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VOC MANAGEMENT PLANVOC MANAGEMENT PLAN SHIP NAME: IMO NUMBER: DOCUMENT REVISION NO. RECORDS OF CHANGES Rev. Section Page Date Description Sign. No. LIST OF CONTENTS a/a Section page Introduction I Objectives II Additional Considerations III SECTION 1 Cargo tanks parti...

VOC MANAGEMENT PLAN
VOC MANAGEMENT PLAN SHIP NAME: IMO NUMBER: DOCUMENT REVISION NO. RECORDS OF CHANGES Rev. Section Page Date Description Sign. No. LIST OF CONTENTS a/a Section page Introduction I Objectives II Additional Considerations III SECTION 1 Cargo tanks particulars 1.1 Tank arrangements 1.2 Design Particulars SECTION 2 Cargo Tank venting systems 2.1 Description of the vessel’s venting system 2.2 Set opening pressures of venting devices SECTION 3 Volatility of crude oils - VOC generation mechanisms 3.1 Background 3.2 The volatility or vapour pressure of the crude oil 3.3 VOC generation mechanisms SECTION 4 Means for reduction of VOC emissions. 4.1 Installations for reduction of VOC emissions 4.2 Operational measures for the reduction of VOC emissions SECTION 5 The monitoring and control of VOC releases SECTION 6 Training programme SECTION 7 Designated person SECTION 8 List of drawings, plans and manuals Introduction This Manual contains specific information and procedures for this crude oil tanker to conform with the operational requirements and objectives of the IMO Guidelines for the Development of a VOC Management Plan which stipulate as follows: 1.1 Objectives .1 The purpose of the VOC management plan is to ensure that the operation of a tanker, to which regulation 15 of MARPOL Annex VI applies, prevents or minimizes VOC emissions to the extent possible. .2 Emissions of VOC can be prevented or minimized by: .1 optimizing operational procedures to minimize the release of VOC emissions; and/or .2 using devices, equipment or design changes to prevent or minimize VOC emissions. .3 To comply with this plan, the loading and carriage of cargoes which generate VOC emissions should be evaluated and procedures written to ensure that the operations of a ship follow best management practices for the preventing or minimizing VOC emissions to the extent possible. If devices, equipment or design changes are implemented to prevent or minimize VOC emissions, they shall also be incorporated and described in the VOC management plan as appropriate. .4 While maintaining the safety of the ship, the VOC management plan should encourage and, as appropriate, set forth the following best management practices: .1 the loading procedures should take into account potential gas releases due to low pressure and, where possible, the routing of oil from crude oil manifolds into the tanks should be done so as to avoid or minimize excessive throttling and high flow velocity in pipes; .2 (in case of manual release/blow-down of ullage pressure is practiced) the ship should define a target operating pressure for the cargo tanks. This pressure should be as high as safely possible and the ship should aim to maintain tanks at this level during loading and carriage of the relevant cargo; .3 when venting to reduce tank pressure is required; the decrease in the pressure in the tanks should be as small as possible to maintain the tank pressure as high as possible; .4 the amount of inert gas added should be minimized. Increasing tank pressure by adding inert gas does not prevent VOC release but it may increase venting and therefore increased VOC emissions; and .5 when crude oil washing is considered, its effect on VOC emissions should be taken into account. VOC emissions can be reduced by shortening the duration of the washing or by using a closed cycle crude oil washing programme. 1.2 Additional considerations .1 A person in charge of carrying out the plan .1 A person shall be designated in the VOC management plan to be responsible for implementing the plan and that person may assign appropriate personnel to carry out the relevant tasks; .2 Procedures for preventing or minimizing VOC emissions .1 Ship-specific procedures should be written or modified to address relevant VOC emissions, such as the following operations: .1 Loading; .2 Laden Voyage .3 Crude oil washing. .2 If the ship is equipped with VOC reduction devices or equipment, the use of these devices or equipment should be incorporated into the above procedures as appropriate. .3 Training .1 The plan should describe the training programmes to facilitate best management practices for the ship to prevent or minimize VOC emissions. Section 1 – Cargo tank particulars 1.1 Allowable cargo tank ullage pressure The cargo tank structure is designed to withstand a range of design loads and parts of the tank structure will also contribute to the global longitudinal strength of the ship. The