed. HSEQ - SHIPBOARD MANUAL – DECK / ENGINE PROCEDURES. Amsterdam: Reederei Nord BV, pp. 3-3, Line 29

2. Bibliography:

1.    Toomey, G., 2006. Harnessing the power of maintenance. Power Engineering (Barrington). [Online]. 110(3), 42-47. [20 February 2018]. Available from: https://www.osti.gov/biblio/20741054

2.    Da Silva, C.M.I, Cabrita, C.M.P & De Oliveira Matias, J.C. 2008. Proactive reliability maintenance: a case study concerning maintenance service costs. Journal of Quality in Maintenance Engineering. 14(2), pp. 346-356.

3.    Ballou, R (2003). Business Logistics Management. (5 Ed.). Englewood Cliffs, NJ, USA: Prentice-Hall.

4.    Mabert, V.A., 2007. The early road to material requirements planning. Journal of Operations Management. [Online]. 25(2), 346-356. [20 February 2018]. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0272696306000301  

5.    Chukwuekwe, D.O (2016). Condition Monitoring for Predictive Maintenance: A Tool for Systems Prognosis within the Industrial Internet Applications. [Online]. NTNU-Trondheim: MASTER THESIS (TPK4950) - Norwegian University of Science and Technology Department of Production and Quality Engineering. [27 February 2018].Available from: https://brage.bibsys.no/xmlui/handle/11250/2404760?show=full

6.  Mullai, A (2006). RISK MANAGEMENT SYSTEM – RISK ASSESSMENT FRAMEWORKS AND TECHNIQUES. (1 Ed.). DaGoB Project Office - Turku School of Economics: DaGoB publication series.

7.  Maria Elena Nenni, Et. al., 2013. Optimizing Spare Parts Inventory in Shipping Industry. International Journal of Engineering and Technology (IJET). ISSN: 0975-4024 / Vol.5. (Jun- Jul 3), pp. 3152-3157.

8.  Stump, E., 2018. Using the Poisson Probability Distribution to Estimate Cost of Re-supply Spares - Galorath, Inc. no-date. Galorath, Inc. [Online]. [16 March 2018].Available from: http://galorath.com/library/abstract/using-the-poisson-probability-distribution-to-estimate-cost-of-re-supply-sp

3. Snapshots and Tables:

1.    Snapshot 1 - Inventory - taken by Author from Danaos Enterprise –Supplies Control Module

2.    Snapshot 2 - Critical Spare Part List - taken by Author from Danaos Enterprise –Technical module

3.    Table 1- Critical Spare Parts Calculator - Modified by Author using Excel Template purchased from ©2009 Oskar Olofsson - www.wcm.nu

4.       Table 2 – “Vessel Spares Quantity (Poison Distribution) Calculator.” – created by 3^rd Officer Stefan Grozev - 2018©Reederei Nord BV - www.reederei-nord.com

5.     Table 3 - Extract from RNBV -“SHIPBOARD MANUAL – DECK / ENGINE PROCEDURES 2.3 – Critical Equipment and System APPENDIX I: RISK ASSESSMENT FOR CRITICAL EQUIPMENT IDENTIFICATION.”

[1] The form is used to calculate the costs if you buy and keep the critical spares, or not. The calculation is based on statistical methods and is used to optimize your maintenance stores. Fill in figures and estimations, and will be presented with a critical spare part or non-critical spare part (a buy, or not buy,) recommendation.

For the calculation: estimate downtime costs, the failure frequency, and the lifetime of the machinery where it will be used

[2] In probability theory and statistics, the Poisson distribution (French pronunciation: [pwasɔ̃]; in English often rendered /ˈpwɑːsɒn/), named after French mathematician Siméon Denis Poisson, is a discrete probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time or space if these events occur with a known constant rate and independently of the time since the last event.[1]The Poisson distribution can also be used for the number of events in other specified intervals such as distance, area or volume.

