Low Friction Coating Guidelines

Note: These guidelines for generation of ship-specific EVDI calculations where a low friction coating has been applied can be used only for vessels at draft as defined in paragraph 2.2.2 of the EEDI calculation guidelines where all below conditions are met: 

1. Model test reports and Speed-Power curves (from sea trial or CFD), without the effect of low friction coating, should be as per IACS Rec 172 Rev 1 and approved by the Class.
   
   a. Where Speed-Power curve is unavailable and Vref,app has been approximated as specified in EEXI calculation guidelines, the procedure mentioned herein cannot be applied.
   
   
2. Conventional anti-fouling (e.g. Self-polishing copolymer – SPC etc.) was applied while obtaining the Speed-Power curve, without the effect of low friction coating, at the as-designed condition from yard.
   
   
3. The low friction coating application was done during the latest drydock within the last five years from the date being submitted to RightShip. This date cannot be before 1st January 2021. 

 

Where new sea trials have been conducted after application of low friction coatings, these guidelines do not need to be adhered to since the impact of such coating is inherently present in the trial record. 

 

EXPERIMENTAL STUDIES 

1. Coating Manufacturers should follow ITTC 7.5-02-02-03 – Resistance and Propulsion Test and Performance Prediction with Skin Frictional Drag Reduction Techniques - Effective Date: 2017 - Rev.00 for conducting their comparative experimental studies between a conventional anti-fouling as well as the advanced low friction coating under consideration.

1. The baseline coating used in the experiments should be as close in similarity to conventional anti-fouling coating.
   
   
2. The preparation of the substrate for the experiments should be representative of real-world conditions of a new shipbuilding steel with uniform and homogeneous roughness. Polished surfaces such as acrylic, plastic, polished steel etc. should be avoided.
   
   
3. The results of these experiments together with uncertainty estimates for evaluating the repeatability of these experiments need to be approved by an IACS Class Society before the EVDI calculation is undertaken for submission to RightShip.
   
   
4. Such experimental studies should provide the details of the surface preparation of the geometry being studied to ensure uniform, homogeneous and suitable roughness like those observed in new-built ship steel prior to coating application, and alignment and preparation of the geometry being experimented upon for verification of any misalignments and distortions which may affect the results.
   
   
5. The Class approved experimental study must be submitted to RightShip as an appendix to the EVDI Technical file detailed in the next steps. 

 

EVDI CALCULATION AND REPORTING STRUCTURE 

The calculation in the next steps should be shown in a separate EVDI Technical file. Note that this file is like the standard EEDI/EEXI Technical file format defined by IMO’s MEPC.351(78). 

2. EVDI calculations are to be done at 75% of the original nameplate MCR of the main propulsion engine as per EEDI guidelines irrespective of any power limitations applied i.e. NOT AT MCR_lim and at draft corresponding to that defined in paragraph 2.2.2 of the EEDI Guideline. 

3. In Section 2 – Power Curve, of the EVDI technical file, mention the before (including effect of any ESD except paint) and after coating effect (including effect of any ESD) adjusted Vref speed values. Also provide curves as per the flowchart below marked with related legends. The speed-power curves to be considered for EVDI calculation should be at drafts corresponding to the EEDI/ EEXI regulations. 

1. This graph should show a straight line at 75% MCR value cutting both the original (before the low friction coating) and the updated curves (after low friction coating and Energy Saving Device enhancement) demonstrating the corresponding Vref values.  
2. If other energy saving devices are also being implemented together with coatings, evaluation should be done for the coatings independent of these retrofits since coating effect needs to be studied resembling the conditions of the hull as per the original speed profile whence the other ESDs were not present. Thereafter, the ESD improvement needs to be adjusted over the coating improvement. All required curves as per flowchart below should be submitted. 
   
    
   
   Below flow chart explains the process: 

 

Figure 1: Updated Speed-Power curve creation guideline at EEDI draft 

 

 

 4. In Section 4 – Estimation Process of Speed-Power curve, of the EVDI Technical file, mention the process followed to derive the revised speed-power curve at the EEDI draft. Additionally. The Cf calculation as stated in step 4.b and the table of improvement as stated in Step 5.a below should also be mentioned in this section. The detailed calculation steps described below should be added as an appendix to the EVDI Technical file. 

 

1. Basis the approval mentioned in Step 1 of the experimental studies section above, model-scale frictional resistance coefficient, Cf, needs to be scaled to specific full-scale vessel under consideration as per ITTC 7.5-02-02-03 for both - the baseline coating representative of conventional anti-fouling and low friction coating. This scaling should include a range of ship speeds covering Vref value, therefore, extrapolation of curves where needed can be performed.
   
