SynergizingTechnologies
Sustainable Technologies towards a greener future.
Plate heat exchangers — gasketed, semi-welded and fully welded — and non-OEM plates and gaskets for Alfa Laval, Kelvion, Sondex, Tranter, APV and more.
Sustainable Technologies towards a greener future.
Choose your industry to narrow down to the duty.
Blow-by gas cooling
Cooling crankcase blow-by gas on gas and dual-fuel engines so the oil vapour condenses and drains back to the sump before the gas reaches the separator.
Also called: blow-by cooler, blow-by gas cooler, crankcase gas cooler, crankcase ventilation cooler, gas engine blow-by.
Recommended type
Brazed Plate Heat Exchanger
Blow-by is the gas that slips past the piston rings into the crankcase, carrying oil vapour, water vapour and, on a gas engine, unburnt fuel gas and sulphur compounds. Cooled to about the charge-air temperature, the oil condenses and can be caught and returned; cooled much further, the water condenses too and turns acidic with the sulphur. The heat duty is small and 80 °C is easy for any plate unit, so the selection is set by gas-side pressure drop: about 1 mbar for the whole vent line. Up to roughly 60 m³/h of blow-by, about a 2–3 MW engine, a brazed plate unit does it in the least space with no gasket for fuel gas to leak past — nickel-brazed or all-stainless, never copper, against the sulphur, with large ports and enough plates to keep the gas slow. Above that, or on sour fuels such as biogas, a gasketed unit with wide-gap plates on the gas side holds the pressure drop and opens for cleaning out oil sludge; semi-welded keeps the fuel-bearing gas in welded channels, which matters at sea. Shell & tube is the answer where there is no extraction fan and the pressure-drop budget is tighter still. Mount any of them vertically, gas in at the top, so the oil drains with the gas to the trap.
Typical design data
- Hot side
- Crankcase blow-by gas: combustion gas, oil mist and vapour, water vapour, and on gas engines unburnt fuel gas and sulphur compounds.
- Cold side
- Low-temperature cooling water, charge air, or seawater on marine engines.
- Gas inlet
- 60–80 °C, about 5 K above the engine’s lube oil inlet temperature.
- Gas outlet
- About the charge-air temperature, typically 40–60 °C: cold enough to condense the oil, warm enough to keep the water in the gas.
- Gas flow
- About 0.02 m³/h per kW on a new engine, rising to 0.04 m³/h per kW as it wears; roughly 0.1 % of the engine’s air flow. A 3 MW engine vents about 60–120 m³/h.
- Heat duty
- Small: roughly 1–10 kW, depending on engine size and wear.
- Gas-side pressure drop
- About 1 mbar (10 mm water column) across the whole vent line, unless an extraction fan is fitted. This, not the heat duty, sizes the cooler.
- Condensate
- Oil drained from the gas side back to the sump through a trap.