Elastomer Selection for Bio-Fuel Requires a Systems Approach

Transcription

1

2 Elastomer Selection for Bio-Fuel Requires a Systems Approach From an Article in Sealing Technology by Gordon Micallef, Trelleborg Sealing Solutions, Malta and Axel Weimann, Trelleborg Sealing Solutions, Germany

3 The Challenge Use of Biofuels presents a means of: Reducing Carbon emissions Reducing Western dependence on imported fuels; However: Traditional / existing elastomers (seal materials) are not optimum for Biofuels or Biofuel Mixes: Fatty Acid Methyl Esters are chemically different, to Diesel distillates; Increased water absorption in Biofuel content can lead to acid attack. Changes to Aromatic content of fuel can also change seal performance.

4 Laboratory Trials of Seal Elastomers Trelleborg Sealing Solutions identified that traditional laboratory trials of materials can hide the effects of elastomer performance; Experience and re-creation of engine operational working conditions, in trials are important, to establish more realistic trial results; Trelleborg s trials subjected seven seal materials to heat, pressure and chemical environment typical of seal locations in engines.

5 Laboratory Trials of Seal Elastomers Trelleborg s full trials process considered: Biodiesel, for use in Compression Ignition engines; and Different Ethanol / Methanol mixtures, for use in Spark ignition engines. For Compression Ignition engines, the fuels compared were: Diesel Fuel : To EN590:1999 (zero FAME content) B30 Fuel: EN590:1999 plus 30% natural FAME content

6 Laboratory Trials of Seal Elastomers Trelleborg s Diesel trials process considered seven different elastomer materials known for good sealing properties: 1: FVMQ Flourosilicone, Peroxide cure: (preferred for Diesel connectors); 2: FKM Flourocarbon copolymer, 66%Flourine, Bisphenol cure (OK for conns); 4: FKM terpolymer, 66% Flourine, Bisphenol cure (preferred for Diesel pumps); 5: FKM terpolymer, 70% Flourine, Bisphenol cure (preferred for Diesel conns); 6: FKM tetrapolymer, 68% Flourine, Peroxide cure (OK for Diesel pumps); 7: FKM tetrapolymer, 64% Flourine, Peroxide cure (OK for LP Diesel injectors); 9: FKM tetrapolymer, 65% Flourine, Peroxide cure (OK for HP Diesel injectors).

7 Laboratory Trials of Seal Elastomers Trelleborg s Diesel trials process undertook tests for: Volumetric Swell (important to keep the fuel in and dirt out); Change in Tensile Strength (important to prevent breakage under load); Change in Hardness (Too soft: the seal will extrude; too hard: it will shear); Changes in Elongation (important to maintain seal effectiveness). However, seal performance with water contaminated fuel was also tested: B30 Biodiesel Fuel; and 1% w/w Water in B30 Biodiesel fuel.

8 Volumetric Swell/Hardness/Strength Trials of Seal Elastomers

9 Volumetric Swell/Hardness/Strength Trials of Seal Elastomers The volume changes for selected compounds are less than 10% between Diesel and B30 Biodiesel fuels; Tensile strength and hardness are reduced by extended exposure to fuels but the differential performance is less than 5% in all seal materials; Elongation is generally reduced in B30 Biofuel but, again, to little real effect on performance. SO THIS LOOKS OK, THEN?

10 Seal Performance with Water Contaminated Fuel

11 Seal Performance with Water Contaminated Fuel Volumetric swell performance consistently good EXCEPT Seal Material 2 and 5; Tensile Strength performance seriously degraded when water contamination present Sample 1 cracked before test; others poor; Hardness affected in all but Seal Material 9; Elongation results varied Seal Material 4, 5, 6 & 9 gave better results than others.

12 Seal Performance with Water Contaminated Fuel When contaminated with 1% water, Samples 2, 4 and 5 (all Bisphenol cured flourocarbon have deteriorated seriously, due to volumetric change and blistering. It has been suggested that hydrolysis of the esters in Biodiesel forms carboxylic acid, which attacks the seal material. The peroxide cured materials were significantly less affected.

13 Elastomer Selection for Bio-Fuel Requires a Systems Approach Conclusions: Seal material choice requires careful testing under laboratory circumstances replicating engine environment and working conditions; Seal performance is demonstrated as acceptable, with Biodiesel mix, so long as fuel is kept clean and free of water. Seal performance can be seriously degraded by presence of dissolved water in the fuel. KEEP YOUR FUEL SYSTEMS CLEAN AND WATER FREE!!

14 Acknowledgements Gordon Micallef, Trelleborg Sealing Solutions, Malta; Axel Weimann, Trelleborg Sealing Solutions, Germany; Sally Beken, Knowledge Transfer Network, UK. Full Details of the Trelleborg Report is available at today s Guest Publication : Sealing Technology ISSN January