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  Disclaimer:

         “ Out of Box Maritime Thinker” © 2018 and Aleksandar Pudar assumes no responsibility or liability for any errors or omissions in the content of this paper. The information contained in this paper is provided on an “as is” basis with no guarantees of completeness, accuracy, usefulness or timeliness or of the results obtained from the use of this information. The ideas and strategies should never be used without first assessing your own company situation or system, or without consulting a consultancy professional. The content of this paper is intended to be used and must be used for informational purposes only

JOB POSTPONEMENT

Job postponement in Maritime Industry

Definition Job postponement

When some job is delayed until a later time or date, that is a job postponement.
A job postponement can also be called a job deferral, and it means rescheduling job for later.
The postponement has a Latin root, postpone, "put after, neglect, or postpone."

In the maritime industry especially on tankers, there are procedures in use for job postponements.

Job postponements procedures aid in maintenance planning and will ensure that all machinery on board is adequately maintained and aim to achieve optimum reliability and safety of the personnel, vessel and environment protection.

Responsibilities

Usually, Chief Engineer and Chief Officer are the ones  responsible for making sure that job planning is done regularly and that postponement is requested as needed, following the predetermined procedure, for their respective departments

As the part o the procedure Technical Superintendent reviews postponement request and accompanying Risk Assessment together with any provided documentation following existing company ISM policies and industries regulations. Based on the Technical Superintendent’s review, the postponement will be approved or rejected.

Job Postponement Standard Procedure

While planning for maintenance jobs in PMS vessel might request, in exceptional cases, for extension/postponement.
Postponement is done following PMS software set up, but logically, the person in charge of the department will go to job planning section in order to retrieve the jobs and then highlight one or more jobs in order to request an extension filling up attaching necessary docs and sending the postponement for approval to TSI.
The person in charge should request a new date for doing the job (proposed date)  and the reason for this postponement request. Also, he or she must attach RA for every postponement request. RA must be done to ensure that every possible aspect and risk of allowing the postponement has been thought about and that mitigating risk measures have been implemented.
Upon receiving the postponement request, Technical Superintend in charge of the vessel will review the request  and will nominate criticality level basis on RA results, after mitigating measures have been implemented (LOW, MEDIUM and HIGH)
If postponement request RA is still with High Risk after mitigation measure is introduced, the postponement will be refused. The job will have to be done, if the job cannot be done due to lack of spares, lack of knowledge on board, or simply because for some reason it is impossible to do it safely. In that case, a temporary MOC will have to be done to introduce a temporary procedure for handling that equipment while spares are received or conditions for safe work are obtained.
( for MOC procedure visit https://www.academia.edu/38529460/Management_of_Change_Procedure_and_Guidelines_for_Oil_Tanker_Shipping_Company_.docx?source=swp_share )

The Technical superintendent can approve or reject the proposed date using the Approve or Cancel (depending on the reason and RA) but whatever the decision it must be communicated to the vessel ( approval or rejection).

When some job postponement has been approved, and new due date is implemented, both vessel and office has to keep control of the planning for doing postpone job as approved by the postponement. Usually, the PMS system highlight the jobs that have been already postponed and they come due again, the jobs are highlighted.

Following adequately set up a job postponement procedure is essential for safe and economically viable management of any vessel. In this as in everything proper communication between vessel and the office is the key to success.

  

Bibliography

Aimi, G. (2019). Advantages Of Postponement. [online] Forbes.com. Available at: https://www.forbes.com/2006/12/08/amr-product-postponement-biz-logistics-cx_ga_1208postpone.html#24cc68c517d6 [Accessed 26 Jun. 2019].

Aimi, G. (2019). Advantages Of Postponement. [online] Forbes.com. Available at: https://www.forbes.com/2006/12/08/amr-product-postponement-biz-logistics-cx_ga_1208postpone.html#24cc68c517d6 [Accessed 26 Jun. 2019].

  Disclaimer:

         “ Out of Box Maritime Thinker” © 2018 and Aleksandar Pudar assumes no responsibility or liability for any errors or omissions in the content of this paper. The information contained in this paper is provided on an “as is” basis with no guarantees of completeness, accuracy, usefulness or timeliness or of the results obtained from the use of this information. The ideas and strategies should never be used without first assessing your own company situation or system, or without consulting a consultancy professional. The content of this paper is intended to be used and must be used for informational purposes only.

