Nida Afaq Student of University of Engineering and Technology, Taxila. University Registration number: 08-EE-128
Acknowledgment:
It is not easy for a student of any university to gain practical knowledge and experience at the very time he/she is studying. For such purpose, internship in an industry is very helpful. I am thankful to Wah Nobel (Pvt) Limited to give me such opportunity to intern in Wah Nobel Chemicals limited and Wah Nobel Acetates limited. I am thankful to Mr. Ejaz Ali (D.G.M Wah Nobel Chemicals), Mr. Muhammad Afzal a nd Mr. Qamar Iqbal from Wah Nobel Chemicals and Mr. Abdullah Zafar from Wah Nobel Acetates Limited to teach me and guide me throughout my internship.
Introduction to Wah Nobel Group of Companies: Wah Nobel develops, manufactures, markets and maintains a wide range of commercial explosives, accessories and industrial chemicals of international standard. Wah Nobel is a joint venture between Saab, Sweden and Pakistan ordinance factories, which was founded in 1962. Explosives for Industrial Applications:
Since its inception Wah Nobel has continued to develop and refine the company’s core expertise in traditional explosives (the NG based dynamites and powder explosives). In doing so, it has expanded the range of products to latest emulsion explosives and shock tube initiation systems. Chemical Specialities: Specialities:
Wah Nobel produces an impressive range of high quality industrial chemicals which have wide applications in numerous products. These products are used in industries like textile, leather, food, agriculture, pharmaceutical, printing, dying, paint, lacquer, varnish, plywood, chipboard, hardboard, sugar and in foundries. Training Facilities: Facilities:
Our Blasting Services Division serves costumers at home and abroad by providing state-of-the-art training for a variety of blasting needs through courses, seminars and on-site demonstration. Wah Nobel’s most popular annual annua l course on Rock Blasting Techniques provides an opportunity to the mining and construction engineers for updating their knowledge and skills. Wah Nobel (PVT) LTD.:
Wah Nobel (PVT) Ltd. are the pioneers in the manufacture of commercial explosives and blasting accessories in Pakistan. It’s products have made valuable contribution in the national development projects like Tarbela and Mangla Dams, Karakurram Highway, Islamabad Lahore motorway and other projects involving tunneling, mining and quarrying etc. Commercial explosives produced include Wabox, Wabofite and Wabonite. The latest explosive by Wah Nobel is Emulite which is a emulsion explosive; its advantages include absence of headache, safety, rock breaking characteristics(due to large amount of energy produced on initiation), stability in heat and cold and its resistant to water. Wah Nobel Detonators (PVT) LTD:
The Wah Nobel detonator (PVT) Ltd. is a wholly owned subsidiary company of Wah Nobel and has been set up for the manufacture of commercial detonators. The factory is situated in S.D.A. industrial estate, Hattar, N.W.F.P, which is in full production since May, 1992. The industrial units of Wah Nobel Detonators are equipped with sophisticated plants and machinery to manufacture initiatory
explosives for undertaking production of Detonators and Non-Electric initiations system under the trade name of ’LEHER’. The company also plans to undertake production of Delay Electric Detonators in the near future. Leher Ignition System:
LEHER non-electric initiation system developed by Wah Nobel’s Research & Development Laboratories and launched in the market m arket is based on the shock tube technology. The inner wall of hollow plastic tube is coated with a thin layer of reactive material. A shock wave initiated by a special initiator passes through the tube with the speed of approximately 2000 meters per second. The flash of shock wave initiates the detonator assembled at the other end of the tube which in turn initiates the explosives charge. Wah Nobel Chemicals Limited:
Wah Nobel Chemicals Limited is a subsidiary Company of Wah Nobel (PVT) limited and was established in the year 1983 for the manufacture of Formaldehyde and Formaldehyde Resins for different applications in the industrial field. The industrial units of Wah Nobel Chemicals Limited comprise of two plants, one for the manufacture of Formaldehyde and the other for production of Urea & Phenol Formaldehyde Forma ldehyde Resins. Formaldehyde unit is based on the license and technical know-how supplied by Messrs. Perstorp A.B. of Sweden who are the manufacturers of wide range of products based on Formaldehyde for various trades and applications. The resin unit of WNC has been licensed by a very reputed firm of Spain namely Foresa. Foresa is linked to TAFISA group of industries, who are important producers of various qualities of fiber-board, plywood and chipboard. As such Foresa is a firm which has vast experience in the production of Urea Formaldehyde, Phenol Formaldehyde and Melamine Formaldehyde Resins for application in wood industries and laminates. Thus the technical know-how supplied to us is backed by their long experience in this field. The laboratory of WNC is equipped to manufacture plywood and chipboard on lab scale from clients’ raw material and carry out testing of the finished materials in accordance with international standards. Wah Nobel Chemicals is also an accredited agent of reputed firms world wide for chemicals, plant, machinery, ferrous and a nd nonferrous materials, moulding compounds and laminates etc. Wah Nobel Acetates LTD:
Wah Nobel Acetates Limited is manufacturing Glacial Acetic Acid, Ethyl Acetate and Butyl Acetate. Technical know-how for the unit has been acquired from China. The technology selected is based on Ethanol air oxidation method and has the vital characteristic of major consumption of indigenous raw material. The annual production capacity of the plant is 5000 ton for Acetic Acid and 4000 ton for Ethyl/Butyl acetate. a cetate. This
capacity is sufficient to meet the entire domestic demand, thus avoiding dependence upon imports of these products and eventually saving big amount of precious foreign exchange for the country.