Classification Societies’ specified load conditions and loads are applied in verification of the structural design. Exceeding the maximum allowable pressures could lead to structural failures. If such a structural failure results in opening of the tank structure to atmosphere, uncontrolled VOC emissions will occur together with the possibility of oil pollution to the seas. Further, it could result in loss of inert gas protection with subsequent hazards related to fire and explosion. This ship has XX cargo tanks and Y slop tanks: 3 - Total volume of cargo tanks: ______m - 3 Total Volume of slop tank(s): _______ m - Number of cargo segregations: _______ Design particulars: - Design vapour pressure: 0.XX bar - Max. permitted vacuum: 0.0Y bar Section 2 – Cargo tank venting systems 2.1 Description of the ship’s venting system: The ship’s cargo tank venting system is included in Section 8. 2.5.1 Set pressures of venting devices: - Cargo/Slop tank’s P/V-valves: _______ barg/_________bar vacuum - Mast riser by-pass breather valve: _______ barg/_________bar vacuum (if fitted) - Mast riser by-pass pressure control valve: _______ barg/_________bar vacuum (if fitted) - Liquid P/V-breaker: _________barg/________bar vacuum Any ship that has a P/V-valve setting above the standard 1400 mmWG, may be considered to have implemented a measure for VOC reduction and this could be specified in the manual. Section 3 – Volatility of crude oils - VOC generation mechanisms 3.1 Background Why limit NMVOC Emissions to the atmosphere? NMVOCs are a pollutant to the air and act as a precursor to the formation of Tropospheric Ozone – commonly termed Smog. Tropospheric Ozone is identified as a Greenhouse Gas with a greater contribution per unit volume or tonnage to Climate Change than the base gas, namely Carbon Dioxide. 3.2 The volatility or vapour pressure of the crude oil Crude oil is a mixture of hydrocarbon compounds ranging from heavy liquids to light liquids and with absorbed hydrocarbon gases not existing as liquids under normal ambient conditions. The measure of volatility is the vapour pressure of the crude oil. Vapour pressure is given either as: - Reid Vapour Pressure (RVP) or - True Vapour Pressure (TVP) RVP is the most commonly used measure for vapour pressure of oils in the oil industry and is the saturated vapour pressure above the liquid measured in a special apparatus at a temperature of 37.8 ºC. The measuring apparatus is a closed container where a sample of the liquid with a volume of 20% of the container volume is filled, i.e. the vapour space is 4 times the volume of the liquid sample. The liquid is heated to 37.8 ºC and the gauge pressure reading is the RVP in absolute pressure. TVP is the saturated vapour pressure above a liquid at a specified temperature. Compared to RVP the TVP represent the partial vapour pressure measured in a container with a negligible vapour space. For a homogenous liquid not containing absorbed gases, the RVP and TVP measured at 37.8 ºC will be approximately equal. For a crude oil which contain absorbed gases, e.g. methane, ethane, propane etc., the RVP will be lower than TVP at 37.8 ºC. The reason is that when the absorbed gases migrates into a vapour space 4 times the volume of the liquid sample the concentration of these components in the liquid is reduced. Consequently the measured saturated vapour pressure represent a ‘de-gassed’ crude oil and will be lower than the true vapour pressure. In a closed and fully loaded cargo tank with a vapour space about 2% of the tank volume, the actual partial hydrocarbon vapour pressure will be the true vapour pressure, TVP. 3.3 VOC generation mechanisms 3.3.1 ‘Flashing’ During loading, low pressure in the loading system may cause absorbed gases to form gas bubbles and light liquid fractions to evaporate. This will in particular happen in the top of the drop line. The pressure at this point will be below atmospheric pressure determined by the specific weight of the liquid column in the drop line minus the tank atmosphere pressure and the liquid height above the drop line outlet in the tank. If the pressure falls below TVP, vapour bubbles will be formed in the drop line and transported into the tank by the liquid flow. Re-absorption in the crude oil will be minimal and the ‘flash’ gases will increase the pressure in the vapour space of the tank. As the liquid level in the tank rises, the underpressure in top of the drop line will be reduced, i.e. the absolute pressure rises.. When the absolute pressure in the top of the dropline exceeds the TVP, ‘flashing’ will cease. 