ABSTRACT

The objectives of this experiment are to study gas volumetric flow rate (Fv) measurement using

the orifice plate-pressure drop (h) method, assuming the gas pressure/temperature (i.e. density)

remain unchanged and at the values used in the sizing of the orifice and also to study gas mass

flow rate (Fm) measurement using the orifice plate-pressure drop (h) method, using the Perfect

Gas Law to compute the gas density from the flowing pressure and temperature. This experiment

is started by concentrate on the unit panel controller PIC91/PIC911/FIC90 in particular FIC91.

Firstly, the set point SV1 is adjusted to 15 kg/hr when FIC911 in manual mode (M) and first (I)

PID values for FIC91 which is PB1=200%, TI1=6 seconds and TD1=0seconds is set. The panel

controller FIC911 is changed to Auto (A) mode and watched the recorder responses until the

flow Fm (green pen) is fairly steady state at its set point SV1 to within ±0.1 kg/hr. Then, the

manual bypass valve is quickly opened by one turn and then shutting fully the manual bypass

valve to make pulse load disturbance changes. The experiment is repeated with first trial second

(II) and third (III) set of trial values which second (II) set values is PB1=100%, TI1=6 seconds

and TD1=0 seconds and third (III) set values is PB1=150%, TI1=10 seconds and TD1= 0

seconds by using the same sharp pulse load disturbance. As a result, from observation of these

three trials, we can see when the PB value is highest which is at 200%, the reading for every

meter is the lowest. When the PB value is adjusted to the lowest which is 100%, the reading for

every meter is the highest. In order to get more precise result, the time for disturbance take place

should be mentioned let say few seconds. Secondly, doing these test regularly with changing its

tuning will raise and give to us the best tuning for this system with the most minimum set point

change for given pass load disturbance. In conclusion, we can conclude that the experiment

achieved the objective by giving slightly accurate outcome as in the theory especially for first

objective.

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CHAPTER 1

INTRODUCTION

PCI’s Flow Control Systems (FC Series) and Pressure Control Systems (PC Series) are

offered as a control centre’ which is designed to perform the required airflow, static or pressure

control functions for a specified control process. This control system contains all the

instrumentation necessary to perform the specified control process. The centre of the control

systems id connected to a computer, a shutdown or any troubleshooting in the computer or

connecting lines will not interrupt the dedicated control centre’s operation.

This control system represents a major advancement in affordable airflow and pressure

control instrumentation. The control system offered a few advantages which is accurate and

dependable, easy to install, start-up, and maintain are available with a complete line of optional

features to customize packages for the most complex systems and have "off the shelf'"

availability for standard applications.

There are four elements need to be highlighted in the process control which including the

process, measurement, control and final control element. In this experiment, air flow rate is the

process required. Therefore, another three elements which is measurement, control and final

control element will start with the initial F, which can be further defines as flow. In this process,

the control systems involved are FT (Flow Transmitter), FIC (Flow Indicator Controller) and

FCV (Flow Control Valve). From the P&ID provided, the process that needs to be controlled is

at pipe no 91. Therefore, all the controlled system process will be labelled as FT91, FIC91 and

FCV91. The type of valve for FCV91 is air to close based on the P&ID.

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In this experiment, the disturbance will be considered instead of the set point change. It will set

up and the changes of the reading will be considered.

Experiment system AFMS211 is carried out in Model AFPT921 Gas Flow Pressure

Temperature Process Control Training System. This Model AFPT921 plant is a scale-down Real

Industrial Process Plant built on 5ft X 10ft steel platform, complete with its own dedicated

control panel. The process equipment and process instrumentation are real Industrial Process

type. The plant is constructed in accordance to industrial process plant standard and practices,

with fail-safe features. For example, the air heater cannot be turned on unless there is enough air

flow in the pipeline. The process flow rates are at commercial production flow rates, using pipes

and not tubing.

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CHAPTER 2

LITERATURE REVIEW

2.1 Orifice Plate

A throttling device for hydraulic systems which prevents the cavitation of metal conduits

by liquid under differential pressure comprising a series of orifice plates spaced at interval along

the axis of the conduits.

