At present, the butterfly valves widely used in the water supply and drainage industry such as municipal, petroleum, chemical and light industry have many types, such as centerline type, single-eccentricity, double-eccentricity and even three eccentricities. However, they all share a common feature: Usually have valve cover, but also because the disc is cast iron, long-term exposure to air, water and other media, serious corrosion, polluting the environment, while the valve stem is used throughout the butterfly plate, circulation area is small, torque is too large Coupled with more parts in the valve, resulting in maintenance difficulties. "M" type butterfly valve is a new type of unique valve, which completely overcomes some of the existing technical deficiencies in the butterfly valve industry, and comprehensively improve the valve performance. Second, the structure and working principle The "M" type butterfly valve has a simple structure. It is a single eccentric soft sealing butterfly valve with upper and lower two-stage valve stems. The surface of the butterfly plate is provided with a sealant layer. The "M" , So that the formation of a double seal between the disc and the valve body, in the "M" -shaped layer between the seal will be a period of air, so the sealing effect will be better. Third, the assembly method Assembly, the kerosene wash all the components, the first butterfly moved to the valve body, the main stem, vice stem surface coated with silicone grease, install the ring 2 and "O" ring 4, so that the butterfly plate Of the hole connected, and then tapping the disc with a rubber mallet so that it is fully embedded in the valve body, matched with the internal thread cylindrical pin 5, until the test water is completed, the top of the pin into the liquid sealant. Fourth, performance "M" type butterfly valve in the sealing surface of the disc at both ends of the design of the "M" shape (see Figure 1), so that when sealed with the valve, forming a double seal, effectively solve the valve opening and closing process In the sealing surface wear problems, long service life, combined with the valve with the upper and lower two-stage stem, single eccentric structure, an increase of the valve flow area, head loss and operating torque than the same size ordinary butterfly valve. Five, design and calculation 1. The minimum valve body wall thickness for "M" butterfly valves is calculated using the formula given in the appendix ASME B16.34. Eccentric butterfly valve stem torque calculation using the following formula, torque calculation diagram in Figure 2. qM --- sealing surface required specific pressure, in units of MPa (look-up table or calculation); 3 disc thickness calculation (Figure 3) Δp --- butterfly valve quickly off valve, the water hammer in the pipeline pressure rise value in units of MPa; 4. Cross-section of the strength check (1) cross-section of the disk A2A strength check WA --- A-A section of the bending section coefficient, in units of mm3; (2) check the strength of the B2B cross-section of the plate As the valve with two-stage valve stem support up and down, the deformation of the butterfly plate is very small, so I will not go into details here. Six, concluding remarks The key of M-shaped butterfly valve design lies in the strength calculation of the upper and lower stems, body and disc of the transmission, as well as the rational selection and heat treatment of the body, disc, stem, pin and other parts. The valve is a single eccentric butterfly valve, torque is small, the entire surface of the disc is covered with a sealant, sealing performance is good, do not pollute the environment, disassembly and maintenance is very convenient. Drive mode handlebar, worm gear, electric and pneumatic, etc., is a wide range of adaptable valves.
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The valve is mainly composed of the valve body, the upper and lower stems, all-inclusive plastic valve plate, cylindrical pin and other components. The structure shown in Figure 1.
Turn on the valve, with a wrench counterclockwise slowly turn the upper part of the main stem tenon, the butterfly plate and the flange perpendicular to the valve, turn the valve with a wrench clockwise slowly turn the upper part of the main stem tenon, the butterfly plate Parallel to the flange.
Butterfly overall plastic package, does not pollute the water quality, but also protect the butterfly, especially for food and beverage industries. Stem and disc connections using the internal thread cylindrical pin, the pin end with irrigation liquid sealant, demolition and maintenance in the actual use of extremely convenient, lower production costs.
MD = MM + MT + Mj + Md (1)
Where MD --- butterfly valve stem torque, in units of N · mm;
MM --- sealing surface friction torque, in units of N · mm.
R --- butterfly seal radius, in units of mm;
bM --- sealing surface contact width, in units of mm;
fM --- friction coefficient between the sealing surface (for rubber 018 ~ 110);
h --- stem and butterfly center eccentricity, in units of mm;
MT --- sealing packing friction torque (due to the stem with "O" ring seal can be neglected);
Mj --- hydrostatic torque in N · mm (look-up table or calculation);
Md --- Moive moment, in N · mm (look-up table or calculation).
b = 01054 D3 H (3)
Where b --- disc maximum thickness, in units of mm;
D --- butterfly valve flow path diameter, in units of mm
(Look-up table, the general b / D = 0115 ~ 0125 (Figure 2);
H --- maximum hydrostatic head (water hammer boost media), the unit is m.
H = 100 (p + Δp) (4)
p --- design pressure (often take p = PN), the unit is MPa.
v --- medium flow rate, (check the table) in units of m / h;
t --- butterfly from full open to the full experience of the time (look-up table selection), the unit is s.
Where σWA --- verify A2A section of the bending stress, in units of MPa;
MA --- A2A section of the bending moment, in units of N · mm;
MA = 01113 pD31 (7)
p --- design pressure (often take p = PN), the unit is MPa;
D1 --- disc diameter, in units of mm.
JA --- A-A section moment of inertia (look-up table or calculation) unit mm4;
b --- butterfly maximum thickness in mm.
If the A-A section of the actual bending stress, that is, σWA <[σWA] butterfly plate design is reasonable, [σWA] for the material allowable bending stress.
"M" type butterfly valve design
Overview