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MEP201 Mechanical Engineering Drawing 1 st semester 2005-2006 S R Kale Lecture Control Diagrams.

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Presentation on theme: "MEP201 Mechanical Engineering Drawing 1 st semester 2005-2006 S R Kale Lecture Control Diagrams."— Presentation transcript:

1 MEP201 Mechanical Engineering Drawing 1 st semester S R Kale Lecture Control Diagrams

2 Controls (2005)2 Control Drawings - Background Pre-requisites Schematic, P&I drawings Control philosophy About the plant From equipment/package manufacturers Team: All designers (EE, ME, ChE, I&C, …) Output Wiring of control cables Governing logic for control software development Interdisciplinary: Chem, EE, Aero, BioMed,..

3 Controls (2005)3 Control Drawings - Types Sequence Control Sequence Control drawings Interlock Drawings Block Interlock Diagrams ON/OFF : If … then … Modulating Control Control Logic Diagram (feedback, modulating type) Sense feedback signal, Set point  Controller (PID)  Output signal  Device  Feedback signal

4 Controls (2005)4 Sequence Control Drawings / Block Interlock Diagram / Interlock Diagrams

5 Controls (2005)5 Sequence Control Drawings (Block) Interlock Diagram Schematic Control philosophy Incorporate instruments in schematic to generate P & I drawing Interlock diagram

6 Controls (2005)6 Sequence Control Diagram – Basics Logic from process designer & eqpt. manufacturer: What are the safe operating limits? What action to take if safe limits are exceeded? Logic or its execution – not unique Within the limits, automatic control system operates. Sequence control supercedes automatic control. ON-OFF control Signal processing – via relays and/or software

7 Controls (2005)7 Sequence Control Diagram – Objectives  Operate equipment and system within safe limits.  Auto start / stop of equipment WHY? Avoid damage to equipment (expensive repairs) Initiate automatic protective action in case of malfunction. Avoid plant shut down by switching to stand-by device. Safely shut-down system even if all safety back- ups don’t work. Safe start-up and shut-down of system.

8 Controls (2005)8 Interlock diagram - Elements CONDITIONLOGICACTION PS1 L.O. SUPPY PR. LL1 LAMP ON Parameter Value I.D. Device Action Connect with lines

9 Controls (2005)9 Logic Gates AND OR NOT TIME DELAY On delay/Off delay Period ‘T” &OR

10 Controls (2005)10 Bearing Lube Oil Schematic LUBE OIL TANK BEARING

11 Controls (2005)11 Bearing Lube Oil System Requirements (order by importance):  Oil pressure at inlet Indication on gauge Generate alarm if low Generate signal to trip turbine if low low  Oil temperature at inlet Indication on gauge generate alarm if high  Oil flow rate Measure (?) expensive – not really needed Visual indication of flow  Oil level in tank Indication Alarm if low  Power supply is available for pump Indication Voltage and current drawn

12 Controls (2005)12 Bearing Lube Oil I & C Diagram LUBE OIL TANK BEARING LI1 SG L1 PS1 L L3 TS1 H PI1TI1 LS1 L4 L L2 PS2 LL RLY1

13 Controls (2005)13 Interlock: Bearing L.O. system CONDITIONLOGICACTION PS1 L.O. SUPPY PR. LL1 L.O. PR. L -LAMP ONPS2 L.O. SUPPY PR. LLRLY1 FRANCIS TURBINE TRIPL2 L.O. PR. LL -LAMP ONTS1 L.O. SUPPLY TEMP. HL3 L.O. TEMP. H -LAMP ONLS1 L.O. TANK LEVEL LL4 L.O. T. LVL L -LAMP ON

14 Controls (2005)14 Domestic water booster system Booster pump, ground tank, overhead tank Pump to start if Overhead tank is empty AND Ground tank has enough water Pump to stop if Overhead tank is full OR Ground tank is empty Indications to operator (panel lights or PLC display): Overhead tank - Full, Empty. Ground tank – Full, Empty. No power supply. Pump status – Running, Stopped.

