Instrumentation Adapter | Instrumentation Connectors Zeff ...
discussion exp 4 process instrumentation
2
Discuss on the findings and relations to the theory and objective of experiment This experiment is conducted in order to determine the characteristic curve of linear, equal percentage and quick opening control valve. The characteristic curve is the study of the effect of opening on the pressure drop and flow rate. The graphs obtain in this experiment shows the relationshi p between stoke p e r c e n t a g e (opening) of control valve, flow rate percentage and pressure drop. The controller output signal is the input to the valve, and the flow is the output of the valve. Based on figure 1, figure 2 and figure 3, the value of flowrate obtained from big pump is higher than the small pump. This is because the size of the pump affect the value of fluid flowrate that flow in the pump. The first valve is the linear valve. It is designed so that the flow rate characteristic is directly proportional to the valve opening, at a constant differential pressure. A linear characteristic valve is obtained with linear relationship between the valve lift and the orifice pass area. For example, at 58% valve lift, a 58% orifice size allows 58% of the full flow to pass. However, the graph obtained for linear control valve from this experiment does not show a linear characteristic that may caused by some error happen during conducting the experiment. The second valve is the equal percentage open valve.
-
Upload
alimah-azeli -
Category
Documents
-
view
213 -
download
0
description
process instrumentation
Transcript of discussion exp 4 process instrumentation
Discuss on the findings and relations to the theory and objective of experimentThis experiment isconducted inordertodetermine thecharacteristiccurveoflinear, equal percentage and quick opening control valve. The characteristic curve is the study of the effect of opening on the pressure drop and flow rate. The graphs obtaininthisexperimentshowstherelationshipbetweenstokepercentage (opening) of control valve, flow ratepercentage and pressure drop. The controller output signal is the input to the valve, and the flow is the output of the valve. Based on figure 1, figure 2 and figure 3, the value of flowrate obtained from big pump is higher than the small pump. This is because the size of the pump affect the value of fluid flowrate that flow in the pump.
The first valve is the linear valve.It is designed sothat the flow rate characteristic is directly proportional to the valveopening, at a constant differential pressure. A linear characteristic valve is obtained withlinear relationship between the valve lift and theorifice pass area. For example, at 58% valve lift, a58% orifice size allows 58% of the full flow to pass. However, the graph obtained for linear control valve from this experiment does not show a linear characteristic that may caused by some error happen during conducting the experiment.
The second valve is the equal percentage open valve.Inthisflowcharacteristic,equalincrementsofvalve produce equal percentage changes in the existing flow. The change in flow rate is always proportional to the flow rate just before the change in position is made for a valveplug. When the valve plug is near its seat & the flow is small, the change in flow rate will be small; with a large flow, the change in flow ratewill be large. The characteristic curve obtained is a logarithmic curve.
The third valve is the quick opening control valve. This type of valve gives a large change in flow rate for a small valve opening from the closed position. For example, a valve opening of 60% may result in an orifice pass areaand flow rate up to95% of its maximum potential. Thats why the graph we obtain from this experiment show a very fast increment of flow rate percentage. A valve using this type of plug usually has too high a valve gain for use in modulating control.
