OPTIMIZATION AND AUTOMATION OF WATER COOLING FACILITY USING PLC full report
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OPTIMIZATION AND AUTOMATION OF WATER COOLING FACILITY USING PLC
PROJECT REPORT
Submitted by AKHILA. K BEETHA BABY SHAMNA.M.U SREEKALA.V
SYNOPSIS
The project and implimentation Optimization and automation of operation of cooling Water Facility in FACT Udyogamandal aims at three objectives. Energy conservation measures by selective switching & speed control, automation of the Plant and energy saving by way of PF improvement. The Cooling water facility in a Process industry offers great scope for energy efficient operation by way of selective switching and speed control of various equipments. As the power consumption of pumps and fans is directly proportional to cube of speed, a reduction in speed, based on quality and quantity of cooling water required, results in saving of huge quantum of energy. A Programmable Logic Controller (PLC) is proposed to be incorporated for the automation part of the project and implimentation. PLCs have, in a short period of time, played a major role in the evolution of automation, both in discrete and process application in industrial control. PLCs are being used extensively in Control systems now, where electromechanical relays were in use formerly. The introduction of PLC will make the system more flexible, easily up-gradable and maintenance-friendly. An attempt is also made to explore the possibility of introducing equipment-connected PF improving capacitors for energy saving. Group-connected PF improving capacitors are being used in FACT, but it is intended for a reduction in maximum demand rather than energy saving. A part of the project and implimentation forms a techno-economic feasibility study of equipment-connected PF improving capacitors for the equipments in Cooling Tower.
CONTENTS
i. Introduction
ii. Objectives of the Project
i. Selective switching and speed control of Cooling Tower Fans for energy saving
ii. Switching of Cooling Water Pumps
iii. Techno-economic feasibility study of equipment-connected PF improving
capacitors
iv. Automation of operation of Cooling Water facility using PLC
iii. Research Methodology
i. The Plant and the operation
ii. Collection of operational data
iii. Analysis and interpretation
iv. Findings and Recommendations
i. Operation of Cooling Water Facility - Findings
ii. Recommendations for improvement
iii. Automation of operation using PLC
v. Limitations and Constraints of the Project
vi. Scope for future improvements
vii. Conclusion
viii. References
ix. Annexure:
i. Programmable Logic Controllers (PLC)
ii. Variable Frequency Drives
1. INTRODUCTION
The Cooling water facility in a Process industry offers great scope for energy efficient operation by way of selective switching and speed control of various equipments. By this project and implimentation, the operation of a Cooling Water Facility in FACT Udyogamandal is examined from the energy conservation angle. As the power consumption of pumps and fans is directly proportional to cube of speed, a reduction in speed, based on quality and quantity of cooling water required, results in saving of huge quantum of energy. Incorporation of a Programmable Logic Controller (PLC) for automation of operation of plant is also aimed in this project and implimentation. Switching of Cooling water pumps and fans, based on requirement can also be achieved by incorporation of PLC. An attempt is also made to explore the possibility of introducing equipment-connected PF improving capacitors for energy saving. FACT, the Fertilisers And Chemicals Travancore Ltd. was founded at the banks of river Periyar in 1944 by Dr.C.P.Ramaswamy Iyer. It was then the first large scale fertilizer factory in the entire country and the largest public sector undertaking in Kerala. The setting up of FACT in Udyogamandal with adequate infrastructure facilities built up along with it, in course of years attracted a number of other chemical industries to its neighbourhood. FACT has the widest range of fertilisers like FACTAMFOS, DAP, NPK mixtures and Ammonium Sulphate to suit all crops and all soils.FACT has, since then, diversified its activities into several fields viz. manufacturing of caprolactam, consultancy services, fabrication of pressure vessels, tanks etc. FACT has six divisions now; three production units, one design and consultancy division (FEDO), one fabrication division (FEW) and a Marketing division
11. OBJECTIVES OF THE PROJECT
i. Selective switching and speed control of cooling tower fans for energy saving.
ii. Selective Switching of cooling water pumps.
iii. Techno-economic feasibility study of equipment-connected PF improving capacitors
iv. Automation of operation of cooling water facility using PLC.
i. SELECTIVE SWITCHING AND SPEED CONTROL OF COOLING TOWER FANS FOR ENERGY SAVING
The entire operation of the existing cooling water facility in FACT is manual. Most important drawback of the present system is that the operation is inefficient from the energy point of view. The purpose of the cooling tower is to supply cooling water to various plants for taking away the excess heat from the plants. While considering this purpose, the existing facility meets the requirement as it continuously supply enough cooling water to various plants. But the drawback with the system is that it does not consider the opportunities for saving the rapidly diminishing energy. The system does not take any advantage from the dropping temperature in night or the usual low temperature in winter season. By running the fans all the time without monitoring the outlet water temperature, a lot of energy is being wasted. The first objective of this project and implimentation is to examine the potential energy saving by way of selective switching of fans; and by way of running the fans at reduced speed. A change in speed of any fan will predictably change the pressure rise and power necessary to operate it at the new speed. The power consumption of fans is directly proportional to cube of speed, and this fact makes obvious the reasons why the speed of the fans need to be controlled. A reduction in speed of fans, based on quality and quantity of cooling water required, results in saving of huge quantum of energy.
