Bellow Sealed Valve

Bellow Sealed Valves are a new breed of industrial Process valves, designed to eliminate valve leakage and are also known as Zero Leak Valves or Emission Free Valves. In these valves, conventional gland packing is appended /supplemented by a metallic Bellow Cartridge joined to the valve bonnet at one end, and the stem at the other end. A bellow is a long accordion-like tube. As the valve stem strokes, the bellow expands or compresses with the stroke movement. The stem is fully covered with metallic bellow in wet zone, process  fluid never reach to the gland area. Thus the fluid will enter the valve from the seat of the valve & come in contact with the bellow, but will not come in contact with the stem. Since the stem is the only moving part in the valve, it is a source of potential leakage through the gland due to constant friction caused by the axial movement. In a bellow sealed valve this potential leak through gland is totally avoided due to the metallic bellow which blocks the leak path effectively by not allowing the media to come in contact with the stem and thus the gland. A bellow is the heart of this type of valve. We use only formed bellows, as in spite of being more expensive than welded bellows, their life is many times more than welded bellows.