Connection type valve electric device and the valve rod nut can be divided into thrust and torque type. Thrust type electric device to the valve stem to withstand axial thrust and torque, electric device to the valve stem torque transfer. Install thrust type electric device of the valve can not directly change the torque type electric device. Because, with thrust type electric device of valve with torque type electric device of valve the bracket structure. When the thrust type electric device of valve should install torque type electric device, should be added in brackets after the original thrust valve is connected with the torque type electric device, so as to solve problems connected with conversion thrust type electric device and torque of electric apparatus.
Install thrust type electric device of valve (Figure 1) into the mounting torque type electric device of valve (Figure 2), the thrust plate used as shown in figure 3. The thrust plate's role is to undertake the electric device by trapezoidal screw stem nut torque, axial force of the transfer of the valve opening and closing, so in the calculation of the axial force under the valve opening and closing parts strength, to undertake the design of axial force is becoming a key design of disk structure model of thrust.
Ordinary type thrust plate by flange box, a gland nut, locking screws and oil etc.. The bearing and the stem nut loading blue box, and then screwed into the gland nut. To ensure the bearing running clearance, screw-in depth gland nut to control, the gap is too large or too small to drive not figure 1 installed thrust type electric device of valve and. On the other hand, gland nut to bear the axial force the valve closed, so the flange box and the gland nut to be connected by threads, and ensure sufficient strength. In order to guarantee the fixed position of the gland nut, also install locking screws. The thrust plate structure of such complex parts processing, assembly, large quantity, strict quality requirements, testing time is long, cost is high. The thrust plate is closed structure, bear two-way axial force, so the flange box and the gland nut to be connected by threads, and ensure sufficient strength. Model (Figure 4) the thrust plate is a one-way opening design, through the ball bearing is to the axial force, the downward axial force directly acts on the bracket, so the structure is simple. The new thrust plate is connected with the electric device and a bracket, at the same time as much as possible to reduce its height, weight. Such as, the thrust plate and bracket connected to drill holes in the thrust plate flange, bolt connection.
Strength calculation
Thrust bearing axial force according to the opening and closing valve selection. Co ≥ F
Type Co -- thrust bearing static load rating, N
F -- to open and close the valve the maximum axial force, N
Stem nut (Fig 5) A-A section stress for the type of τ a -- A-A section of shear stress, MPa Sa -- the cross-sectional area of the A-A, M2 [sigma] -- stem nut material allowable stress, MP
In general, the inner and outer diameter of stem nut B-B section should be matched with the electric device is consistent with the dimension of the corresponding, but sometimes from economic considerations, but also to take into account the size series of thrust bearings, B-B section diameter or diameter and electric device with end of different sizes, but the cross-sectional area should be similar or the same.
Flange box (Figure 6) for the stress of a ′ -a ′ section
Type of τ a '-- Shear flange box a ′ -a ′ section stress, MP
Sa '-- - flange box a ′ -a ′ section area, M2
[sigma '] -- - flange box the allowable material stress, the stress of flange box MPa B' -b 'section
Type of σ B '-- - flange box of B' -b 'section of the tensile stress, MP
Sb '-- - flange Box B ′ -b ′ cross-sectional area, M2
Comparative analysis
(1) reduce the cost. Reducing flange box and stem nut height, reduce the quality, cancel the gland nut and locking screws, saving material.
(2) the simplified structure. The processing is convenient, from the original flange box in processing large threaded hole, machining of complex, high cost; now the light hole, simple processing, low cost, cancel the anti-loose screws matching.
(3) convenient assembly. Because the new thrust plate reduces parts, especially the removal of the gland nut assembly needs adjustment, remove the locking screws alone with the flange box, only into two parts of bearings and the stem nut, and avoids the adjustment process and simplify the operation procedure, the assembly is more convenient, the assembly time is greatly shortening. L good, good.
Conclusion
Through the analysis and optimization of structure stress, the new thrust plate flange box and reduce the height of stem nut, quality decreased. Cancel the gland nut and locking screws, which has the advantages of simple structure, easy processing and convenient assembly, to reduce the cost and improve the benefit of.
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