Various parameters of the cooling water viz. outlet temperature, flow and pressure are measured and monitored continuously so as to run the equipments in an optimum way. Based on these parameters, fans just required for keeping the outlet temperature within acceptable value, are only switched on. When a fan at full speed is not required for keeping the temperature of water within limit, it is run at reduced speed by using a Variable Frequency Drive (VFD). The cooling water facility at the FACT Udyogamandal is designed for an inlet of 42 degree celcius and outlet temperature of 30.5 degrees. Selective switching also helps in energy conservation. During nights and winter seasons, .there is no need to switch on as many fans as during day time or summer ii. SELECTIVE SWITCHING OF COOLING WATER PUMPS
There are seven distribution pumps for the cooling system. The designed discharge requirement is 14100 m3 / nr. The capacity of each pump is 3000 m3 / hr. At a time , three pump in anone header and two pumps in Hyam header are in operation with two stand by units. Presently, Cooling Water Pumps are run without monitoring the actual requirement in various plants. The operation people at Cooling Tower run all the pumps as per the design parameters without monitoring the quantity of water required by other plants. This results in higher operating pressure for water when some of the plants stop consumption. And, in order to compensate reduction in flow and subsequent rise in pressure, the operators adjust the control valves so as to keep the pressure within limits. This results in wastage of energy at the valves. If switching of pumps is done based on requirement of plants, this energy which is otherwise being wasted can be saved. A closed loop control system in which pumps are selectively switched on together with control of pump speed for optimum pressure and flow of water would eliminate this energy wastage completely. However, this would require VFDs for the existing 585 kW, 3.3 kV motors, which would be difficult in the present scenario. Hence, selective switching of Cooling Water Pumps alone is considered for energy saving as an initial improvement.
iii. TECHNO-ECONOMIC FEASIBILITY STUDY OF EQUIPMENT-CONNECTED PF IMPROVING CAPACITORS
The existing system in FACT looks improvement of power factor from maximum demand (MD) only. As a two-part tariff is applicable for the power drawn by FACT -charges for maximum demand and energy have to be paid to KSEB - the Company takes effort to keep the MD minimum by improving pf by switching on group-connected capacitors. The Company gets incentive for better pf too. However, improvement of pf for better energy utilization has not been tried in FACT. A techno-economic feasibility study of equipment-connected pf improving capacitor forms as the third objective of this project and implimentation. The feasibility study comprises two parts viz. technical part for finding out the capacitance required for bringing the pf to unity and the economic evaluation part consisting of life cycle cost analysis. If the future value of the initial investment for the capacitor for better pf of the motor is less than the sum of future returns by way of energy saving, the investment is justified.
Here, the value of capacitance required for bringing the pf of CT Fan to unity is found out by measuring the various parameters like active power, present pf, running current etc. The resultant saving in energy, by running the motor at unity, is computed by measuring the circuit resistances involved viz. cable resistance, winding resistance, switch, fuse and contactor resistances. The life cycle cost is then calculated to find out whether the investment is worth making.
Power factor is the cosine of angle between voltage and current in an ac circuit. Distribution lines consume reactive power depending on series reactance and load current. LT capacitors are installed on the distribution system on individual lines at distribution transformers or consumer load points such as motors to reduce system losses and improve system voltage as well as system capacity. In addition they provide other advantages for consumers such as reduction in KVA demand losses and give rise to stable voltage. The optimum benefit desired from capacitors largely depends on correct positioning capacitors in the system. However the provision of LT capacitors on individual service such as motors is generally preferred due to following reasons :¬i.It can be controlled by same control gear which controls motor and can be connected at outlet sites of motor starter ie, parallel to motor winding . The rating of capacitors is such that its current shall not exceed 90% of no-load or magnetizing current of motors.
ii.If capacitors are connected on LT motor's terminals, loading current flowing through HT and LT lines ie, cables, motors, etc will also be reduced and hence IA2*R losses of cable, secondary and primary windings of transformers etc can be reduced, iii.Capacitors being directly connected to motors come into operation when motors are in service and switched off automatically when motors are not in use.
ECONOMICS OF CAPACITOR INSTALLATION
The installation of capacitor at load points substantially reduces KVA demand. The tariff charges levied on basis of energy consumed and maximum KVA demand are accordingly reduced by reduction in KVA demand.
SIZE OF CAPACITORS: - Size of capacitor connected to a motor should be such that the capacitor current do not exceed the no load current of the motor at normal voltage. Otherwise dangerously high voltages will be generated when motors come to a halt because after disconnection of motor from supply motor will be still revolving and act as generator by self excitation.