In flow measurement fluid delivery systems, orifice plates are the main device that been

used. As stated by Ward Smith (1971), the great deal of work had been done is showed on the

pressure drop characteristic of orifices plates in ducts. Cylindrical tube orifices have also been

tested with the aim of achieving better measurement performance than that of orifice plates. Five

cylindrical nozzles of various dimensions in a 4 inch pipeline had been studied and they found

that the nozzles maintained a constant coefficient of discharge at Reynolds numbers much lower

than standard pressure difference devices (Jorissen & Newton, 1952).

Measurement of flow rate that been use an orifice plate requires a long straight upstream

duct because the upstream velocity profile affects the discharge coefficient of the plate and also

induces a large pressure loss through the device (Morisson, Hall, Macek et. al, 1994). The

straight section in heating, ventilation and air-conditioning (HVAC) systems, duct cross sections

are generally large, so that it is required extra fan power for the installation of such plates.

2.2 Application of Orifice Plate-pressure Drop Method

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Generally, orifice plate is used for continuous measurement of fluid flow in pipes. In

order to measure the flow rates at locations where the river passes through a culvert as well as

drain, they are also are applied in some small river systems. But only the small numbers of rivers

are appropriate to apply this device since the plate must remain completely immersed besides the

river must be free of debris (“Orifice plate,” n.d.).

2.3 Theory

The pressure loss coefficient of an orifice plate or perforated plate, k is defined as

k=∆ PsPv

Where ∆ Ps is the static pressure loss across the plate (Pa), Pv = [(1/2)ρV2] .

Foe an orifice plate whose axis is coincident with that of a duct or for a perforated plate

with regularly spaced holes, the pressure loss coefficient is influenced by the free area ratio and

the thickness/ diameter ratio as well as Reynolds numbers. The free area ratio is defined as the

ratio of the total cross sectional area within the orifices to cross sectional area of the duct and is a

measure of the extent to which the constriction obstruct the flow. The thickness/ diameter ratio is

the ratio of plate thickness to the diameter of orifice (Gan, 1997)

2.4 Application of Perfect Gas Law / Ideal Gas Law

Ideal gas law equation is expressed in term of mass, m (grams) and molar mass, M (grams per

mole),

PV = mM

RT

Expressed density, (ρ) also in term of mass, m (grams) and volume, V,

ρ=mV

Solve for m:

m=ρ V

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Substitute ρV for m in the ideal gas law equation:

PV= ρ VM

RT

Both V terms can be cancelling and rearranged the equation become:

PM=ρ RTor ρ=PM / RT

This equation can be used to compute the density of a gas under any conditions of temperature

and pressure (“Applications of the ideal gas law,” Holt, Rinehart & Winston)

2.5 Experiment Objectives

The objectives of this experiment is to study gas volumetric flow rate (Fv) measurement

using the orifice plate-pressure drop (h) method, assuming the gas pressure/temperature (i.e.

density) remain unchanged and at the values used in the sizing of the orifice. Secondly, to study

gas mass flow rate (Fm) measurement using the orifice plate-pressure drop (h) method, using the

Perfect Gas Law to compute the gas density from the flowing pressure and temperature. Thirdly,

to study gas mass flow rate (Fm) control using PID control mode.

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CHAPTER 3

METHODOLOGY

3.1 Material and equipment

In this experiment, the material used was compressed air. The equipment used was the

gas flow pressure temperature process training system.

3.2 Procedure

This experiment was split into two sections. The first section covers the study on gas

volumetric flow rate and gas mass flow rate measurement using the orifice plate-pressure drop.

The second section covers the study on gas mass flow rate control using PID control mode.

The first section of the experiment requires the collection of data on volumetric flow rate

on the orifice plate. First, the compressed air was supplied to the system. The system was set to

open system by letting the compressed air flow from supply directly to heater, then pipeline PL1,

passing FT911 and FT91, exiting the system by bypassing all equipment and instrument. Second,

the FCV91 was set to fully open by manually control MV to -6.3% on faceplate FIC91. The

reading on the FIC91 showed the maximum flow rate achieved.

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Finally, the FCV91 was set to fully close by manually control MV to 100% on faceplate

FIC91. The reading on FIC91 should show zero value. The gas flow rate was calculated from the

data of volumetric flow rate obtained.

