OBJECTIVES 1. To determine and study the installed characteristics of three control valves in their respective piping system. 2. To determine and study the installed characteristics of three control valves in their respective piping system.
INTRODUCTION
This experiment conducted to identify the installed characteristics of three control valves in their respective piping system. Process that used in this experiment is Control Valve. Control valves are valves used to control conditions such as flow, pressure, temperature, and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "set point" to a "process variable" whose value is provided by sensors that monitor changes in such conditions. The opening or closing of control valves is usually done automatically by electrical, hydraulic or pneumatic actuators. A control valve consists of three main parts in which each part exist in several types and designs. There were valve's actuator, valve's positi oner and valve's body. There were two pumps in the process. Both of the pumps were small pump and big pump. Big pump has a larger flow capacity compared to. The small pump conducted first and followed by big pump. A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid. The results are taking from recorder FDPZR and the pressure gauge. What is pressure gauge? Typically, pressure gauges are devices used for measuring the pressure of a gas or liquid. Pressure Gauges is most often used instrument in a plant because of their great numbers, attention to maintenance and reliability can be compromised.
SUMMARY
The purpose of this experiment was to identify and study installed characteristics of three control valves in their respective piping system. The process use to run this experiment control valve. Control valve is process to control conditions such as flow, temperature, pressure and liquid level. In this experiment, the process consist tank 1 and tank 2. Both of the tanks should be filled up with water until the level of their overflow pipe. This experiment consist two part which is part 1 control valve running with small pump (PS). Part 2 was control valve running with big pump (PB). Pump PB has a larger flow capacity compared to pump PS. Both parts consist three tables, table AL for Linear Valve Operation, and table AE for Equal Percentage (%) Valve Operation and table AQ for Quick Opening Valve Operation. Controller FIC must be in manual mode with its MV=100% and then continue with the MV that state in the table. Record the data in the recorder FDPZR. The conclusion is make sure to read and understand the methodology properly so the experiment can done successfully. The objective also can successfully achieve.
THEORY The control valve characteristics refers to the relationship between the volumetric flowrate F (Y-axis) through the valve AND the valve travel or opening position m (X-axis), as the valve is opened from its closed position to various degree of opening.(Note that the symbol m or Z is used here to represent the valve travel or opening position, in %).Flow is flow rate percentage. The characteristic of curve for all the control valves are different because of their designing in valve plug.
DISCUSSION
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 show the relationship between stoke percentage (opening) of control valve and flow rate percentage and pressure drop. The linear control valve is designed so that the flow rate characteristic is directly proportional to the valve lift (H) (valve opening), at a constant differential pressure. A linear valve achieves this by having a linear relationship between the valve lift and the orifice pass area.For example, at 60% valve lift, a 60% orifice size allows 60% of the full flow to pass. However, the graph we obtain for linear control valve from this experiment does not shown a linear characteristic. This maybe because of some error happen during conducting the experiment. In this flow characteristic, equal increments of valve opening (stoke percentage) produce equal percentage changes in the existing flow. The change inflow rate is always proportional to the flow rate just before the change in position is made for a valve plug, disc or ball position. When the valve plug, disc or ball is near its seat & the flow is small, the change in flow rate will be small; with a large flow, the change in flow rate will be large. Equal percentage control valves are widely used in industrial purpose. They are generally used for pressure control applications. They are also used where a large percentage of the total system pressure drop is normally absorbed by the system itself, with only a relatively small percentage by the control valve. These are also recommended for applications where highly varying pressure conditions can be expected. The quick opening control valve will give a large change in flow rate for a small valve opening from the closed position. For example, a valve opening (stoke percentage) of 50% may result in an orifice pass area and flow rate up to 90% of its maximum potential. That’s why the graph we obtain from this experiment show a very fast increment of flow rate percentage when we open the valve which is at25% stoke opening, the flow rate percentage is 53.84%A valve using this type of plug usually has too high a valve gain for use in modulating control. So it is limited to on-off service, such as sequential operation in either batch or semicontinuous processes.
CONCLUSION
Generally, a closed-loop control system consists of the sensor which is used to detect the changes in the process and sends the signal to transmitter. The transmitter receives signal from the sensor and send it to controller in order to do the calculation to adjust it according to the input set point value. Finally, the signal is send to the final control element in order to carry out the task. In this experiment, the final control element used is the control valves. There are three types of control valve used which is linear, equal percentage and quick opening control valves. Linear control valve is the most expensive control valve among the three. Equal percentage control valve is widely used control valve such as piping purposes at our home. Whereas quick opening control valve is used for safety purposes. In this experiment, we can conclude that for linear control valve, the flow capacity increases linearly with the valve travel. For equal percentage control valve, the flow capacity increases exponentially with valve trim travel. Lastly, quick opening control valve provides large changes in flow for very small changes in lift.
ERROR AND RECOMMENDATION
The tuning input can only reach a maximum value of 99.7% which is less than the required value of 100%. This is because the equipment is frequently used by the students. Thus, it is advised to do a regular checking and fix the error of the equipment
REFERRENCES 1. R. Petitjean, Total Hydronic Balancing, Tour and Andersson, 1994 and 2004 Editions. 2. ASHRAE System and Handbooks, Chapter 12, Hydronic Cooling and Heating System Design, 2000. 3. J. Siegenthaler, Modern Hydronic Heating 3 rd Edition, 2011. 4. L. Sommurland, 8-steps – Control of Heating System, Danfoss, 2011