3.3.2 De-gassing & evaporation. The surface layer of the liquid in the tank will give off vapours until the partial pressure of the various vapour components in the atmosphere layer above the liquid surface reaches saturation with the concentration of absorbed gases in the liquid. Assuming there is no agitation of the liquid and of the vapour space a concentration difference of absorbed gases between the top layer of the liquid and liquid lower in the tank. Above the liquid a similar concentration gradient will occur. Diffusion will over time even out the concentration differences but this is a slow process (concentration gradient is the driving force). If agitation of the liquid and/or tank atmosphere takes place this will greatly speed up the reduction of the concentration differences and thereby substantially increase vapour release from the liquid. 3.3.3 Temperature increase. The saturated partial pressures of vapour increases with temperature of the liquid. An increase in the cargo temperature during a voyage will therefore increase the vapour space pressure and cause opening of P/V valves.. If the temperature increase causes the TVP of the crude oil to exceed the opening pressure of the P/V valves, vapour release to the atmosphere will continue until the concentration of absorbed gases in the liquid reaches an equilibrium with the partial vapour pressure. Temperature increase of the atmosphere in the vapour space without corresponding temperature increase of the cargo (sun heating of deck plating) will increase the vapour space pressure due to thermal expansion of the gas mixture. Typically one will see pressure variations during day-night. However, this will not cause more vapour release from the liquid. 3.3.4 Pressure decrease in vapour space Leakages, e.g. through P/V valves or hatch gaskets, will decrease the vapour space pressure. This will cause the crude oil to give off vapours to restore the saturated partial vapour pressure, i.e. TVP if fully loaded tank. The same takes place if manual blow-down of vapour space pressure is done by e.g. opening of mast riser valve. 3.3.5 Crude oil washing. When a cargo tank is discharged inert gas is supplied to fill the increasing vapour space. If the agitation of the liquid and the vapour space is small or moderate the resulting atmosphere in the tank at the end of discharge will be a layer of saturated vapour/inert gas mixture and a progressively leaner mixture towards the top of the tank. This mean that less cargo vapours will be displaced at next loading. However, if the tank is crude oil washed during cargo discharge this causes severe agitation of the tank atmosphere and release of cargo vapours from the washing liquid as well as from the cargo residues in the tank. If washing is done using ‘fresh’ crude oil (bleed-off from discharge line) the resulting tank atmosphere will be saturated with vapours which subsequently will be displaced at next loading. If ‘closed’ crude oil washing is done, i.e. a crude oil charge in slop tanks is re-circulated, less vapour will be released to the tank atmosphere as the washing liquid is de-gassed. 3.3.6 Loading high TVP cargo The SOLAS convention permits loading of crude oils with RVP up to 1 bar (atmospheric pressure). If such a cargo is loaded having a temperature of e.g. 45 ºC (may well happen during summer season in the Arabian Gulf), the cargo will release absorbed gases until the partial vapour pressure, i.e. TVP, is below set opening pressure of the P/V valves. This means release to the environment quite substantial volumes of vapour. Section 4 – Measures for reduction of VOC emissions. 4.1 Installations for reduction of VOC emissions 4.1.1 Vapour Emission Control Systems (Delete as applicable) For ships provided with a VECS system as per IMO or USCG regulations USCF 46 CFR Part 39 and IMO MSC.Circ.585), the control of NMVOC emissions will be through returning VOC to shore terminal in accordance with the procedures found in the onboard VECS manual. For this vessel the design cargo loading rate of the ship is approximately UUUUU m3/h when loading through all cargo manifolds and loading all cargo oil tanks. The design a cargo discharge rate is approximately VVVVV m3/h with the use of all three main cargo pumps. Note however that as per the VECS manual the following loading rate restrictions apply: - Maximum loading rate of a single cargo tank: approx. XXXX m3/h - Maximum loading rate of slop tanks: approx. YYYY m3/h - Maximum loading rate of all cargo tanks: approx. ZZZZZ m3/h The above limitations apply for a cargo with a maximum vapour growth rate of XXX and a maximum density of YYY kg/m3. For lower vapour growth rates and densities, the loading rate may be increased in accordance with that stated in the VECS manual.” . 