The ASA Flange system is illustrated below.
A seal is effected with this flange system when nuts and bolts are tightened compressing an "O"-ring between the flanges as shown above. When ordering, please specify which flange will need an "O"-ring groove in order to achieve this seal. This applies especially to elbows, crosses and tees. All types of custom adapters and fittings can be made to your specifications.
