Crude-Oil VOC Vapour Recovery, Compressor Capacity & Emissions-Capture ROI Tool

Regulatory & Operating Basis

MARPOL Annex VI regulation 15 requires crude-oil tankers to carry and implement an approved ship-specific VOC Management Plan. VECS use is mandatory where the relevant Party has designated a port/terminal for VOC control. Project-specific terminal rules, approved VECS manuals and cargo-tank venting limits remain controlling.

Ship / operation

Terminal VOC-control status

Future 0.20 barg P/V-valve screenMEPC 84 approved a draft 0.20 bar gauge minimum opening-pressure amendment for new crude-oil tankers. It is not yet adopted as of Sep. 3, 2026.

Installed VOC-control concept

Loading & Vapour Generation

Crude loading ratem³/h liquid cargo.

Vapour growth ratioActual m³ tank vapour generated per m³ liquid loaded. Use cargo/terminal/VECS-manual data where available.

Loading temperature°C vapour temperature basis.

Cargo tank pressurebar gauge.

Atmospheric pressurebar absolute.

Measured / estimated VOC concentrationvol% non-methane hydrocarbon in tank vapour.

VOC average molecular weightkg/kmol. Enter representative crude-vapour composition.

Direct measured VOC mass-flow overridekg/h. Enter 0 to use the ideal-gas concentration estimate.

Advanced Cargo / Terminal Register

Compare different crude parcels, loading rates and terminals. Each row estimates normalized vapour flow, VOC mass generation and annual exposure independently.

Cargo / Terminal	Load m³/h	Growth	Temp °C	Tank barg	VOC vol%	MW	Hours/call	Calls/yr

Tank Pressure, VECS & Venting Margin

Target cargo-tank operating pressurebar gauge. IMO VOC guidance encourages the highest safely practicable target pressure under the approved system.

P/V valve positive opening pressurebar gauge, vessel-specific approved setting.

Calculated VECS line pressure dropbar at maximum loading/vapour rate.

VECS pressure-drop screen% of P/V setting. 80% is a useful approved-manual/VECS screening basis discussed in MEPC.1/Circ.680; confirm the ship's approved manual.

Maximum approved loading ratem³/h from VECS manual / terminal / cargo plan.

Terminal vapour-return limitNm³/h.

Recovery Compressor & Processing Train

Compressors installed

Compressors available

Rated capacity per compressorNm³/h.

Available-capacity derating% after fouling, ambient and control margin.

Minimum stable turndown% of one compressor rated capacity.

Capture / collection efficiency% of generated VOC entering recovery train.

Hydrocarbon recovery yield% of captured VOC converted to reusable/recovered hydrocarbon rather than residual vent/off-gas.

Design flow margin% above calculated normalized vapour generation.

Compressor suction pressurebar gauge.

Compressor discharge pressurebar gauge.

Gas heat-capacity ratio k

Overall compression efficiency% indicative thermodynamic + mechanical efficiency.

Annual Utilization & Economics

VOC-control operating hours / year

Recovered hydrocarbon valueper tonne recovered.

Electricity costper kWh.

Annual service / maintenance OPEX

Installed CAPEX

Other avoided VOC / compliance valueper tonne VOC captured. Optional user-entered value only, not an assumed carbon credit.

Annual avoided terminal / delay costOptional savings from avoiding loading-rate restrictions, venting interruptions or terminal delay.

Baseline vented fraction without recovery% of modeled VOC generation that would otherwise reach atmosphere.

Engineering limitation: Vapour growth, VOC composition, molecular weight, actual compressor performance, condensation yield and vent-system hydraulics are strongly cargo- and installation-specific. This tool is a screening and investment-planning model. It does not replace the ship's approved VOC Management Plan, VECS manual, cargo-tank venting calculations, P/V valve capacity, terminal compatibility study, class/flag approval, hazardous-area review, maker performance curves or ship/shore operating procedures.