DEFECT MANAGEMENT

DEFECT MANAGEMENT PROCESS ON TANKER VESSELS

Definition.

Before we start talking about the defect, let us first understand what defect is, in tanker industry defect is usually defined as:

"Any damages/breakdowns on critical equipment outside of planned maintenance that cannot be immediately repaired on board using existing spares and resources, i.e. require assistance/advice from office or third party."

Everything else falls under the category of unscheduled /corrective job or straight forward repair.

Defect management.

As far as tanker vessel maritime industry goes, defects are managed mostly by use of integrated software management system, i.e. Marine ERP that contains PMS.

The defect management process usually consists of four steps.

     The process starts when the vessel has a breakdown of critical equipment, then in software vessel creates defects and informs the office.

      The defect, as a rule, is always proposed by the vessel. Before opening a defect, the vessel management team will identify, by use of Risk assessment process, the risk involved in that defect and will implement risk-mitigating factors. Results of the Risk assessment will be used for Risk level notation of the defect.

     The Risk level is noted using the following wording: LOW-RISK DEFECT, MEDIUM RISK DEFECT and HIGH-RISK DEFECT each notation is obtained by using Risk assessment and getting results by implementing risk-mitigating factors.

     

     By Completing  all of the above the vessel sends defect proposal to the office, and that is when the next step in the defect reporting process and management starts.

     Here the Technical superintendent in charge of the vessel reviews the defect and checks all the corresponding documentation. The documentation consists of, but it is not limited to, Risk assessment, Root cause analysis (identifying what caused the defect in the first place), proposal to avoid reoccurrence, requirements for fixing the defect together with additional documents and photos.

      In step three, the vessel obtains feedback on a proposed defect ( Accepted, rejected, approved, acknowledged). In case of approval also proposed, and an approximate date for fixing the defect and getting equipment back online is given. If the due date for the defect is too far away and normal working condition cannot be obtained soon, temporary management of change should be implemented until the defect is closed, i.e. equipment condition restored to normal.

      In step four, the final step, the vessel is closing defect providing objective evidence together with comments and providing date completed. Defect becomes closed, and that means that all is done. When closing the defect, the extensive reason must be given, e.g., repairs and service reports, photos etc.

      Important

     The above process requires ship and office staff to communicate through all available channels, to ensure all are aware of the defect and of the measures to resolve the same (including near miss reporting, accident reports and typical day to day communications as appropriate).

       Disclaimer:

         “ Out of Box Maritime Thinker” © 2018 and Aleksandar Pudar assumes no responsibility or liability for any errors or omissions in the content of this paper. The information contained in this paper is provided on an “as is” basis with no guarantees of completeness, accuracy, usefulness or timeliness or of the results obtained from the use of this information. The ideas and strategies should never be used without first assessing your own company situation or system, or without consulting a consultancy professional. The content of this paper is intended to be used and must be used for informational purposes only.

Hull Inspection, Damage & Repair - Part IV

Hull Inspection, Damage and Repair ( Reporting and Assessing Structural Defects )  Part IV

Measures to Improve Fatigue Life 5 (+1)

Fit / Extend Bracket

Full Penetration Weld

Full penetration weld for about 250-300 mm at the end of the bracket.

Increase Thickness of Bracket at End

Improve Taper of the Face Bar

Reduce Thickness of the Face Bar

+1. Fix the End of the Stiffener

Care needs to be taken not to induce new hardpoints. In this case, the ends of the new bracket are directly above under –deck stiffeners.

Critical Areas- General

1. Frames in way of side ballast tanks and holds
2. Bottom plates in way of suctions
3. Hold bilge wells ( when they continue to shell plating)
4. Engine room wells ( when they continue to shell plating)
5. Distance pieces
6. Frames in ER close to SW pumps
7. Frames in way of chain locker when continued to shell plating
8. Plating below windlass
9. Structure in way of septic tanks
10. Areas not generally inspected
11. Floors separating FO and ballast tanks

Regular inspection, proper maintenance, planning and comprehensive record keeping is essential in maintaining vessels in good shape and in the safe condition.