15 Controls (2005)15 Domestic Booster Schematic LS1 H LS2 L LS3 L LS4 H GROUND LEVEL TANK GROUND LEVEL TANK GROUND LEVEL TANK OVERHEAD TANK BOOSTER PUMP 4 Signals – One motor. RELAYS

16 Controls (2005)16 Interlock: Domestic water system CONDITIONLOGICACTION LS1 G/L TANK LEVEL HLS3 O/H TANK LEVEL LSW1 BOOSTER PUMP ONSW1 BOOSTER PUMP OFFLS2 G/L TANK LEVEL LLS4 O/H TANK LEVEL H

17 Controls (2005)17 Domestic water system - Alternate Domestic water system LS4 OVERHEAD TANK LEVEL HIGH HLS2 GROUND TANK LEVEL HIGH HLS3 OVERHEAD TANK LEVEL LOW LLS1 GROUND TANK LEVEL LOW L START PUMP STOP PUMP &

18 Controls (2005)18 Diesel engine of DG set/Loco Diesel engine On engine start signal (key) energize starter motor if Water temperature is OK AND Fuel tank is not empty After starting if Lube oil pressure is low after 3 seconds, then SHUT-OFF (TIME DELAY) Engine is running, then SHUT-OFF if Lube oil pressure falls to 3 bar(g) OR Jacket water temperature rises to 105 o C OR Speed increases to 1545 RPM OR Speed decreases to 1425 RPM.

19 Controls (2005)19 Air conditioner (window/split) After power switch is turned ON Wait 2 minutes then start compressor (TIME DELAY) Switch-off running compressor if Cool space temperature falls to  o C Switch-on compressor if Cool space temperature rises to  o C AND 2 minutes have elapsed since compressor was shut-off (TIME DELAY) SET POINT OFFSET for cut out/cut in

20 Controls (2005)20 Airplanes (ref.: aeroPeru603/Air Crash Investigation) Auto-pilot gets engaged if 2 out of 3 readings of altitude/speed are same. (TWO OUT OF THREE LOGIC) IF NOT, fly the plane manually

21 Controls (2005)21 Francis turbine Francis Turbine (Badagrah Nala) 2 x 100 % Lube oil pumps, give START signal to stand-by pump if Turbine is running AND L.O. level in tank in NOT low AND Standby pump is available AND (Other pump has been switched OFF OR Lube oil header pressure is LOW)

22 Controls (2005)22 Set point values Geyser thermostat * switch is in the power line itself. Set-point is say 55 o C  At water temp. 55 o C, power is switched off.  At what temp. is it switched on? If at 55 o C then ??? Confusion! Therefore: one switch for one sensing only, i.e. one TS for HIGH and another TS for LOW. And, offset cut-out and cut-in HIGH set at 55 o C +  T, and LOW set at 55 o C -  T.

23 Controls (2005)23 Sequence Control Diagram – Examples BFP of CCPP : start and trip permissive Standby BFP of CCPP : start permissive Representation on P&I diagram Typical interlock diagram - CCPP

24 Controls (2005)24 Sequence Control – Haywire Equipment damage Equipment/device does not start or shut-off

25 Controls (2005)25 Sequence control - Summary Outcome: Details of signal sources Signal connections Control logic for programming and hardware Merge with layouts to generate control cable routing, its length and size (BoM) Modify piping drawings to accommodate instruments/switches

26 Controls (2005)26 Modulating Control

27 Controls (2005)27 Automatic Control System Automatic modulating control Dynamic real-time control Sense signals (parameters)  Generate control signal  Adjust control device Feedback control loops Every machine has its control system  P-based, PLC-based, DAS Expensive, need maintenance, critical.

28 Controls (2005)28 Automatic controls- Example Control loop #1 (CCPP steam system) :Flow control Control loop #2 (CCPP steam system) : Pressure & temperature controlControl loop #2 (CCPP steam system) : Pressure & temperature control

29 Controls (2005)29 Automatic controls - Elements Name and symbol Controller output not taken as input for sensing resulting action, e.g. signal produced for adjusting valve stem. As a result of this action what is the position of the valve stem?  Sense valve stem position with a position sensor.

30 Controls (2005)30 Automatic controls More in course MEL312 Control Theory & Applications


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