1.Centerline butterfly valve and eccentric butterfly valve
Centerline butterfly valve and eccentric butterfly valve have their own advantages and disadvantages，When selecting a model, it must be considered comprehensively in combination with its cost performance. Generally speaking, the center line butterfly valve is cheaper than the eccentric butterfly valve. Centerline butterfly valves are widely used in my country’s small-diameter butterfly valves, and the effect is relatively good. Its closing seal is essentially a rubber lining squeeze seal, especially near the valve shaft is more squeezed, so that the service life of the valve is affected, and the opening and closing torque of the valve is too large. In order to alleviate the shortcomings of this aspect, the eccentric butterfly valve appeared. The theoretical sealing state is a contact sealing state. Many manufacturers have developed this aspect. The eccentric butterfly valve is directional in bearing water pressure, especially the three-dimensional eccentric butterfly valve. The reverse pressure bearing capacity is weak. Because the pipe network is ring-shaped, the requirements for the valve to bear pressure in both directions are the same, so this requirement should be emphasized when selecting the valve.
2.Vertical and horizontal butterfly valves
In medium and large butterfly valves, there is a difference between vertical and horizontal valve shafts. Generally, vertical butterfly valves are covered with deep soil, and debris in the water is likely to wrap around the shaft ends and affect opening and closing; the variable speed transmission box of horizontal butterfly valves is on the side. The valve well occupies a wider plane position on the road, which affects the arrangement of other pipelines. Therefore, in view of the above problems, it must be clear in the valve selection process: medium-diameter butterfly valves are mostly vertical, and large-diameter butterfly valves should first be horizontal if the condition of the plane position is permitted. This not only greatly improves the flow conditions of the valve, but also completely solves the problem of sundries in the water entangled with the valve shaft.
3.Soft seal and metal seal.
Most of the butterfly valves used in the water supply industry are soft-sealed butterfly valves. Due to some problems in the use of this sealing method, many manufacturers have introduced metal-sealed butterfly valves to replace rubber-sealed butterfly valves. When we select soft seal and metal seal valves, we still need to consider the cost-effectiveness of the two.
①The main problems of soft sealing butterfly valve in use are: poor rubber quality, easy to age, long-term compression deformation, and extrusion cracking. Therefore, some manufacturers generally choose EPDM rubber and nitrile rubber and use natural rubber in small amounts. It is strictly forbidden to mix recycled rubber to improve the wear resistance and aging resistance of the sealing ring.
②The metal-sealed butterfly valve generally adopts an eccentric structure, especially a three-dimensional eccentric structure, because of the small elasticity of the seal. The metal-sealed butterfly valve was originally used on high-pressure steam pipelines, and the price is relatively expensive. Its sealing surface is not easy to be damaged during operation, but its manufacturing accuracy is high, and once it leaks, it is difficult to repair.
Post time: Oct-18-2021