I am looking for a differential pressure valve which will control the differentail pressure between a vessel and flare header.

The vessel and the flare header are at 10-15 psia but the system will operate at higher pressures but cannot tolerate any pressure surges.

I want a valve which will be normally closed but open slowly if either of the pressures rise, the valve will then close as the diff reduces. I would prefer a bleed free system and preferentailly a process actuated valve. Reliability is a premium but cost is not.

Any help would be appreciated