Titanium alloy valve structure design

1. Seal

Globe valve uses plane sealing structure, valve body and disc sealing auxiliary check is made directly.

Valve as a fluid control mechanism, the sealing effect of valve disc and valve seat is very important. According to the different valve working conditions, the valve sealing surface is generally required to have good abrasion resistance, corrosion resistance, appropriate hardness, good thermal structure stability, crack resistance and reasonable process. Therefore, the material of valve disc and seat stop is titanium alloy Ti60, 260 ~ 300HB, and the allowable specific pressure of sealing surface is 45MPa.

2. Upper seal setting

In order to improve the sealing quality, the upper sealing structure is set, that is, the chamfering match between the disc nut and the valve cover when the globe valve is fully opened, and the precision of chamfering processing is higher.

3. Valve body and bonnet seal

The sealing between the flange and the valve cover of the valve body with rubber gasket, its sealing effect is mainly through the installation of pre-pressure and at work by the pressure of the working medium so that the sealing ring deformation to achieve.

4. Packing seal

The size of the packing box is designed according to GB standard, and the packing gland and packing seat are serialized. When installing packing, avoid scratching the valve stem, and when pressing the packing gland, the force of the nuts should be uniform. The valve stem is easy to cause spot corrosion and abrasion by the packing, which is one of the reasons for the leakage of the packing. The solution is to reduce the content of chloride ion and sulfur ion in the packing, or to use corrosion inhibiting packing and improve the finish of the valve stem. The friction resistance of the packing must be overcome in the state of stem movement. According to the analysis, packing selection of polytetrafluoroethylene cut wire braided sealing packing. The material has high temperature resistance, self-lubrication and chemical corrosion resistance, good flexibility, impermeability, low friction coefficient, improve the valve leakage ability.

5. The body

The structure size, form, material, flange structure, connecting bolt size and medium flow channel of valve body are designed according to GB standard. Due to the high price of titanium, thin wall formula is used to calculate the thickness of the design, and the strength of the valve body and the number of flange connecting bolts are checked.

6. The cover

The valve cover and the valve body together constitute a pressure shell, the valve cover under the medium pressure and temperature and other technical parameters and the valve body are basically the same. Therefore, there are some commonalities in design and calculation methods. The structure size and form of the valve cover according to the GB standard, the flange size of the valve cover design calculation and the valve body flange is the same.

7. The valve stem

When the medium flows from below the disc, the stem force and torque along the stem axial maximum load in the closed position, then the stem pressure. When medium flows in from above the disc, the maximum load is in the open position, when the stem is pulled.