   
2. The resultant Cf value from above should be calculated as per the proportion of the ship’s wetted surface area applied with different coatings (Example – 80% of wetted surface is low friction coating and 20% is conventional anti-fouling coating).  
   
   
   i. The approved coating scheme stating the percentage proportion used in this calculation should be approved by the attending Class surveyor and attached as evidence of coating application in the appendix. This approval can be performed during the Average Hull Roughness (AHR) and hull preparation standard measurements mentioned in points 6.b (iii and iv) below. This is mandatory from 1st January 2025 onwards. For coatings done prior to this date, acceptable evidence of such proportion post the coating application should be submitted as appendix to the EVDI Technical file to RightShip. 
   
   ii. The proportions of different coating types used and the Resultant Cf calculation as per these proportions should be present in Section 4 – Estimation Process of Speed-Power curve of the EVDI technical file. 
   
   
   
3. The total resistance coefficient value (CT) for the low-friction coating scheme using the above obtained Cf values in step (c) should be determined in accordance with ITTC 7.5-02-02-03 - Effective Date 2017 - Revision: 00.
4. For the new low friction coating as derived above in step (c) and the initial conventional anti-foul coating applied at the time of the vessel’s delivery, corresponding estimated speed-power curves should be determined according to ITTC 7.5-02-03-01.4 – 1978 ITTC Performance Prediction Method - Effective Date 2021- Rev. 05. For cases where there is no measured data for the hull roughness of the initial conventional anti-foul coating, roughness of hull surface (ks) = 150 microns can be used as mentioned in the ITTC guideline.  

5. The percentage power improvement obtained from step 4.d between the low friction and the conventional anti-foul coating at each speed shall be applied to the vessel’s Speed-Power curve at its corresponding EEDI draft to derive the final speed-power curves for the low-friction coating scheme implemented.

1. The table including percentage power improvement and the final Speed-Power values at each corresponding speed should be included in Section 4 – Estimation Process of Speed-Power curve, of the EVDI Technical file.
2. These final curves should be included in the EVDI Technical file as stated in Step 3 above and identified with the related legends.
3. If there is any other Energy Saving Device (ESD) retrofit other than paints done simultaneously, and its improvement being calculated, then the improvement due to that ESD should be applied after the paint calculations described above. This ensures that the paint improvement is based on the original delivery condition state when the retrofit ESD was not present.
    

 6. In Section 5.2 - Description of Energy Saving Equipment, of the EVDI Technical file, provide below details of the coating application: 

1. Initial sea trial stage details: 
   i. Name of original coating 
   ii. Type of original coating: SPC, low friction, etc.  
   
   Name of the evidence document such as coating datasheet, original vendor statement with technical details etc. of the original coating as a conventional anti-fouling or SPC can be mentioned and submitted. If such a document is unavailable, especially for ships built before 1st January 2013, submitters are suggested to contact RightShip team at Environment@rightship.com to understand the situation. 
   
   
2. New Low Friction Coating details: 

            i. Name of the coating manufacturer,  
            ii. Low friction coating product name, 
            iii. Date of application,
             iv. Average Hull Roughness (in microns; measured post application as per NACE SP0616-2022: Standard for Hull Roughness Measurements on Ship Hulls in Dry Dock). Witness by a Class surveyor is needed, and measurements shall be done as per guidelines defined in IACS Rec 172 Rev 1 Annex -Witnessing and acceptance of measurements). This is mandatory for coatings applied from 1st January 2025 onwards.

             v. Hull preparation standard (Sa equivalent) followed for coating application and confirmed by the attending surveyor performing the AHR measurement (Reference: ISO 8501- Preparation of steel substrates before application of paints and related products — Visual assessment of surface cleanliness)). 

 

Process of submission and approval of EVDI Technical File: 

The prepared EVDI Technical file can be submitted for review and acceptance through either of two pathways: 

1. An approval from the same IACS member Class which also approved the experimental studies mentioned in point 1-a earlier and is the main Class of the vessel for all other regulatory perspectives.
2.  An active coating partner of RightShip’s Zero Harm Innovation Partners Program (ZHIP) for each coating product that has been reviewed and approved by RightShip as per the guidelines stated herein. 

 

Evaluation of accepted improvements: 

Since coatings degrade in actual operations, their effect needs to be removed over a period. As EVDI is an as-designed vessel performance metric, it is not sensitive to real world operational circumstances and therefore a model to account for the real-world degradation cannot be incorporated within these guidelines. 

However, given ships dry-dock usually every five years, the coating can be assumed to have lost its effect over a five-year period. This approach is being integrated to reset the EVDI by the RightShip’s Platform which will reset the calculation every fifth year + 3 months from the coating application date as per the before paint application Vref mentioned in point 3 above.  This 3-month window is to address situations where the drydock can extend beyond a window of 3 months of the fifth anniversary. 

RightShip will continue to review and accept submissions as per these guidelines referencing ITTC 7.5-02-02-03, the current IACS calculation method, as well as any other calculation methods approved by an IACS member Class with a view that these calculations and intended decarbonisation can be achieved by multiple pathways. 


To review the steps on how to submit the above prepared documents, click here