LT CAPACITOR CONNECTION:-The connection of LT Capacitors to a direct starting motor or to an induction motor with slip rings and starting resistors involves no problems if output does not exceed consumed no load power of motor. But over voltages up to three times rated voltage due to self excitation could occur if switching from star to delta and a line is broken before neutral , it may damage motor and capacitor. The above difficulties are avoided if 6-terminal capacitor is used and connected in a single phase so that capacitor discharges across the motor winding while it is disconnected from the line.
ADVANTAGES OF PF IMPROVEMENT:-
i. KVA rating of the equipment is reduced.
ii. Smaller conductor size.
iii. Copper losses are reduced.
iv. Good voltage regulation.
iv. AUTOMATION OF OPERATION OF COOLING WATER FACILITY USING PLC
Today, automation is moving rapidly towards a true point of central control that resides in the system operator's office. It is becoming increasingly necessary for the system operators to have fingertip control of the process. This has been greatly fulfilled by
the use of programmable devices.
Programmable devices eliminate the need of complex components and discrete components. They are also more reliable , cheaper and it can withstand harsh factory environments, perhaps the biggest advantage of programmable devices is that their functions are easily changeable by merely changing the program stored in them thereby eliminating the need for replacing the whole system . Additional changes can be made incrementally. They also allow interaction with other systems and since their outputs are digital, their working can be easily monitored by computers.
In world of automation, the programmable logic controller has become a standard for control. It now not only replaces the earlier relay controls but has taken over many additional control functions. PLCs are used to synchronize the flow of inputs from sensors and events with the flow of outputs to actuators and events. This leads to precisely controlled actions that permit a tight control of the process or machine .This project and implimentation is devoted to the principle upon which PLCs operate.
Until the last decade control were realized through the discrete relays. Relays, though simple, because of their discrete nature and the need for them to be hard-wired for their operation become cumbersome and unfit in cases where a lot of conditions are to be satisfied to achieve automatic control. When the system requirements change, the relay wiring has to be changed or modified. In an industrial environment, such modifications are not only time consuming, but tedious as well. In extreme cases, such as in auto industry, complete panels have to be replaced as it is not economically feasible to old panels with each model changeover.
Bigger the process more is the need for a PLC. We can simply program the PLC to count its inputs and turn the solenoids on for specified time. Used in industrial and
commercial applications, PLC's act as controllers for machines and processes . They monitor inputs, make decisions and control outputs in order to automate machines and processes. A programmable logic controller is a computer designed for use in machines. Unlike a computer, it has been designed to operate in the industrial environment and is equipped with special inputs or outputs and a control program language. Initially the PLC was used to replace relay logic, but its ever-increasing range of function means that it is found in many more complex applications. As the structure of a PLC is same as those employed in computer architecture, it is capable of performing not only relay switching tasks but also other applications such as counting, calculating, comparing and the processing of analog signals. In this project and implimentation, automation of water cooling system is done using a PLC. The Ladder Diagram technique of programming PLC has been utilized .The implementation of this system would replace existing constant speed drive with variable speed drive and also make the system more reliable and upgradeable in future.
111. RESEARCH METHODOLOGY
«
i. THE PLANT AND THE OPERATION
Presently, the cooling water system of FACT petrochemical division is mainly used by 3 plants : Anon, Hyam and Lactum. It's also used in some other sub plant. The cooling water tower is cross flow induced draft splash fill type. It contains 8 fans; seven of them are working and one is kept as standby . The hot water inlet of the tower is designed as 42 degrees. In this tower the water flows through the two ends of the tower and is situated at the top of the system. In case of single cell there will be two inlets. The cooling fan is at the top centre of the cell. As the name specified the air flows cross to the water. The hot water from the hot water inlet is falling on specially arranged timbers. After falling on timbers it splashes around. This splashed water drops may be drifted by high speed cooling tower fans. This is prevented by placing drift eliminator. It prevents the water drops through it and maintained the water inside it. After striking the water drops in the timbers, they are transformed into tiny drops. Therefore, cross sectional area of water drops increases, therefore the surface contacts with air also increases. This will lead to increase the latent heat of evaporation. Thus the cooling of water is to take place quickly. The whole water is to fall into a common sump. From this cooling water sump the water is distributed using pumps.
