A manufacturer of plastic products has historically used EPDM rubber gaskets on their 30” custom FRP (fiber-reinforced plastic) manway lids due to the low allowable torque of 60ftlbs. After recognizing repeat gasket failures, the company contacted our applications engineering team for a better solution.
FRP flanges are designed for elastomeric or rubber gaskets and have low allowable torque. This is challenging when the service media and conditions preclude using elastomeric-based gasket materials. For this application, the EPDM gasket sealing the manway connection on the sodium hypochlorite tank was leaking and showing signs of chemical degradation from the sodium hypochlorite. Due to the low allowable torque, upgrading to a traditional PTFE material for improved chemical resistance was not an option.
GYLON EPIX® Style 3504 modified PTFE gasket with aluminosilicate microspheres is designed with raised surface profiles that create stress optimization and reduce the gasket contact surface area. Testing proved that GYLON EPIX® Style 3504 seals lower-pressure liquid services (<150 psig) at stresses as low as 300 psi. The gasket was further enhanced by reducing unnecessary material between the bolt holes, which added surface area and reduced the amount of stress on the gasket.
The reduced area solution achieved a final assembly stress of 1200 psi while still staying within the flange manufacturer’s recommended torque of 60 ft. lbs. In addition, the design maintained the necessary full-face configuration to prevent any rotational bending moments within the FRP flanges. Overall, the reduced area gasket design created a leak-free, chemically resistant seal that continues to function without any issues after two years of continuous service, eliminating unscheduled system downtime and the labor cost associated with the regular replacement of the previous EPDM gaskets.