High Pressure Water Mist for the Protection of Risk of Oil Mist Explosions Stefan Kratzmeir IFAB Institute for applied fire safety research Kratzmeir@ifab-fire.com
Background Oil mist causes fires and explosions in ship s engine rooms Creation of oil mists by mechanical and thermal processes Example: Lub oil evaporates on overheated surfaces due to installation failures of bearings in crank cases, explosion even with oil mist detection Consequence: Repairs under thread of life Loss of the whole ship Thread of health by risk of cancer 03.11.2010 2
Aim of the whole project RedOMir Research Project on behalf of the German government In cooperation with the Institute of Safety Engineering, Rostock Major Questions and Tasks for the project: Is it possible to influence an developing oil mist in a way that its thread of an explosion or as an health hazard can be rapidly reduced without endangering people? Is it possible to prevent the creation of explosible oil mists by cooling, dilution or reduction of ignition energy of oil mists? Reduction of oil mist explosion risks by the development of tests with: Application of water mist Application of cold air/pressurised air 03.11.2010 3
Targets of the Research Project (Subproject: Water Mist) Prevention of the development of an explosible oil mist atmosphere with activation of water mist Approach: Investigation of the physical properties of oil mists in explosion tests Investigation of influence of HPWM on explosible properties of oil mists by condensation & coagulation of HPWM on oil droplets 03.11.2010 4
Creation of explosible oil mists Investigation of behaviour of oil mists Reasons for explosivity Comparable results Test scenarios with and without igniter Development of Temperatures Overload pressure Gases Ignition with igniter and without igniter 03.11.2010 5
Method: Creation of explosible oil mists Lower explosion limit of oil mist (LEL) in litererature: LEL mass concentration [mg/l] Burgyone et al.: basic experiments to determine the LEL of oil mist at about 50 g/m 3 used in safety data sheets or safety guides until today LEL of oil mist depends on the droplet size and decreases with increasing droplet diameter Diameter of droplets [µm] 03.11.2010 6
Method: Creation of explosible oil mists Attempts to create an explosible atmosphere Spraying of mechanical produced oil mist from an oil mist generator into a defined test volume (1m 3 ) with variation of the droplets diameter (from 1 to 5 µm), variation of the pressure and/or the oil temperature, using 1 to 3 nozzles Inserting of thermal produced oil mist from an oil mist generator into a defined test volume (1m 3 ) Heating of oil directly in the test volume (1 m 3 ) 03.11.2010 7
Method: Creation of explosible oil mists Test set up Suction of gas for analyses Pressure sensores (overload pressure) Lid Drum Igniter 20000V Window Pot with engine oil Burner 800W T 8 T 7 6 T 5 T 4 T 3 2 T 1 90 cm Thermo couples T 1 T 8 60 cm 03.11.2010 8
Creation of explosible oil mists Droplet concentration [g/m3] max ca. 3,5 g / m 3 Oil: Mozart Q8 preheatet on 100 C, 1 bar Time [s:mm] 03.11.2010 9
Creation of explosible oil mists Max. oil mist concentration 3 4 g/m 3 (compared to literature 50 g/m 3 ) Possible Reason: Adjusting equilibrium between new droplets and coagulating or sinking droplets Explosivity of oil mists Not caused by fine droplets But caused by explosive decombustion gases Oil mist detectors relay on a LEL of 50 g/m³ Oil mist explosions happened in the past although no alarm by oil mist detectors 03.11.2010 10