4.1.2 Vapour Pressure Release Control Valve (Delete as applicable) A vapour pressure control valve may be installed in a by-pass to the mast riser valve to control the opening and closing pressure for vapour pressure release. If such valves have the capacity to handle the total gas flow during loading, it can also be used to maintain a higher pressure throughout the loading process. The effect is to reduce the vapour evaporation from the crude oil. The setting of the valve should be just below the P/V-valve setting. 4.2 Operational measures for the reduction of VOC emissions (Example only- amend/delete as applicable) 4.2.1 Operational measures, general Carry out regular inspection of P/V valves, hatches and pipe connections for tightness. Any leakages detected shall be entered into the maintenance program for rectification at first opportunity. 4.2.2 Operational measures during loading with no vapour return (VECS) (Example only- amend/delete as applicable) Loading should be started with low to moderate loading rate until loading outlets (bellmouths) in tanks are well submerged, e.g. filling to 1m. High loading rate per tank means shorter filling time and less vapour release from the crude oil. If practicable, considering trim and bending moment/shear force, loading segregation by segregation at max rate is favourable. High vapour space pressure reduces vapour release from the cargo during loading. A procedure where the initial slow loading takes place with the mast riser valve open followed by closing the riser valve and let the P/V valves on the tanks take care of the release of excess vapour/inert gas during the subsequent loading will be beneficial. 4.2.3 Operational measures during laden voyage (Example only- amend/delete as applicable) Manual release/blow-down of ullage (vapour space) pressure should be avoided as far as practicable. If carried out the VOCCON procedure should be considered applied. If low tank pressure occurs making inert gas top-up necessary make sure that the supply pressure is kept below opening pressure of the P/V valves. 4.2.4 Operational measures during discharging and COW (Example only- amend/delete as applicable) Do not wash more tanks than what is required by the Convention (1/4 of the tanks) unless special circumstances make it necessary. A full cycle (top-bottom-top for single nozzle machines) will normally not be necessary. Washing covering lower stringers and tank bottom will in most cases be enough for sediment control. Closed cycle COW may be considered. I.e. re-circulate crude oil used for washing to/from slop tanks. This reduces vapour release from the crude oil compared to using ’fresh’ oil bleed from discharge lines. If vessel’s trim/bending moment permit, tanks intended to be washed should be discharged first. Vapour released when these tanks are washed may then be used to fill the other tanks being discharged 4.2.5 Operational measures during ballast voyage (Example only- amend/delete as applicable) If low tank pressure occurs making inert gas top-up necessary make sure that the supply pressure is kept below opening pressure of the P/V valves. Section 5.0 - The Monitoring and Control of NMVOC Releases 5.1 Ships that are not provided with VOC recovery/reduction installations have limited control over VOC releases during loading or as a result of automatic opening of P/V- valves. I.e. record keeping is considered relevant only if manual release/blow-down of the ullage pressure is carried out onboard. 5.2 For ships that do not perform manual release/blow-down, recording is not deemed necessary. Section 6.0 - Training Programme 6.1 Persons in charge of the VOC management onboard have completed a training programme comprising: 1 An introduction to the purpose of VOC emission control: - Regulation 15 of Annex VI to MARPOL 73/78 2 An introduction to the principles of VOC emission control: 3 General VOC emission control options 4 Ship specific VOC emission control options Monitoring and recording of VOC release 5 6 Hazards and Safety related to VOC emission control Section 7.0 - Designated Person 7.1 The person designated to assume overall charge of the VOC management onboard the ship is; _____________________. Section 8.0 - List of drawings 8.1 The following drawings are recommended included as appendices to the management plan: - General Arrangement drawing - Tank plan - Schematic drawing(s) of the Cargo tank venting system - Schematic drawing of the inert gas system - Schematic drawing of the vapour emission control systems (if applicable) - Schematic drawing(s) Vapour Recovery System or other VOC control systems. - Details of pressure vacuum relief devices including settings and capacities. Cross References to ship specific manuals or documents such as: - Vapour Emission Control System manual (if applicable) - Vapour Recovery System manual (if applicable). - Other VOC control system manual (if applicable) - Inert Gas manual - COW manual
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