VALVINOX Top entry ball valve is assembled from the upper body. The stem and the ball are fixed to eliminate the possibility of stem blowout. Graphite is chosen for the packing seal and the bonnet joint is flexible graphite and metal. The seats are inserted from both ends and sealed with flexible graphite. The spring is mounted on the seat step to help close the valve. When the pressure increases, the media flows to the back of the seat and forces the seats against the ball to ensure a tight seal.