The second section of the experiment required collection on all instrument located on

pipeline PL1. The PID values were manipulated. Then, the disturbance was introduced to

observe the effectiveness of the PID values manipulated in controlling the process variable. First,

the PID was set to PB = 200%, TI=6 sec, and TD1=0 sec. Then, disturbance was introduced and

when the system back to steady state, data was collected. The experiment were repeated with

value PB = 100%, TI=6 sec, TD1=0 sec, and PB = 150%, TI=10sec, and TD1=0 sec.

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CHAPTER 4

RESULT AND DISCUSSION

RESULT

Table 1

INSTRUMEN

T

READINGS

CONTROLLER

FIC911/PIC911/FIC90

I** II** III**

At the PANEL I/O Data

FT91, Fm X1*, % of 0-50 kg/h 30.1 kg/h 28 kg/h 30 kg/h

TT911, T X2*, % of 0-200 OC 14.1 oC 14.5 oC 14.5 oC

K K K

PT911, P X3*, % of 0-70 psia 82.4 psia 82.5 psia 83.2 psia

DPT911, h X4*, % of 0-

10,000mmH2O

3.7 mmH2O 3.8 mmH2O 3.7 mmH2O

PT Register

Fv P15*, m3/h 4.6% m3/h 4.7% m3/h 4.6% m3/h

Fvf P16*, m3/h 3.1% m3/h 3.2% m3/h 3.1% m3/h

Fvb P17*, Nm3/h 11% Nm3/h 11.5% Nm3/h 11% Nm3/h

f P18*, kg/m3 4.6% kg/m3 4.6% kg/m3 4.6% kg/m3

Main Face Plate

Fm PV1*, kg/h 15 kg/h 14.7 kg/h 15.1 kg/h

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Recorder FPTR91

Recorder

Channel 2

Fm, kg/h 15 kg/h 15.8 kg/h 15 kg/h

Recorder

Channel 4

Density, f, % of 0-

6.165 kg/m3

7.1 kg/m3 7.1 kg/m3 7.1 kg/m3

At the PLANT

m3/h m3/h m3/h

FI911, Nm3/h 18 Nm3/h 19 Nm3/h 18 Nm3/h

PG911A, psig 43.2 psig 43 psig 43.5 psig

*Note: X1, X2, X3, X4 are in % and are at the I/O Data of FIC91/PIC91/FIC90

P15, P16, P17, P18 are at the PT register, Fv, m3/h

PV1 is at the main face plate display of FIC91, Fm, kg/h

X1: % of 0 to 50 kg/h or % of 50 kg/h

X2: % of 0 to 200 oC or % of 200 oC

4.1 Conclusion

The objectives of this experiment is well achieved as the results obtained for the gas mass

flow rate control using PID control mode are stable. The most stable data or gain is for data I.

This is because the PB% is much higher with quicker TI setting time. These combinations ensure

that the system gain is in ideal control mode. However, too large PB% slows down the response

and its recovery to the set point SV. The higher PBI value leads to fasten time taken to stabilize

the graph. PBI at 200% was the best value compare with others in order to the time it takes to regain constant

and it show that the higher value of PBI, the faster the time it takes to stable. Based on this experiment, we

can conclude that it is important for every industrial to have ideal setting value in order to

maintain their production stability in case any disturbances are happening.

4.2 Recommendations

There are some recommendations for while conducting this experiment that will enhance

the stability of result in future. Before doing this experiment, make sure the

pipeline of the plant whether it is still in good condition. Besides that, check

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if the inlet and outlet of the plant is working and functioning well. In addition,

Ultrasonic gas flowmeter technology has many advantages over more

traditional technologies (such as orifice, turbine or vortex meters). This

system contains no moving parts, and does not create an additional pressure

drop. Students must read the manual carefully and make some research about how to control

the model machine and the variable involved. Other than that, make sure some precaution is

applied such as checking whether there is some leakage or not. The bypass pipes also need to be

checked.

REFERENCES

Ward-Smith, A. J. (1971). Pressure Losses in Ducted Flows, from Butterworth, London

Gan, G. (1997). Pressure Loss Characteristic of Orifice and Perforated Plates, Institute of

Building Technology, University of Nottingham

D. E. Seborg, T. F. Edgar, D. A. Mellichamp, and F. J. Doyle III, Process Dynamics and

Control, 3rd ed. Hoboken, NJ: John Wiley & Sons, Inc, 2011, pp. 204.

Holt, Rinehart and Winston (1997), Holt Chemfile: Problem-Solving Workbook, pp. 170.

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