PARTS OF THE COOLING TOWER
Frame CTfan
Hot water inlet
Timbers
Drift eliminator
Air inlet
Plenum
Sump
ii. COLLECTION OF OPERATIONAL DATA
GENERAL:
Name of manufacturer Location of works
Pahrpur cooling tower Calcutta
DESIGN DATA : Water flow
Hot water inlet to tower Cold water outlet from tower
14100 m3/hr
42.6
30.5
TOWER DATA :
Type of tower No: of fans / cell No: of fans for tower
: Induced draft cross flow : One : Eight
WATER DISTRIBUTION SYSTEM:
No: of headers
FAN DETAILS :
Fan speed Fan motor rating Full load current Mounting
Voltage of operation
Enclosure
Make
Connection
: Two
1500 rpm 59.7 kw 94 amp foot
415 volt ordinary
Kirloskar Delta
DISTRIBUTION PUMP:
Pump rating : 585 kw
No: of pumps : 123 amps
Full load current : 7 numbers
Frame : KVD 50030
Speed of operation : 1000 rpm
Mounting : flange
Enclosure : ordinary
Voltage of operation : 3.3 kv
Make : Kirloskar
Connection : Star
DATA FOR POWER FACTOR CORRECTION:
Type of cable : 3 core
Area of crosssection : 3 * 95 sq mm
DC resistance : 0.32
AC resistance : 0.385
Motor winding resistance : 0.18 ohm / pha
CABLE LENGTH :400 m
DATA FROM ENERGY ANALYZER:
Line to line voltage : 425.7 kv
Frequency : 49.93 Hz
Current : 90 amps
True power in KVA : 50.69 KVA
Active power in KVA : 38.47 kw
Reactive power in KVAR : 33.08KVAR
Power factor : 0.76
iii. ANALYSIS AND INTERPRETATION
Capacitive kVAR to be added at the motor terminals for improving the present pf of 0.76 to unity is given by the formula;
kVAR required = kW (tan<D, - tan 02)
where O] is the power factor angle before correction and 02 is the power factor angle
after correction. Considering a pf correction to unity,
kVAR required = 38.47 (0.86 - 0)
33.08 kVAR
However, the maximum capacitive reactance that can be added to the terminals of a
motor should not be more than its no-load reactance. In this case:
No-load kVA of the motor = 1.732 * 425.7 *30/1000
= 22.00 kVAR
The various parameters of the fan, after connecting a capacitive reactance of 22.00 kVAR will be:
Active power =38.47 kW
Reactive power = 40.54 - 22.00 = 18.54
kVAR
Apparent power =42.6 kVA
Current drawn by the motor = 55 A
Reduction in current = 35 A
Power dissipation in cable for a current of 35 A = 35A2*0.154 * 3
= 565.9 W
Energy consumption considering 330 days of operation
for fan = 565.9 *24 * 330
= 4482.3 kWh
Considering an energy cost of Rs.2.88/ kWh; total amount for one year
= 4482.3 * 2.88 = Rs. 12,909/-
Cost of capacitor (22 kVAR) = Rs.25,000/-
ECONOMIC EVALUATION OF INVESTMENT - RETURN ON INVESTMENT METHOD
By evaluating the net present value of the total cash flows, decision can be made whether the investment is economical or not. A positive net present value indicates a good investment, and a negative net present value indicates a bad investment.
Net Present Value (NPV) is given by the formula
CFO + CF1/(1+K) + CF2/(1+K)2 + CF3/(1+K)3 + CF4/91+K)4 + CF5/(1+K)5 + CF6/(1+K)6 + CF7/(1+K)7 + CF8/(1+K)8 + CF9/(1+K)9 + CF10/(1+K)10 = 0
Where CFn is the cash flow in each year. Negative sign is given to indicate cash outflow and positive sign is given for cash inflow (saving). K is the discount factor.
ASSUMPTIONS:
¢ Cost of energy increases by 10% once in every 3 years
¢ Discount rate k is taken as 12%
Year Energy cost Rs. Saving Rs. Cash Flow Rs.
1 2.88 12,909 11,526
2 2.88 12,909 10,291
3 2.88 12,909 9,188
4 3.17 14,200 9,024
5 3.17 14,200 8,057
6 3.17 14,200 7,194
7 3.48 15,620 7,066
8 3.48 15,620 6,309
9 3.48 15,620 5,633
10 3.83 17,182 5,532
Net Saving 79,820
NPV = - 25000 + 79,820 = + 54,820. As NPV is a high positive value, this indicates that it will be an economical investment.
IV. FINDINGS AND RECOMMENDATIONS
i. OPERATION OF COOLING WATER FACILITY
OPERATION OF COOLING TOWER PUMP
The distribution pumps are found to work at the full speed at all the time even there occurs a shut down of one or two plants. At present, even a plant takes shut down they are not closing their inlet water valve in order to avoid the chance of burst in the cooling water pipeline.
So we went for a variable speed drive for the water pumps, there by giving only the required discharge. The control of the variable speed drive can be given by integrating all the value positions at the VFD control input. Thus by varying the speed we can change the discharge output. But the use of VFD can obtain a power saving taking consideration of continuous working of the cooling water system.
