Subject: Swivel Flange Rusting While in Service.

Question:

My company uses a short flange x swivel flange spacer spool between the flange on our choke manifold hose and the studded cross in the center of our choke manifold. While the spool with the swivel flange remains connected, the gap between the swivel ring and the flange hub rusts and binds the flange making the swivel feature useless. Do you have any suggestion as to how we may avoid this problem?

Answer:

Swivel flanges must have weld attachment to make them integral with spools. Weld attachment requires the flange ring placement on the weld neck hub prior to weld assembly. The flange ring, hub, and spool body will experience the heating associated with welding and post weld stress relief, coatings or platings will be degraded by this heat.

The first and easiest suggestion we have: before installation and between subsequent make-ups, remove the swivel flange snap ring, slide the swivel ring back so as to expose the hub and neck of the swivel flange and clean the surfaces exposed, then apply abundant grease to the exposed swivel flange hub neck. Apply so much grease that the grease squeezes out when you push the swivel ring back in place to make-up with a matching flange or studded face. Be sure to replace the swivel flange snap ring, and then wipe away surplus grease squeezed out. Abundant grease should prevent entry of corrosive liquids and resist the tendency for rust to pack the clearance between the swivel ring and the swivel flange hub. Do this with every make-up of the swivel flange and your problem should be minimized. (Application of grease in this manor would also protect the spool during extended disuse or storage). 1

A second, but much more expensive solution: you could specify that your flange x swivel flange spool manufacturer make the spool with the neck of the swivel flange hub and the inside of the swivel ring with CRA cladding to prevent the possibility of rust. Lubrication of the inside of the ring and the hub would still be advisable.