Installed Control Valve Flow Characteristics

Control Valve Flow Characteristic Curve showing the relationship between control valve capacity and range of motion of the valve stem of the valve which has a different design, Trim it. Indeed, by its very nature, valves typically have a non-linear behavior, but the design is different Trim enables Control Valve Flow Characteristic. In various ways as shown.

Inherent Control Valve Flow Characteristics.

The above was compiled. characteristics. Can be found often on% volume flow through the valve can be plotted versus the distance of movement of the valve stem on the condition that the pressure loss through the valve needs to be fixed, we refer to grap that the inherent flow characteristics. By the following graph.

Linear - the volume of flow will be greater when compared to the movement of the valve is in a straight line.
Equal percentage - the amount of flow will be greater when compared to the movement of the valve to the line exponentially.
% Change in the movement of the valve is equal to% change the value of Cv.
A modified parabolic characteristic. Centered approximately linear and equal%.
It has good control on the flow volume is less. And a linear behavior at higher flow.
Quick opening of the flow is changed while the valve is opened from the closed position, indicating that the valve has a high gain is not commonly used in control. It is only used for on-off, as in the sequential system is a batch or semi-continuous processes.
Hyperbolic.
Square Root.
Primarily used in control systems and control valves with flow characteristic curve is linear, equal-percentage, or modified-flow characteristics.

Installed Control Valve Flow Characteristics.

When the valves are installed in the piping system. Transmembrane pressure across the valve is not fixed, is proportional to the movement of the plug to draw a graph of the actual flow% compared with the opening of the valve. The resulting graph is called Installed Flow Characteristic.

In most cases, when the valve opens up a part of the flow in the pipe before it reaches the valve, which will result in the loss of pressure lose a lot of pressure to it. Since the resistance of the pipe it. In this case, it will keep the pressure before the valve P 1 decreases the pressure drop across the valve decreases, which results in movement of the graph and the curve that is Installed Flow Characteristic Curve by me. an example.

The curve is linear up to look like the quick opening.
curve will shift up to an equal% similar to a linear curve.

Control Valve Calculation

Today I will be a simple matter to calculate the amount of water needed to reduce the temperature of the superheat steam to come down to the desired temperature using the desuperheater as we know it.
- If the water is less than the amount needed to prevent a pharmacist in the superheat steam temperature down to the desired temperature.
- If the amount of water required to superheat steam, which can become saturated steam will be dry again by the saturated steam through the separator.

Therefore, by the basic equation of energy conservation. "Conservation of energy" to determine the amount of water they can find it easily.


Enthalpy into process = Enthalpy out of process.
McwHcw + MsHs = MsHd + McwHd.
Mcw = Ms (Hs-Hd) / (Hd-Hcw).


By that.
Cw = Mass flowrate of cooling water (kg / h).
Ms = Mass flowrate of superheated steam (kg / h).
Hs = Enthalpy at superheat condition (kJ / kg).
Hd = Enthalpy at desuperheated condition (kJ / kg).
Hcw = Enthalpy of cooling water at inlet connection (kJ / kg).
Sample quantities of steam to 10,000 kg / hr at 10 bar, temperatures Sat Temp + 5 C, a decrease from 300 C to use much water.


How do Steam Table.
Ms = Mass flowrate of superheated steam = 10000 kg / h.
Hs = Enthalpy at superheat condition = 3052 kJ / kg.
Hcw = Enthalpy of the cooling liquid = 4.2 kJ / kg ° C x 150 ° C = 630 kJ / kg.
Saturation temperature (Ts) at 10 bar a of 180 ° C,.
The desired temperature must be Ts + 5 ° C = 185 ° C.
Hd = (Enthalpy at desuperheated condition (kJ / kg) = 2829 kJ / kg.
From the equation given.


Mcw = 10000x (3052 - 2791) / (2791-630).
Mcw = 1208 kg / h.


Therefore desuperheated steam = 10000 + 1208 kg / h = 11208 kg / h.
However, due to problems with the steam flow rate of 10000 kg / h, so the superheated steam flow rate can be determined by the ratio of the post.
10000/11208 = Ms/10000.
Ms = 8923 kg / hr.


-------------------------------------------

Control Valve: ISA-75.01 Flow Equations for Sizing Control Valves.


Usually, the size of the control valve to the vendor, then it calculates the value (Cv and Fd is the vendor's catalogue), but the purpose of this article so it can be calculated initially on their own. I will provide important information that I have. ANSI/ISA-75.01-1985 (R1995), Flow Equations for Sizing Control Valves. ISA - The Instrumentation, Systems, and Automation Society, by the Table D-1 of ANSI/ISA-75.01-1985. This shows the value of any Valve capacity factors that can be put in the value of my ISA.

Valve Type	Trim Type	Flow Direction	Xt	Fl	Fd	Cv/d 2
GLOBE Single Port	Ported Plug	Either	0.75	0.9	1.0	9.5
"	Contoured Plug	Open	0.72	0.9	1.0	11
"	"	Close	0.55	0.8	1.0	11
"	Characterized Cage	Open	0.75	0.9	1.0	14
"	"	Close	0.70	0.85	1.0	16
"	Wing Guided	Either	0.75	0.9	1.0	11
GLOBE Double Port	Ported Plug	Either	0.75	0.9	0.7	12.5
"	Contoured Plug	Either	0.70	0.85	0.7	13
"	Wing Guided	Either	0.75	0.9	0.7	14
GLOBE Rotary	Eccentric Spherical Plug	Open	0.61	0.85	1.0	12
"	"	Close	0.40	0.68	1.0	13.5
ANGLE	Contoured Plug	Open	0.72	0.9	1.0	17
"	"	Close	0.65	0.8	1.0	20
"	Characterized Plug	Open	0.65	0.85	1.0	12
"	"	Close	0.60	0.8	1.0	12
"	Venturi	Close	0.20	0.5	1.0	22
BALL	Segmental	Open	0.25	0.6	1.0	25
"	Standard 80% Port	Either	0.15	0.55	1.0	30
BUTTERFLY	60 0 aligned	Either	0.38	0.68	0.7	17.5
"	Fluted Vane	Either	0.41	0.7	0.7	25
"	90 0Offset Seat	Either	0.35	0.60	0.7	29