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The selection of suitable valves must be checked one by one according to the following procedures, so that the selected valve can meet its function and perform the assigned task.
1) Valve characteristics and main executive functions to understand the characteristics of various valves and their executive functions, this is the first step in selecting suitable valves. The characteristics, classifications and main executive functions of various valves are described in Section 2 and 3 It has been mentioned and is summarized in table 1 and table 2 for reference.
Expanding Gate Valves
2) Caliber or flow (capacity) "shown in Table 3"
A. The nominal diameter of the valve is not necessarily the same as the diameter of the flow channel. The selected size is calculated by calculating the required Cv value from the conditions of the conveying fluid, and then the Cv value (refer to the manufacturer's catalog) selects the appropriate valve diameter.
B. The Cv value is defined as the Cv value of the valve when the pressure drops at 1 when the water at 60 degrees fahrenheit flows through the valve.
C. The Cv value can calculate the flow rate (Q) flowing through the valve.
P=The density of the liquid, LB/FT3
ΔP=pressure drop after passing the valve, PSI
3) Temperature VS pressure
The "temperature VS pressure" of the valve refers to the allowable and safe pressure specified by the valve at a certain temperature (but this pressure is the maximum allowable pressure without impact).
Valve structure material The choice of valve structure material is extremely important in the functional life of the valve, but the general valve structure material is mainly divided into two categories: A. Pressure main material: valve body, valve cover, bottom cover , bolts, etc.
The main factors considered in the selection of pressure main body materials:
A. Fluid temperature and pressure:
A) High-temperature use: Metal materials are generally in a high-temperature environment, and their tensile strength and service life decrease with the increase of temperature, and their creep strength also affects.
B) Low-temperature use: When metal materials are used in low-temperature applications, the toughness of their destruction is sharply reduced, resulting in low-temperature brittleness.
B. Corrosion resistance of materials:
Causes of corrosion of valve structure metal:
(A) Type of fluid (B) Concentration (C) Temperature
Forms of corrosion damage: (A) uniform corrosion (B) pitting corrosion (C) dezincification and peeling
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