Tanker Nomenclature – Typical Midship Section

Tanker Nomenclature – Typical Transverse Bulkhead

1. Bureau Veritas (2006). Mini Survey Handbook Part A - Ships in Service. (First ed.). France: Marine Division Ships in Service Management ( DNS).
2. Gutierrez, M. – Retired Senior Surveyor LR, 2018. Conversation/Lecture to/with Aleksandar Pudar from 18 to 21/9/2018.
3. Lloyd's Register Marine (2014). Hull Inspection, Damage and Repair. (Third Edition ed.). United Kingdom: First published by Lloyd's Register ,2009. 
4. Lloyd's register marine (2015). Hull Inspection, Damage and Repair. (First ed.). United Kingdom: Lloyds Register.
5. Researchgate.net. 2018. “ Pitting intensity diagrams” www.ResearchGate.com [Online]. Available from: <https://www.researchgate.net/figure/Pitting-intensity-diagrams-Figure-taken-from-2_fig4_320716318 > [Accessed on : 2 October 2018]. 
6. Marchant , T, Dr.Lomas, J & Dr.Callow, L (2009). WHITE PAPER:THE FEASIBILITY OF A CORROSION RESISTANT SHIP. [Online]. (1 ed.). United Kingdom: © BMT Defence Services Limited 2009 © Amtec Consultants Ltd 2009. Available from: <https://www.bmtdsl.co.uk/media/6098421/BMTDSL-Corrosion-Resistant-Ship-Whitepaper.pdf >[Accessed on : 2 October 2018]. 
7. Tanker Structure Co-operative Forum (1995). GUIDELINES FOR THE INSPECTION AND MAINTENANCE OF DOUBLE HULL TANKER STRUCTURES. (1st  ed.). England: Witherby & Co.Ltd.
8. Tanker Structure Co-operative forum (2014). Guidance Manual for Tanker Structures - Consolidated Edition 2014. (2nd ed.). Great Britain: Witherby Seamanship International.
9. Tanker Structure Co-operative forum (1986). Guidance Manual for the Inspection and Condition Assessment of Tanker Structures. (1st  ed.). England: Witherby Marine Publishing.
10. Tanker structure co-operative forum (1992). Condition Evaluation and Maintenance of Tanker Structures . (1st ed.). England: Witherby & Co.Ltd.

Hull Inspection, Damage & Repair - Part III

Hull Inspection, Damage and Repair ( Reporting and Assessing Structural Defects )  Part III

Stress Concentrations

Stress concentrations occur at any discontinuity in the structure with an intensity related to the abruptness of the change. For convenience, areas of stress can be divided into the following seven types.

Hard Point (more than 80mm from the structure)

The hard spot (or hard area) can be defined as:

• a point (or area) locally rigid in a flexible or less rigid structural element.
• also as a point (or area) where the deflection curve of a plate is
• abruptly interrupted by the effect of a very rigid member supported by the plate.
• as a point (or area) where there is an abrupt change in rigidity.

These abrupt changes in the deflection lines induce high local stresses. In those points (or areas) there is a great possibility to find cracks.

There are 3 types of hardpoints:

Hardpoint Nº 1. 

Bracket welded to a plate. Distance to the nearest stiffener >= 80 mm Consequences > Crack perpendicular to the bracket in the plate. Also, it can be caused by a “doubler”.

Hardpoint Nº 2. 

End of a face flat in a bracket Consequences > Crack in the bracket plating

Hardpoint Nº 3. 

Different deformation, under the same loads = Change of rigidity = Hardpoint 

The brackets should not end on unsupported plating.

The corners of trunks should not end on unsupported plating

SOLUTIONS:

The solution, although it may sound trivial, is to avoid or eliminate the hard points or to make a gradual change of rigidity

1) To place a small pad under the bracket toe. 

2) To extend the bracket to the next support.  

3) To place longitudinal support underneath the bracket.

4) To place transverse support underneath the bracket toe.

In other cases, we have to make the change of rigidity more gradual. Among the many possible solutions, we have to elect the best under the quality/cost criteria.