OPERATION OF COOLING TOWER FANS
The complete operation of all the plants using the cooling water supply rarely occurs in FACT Udyogamandal. And all cooling water fans are made to work for the whole time. Even if the personnel at the control room know about a shut down at the plant the number of fans to be switched off as on is unknown. It requires a periodic or a continuous examination of the temperature of the sump for the switching purpose. So a person has to be appointed just for monitoring the temperature and do the switching operations. This is a cumbersome duty and wastage of labor. These problems can be avoided by an automated switching operation of the fans using a PIC. This will account to saving of annual energy consumption and a reduction in labor.
ii. RECOMMENDATIONS FOR IMPROVEMENT
Selective switching of Cooling Water Pumps and Cooling Tower fans:-Fans will make the system energy efficient. Such a system takes advantage of the favorable ambient conditions. By continuously monitoring the outlet cooling water temperature, and switching on just enough fans for keeping the temperature within limit, wastage of energy can be minimized. Similarly, monitoring the pressure and flow of cooling water enables switching off of Cooling Water Pumps when they are not needed. A closed-loop system incorporating temperature switches for fan control, and pressure and flow transducers for pump control is recommended for the Cooling Water Facility in FACT. And, the operation of the entire facility is proposed to be controlled using Programmable Logic Controller (PLC) for making it automated. The recommended system incorporates a Variable Frequency Drive (VFD) also for speed control of one Cooling Tower Fan. The philosophy recommended follows a pattern in which each Cooling Tower Fan will be switched on based on the condition of the temperature switch of the cooling water line. If a fan at normal rated speed is not required for keeping the temperature, a fan connected to VFD will only be switched on, and it will be allowed to run at a speed sufficient for meeting the temperature requirement. This ensures that energy is not wasted in fans by way of over cooling the water. A similar logic, but without a VFD, is recommended for the operation of Cooling Water Pumps. Pumps just required for meeting the demand (required flow at specified pressure) will only be switched on. By adopting such a system, the wastage of energy at control valves can be minimized to a certain extent. Though, incorporation of a VFD is essential for complete elimination of energy wastage, it is not recommended for the time being. The Cooling Water Pumps are 585 kW, 3.3 kV motors, and since 3.3 kV VFDs are still not very popular in India, that option has not been considered in this project and implimentation. Finally, it is suggested to introduce equipment-connected pf improving capacitors for the fan motors for energy saving. Introduction of these capacitors will minimize the energy being dissipated in switchgear, cable and motor winding.
iii. AUTOMATION OF OPERATION USING PLC INPUTS
0000 Trip switch
0001 System in auto
0002 Plants in running
0003 Power OK
0004 Pump A ready
0005 Pump A auxiliary contact
0006 Pump B ready
0007 Pump B auxiliary contact
0008 Pump C ready
0009 Pump C auxiliary contact
0010 Pump D ready
0011 Pump D auxiliary contact
0100 Pump E ready
0101 Pump E auxiliary contact
0102 Pressure > 2.5 kg/m2
0103 Flow< 12000 m3/hr
0104 Flow < 9000 m3/hr
0105 Flow < 6000 m3/hr
0106 Flow < 3000 m3/hr
0107 Inlet temperature > 42
0108 Sump temperature > 31.5
0109 Outlet temperature< 30.5
0110' Fan A ready
0111 Fan A auxiliary contact
0200 Fan B ready
0201 Fan B auxiliary contact
0202 Fan C ready
0203 Fan C auxiliary contact
0204 Fan D ready
0205 Fan D auxiliary contact
0206 Fan E ready
0207 Fan E auxiliary contact
0208 Fan F ready
0209 Fan F auxiliary contact
0210 Fan G ready
0211 Fan G auxiliary contact
0300 Fan H auxiliary contact
0301 Lamp test switch
OUTPUTS
1000 System ready indication
1001 Command to pump A
1002 Pump A ON indication
1003 Command to pump B
1004 Pump B ON indication
1005 Command to pump C
1006 Pump C ON indication
1007 Command to pump D
1010 Pump D ON indication
1011 Command to pump E
1012 Pump E ON indication
1013 Command to switch OFF pump A
1014 Command to switch OFF pump B
1015 Command to switch OFF pump C
1016 Command to switch OFF pump D
1017 Fan A ON
1100 Fan A LED ON
1101 Fan B ON
1102 Fan B LED ON
1103 Fan C ON
1104 Fan C LED ON
1105 Fan D ON
1106 Fan D LED ON
1107 Fan E ON
1110 Fan E LED ON
1111 Fan F ON
1112 Fan F LED ON
1113 Fan G LED ON
1114 Fan G LED ON
1115 Fan H LED ON
