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MEP201

Pump to start if. Overhead tank is empty AND Ground tank has enough water. Pump to stop if ... 2 x 100 % Lube oil pumps, give START signal to stand-by pump if ...

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MEP201

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    Slide 1:MEP201 Mechanical Engineering Drawing 1st semester 2005-2006

    S R Kale Lecture Control Diagrams

    Slide 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, ..

    Slide 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

    Slide 4:Sequence Control Drawings / Block Interlock Diagram / Interlock Diagrams

    Slide 5:Sequence Control Drawings (Block) Interlock Diagram

    Schematic Control philosophy Incorporate instruments in schematic to generate P & I drawing Interlock diagram

    Slide 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

    Slide 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 dont work. Safe start-up and shut-down of system.

    Slide 8:Interlock diagram - Elements

    Parameter Value I.D. I.D. Device Action Connect with lines

    Slide 9:Logic Gates

    AND OR NOT TIME DELAY On delay/Off delay Period T

    Slide 10:Bearing Lube Oil Schematic

    LUBE OIL TANK BEARING

    Slide 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

    Slide 12:Bearing Lube Oil I & C Diagram

    SG

    Slide 13:Interlock: Bearing L.O. system

    Slide 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.

    Slide 15:Domestic Booster Schematic

    4 Signals One motor. RELAYS

    Slide 16:Interlock: Domestic water system

    Slide 17:Domestic water system - Alternate

    Domestic water system START PUMP STOP PUMP

    Slide 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 oC OR Speed increases to 1545 RPM OR Speed decreases to 1425 RPM.

    Slide 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 oC Switch-on compressor if Cool space temperature rises to oC AND 2 minutes have elapsed since compressor was shut-off (TIME DELAY) SET POINT OFFSET for cut out/cut in

    Slide 20:Airplanes

    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

    Slide 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)

    Slide 22:Set point values

    Geyser thermostat * switch is in the power line itself. Set-point is say 55 oC At water temp. 55 oC, power is switched off. At what temp. is it switched on? If at 55 oC 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 oC + ?T, and LOW set at 55 oC - ?T.

    Slide 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

    Slide 24:Sequence Control Haywire

    Equipment damage Equipment/device does not start or shut-off

    Slide 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

    Slide 26:Modulating Control

    Slide 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.

    Slide 28:Automatic controls- Example

    Control loop #1 (CCPP steam system) :Flow control Control loop #2 (CCPP steam system) : Pressure & temperature control

    Slide 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.

    Slide 30:Automatic controls

    More in course MEL312 Control Theory & Applications

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