By Borevich Z. I., Oskolkov A. P., E. V. Podsypanin

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G. [15,16]. Quantitatively, β is used to recommend a valve characteristic type. 5, implying relatively less variation in pressure drop as the valve operates, then a linear characteristic is recommended. 5, implying relatively more variation in pressure drop as the valve operates, then an equal percentage is recommended. Ultimately, however, valve gain is used to check the valve selection. For a selected valve, the procedure is as follows. 1 Calculate flow. P across the valve for several flows from the minimum to the maximum 2 Calculate the corresponding Cv values (Cg for gases/vapour, or Cs for steam).

The greater this variation, the more the operating characteristic varies from the inherent characteristic. A measure of this deviation is the parameter β, defined by β= Pv (max . flow) Pv (min . 5) The smaller the value of β, the greater the deviation of the operating characteristic from the inherent characteristic. 21 is obtained. With such a characteristic as a small β, nearly full flow is obtained when the valve is opened by a small amount. Thus, the effective stem movement range for throttling flow is greatly reduced and erosion of the valve is increased, since the plug is nearly closed at all flows.

F. for a Cu–Fe system them together. f. is nonlinear except over limited ranges. f. generated, T1 and T2 are the hot and cold junction temperatures in degrees kelvin, and a and b are constants for the given material. 11 for a Cu–Fe thermocouple system. Thermocouple types There are many thermocouple types. Common systems and their ranges are as follows. Base metal thermocouple types 1 Constantan–copper, type T:−75–93◦ C (TP) or 93–371◦ C (TN). 2 Constantan–chromel, type E: 0–316◦ C (EP) or 316–971◦ C (EN).

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