Bellow balanced safety valves
are designed to reduce the effetc of back pressure accumulation, the "Bellows
" located between the bonnet and the valve body, where maintained free from the effetc of back pressure, the opposing pressure on the inlet fluid is only generated by the spring without contribution from any sort of backpressure. The space enclosed by bellows is freely vented to air, the back pressure is expetced to be 10 - 50% of the set pressure. The Bellows
can also protetc the spring and other trim components from corrosive media.