Explosive Decompression in Rubber Seals
Why do rubber seals disintegrate when pressure is suddenly released?
When rubber seals or mouldings operate under high gas pressure for some time, depending on the polymer type and hardness, gas molecules are absorbed into structure of the rubber. This slow leakage is not a problem for the rubber while pressure is maintained, but if the pressure is suddenly relieved, the trapped gas rapidly expands to match the new ambient condition. If the transition from high to low pressure is relatively rapid, the rubber cannot withstand the internal forces generated by the expanding gas and appears to “Explode”. This phenomenon is known as “Rapid Gas Decompression” (RGD) or “Explosive Decompression” (ED) and parts affected in this way exhibit failures ranging from surface blistering to complete fracture. If rubber parts are allowed to equalise pressure more slowly so that the entrapped gas can migrate back out of the structure in the same way it entered, the rubber will remain undamaged, however, if this is not an option for the service conditions encountered, careful polymer selection can minimise or eliminate this effect. Materials such as HNBR find many applications in Down Hole Oil Well tools because of their resistance to ED, as do the more exotic Perfluoroelastomers. Industries such as Offshore and Onshore Oil & Gas, Petrochemical and Pharamceutical sectors all have equipment and processes that mean the rubber elements in their systems encounter these extreme decompression cycles, and with our experience in these applications, we are well placed to advise on the best engineering solution to such problems. If your process encounters compressed natural gas, methane, carbon dioxide, nitrogen or hydrogen sulphide (sour gas), we can help with sealing solutions.
Posted on 07/7/2013 by Adam Hooper in Technical Features