Used Dual Fuel Engines & Gensets for Sale

Fuel supply in frontier markets is not a given. Pipelines are commissioned late. LNG cargoes are delayed. Currency controls interrupt fuel imports. Gas fields come online behind schedule.

A single-fuel plant is hostage to all of that. A dual fuel plant is not.

Gas supply risk. A plant designed around a gas field or LNG terminal that has not yet been commissioned can run on HFO or diesel from day one and transfer to gas when supply arrives — without replacing the engines.

Price arbitrage. Where both fuels are available, the plant runs on whichever is cheaper at that moment. Over a twenty-year concession, that optionality is worth a great deal.

Bankability. Lenders assessing an IPP in a market with uncertain gas supply treat fuel flexibility as genuine risk mitigation rather than a feature. It changes the risk profile of the project.

Island and isolated grids. Caribbean and Pacific island utilities running on imported diesel can transition to LNG progressively as import infrastructure develops, using the same generating plant throughout.

Emissions compliance. Gas mode delivers substantially lower NOx and effectively eliminates SOx and particulates. Where a plant must meet tightening emissions limits but cannot guarantee gas supply, dual fuel is often the only workable answer.

Wartsila 32DF — Based on the Wartsila 32 diesel platform introduced in the mid-1990s, the 32DF is the machine that established medium-speed dual fuel in power generation. An 18V32DF delivers roughly 5.8 MW in gas mode and 6.1 MW in diesel mode. USP&E stocks an 18V32DF.

Wartsila 34DF — The successor to the 32DF, sharing the same dual fuel technology as the larger 50DF. Available in 12V, 16V and 20V configurations covering 5.6 MW to 9.8 MW, at 450 to 520 kW per cylinder. Around 30% higher output than the 32DF, with double-wall gas piping and the UNIC control system. Fully fuel-flexible with gas mode operation from 0% to 100% fuel sharing. USP&E stocks a W20V34DF at 9.7 MW.

Wartsila 50DF — The 500 mm bore machine, widely referenced in LNG carrier propulsion. The 18V50DF reaches 17,100 kW. Suits utility-scale IPP and large marine applications.

Wartsila 46GD — Gas diesel, using high-pressure gas injection rather than lean-burn Otto cycle. A different technology to the DF range, with different fuel and emissions characteristics. USP&E has supplied 18V46GD machines at 64 MW.

MAN — The 35/44DF and 51/60DF platforms, strongly represented in marine and power plant applications.

Hyundai HiMSEN — The H32/40DF and related platforms, competitively priced and increasingly common in Asian and African projects. USP&E stocks HiMSEN 9H25/33 units.

Output differs slightly between modes. A dual fuel engine typically produces marginally less in gas mode than in diesel mode. On a documented Wartsila 32DF installation, plant capacity was 11.6 MWe on gas against 12.2 MWe on diesel — roughly 5% lower on gas. Size the plant against the mode it will spend most of its life in.

Gas quality matters. The Wartsila 34DF has a nominal design point of methane number 80. Gas of lower methane number can be used with altered performance, typically some derating and adjusted timing. Confirm your gas analysis against the engine specification before committing.

Lean-burn combustion. In gas mode the air-fuel mixture is deliberately lean, with more air than combustion requires. This lowers peak combustion temperature, which cuts NOx sharply and permits higher compression ratio and higher brake mean effective pressure without knock.

Pilot fuel is always present. Even in full gas mode the micropilot injection continues, at under 1% of fuel energy. That means a dual fuel plant always needs a liquid fuel supply, however small, and the pilot fuel system must be maintained regardless of operating mode.

HFO operation requires the full liquid fuel train. Heavy fuel oil needs heating, centrifugal separation, viscosity control and appropriate storage. A plant intended to run HFO carries considerably more auxiliary equipment than a gas-only plant.

Emissions differ by mode. Modern dual fuel platforms are IMO Tier II compliant in diesel mode and Tier III compliant in gas mode. Achieving Tier III in diesel mode requires additional aftertreatment such as a NOx reducer.

EPC scope: fuel supply assessment for both modes, gas analysis and treatment, gas pressure reduction and safety systems, HFO handling including heating, separation and viscosity control, engine installation and alignment, exhaust and heat recovery, MV switchgear and grid interconnection, double-wall gas piping and gas detection, control system integration, commissioning and performance testing in both fuel modes.

O&M scope: operator staffing and training on both modes, fuel changeover procedures and drills, scheduled maintenance to OEM intervals, pilot fuel system maintenance, HFO system chemistry and separator management, top-end and major overhauls, spares holding, availability guarantees.

Commission and test in both modes. A plant accepted only in liquid mode may reveal problems the first time it transfers to gas, often years later and outside warranty. Insist on performance testing in gas mode, liquid mode and during transfer.

Typical EPC delivery for a 10 MW to 50 MW dual fuel plant is 12 to 24 months from notice to proceed.

1 MW to 5 MW — Smaller medium-speed units and marine auxiliaries. Suits industrial captive power and vessel applications.

5 MW to 10 MW — The core IPP band. Wartsila 32DF and 34DF machines sit here. USP&E stock includes an 18V32DF at 6.1 MW and a W20V34DF at 9.7 MW.

10 MW to 18 MW — Wartsila 50DF and MAN 51/60DF territory. Utility-scale building blocks, usually deployed in multi-unit arrays.

Above 18 MW — Gas diesel machines and multi-unit plants. USP&E has supplied 18V46GD units at 64 MW.