1116 Fan H LED ON
PLC INPUT CONNECTIONS
34V DC + "
Trip Switch ”J
System in Auto ”^
Plant Ririning ”J
PbwnrO.K. ”J
Puirp A Ready ”J
RinpA _J
AuxfEaryC ort-act *
Pimp B Ready ”|
Pimp B *
AuxiiaiyCoitact
Riirp C Ready ”J
Partp C ”|
Pjiip D Ready ”J
PuitpD __J
AuxiliiiyCcintact
PunpE Ready ”J
RinpE 1
Auxiliary Cortact * ”
Pressure >2.5Kgn2 ”J
Fbw<1200Qrrt%3/h ”] Fbw<9000n^3/li ”] Fbw<6000irf 3fti ”^ Fbw<3000ttf-3Th ”^ Inlet terrpeiatLiiB>35 c ”J Surtp ternpelainm>35 c”J
l lrjv +
Fan DON (x)
Fan D ON Iidication (X)
Fan EON (Xj
Fan EON Iidication (V)
FanF ON Q£
FanF ON Iidication f^j
Fan G ON (£J
Fan G ON Iidication fJJ
Fan HON Q<)
F-an H ON Iidication (Xj
34V DC
+
Out]etteir|teite31c-J
FanA Ready ¦
Fan A AuxiliaryContac t”J
FanB Ready -J
FanB Auxiliary Coitactӣ
FanC Ready *
FanC AuxdiaryCoiiiact ”J
FanD Ready _J
FanD AuxiliaryContac t -J
FanE Ready ¦
FanE Auxiliary Corifect”J
FanF Ready -J
FanF Auxiliary Contact ӣ
FaziG Ready -J
FanG Auxiliary Contac t ”^
FaiiH Auxiliary Contac t”J Lamp Test Switch _£
1
24 V COM -"VE
0109
0110
111
02QD
201
0202
0BE3
iM
0205
0206
020
OG08
0209
QG10
0211. OQ00 0Q01
PLC OUFUTCCONNECTIONS
110 V
S ys fern Ready
Indication V-
C ommand To Pump A fyQ
Funp A ON Indication fV}
C ommand To Pump B [%Q
Pump B ON Indcatbn LXl
C ammand To Pump C Q*0_
Pimp C ON Indication
C cmmand To Pump D fjK.}
Pimp D ON IndEation £<}
C ommand lb Pump E LXj
Funp E ON Indication (5^)~ C oinmand To S with
0FFPuir^AQ<2_
C oinmand To S with
OFF Pimp B 1*1
C onnnand To S with OFT Pump C
C ommand To S w it: h r<~7
Fan A ON
Fan A hdratbn ON
Fan B ON fxj
Fan B Indcatbn ON (x)
FanC ON i/x)
FanChdkatbnON
1_
110V COM -VE 1000
1001 1002 1013 1004 1005 1006 1007 1010 1011 1012 1013 1014 1015 1016 1017 1020 1021 1022 1023 1024
FLOWCHART
System is ready
Start all the five pumps
Switch off pump A
Switch off pump B
0
©
Ifflow<=6000 mA3/h&
last for 2 min& pressure>2.5kg/ cmA2
No ”
i Yes
Switch of pump C
Ifflow<=3000mA3/h&
last for 2 min& pressure>2.5kg/cmA2
No
Yes
T
Switch of pump D
Fan A is ON
After 2 min measure the
sump Temperature
I
Fan B is ON
After 2 min measure the
sump Temperature
After 2 min measure the
sump Temperature
After 2 min measure the
sump Temperature
After 2 min measure the
sump Temperature
After 2 min measure the
sump Temperature
Fan H is ON
Switch OFF Fan A
Reduce the speed by 20%
200.00 Oil svstem in auto
-M Ih
-0¬200.01
-o-
200.01
ijg plants running
21.02 0.03 power o.k
200.02 200.03
200
Si stem ready indication
200.03
>.04 pump A read
O-
10.01
¦O¬
command to Pa
o.os pg
02
Pa ON indication
298.40
M03 0.06 Pb readi
10C3
-0¬
command to Pb
Pb ON indication
2D0.03
m
Pc ready
10.05
<h
10.06
-O-
Command to Pc Pc ON indication
20440
203.03
0.10
cod)
10.07
command to Pel Pd ON indication
200.03
1 00
Pe readv
10.11
ommand to Pt
101
10.12
Pe ON indication
213.43
1.52 pr>2.5kg/eiif2
200
10.02
10.13
command to switch off Pa
200.04 1 g4
HI ”
fifesf-1 1184
fIow<9000mA3/hr
10.14
command to switch off Pb
200.04 1.05 Aow<6000«r
iw2 10.06
command to switch
Off PC
200.04
Ofi
10.06
ti»r3
1-w inlettemp>42deg
sumptemp>31.5deg
11.16 2-DO 05
-o-
200.06
command to switch off Pd
cutlet temp<30.5deg
11.00
.09
200.05
1 1 Fa
1fJ,7runiiiQ 2fis
200.07
-o-
209.68 -§-200.09
imm 200.es 1.18Fa mii
H I M 1 I
in
15.17
11.00
Fa ON
Fa indicatiof
200*0
11.00
:rwi 200.1
200.10
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V. LIMITATIONS AND CONSTRAINTS OF THE PROJECT
Data related to design aspects of Cooling Tower were obtained easily from the operation manuals. However, while going through data collection and analysis, it was observed that many important data related to actual operation were not available. Hot water temperature and cooling water temperature against number of fans running is a data that could be used for estimation of energy saving. This was not available for the seasonal temperature changes of outlet cooling water. Though water requirements of plants under design conditions are given, flow requirements of these plants under varying conditions could not be found out. Instrumentation system for the cooling water facility, available at present, seems to be inadequate. Similarly, the pressure variation of the cooling water line owing to reduction in demand by individual plants is being taken care of by the Cooling Tower operators - by throttling of control valves - but, actual variations have not been recorded. In the absence of the.se data, estimation of number of fans or pumps that would be switched of in a given condition in the post-implementation scenario becomes difficult. And subsequently, that makes the estimation of energy saving resulting from suggested improvements very difficult.