Layout and Equipment of Electric Power distribution in Wah Nobel Chemicals: This part of the factory can systematically analyzed by analyzing each component separately. There are two such systems, one is manually controlled and others is auto-controlled, otherwise there is no difference in setup.
Provides protection from overload
Metering, Control and protection
HT PANEL (11KV)
Step down Transformer (11KV/400V)
Air Circuit Breaker (ACB) Capacitor Panel
Power is distributed to all the system components at this point.
Distribution channels
LT PANELS
Power Factor Correction. Capacitors are connected in parallel.
HT switching panel:
It’s an 11KV panel, which takes supply from primary distribution network of POF (Pakistan Ordinance Factory). It has analog voltmeters, ammeters and energy meters to show voltage, current and KWh ratings respectively. A digital energy meter is also installed recently. HT panel is used for measurement, metering and control and for protection purposes. The switches provided on the panel can be used to switch ON or OFF the system. It uses CT and PT for measurement and protection. CT(current transformer) and PT(potential transformer) step down current and voltage respectively. CT steps down current to 5A from 100A and PT steps down voltage from 11000V/√3 to 110V/√3. There are two CTs used, one is for measurement and a nd other is for protection. The protection CT along with PT gives signal to trip circuit of circuit breaker in case of fault. 11KV/400V Step down Transformer:
A transformer is device used to change the level of voltage and current, keeping the power constant. High voltages are used for
Includes CBs, MCBs, Contactors for Control and protection of motors.
transmission and primary distribution to minimize losses as current is decreased by increasing voltage level, but this voltage has to be stepped down again to meet the needs of consumer. The step down transformer used here is 11KV/400V, 75KVA transformer. It takes input with three lines (RYB) and provides output at 400V with three lines and one neutral. Output is taken at four busbars which are then taken to a separate room through ducts. Capacitor Panel:
Capacitors are used in power in industries to improve the power factor of the connected load. Low power factor means high current from the supplier, hence high KVAs consumed so the consumer has to pay more. Number of capacitors used in each system is six. Each capacitor is 822µF providing 50KVAr. Number of capacitors operating at a time is decided on the basis of requirement; this is done by magnetic contactors inside the panel which operate on their own. The capacitors are connected in parallel with incoming supply through fuses. Panel shows power factor of the load digitally. Switches to turn on or off the capacitor bank are also provided on the panel. Power factor of the plant can be improved upto 0.99 with the use of these capacitors. ACB (Air Circuit Breaker):
Circuit breaker is automatically operated switch designed to protect a circuit from damage caused by over-load or short circuit. Air circuit breaker is used for medium voltage range. The ACBs installed has breaking capacity of 690V, 35KA and 600V, 50KA, it operates on 220V (AC). Distribution Distribution Channels:
At this point, the power is distributed to individual components. Distribution channels have the circuit breakers, which protect their concerned circuits from damage. Each distribution channel is connected to its LT panel separately. They are a re classified as CMOs, for example the first channel is CMO1 Main and its for Fire Fight for the 132KW blower motor, which is the largest KW rating motor installed in the factory. Then second one is CMO2 Main which is for Formaldehyde Pump and Safety System then third is for the Glue plant motors. CMO2 is the ‘safety panel’, it has all a ll the relays for protection, which are interlinked with PLC control and the Motors for which they are providing safety. Some of the relays are for following purposes: For rupture disc: rupture disc burns out in case of interruption in any pump’s operation and change in pressure. Flow of methanol is checked, one relay activates alarm and other operates to cutoff operation.
