Cavity Vent Ball Valve

The vent allows trapped pressure to pass harmlessly away from the system directly into atmosphere when the valve is closed.

Cavity vent ball valve.

The ball contains a vent that is isolated from the ball hollow to prevent continuous leakage from the body vent port when the valve is open. There are a couple ways ball valve manufacturers address the problem of increased cavity pressure due to thermal fluid expansion. As you know the cavity vent is a small hole drilled in the ball of the valve so the lng trapped inside the ball can be relieved and will not cause overpressure if when it warms up and vapourises. 2 make a hole on ball face at upstream side pass to port.

The ball contains a vent passage isolated from the ball orifice to prevent continuous leakage from the body vent port when the valve is open. The downstream vent provides an escape path for system fluid downstream of the valve. 3 in case of increasing tempertaure valve position full close and fluid pressurizing direction non fixed valve should be used trunnion type ball valve. The vent port evacuates trapped pressure from the system directly to atmosphere when the valve is closed.

Manufacturers situate the ball seats in the valve body. The upstream vent provides an escape path for the fluid upstream of the valve. When closed the ball can have a lateral movement between the two elastomeric seats. The valveman explains what a cavity filled ball valve is and the applications in which to consider using one.

The downstream vent provides an exhaust path for the fluid downstream of the valve. 1 make a relief groove on ball seat at upstream side. The pressure relief hole must connect the valve body cavity to the high pressure side of the ball when it s closed per shell mesc spe 77 170 specifications. When closing the valve the media gets trapped in the cavity.

My concern is about the orientation of such vent. While the valve is in the open position any pressure in the cavity created by the ball seats and body can easily be vented by drilling a small hole from the top of the stem slot to the ball flow path. Our zero cavity valves have a unique design in which a ptfe mptfe cft metal cavity filler are used to fill the void in the valve cavity between the body ball and seat.