The limitation as stated above is applicable for estimation of energy saving by introducing equipment-connected pf improving capacitors too. In the absence of relevant data, an assumption was forced to be made regarding average number of fans required to be run during a year. The economic evaluation of energy saving due to this change is based on the assumption that only four fans would be running throughout the year. A more realistic estimation could have been made, if sufficient data were available.
Total power consumption for the Cooling Water Facility could not be measured. Without this data, actual benefits derived - in case of implementation of recommendations - cannot be verified. The fact that 3.3 kV VFDs are not very popular in India was limiting factor in designing an improved system operation for Cooling Water Pumps in our project and implimentation. The introduction of VFD for Cooling Water Pumps as well would have saved huge quantum of energy.
For automation purpose, an input indicating that other plants have started drawing cooling water could not be identified. If such a device were available, that could be used for starting the operation of the Cooling Water Facility in auto mode. As such, the proposed start-up operation in this project and implimentation is initiated by a switch actuated remotely by consuming plants.
VI. SCOPE FOR FUTURE IMPROVEMENT
Since 3.3 kV VFDs are still not very common in India, the option of using them for Cooling Water Pumps was not recommended in this project and implimentation. That alternative can be examined in future, as it seems to be a good proposition once the problems associated with HT VFDs are overcome. Total power consumption for the Cooling Water Facility could not be measured. Without this data, actual benefits derived - in case of implementation of recommendations - cannot be verified. When project and implimentations of this nature are done, preliminary data related to power consumption, annual running hours, temperature variations etc. shall be recorded prior to data analysis and recommendations. An input condition indicating starting up and subsequent usage of cooling water by other plants is required for complete automation of the Cooling Water Facility. Process analysis of other plants for identification of such an input may be incorporated in future.
Vll. CONCLUSION
This project and implimentation titled 'Optimization and automation of operation of cooling tower facility' is a combination of software programming and hardware interfacing circuit designed for the automatic control and power saving of the cooling water in FACT. Our proposed system uses programmable logic controllers and variable frequency drives. Techno economical analysis shows that there could be a greater improvement in the power consumption and also in expenditure.
Vlll. REFERNCES
i. Automating Manufacturing systems with PLCs _ Hugh Jack
ii. Cooling tower design data sheets, petrochemical division, FACT
iii. Omron PLC manual
iv. industrialtext.com
v. trilogic_plc.com
IX. ANNEXURE
i. PROGRAMMABLE LOGIC CONTROLLERS
i Brief history
ii Description
iii Programming methods
BRIEF HISTORY
In a PLC system, all control devices are wired to the PLC. In a traditional system, all control devices are wired direotly to each other. A programmable logic controller, also called a PLC or programmable controller, is a computer-type device used to control equipment in an industrial facility. The kinds of equipment that PLCs can control are as varied as industrial facilities themselves. Conveyor systems, food processing machinery, auto assembly lines ... you name it and there is probably a PLC out there controlling it. In a traditional industrial control system, all control devices are wired directly to each other according to how the system is supposed to operate. In a PLC system, however, the PLC replaces the wiring between the devices. The control program is the computer program stored in the PLC's memory that tells the PLC what is supposed to be going on in the system. The use of PLC to provide wiring connections between system devices is called soft wiring.
WHY WE USE PLCs
The soft wiring advantage provided by programmable logic controllers is tremendous. In fact, it is one of the most important features of PLCs. Soft wiring makes changes in the control system easy and cheap. If you want a device in a PLC system to behave differently or to control a different process element, all you have to do is change
the control program .In a traditional system, making this type of change would involve physically changing the wiring between the devices, a costly and time consuming endeavor.