For changing Jet-point: to check flow of air in blower systems; pressure of air must be kept up to a point, if its its low it will cause a blast, so a relay is provided to operate if pressure is low. Temperature of reactor. Temperature of vaporizer; it is set to 100 degrees normally, if its low the relay will operate. DTH output temp.: if its very high then relay must operate. R1111 safety system is used in main feed line of methanol with a solenoid switch. A timer is provided to link main system with safety system. Whole system is divided into four sub-systems; each system has one absorber, one reactor and other related components which are shown below in the tables: Distributed load of system #1 and #2:
Sr.no.
Load
1 2 3 4 5 6 7 8 9 10 11
Blower CMO 6 DTHY Heaters CMO 4-5 Formaldehyde CMO 2 Glue CMO 3 Utilities Storage area Fire fighting Lighting Resin & Cement areas Office bui building, cant anteen, labs and stores areas Tube well Chiller Total Kilo Watts Formaldehyde pump P-3-3C UF glue pump P-3-8A Glue pump P-3-8B Glue pump P-3-8C Cooling Water Pump P-3-11A Cooling Water Pump P-3-11B Cooling Water Pump P-3-11C Raw water pump P-3-12 Process Water Pump P-3-14 Process Water Pump P-3-15 Cooling tower fan U-3-1A,B,C,D Water treatment U-3-2 Urea Crusher Formaldehyde pump P-3-3D Air compressor U-3-5A & B Air drier U-3-5C Boiler U-3-5C
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Connected KW System #1 & 2 264 200 33 77 281.87 55 15 50 50 30 30 1085.84 5 .5 11 11 11 29.4 29.4 15 3 .6 1 .4 2 .9 22 3 .6 14.5 5 .5 28.14 0.5 10
29
Boiler feed pumps P-1-3A,B,C Total Kilo Watts
39 2151.12
Distributed load of system #3 and #4: Sr.n Sr.no. o. Load Load
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Blower DTH heaters Cooling water pumps Formaldehyde pumps Boiler feed water pumps Glue Vacuum pumps Glue pumps Reactor-2 stattier Reactor-3 stattier Cooling drums Air compressor Methanol offloading pumps Cooling Tower C Fan Cooling towers fans Process Water pumps DTH pumps Process Vacuum pumps Methanol Pump Day tank pumps Urea solution pumps Urea elevator Caustic soda pump Air drier Steam chiller Workshop Total Kilo Watts
Conn Connec ecte ted d KW System #3 & 4 264 200 120 30 30 30 66 15 10 18.65 30 3 .7 20 2 2 .5 5 3 1.49 3.65 30 15 15 0.16 0.55 35 50 1018.7
LT Panels:
Each LT panel mainly comprises of: Magnetic contactors Miniature circuit breakers Circuit breakers Timers Terminal blocks LT Panels for manually controlled system are provided by ‘agelectric’ of Barcelona and for second system, the company is Electromech Engineering Services of Islamabad, Pakistan. Magnetic Contactors: Contactors:
A magnetic contactor is a relay-controlled switch used to turn a power control circuit on and off. It is electrically controlled and uses less power than other circuits. A magnetic contactor comes in different forms and capacities. Components:
A magnetic contactor has three parts: power contacts, contact springs and auxiliary contacts. The power contact creates, carries and a nd breaks the current in a magnetic contactor. The contact springs create a sufficient amount of pressure on the contacts. Auxiliary contacts perform signaling and interlocking maneuvers. Here two types of starting is needed, one is Direct On Line (DOL) starting) . For DOL type, and second is Star-Delta starting (Y-∆ starting) the contactor has just to make the contact of motor directly to the supply. For motors with ratings greater than 7.5KW star-delta starting is used. In star-delta method, the contact is made in star s tar at starting and after some time, when motor has acquired sufficient speed then the contact is converted to delta. This switching is done by three contactors; one is main contactor, second is delta-contactor delta-contactor and third is star-contactor star-contactor. At starting, main contactor is connected along with star-contactor, whose winding is shorted at one end. At this time, the circuit is series circuit, thus provides large resistance to current so less current flows in winding of the motor, which gives less speed at starting. Less current and speed is apropos at starting as motor is saved from burning due to heavy current and by mechanical damage. Theoretically, for star-delta starting the current at starting(Y-connection) is 1/3 times the current at running(deltaconnection). Main contactor has a timer , either analog or electronic to give time for switching between star or delta connection. The timer has a bimetallic strip to give the delay time through heating. The switching time can be adjusted by turning the knob of timer. After the switching time of timer, star-contactor is opened and deltacontactor is connected; now the circuit becomes a parallel circuit, offers less resistance so large current flows now. With the main contactor, there is a CT for measurement and a thermal protection relay to protect from overheating. Some auxiliary contacts are also provided on the contactors, these are not a part of the contactors, but provided for indication through lighting and for alarms.
