Seal selection for handling and storage of biofuels
By Gerald Ondrey |
Results of 12-mo immersion tests in biodiesel and bioethanol of a range of elastomer polymers typically used in fuel-handling equipment show that the seals are prone to significant swelling, which leads to failure in valves and other equipment, according to Precision Polymer Engineering Ltd., (PPE; Blackburn, U.K.; www.prepol.com). The swelling is caused by increased acidity of the biodiesel due to oxidation. Moreover, the presence of water contamination in the biodiesel was found to accelerate the rate of elastomer swelling.
The research shows that companies handling biofuels need to be aware of the increased acidity risk of biofuels on equipment seals, and either maintain their seals more regularly to check for signs of swelling, or switch to alternative sealing materials, such as peroxide-cured fluoroelastomers, says John Kerwin, head of materials technology at PPE. The 12-mo tests have shown that: conventional NBR elastomers can be used within their normal operating parameters for both conventional gasoline and gasoline-ethanol blends, but they suffer significant swelling with biodiesel; bisphenol-cured FKM elestomers that are prone to a reversal of the rubber curing process should be replaced with peroxide-cured FKM for biofuel…