Creation of explosible oil mists Example Graph : Propan Oil temperature during ignition 240 C 330 C 250 Propan 200 Concentration of engine oils [ppm] 150 100 50 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 Temperature [ C] Oil C5-1 Oil Q8 Oil RSL Oil C5-2 03.11.2010 11
Creation of explosible oil mists Explosivity and flamability of analysed gases: Gas Flash point [ C] Explosion limits [Vol.% ] Propane -104 1,7 10,8 Formaldehyde 32 7-73 Hydrogen -240 4-77 The thermal degradation of lubrication oil as a cause of crankcase explosions is considerably more probable as the assumed oil mist. 03.11.2010 12
Reducing risk of explosion by activation of water mist Prevention of the development of an explosible oil mist atmosphere: Not by condensation or coagulation processes between droplets of oil and water mist By decreasing of the ignition energy with water mist (cooling) 03.11.2010 13
Method: Activation of HPWM Test set up Dropping funnel with shut-of for oil inlet to prevent evaporation Pressure sensor overload Pressure sensor system Lid Barrel Igniter 20000V Window Burner 800W 60 cm T 8 T 7 6 T 5 T 4 T 3 2 T 1 90 cm Thermo couples T 1 T 8 Protector (water splash on hot oil) HPWM pump (Typ KFT25) Solonoid valve 03.11.2010 14
Activation of water mist with variation of Flow rate System pressure Position of nozzles Institute for applied fire safety research Method: Activation of HPWM Dimension of an explosion by the measurement of Overload pressure Explosible gases 03.11.2010 15
Results: Activation of HPWM 600 550 500 450 Activation of HPWM 1 nozzle, 75 bar Aktivierung HDWN Ignition Zündung 80 Increase 70 of propan 60 T [ C]/ Konzentration [ppm] 400 350 300 250 200 50 40 30 Druck bar 150 20 100 50 10 0 0 0:00:00 0:01:26 0:02:53 0:04:19 0:05:46 0:07:12 0:08:38 0:10:05 0:11:31 0:12:58 0:14:24 0:15:50 t [hh:mm:ss] Temp 70 cm [ C] Temp 60 cm [ C] Temp 50 cm [ C] Temp 40 cm [ C] Temp 30 cm [ C] Temp 20 cm [ C] Temp 10 cm [ C] Temp Öl cm [ C] Propan [ppm] Druck [Bar] 03.11.2010 16
Results: Activation of HPWM 600 550 500 450 Aktivierung HDWN Activation of HPWM 2 nozzles, 75 bar No Ignition 80 70 60 T [ C]/ Konzentration [ppm] 400 350 300 250 200 150 100 50 50 Increase of 40 propan 30 20 10 Druck bar 0 0 00:00:00 00:01:26 00:02:53 00:04:19 00:05:46 00:07:12 00:08:38 00:10:05 00:11:31 00:12:58 00:14:24 00:15:50 00:17:17 00:18:43 t [hh:mm:ss] Temp 70 cm [ C] Temp 60 cm [ C] Temp 50 cm [ C] Temp 40 cm [ C] Temp 30 cm [ C] Temp 20 cm [ C] Temp 10 cm [ C] Temp Öl cm [ C] Propan [ppm] Druck [Bar] 03.11.2010 17
Results: Activation of HPWM Decrease of overload pressure by increase of HPWM by Flow rate System pressure Optimised nozzle position 03.11.2010 18
Application of HPWM Institute for applied fire safety research Summary & Conclusion Prevention of ignition of explosible gases By cooling of the surrounding atmosphere in the mock up By decrease of ignition energy with HPWM By dilution of concentration of explosible gases with HPWM Application of Air (cooled/pressurised) No Prevention of ignition of explosible gases Very slow cooling effect of the surrounding atmosphere in the mock up by use of cooled air Acceleration of ignition by use of pressurised air 03.11.2010 19
Economical Benefits Use of present HPWM Systems in ships or other vessels to prevent oil mist explosions by ignition of explosible gases in combination with gas analyses Use of HPWM in crankcases as continuous running system to cool down hot surfaces that cause decomponsition of oil mists Development of new oil mist detectors that are not based on measuring the oil mist concentration rather than the gas concentration of developing explosible gases 03.11.2010 20
THANK YOU FOR YOUR ATTENTION 03.11.2010 21