L1 L2 L3 E
1>
1>
1>
O/L
M 3 Ph DOL STARTER circuit For motors with ratings less than 7.5KW
L1 L2 L3 E
1>
1>
1>
O/L
M 3 Ph STAR-DELTA STARTER for 7.5KW or above KW rating motors.
MCBs:
After starting circuit, MCBs are provided for the protection of part of the circuit after contactors and up to the motor’s own circuit. LT Panel for 132KW Blower Motor:
It has a circuit breaker for further protection, which has two CTs for measurement. It has large size contactors, including main contactor and star- and delta-contactors; it has electronic timer, phase-fault control relay and MCBs. The above starter is also for 132KW motor. =>In the auto-controlled system, there are no distribution channels. Busbars run throughout the LT panels, so main circuit breakers are inside the LT panels and the LT panel’s assembly is also there. Else the circuitry is same as that of previous system. Distributed Control System(DCS): System(DCS):
The DCS is a control system, sys tem, which collects the data from field and decides what to do with them. Data can be stored for future reference, used for simple process control, use in conjunction with data from another part of the plant for advanced control strategies. DCS must have operator console, engineering station, modules for history, data and control and I/O (input/output). In WNC; following softwares are used: RS Logix 5000; for programming of DCS. Intouch; to provide HMI (human-machine interface). RS Links; for networking between above two. In the control room of WNC, there are four computers as operator consoles and PLC panels are also a lso in the same room. Two computers control systems operated through PLC of system #1 and #2 and rest two are for system #3 and#4. PLC/DCS panel: It has following components, shown in a diagram to make the flow clear: • • •
Analog power Supply(24V)
Operator consoles(PC)
Digital Power Supply
DCS
Digital /analog Input Card
Digital output cards
Relays
Contactors
Control through DCS is shown through following circuit:
The process is clearly shown through above circuit, the input cards of PLC panel receive data from transmitters installed in the plants, and then it gives output to control valve, through output cards to the control valve. The operation of control valve depends on the reading received and the set-point given. The output of the PLC is in the range of 4 to 20mA.
Handheld Communicator (HHC):
This is an instrument used to check and calibrate the pressure transmitters installed in the plants. The HHC used in WNC is by the company, Fuji Electric Systems. It can be used to check following things: Tag No. : e.g. Calibration , PT-1209 Output adjust Model No. Data: measured data Serial No. & at the moment Software in percentage Version and bars. Engineering Self diagnoses unit : Bar Printer (printer Range limit : option) Measuring External switch range lock Damping Transmitter Output mode :if display LIN, means Linearize linear oputput. Rerange Burnout direction :it Saturate maybe HOLD current etc. Write protect •
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History
[Ref: http://www.fic-net.jp/eng]
Same instrument or any similar instrument can be used to calibrate Temperature transmitters in the plants. Temperature transmitters’ use sensors to measure temperature, which are bimetallic devices; they sense temperature through heating and unequal expansion of both the metals.
Brief overview of control System in Wah Nobel Acetates Limited: Wah Nobel Acetates produces Acetic acid, Ethyl acetate and Butyl acetate. Here two boilers are used of 5 tons each, because here less air is required, as compared to processes at Wah Nobel Chemicals. Chillers use 125KW motors, largest load is 132KW motor of compressor. Total load is 1100KW. Here I learned mainly about DCS; because electrical power distribution is same as that of WNC. Following softwares are used: DCS (by B&R Company) Intouch 5.1; to provide HMI Profibus network. Panels in the control room has temperature converters (MTL5073), which have 250ohm resistors, they receive signals from RTD and thermocouples in form of current (4-20mA) and convert into 1-5 volts. Safety system’s input is at MTL7187+ and output is MTL7128+. • • •
Loops in a control system:
There can two types of loops, Open loop and Closed loop. Open loop:
If there is just a transmitter connected at any point on the plant, along with a valve, va lve, and a man observes the indication of the transmitter. The observer will open or close the valve as required. It’s an open loop. In this loop, there is no control provided by DCS, only control is through manual control. Closed loop:
Closed loop systems utilize feedback to make decisions. Feedback is the state of the system/valve in response to output signal sent from the controller to the valve in the field. Basically, the closed loop consists of a transmitter, control valve and controller. The controller checks state of the system through transmitter and sends order to control valve va lve to close or open. After action of the valve, controller again checks the state, this makes a closed loop. There are 56 control loops in the system s ystem of Wah Nobel Acetates Ltd. Another type is Cascade Control Loop: In this type of loop, there is one control valve and two controllers. The two controllers are related in such a way that one’s output is other’s set-point. Its used in an interconnected system. For example, if tank no.1 takes steam through an inlet, and its own output goes to another tank (tank no.2), then temperature of second tank depends on temperature of first, which itself depends on the input quantity of steam. So a control valve will be provided at steam inlet pipe and two transmitters will be used to measure temperature of two tanks, and thus two controllers to control these temperatures through control valve.