In addition to the programming flexibility we just mentioned, PLCs offer other advantages over traditional control systems. These include:-
i High reliability
ii Small space requirements
iii Computing capabilities
iv Reduced costs
v Ability to withstand harsh environments
vi Expandability
Inputs to and outputs from a PLC are necessary to monitor and control a process. Both inputs and outputs can be categorized into two basic types: logical or continuous. Consider the example of a light bulb. If it can be turned on or off, it is logical control. If the light can be dimmed to different levels, it is continuous. Continuous values seem more initiative, but logical values are preferred because they allow more certainty, and simplified control. As a result most controls applications use logical inputs and outputs for most applications
DESCRIPTION
PLC basically consists of two elements: The Central Processing Unit & input / output system
THE CPU:
The central processing unit is the part of a programmable controller that retrieves, decodes, stores, and processes information. It also executes the control program stored in the PLC's memory. In essence, the CPU is the brain of a programmable controller. It functions much the same way the CPU of a regular computer does, except that it uses special instructions and coding to perform its functions. The CPU has three parts:-The processor The memory system The power supply
The processor is the section of the CPU that codes, decodes, and computes data. The memory system is the section of the CPU that stores both the control program and data from the equipment connected to the PLC. The power supply is the section that provides the PLC with the voltage and current it needs to operate.
THE INPUT / OUTPUT SYSTEM :
The input / output system is the section of a PLC to which all of the field devices are connected. If the CPU can be thought to be the brain of a PLC, then the I/O system can be thought of as the arms and legs. The I/O system is what actually physically carries out the control commands from the program stored in the PLC's memory. The I/O system consists of two main parts : The rack and I/O modules. The rack is an enclosure with slots in it that is connected to CPU. I/O modules are devices with connection terminals to which the field devices are wired. Together, the rack and the I/O modules form the interface between the field devices and the PLC. When set up properly, each I/O module is both securely wired to its corresponding field devices and securely installed in a slot in the rack. This creates the physical connection between the field equipment and the PLC. In some small PLCs the rack and the I/O modules come prepackaged as one unit.
LADDER LOGIC INPUTS :
PLC inputs are easily represented in ladder logic. In the figure there are three types of inputs shown. The first two are normally open and normally closed inputs, discussed previously. The IIT(Immediate input) function allows inputs to be read after
the input scan, while the ladder logic is being scanned. This allows ladder logic to examine the input values more often than once every cycle. Normally open, an active input x will close the contact and power to flow. Normally closed, power flows when the input x is not open. The immediate inputs will take current values, not those for previous inputscan
LADDER LOGIC OUTPUTS:
In ladder logic there are multiple types of outputs, but these are not consistently available on all PLCs .Some of the outputs will be externally connected to devices outside the PLC but it is also possible to use internal memory locations in the PLC . Different types of outputs are shown The first is a normal output, when energized the output will turn on, and energize an output. The Circle with a diagonal line through is a normally on output. When energized, the output will turn off. This type of output is not available on all PLC types. When initially energized the OSR ( On Shot Relay ) instruction will turn on for one scan, but then be off for all scans after, until it is turned off. The L(latch) and U(unlatch) instructions can be used to lock outputs on. When an output L is energized, the output will turn on indefinitely, even when the output coil is de energized. The output can only be turned off using a U output. The last instruction is the IOT (Immediate Output) that will allow outputs to be updated without having to wait for the ladder logic scan to be completed. When power is applied the output x is activated for the left output, but turned off for the output on the right. An input transition on will cause the output x to go on for scan( this is also known as a one shot relay).
ii. VARIABLE FREQUENCY DRIVES
An integrated fan speed control solution can lower system costs, reduce acoustic noise, power consumption and enhance system reliability. Many utilities are now offering rebates for the installation of VFD's or retro-fitting existing equipment with variable frequency drives.
Fan Speed Controlled by
Cooling towers are at the heart of many industrial processes. While tower designs vary from manufacturer to manufacturer, fans are always used to move air through the cooling tower, cooling the process water. Operating requirements for a cooling tower may include the ability to start and stop the fan, change the fan speed (based on the sump water temperature).If fan motors are running at constant speed, the problems arising are:-fan speed control not taken into consideration at system design stage increased maintenance costs and process water temperatures are not accurately controlled Applying variable frequency drives or VFD's on cooling towers eliminate many drawbacks associated with starter-controlled fans. Reduced energy consumption (lower utility costs), reduced maintenance requirements (personnel & equipment replacement costs) and
process water temperature stabilization are among the benefits. The fan may be spinning when a VFD is commanded to start. A VFD must correctly identify motor rotation, slow the motor down to zero speed (when opposite rotation is detected), accelerate the motor in the correct direction and not trip on an over-voltage or over-current condition. Mechanical brakes or anti-ratcheting devices can be used to ensure that a fan doesn't rotate in the wrong direction. A VFD eliminates mechanical and electrical brakes as well as anti-ratcheting devices, time delay relays, etc. A VFD rectifies ac to dc and then inverts to ac of required frequency. It is possible to achieve speed reduction ratio up to 9:1 using VFD.
Reply
ravivarmak306
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Posts: 1
Joined: Sep 2010
#2
03-09-2010, 10:49 PM

can i have the ciruit diagram and ladder logics
please urgent
Reply
Praveenprahaladan
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Posts: 1
Joined: Oct 2010
#3
08-10-2010, 03:58 PM

please send the report..
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