End of Bracket

The ends of brackets and of stiffeners are prone to fractures and therefore, should be examined carefully. 

We can consider three types of more frequent failures:

End of bracket Nº 1) - In this case, the welding connection of bracket or stiffener with the plating is fractured

End of bracket Nº 2) 

In this case, the bracket or stiffener breaks the support element

End of bracket Nº 3) 

In this case, the bracket or stiffener breaks the support plate.

In addition to three listed above there is also, Bracket Nº4) 

In this case, the bracket itself is broken.

SOLUTIONS for End of Bracket 

Change of Section

No1

No2

No3

In general, the solution is to modify the shape of the bracket (or to add a new one), although, sometimes, it is necessary to increase the size of the bracket.

In other cases, it will be necessary to extend the bracket to the adjacent stiffener or to incorporate a new stiffener to fix end the bracket.

Change of Section

Change of Section –Solution –Fit bracket

Change of Thickness

Solution – Insert an intermediate thickness 

Diminish the thickness difference and make the transition as gradual as possible, in the order of 3:1 or 4:1. 

Insert an intermediate thickness plate when the difference in thickness is more than about 1.5-2 times. Otherwise, improve the transition to 4-5: 1 by chamfering *

*A chamfer is a transitional edge between two faces of an object. A form of a bevel, it is created at 45° angle to two adjoining right-angled faces. A lark's tongue is a chamfer which ends short of a piece in a gradual upward curve, leaving the balance as a right angle.

Openings

Case 1

The solution for the photo above is to close the opening.

Case 2

The solution for case 2 – Increase the radius

If a flange is present on the opening ( as above) increasing the flange thickness in addition to increasing the radius will also reduce the stress.

Misalignments

Solution 1- Full penetration weld

Changing the fillet weld to a full penetration weld ( allows better continuity of the stresses through the misalignment.

Solution 2- Thicker insert

A thicker insert will also allow for better continuity of the stresses through the misalignment. Care should be taken to chamfer the ticker plate

to minimise the effect of the change of thickness.

Solution 3 Re –align

Re-alignment of structure in existing ships is never recommended as it will require a great deal of work to disconnect adjoining structure, and will induce other misalignments in the vicinity

Full penetration weld and a thicker insert will always be easier and cheaper.

Three Planes

(crack always on fillet weld)

When the three planes meet, such as at the intersection of a longitudinal and transverse bulkhead with a platform /stringer deck, there is always the possibility of the stress concentration arising at the point where they intersect. This can lead to fractures, although the type of damage depends on the size and type of the ship.

Solution 1 – Fit bracket (no scallop) in line with the plane on the other side

Solution 2 – Close scallops ( where the bracket is already fitted)

Difference Between Hard Points and End of Brackets

References :

1. Bureau Veritas (2006). Mini Survey Handbook Part A - Ships in Service. (First ed.). France: Marine Division Ships in Service Management ( DNS).
2. Gutierrez, M. – Retired Senior Surveyor LR, 2018. Conversation/Lecture to/with Aleksandar Pudar from 18 to 21/9/2018.
3. Lloyd's Register Marine (2014). Hull Inspection, Damage and Repair. (Third Edition ed.). United Kingdom: First published by Lloyd's Register ,2009. 
4. Lloyd's register marine (2015). Hull Inspection, Damage and Repair. (First ed.). United Kingdom: Lloyds Register.
5. Researchgate.net. 2018. “ Pitting intensity diagrams” www.ResearchGate.com [Online]. Available from: <https://www.researchgate.net/figure/Pitting-intensity-diagrams-Figure-taken-from-2_fig4_320716318 > [Accessed on : 2 October 2018]. 
6. Marchant , T, Dr.Lomas, J & Dr.Callow, L (2009). WHITE PAPER:THE FEASIBILITY OF A CORROSION RESISTANT SHIP. [Online]. (1 ed.). United Kingdom: © BMT Defence Services Limited 2009 © Amtec Consultants Ltd 2009. Available from: <https://www.bmtdsl.co.uk/media/6098421/BMTDSL-Corrosion-Resistant-Ship-Whitepaper.pdf >[Accessed on : 2 October 2018]. 
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