Described here is a mechanism for a flow control device comprising of a valve casing, a plurality of buffer chambers, an elongated stem, and an actuating mechanism. The valve casing includes an inlet flow passage, an outlet flow passage, a valve seat in between, and a barrel housing extended from the flow passage. The buffer chamber is partitioned from the barrel housing by a moveable valve member and is comprised of a first channel and a second channel. The second channel is defined as a pilot valve and functions to adjust the inside pressure of the chamber. The elongated stem comprises of a plug that couples together with a pilot valve port.