1, valve body
1.1 Casting materials such as valve body and butterfly plate adopt ductile iron QT450-10 or materials with higher mechanical properties. Casting process is resin sand and lost foam. Hot metal castings produced by electric furnace are used to ensure the physical and chemical properties of castings. The surface of butterfly valve castings should be smooth and meet the technical requirements of GB12227. The castings should be heat treated to eliminate internal stress. Trademark and material grades are cast on the valve body.
1.2 The material of flange is the same as that of valve body. The flange shall be cast into one body, and the flange shall conform to the relevant provisions of GB/T 17241.6-98.
2. Butterfly plate
2.1 The design stress of butterfly plate can withstand the load of 1.5 times maximum pressure difference acting on butterfly valve (closed state). The structure design of butterfly plate has smaller flow resistance.
2.2 When the valve is opened, the resistance coefficient is not more than 0.3.
3.1 Stem material is made of horse-shaped stainless steel and above, which meets the technical requirements of GB1220. The stem is designed as an integral shaft, and the length of the insertion hole is not less than 1.5 times the diameter of the shaft.
4.1 Valve body bearings are bronze. At the maximum valve load, the friction coefficient of the bearing does not exceed 0.25.
5. Valve drive mechanism
5.1 The drive mechanism of the valve has sufficient stiffness to withstand the required moment, to ensure the stability of the butterfly plate when it is opened or closed, and to ensure that the butterfly plate can stay at any opening position stably. The material of the transmission mechanism and the shell is the same as the valve body, which improves the mechanical properties of the material.
5.2 Guarantee the processing and assembling accuracy of the parts in the secondary transmission box, and guarantee the self-locking function of the worm wheel and worm.
5.3 The force components of all transmission mechanisms shall withstand twice the rated moment without any damage, and the manual operating moment shall not be greater than 200N.m. For this reason, the structure design should be reasonable, the processing accuracy should be improved, the assembly should be meticulous, and the requirement of torque should be gradually raised.
5.4 The sealing performance of the gearbox is reliable. It is soaked in 6 meters deep water for 72 hours and operated under water for 10 times without water. The sealing grade is above IP68.
5.5 Handwheel is made of cast steel or tougher material with higher mechanical properties, which is removable. The direction of opening and closing is indicated on the handwheel. The surface of handwheel should be smooth, without burrs, nodules, pits and other surface quality defects.
5.6 The maximum force of manual handwheel opening or closing valve under rated pressure is not more than 300N.
5.7 The adjusting screw material of valve body and gearbox limit is made of martensitic stainless steel and tempered.
6.1 Sealing between butterfly plate and stem
The design and manufacture of the sealing ring ensures that both directions can bear pressure when the butterfly plate is closed. The seal between butterfly plate and valve body adopts rubber soft seal. The contact part between valve body or butterfly plate and rubber sealing ring is processed after inlaying stainless steel ring or welding stainless steel ring, or better forming process. Material used above martensitic stainless steel materials. Rubber seals are all made of NBR and rubber rings are integrally moulded and meet the requirements of HG/T3091-2000. The sealing test shall be carried out in accordance with the relevant national standards.
6.2 stem seal
Choose durable material for shaft seals. The sealing method adopts more than two V-shaped sealing rings, NBR or EPDM. The sealing rings can be replaced without removing any parts of the valve body and operating mechanism.
More than 6.3 sealing tests and strength tests (1.5 times nominal pressure) of the two seals shall comply with the requirements of GB/T13927-92.
The surface of valve body and butterfly plate before anticorrosion is sandblasted and rusted to Sa2.5 grade, then the casting is heated before electrostatic spraying epoxy powder process, and finally dried and cured. The coating thickness is not less than 1.0 mm, but not less than 0.3 mm. The anti-corrosion inside the valve is sprayed to ensure uniform coating thickness, uniform color, smooth coating surface and no mark. For the use of open-air valves, the surface of epoxy coating should be coated with a layer of ultraviolet resistant acrylic paint (epoxy coating does not resist ultraviolet radiation).
Non-toxic epoxy resin coating or electrostatic spraying epoxy powder process are used for external corrosion protection of valves. The external color of valves is blue.
Butterfly valves for water supply and drainage conform to CJ/T 261-2007
The structure length of metal valve meets GB/T 12221-2005 standard.
The design and manufacture of universal valve flange and butterfly valve with clamp connection conform to GB/T 17241.6-2008 standard.
The technical conditions of ductile iron castings for general purpose valves meet the GB/T 12227-2005 standard.
The marking and painting of the valve conform to JB/T 106-2004 standard.
General valve marking conforms to GB12220-89;
The static pressure life test procedure of Butterfly Valve conforms to JB/T8863-2004 standard.
Valve inspection and test conform to JB/T9092-1999 standard.
Standard GB/T 17219-200 for safety evaluation of drinking water conveyance and distribution equipment and protective materials;
Stainless steel bars meet the requirements of GB/T 1220.
Rubber Sealing Ring - Joint Sealing Ring for Water Supply and Drainage Pipeline: HG/T3091-2000;
Part of the valve rotary drive device conforms to GB12223 standard.
V. Opening and closing force and moment of butterfly valve
The opening and closing force and moment of butterfly valve refer to the force or moment that must be applied to open or close butterfly valve. When closing the butterfly valve, it is necessary to form a certain specific pressure between the butterfly plate and the sealing surface of the valve seat. At the same time, it is necessary to overcome the friction between the stem and packing and other friction parts. Therefore, a certain closing force and closing moment must be applied.
The opening and closing force and opening and closing moment of butterfly valves vary during the opening and closing process. When operated by handwheel, the maximum instantaneous operating moment of initial opening and terminal closing is not more than 400N. When using transmission cap, the operating torque should not exceed 200N. The maximum value is to design and manufacture butterfly valves at the final moment of closure or the initial moment of opening in order to reduce the closing force and closing moment.