(Figure shows cascade loop of the example discussed above)
Instrumentation:
Instrumentation is basically about measuring flow, temperature, pressure and level at any point in the plant through transmitters and RTDs/thermocouples (temperature). At Wah Nobel Acetates, Fuji’s transmitters are used (LT, PT and pneumatic flow transmitter), control valves are of Samson and Koso, magnetic flow transmitters are from Krone (German). RTDs (PT100) are of E+H (German company). The transmitters in the plant, when take a signal in the form of current (4-20mA), convert it into Kg/cm2 (flow) or KPa or psi (pressure) or degrees centigrade or centimeters of level, and that signal is converted into volts for input cards of the DCS. All these signals have a defined limit of minimum and maximum values, as in following table: Standard signals psi Kg/cm2
Percentag mA e 0% 4 3 0. 2 25 % 8 6 0. 4 50 % 12 9 0. 6 75 % 16 12 0 .8 100 % 20 15 1. 0 The value of 4mA is also called live zero, because if current is 4mA, it means a temperature of 0oC. Same is the case with other parameters.
KPa
Volt
20 40 60 80 100
1 2 3 4 5
Following diagrams show travel of input and output signal from DCS to valves in the field: Output signal Network card (NW100)
HMI
MP100
CP100
Output Card (A/O or D/O)
On/Off or Control Valve
Transmitter at field
Input Signal
HMI
NW100
CP100
MP100
Here CP is the central processing unit of DCS and a nd MP is mega-processor. There is a memory card attached to MP. Following are some parameters, which I practically examined: 1) Checking Checking value value of current/volt current/voltage age at input/output input/output cards (of any signal): i.
Indicator’s tag at HMI gives the title of the controller e.g. TRC2305. This will be same on profibus or may differ from it, in that case; it will be written on the indicator’s small window (that appears by clicking on it).
Input Card (A/I or D/I)
ii.
iii iii.
iv.
v.
Address of this indicator is found from data shown on profibus; this address is in the form R1-S3-C1-P, means rack1, slot 3, channel 1. Above bove addr addre ess doe does no not gi give pin numbers. They can be found from the charts which show the pin numbers along with addresses (pinned at panel’s doors). Now, as pin numbers are also known, we can locate pins and using a multi-meter, current or voltage can be checked. Suppose valve is opened 30%: Current should be: (16/100)*30=4.8 4+4.8=8.8mA Voltage should be: (4/100)*30=1.2 1+1.2=2.2Volts
2) To check check validity validity of of any reading reading of indicator on HMI:
a) Through Through Temperature Temperature converters: converters: i. By Re Resistanc ance’s va value (a (at input): check value of resistance by multi-meter, then locate value in resistance-temperature chart, adding the row and column will give temperature in degrees centigrade. ii. By current at input: measure current by multi-meter, subtract 4 from measured value (let say ‘I’)… the maximum and minimum values allowed are given at profibus and also shown at HMI, using these: Actual_value=(I4)x[max_value-min_value]/16
iii iii.
By volt voltag age e at outpu utput: t: now now measure voltage at output (let say V); now the actual value is given by: Actual_value=(V1)x[max_value-min_value]/4 b) throug through h sensing sensing elem element ent:: By thermocouple: resistance of thermocouple is measured, by measuring values of two paths, and subtracting resistance of return path. Again the temperature will be measured by the chart for resistance and temperature. If value shown on indicator and that calculated by above method match, means that DCS is working fine, the problem is in the transmitter itself, if the value shown is unusual.
