Section 04 Shutdowns & Interlocks CAPC

8/17/2019 Section 04 Shutdowns & Interlocks CAPC

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BASIC SHUTDOWN SYSTEMS & INTERLOCKS

PT Chandra Asri Petrochemical Company

Ciwandan, Cilegon, Indonesia

July 2007CAUTIONARY NOTICE

This document contains information which is proprietary to Kellogg Brown & Root, Inc. This information is to be held in confidence. No disclosure,

reproduction or other use of this document is to be made without the prior written consent of the Kellogg Brown & Root, Inc.


2/31

CONFIDENTIAL

Shutdown System / Permissives

• Low Fire Trip

• Complete Trip

• Permissives for Hydrocarbon Cracking

• Permissives for Decoking

• Permissives for Burner Lightoff

• Burner Lightoff Procedure

• Permissives for MOV Switching


3/31

CONFIDENTIAL

Furnace Shutdown Systems

• Low Fire Trip – Not a complete shutdown

– Furnace remains hot (so-called hot standby condition)

– Rarely results in mechanical work

• Complete trip

– No firing – Furnace cold

– May require mechanical work if furnace has been cracking more

than ~10 days


4/31

CONFIDENTIAL


LOW FIRE TRIP ACTIONS – 6376-IC3522-01 Sheet 1 of 9

– Isolates HC Feed

– Trips Main Burners Leaving Decoke Burners On – Resets Fuel Gas Control Valve Set Point

– Dilution Steam Flow Set Same As SAD

– Purge Steam To FPHT I Coil Initiated

– Firing Rate Reduced To LFT Setpoint – Isolates Decoke Air (If In SAD Prior To LFT)

– Isolates Decoke Water (If In SWD Prior To LFT)

– Isolates Cracked Gas Analyzer

– Disables Total Feed Controllers

– Isolates DMDS


5/31

CONFIDENTIAL

Low Fire Trip

• Avoids a complete trip!

• Furnace sent to “safe condition” (similar to decoke)

• Thermal swing reduced

– Furnace remains hot (no shut down)

– Possibility of mechanical work reduced

• Hydrocarbon operation resumed after decoking


6/31

CONFIDENTIAL


COMPLETE TRIP ACTIONS – 6376-IC3522-01 Sheet 1 of 9

– Close Decoke Burners – Pilots Remain On

– Open Main Burner XV-10850 – Isolates HC Feed

– Isolates Decoke Air (If In SAD Prior To CT)

– Isolates Decoke Water (If In SWD Prior To CT)

– Dilution Steam Flow Reset To Complete Trip Rate – Isolate Quench Oil – Purge Quench Oil Nozzles

– Isolates Cracked Gas Analyzer

– Isolates DMDS

– Pilots Typically Stay Lit – Exception If CT Initiated By Operator or High-High-High Furnace Arch Pressure


7/31

CONFIDENTIAL

Complete Trip

Furnace is shut down

• Furnace is cold (pilots typically firing)

• Mechanical work probably required.


8/31

CONFIDENTIAL

Low Fire Trip

• Initiators for Low Fire Trip:

– Low-Low hydrocarbon feed pass flow (any pass)

– Low-Low dilution steam pass flow (any pass)

– Low-Low SHP steam drum level

– High-High SHP steam temperature

– High-High arch pressure (Hot Furnace Only)

– High-High transfer line temperature (either side of furnace)

– Manual trip


9/31

CONFIDENTIAL

Low HC Feed Flow Trip

LOW HC FEED

FLOW

LOW

FIRE

TRIP

IF IN SWD, ADD HC

FEED, DS, DECOKE

STEAM & DECOKEBFW FLOW RATES


10/31

CONFIDENTIAL

Low Dilution Steam Flow Trip

LOW DILUTION

STEAM FLOW

LOW

FIRE

TRIP

IF IN SAD,

ADD DIL STEAM

& PURGE STEAMFLOW RATES

IF FURNACE

COLD, DISABLE

IF IN SWD,

RESET


11/31

CONFIDENTIAL

Low Steam Drum Level Trip

LOW STEAM

DRUM LEVEL

LOW

FIRE

TRIP

60 SEC

DELAY

COMPLETE

FURNACE

TRIP

REQUIRED TO PROTECT PQE’S


12/31

CONFIDENTIAL

High SHP Steam Temperature Trip

HIGH-HIGH

STEAM

TEMP

LOW

FIRE

TRIP

8 MIN

DELAY

COMPLETE

FURNACE

TRIP

HIGH STEAM

TEMP


13/31

CONFIDENTIAL

High Arch Pressure Trip

COMPLETE

FURNACE

TRIP

30 SECDELAY

FIREBOX

COLD?

YES

30 SEC

DELAY

TRIP OPENID FAN

DAMPER

LOWFIRE

TRIP

30 SECDELAY

HIGH ARCH

PRESSURE

(PT’s)

HIGH ARCH

PRESSURE(TT’s)

ARCH

PRESSURE

HIGH?

(TT’S)

NO


14/31

CONFIDENTIAL

High Transfer Line Temperature Trip

HIGH TRANSFERLINE TEMPERATURE

(EITHER SIDE)

COMPLETEFURNACE

TRIP

5 MIN.

DELAY

LOWFIRE

TRIP


15/31

CONFIDENTIAL

Manual Low Fire Trip

LOW

FIRE

TRIP

MANUAL LOWFIRE TRIP

CONTROL ROOM

MANUAL LOW

FIRE TRIP

BURNER PANEL


16/31

CONFIDENTIAL

Checks After Low Fire Trip

LOW TOTAL

DILUTION

STEAM FLOW

COMPLETEFURNACE

TRIP

LOW

FIRETRIP

HIGH FLUE

GAS TEMP

5 MIN

DELAY

30 SEC

DELAY


17/31

CONFIDENTIAL

Complete Trip

Initiators for Complete Trip:

• High-High / Low-Low fuel gas pressure

• High-High-High SHP steam temperature

• High-High-High Firebox Pressure

• ID Fan Failure

• Manual trip


18/31

CONFIDENTIAL

Fuel Gas Complete Trips

COMPLETE

FURNACETRIP

LOW FUELGAS PRESSURE

HIGH FUELGAS PRESSURE

MANUAL

COMPLETE TRIPCONTROL ROOM

MANUAL

COMPLETE TRIP

BURNER PANEL

HIGH ARCH

PRESSURE (COLD)HIGH-HIGH-HIGH

ARCH PRESSURE


19/31

CONFIDENTIAL

Pilot Trips

PILOT

TRIP

LOW PILOTGAS PRESSURE

HIGH PILOT

GAS PRESSURE

MANUAL

COMPLETE TRIP

CONTROL ROOM

MANUAL

COMPLETE TRIP

BURNER PANEL

HIGH-HIGH-HIGH ARCH PRESSURE


20/31

CONFIDENTIAL

Interlocks for MOV Switching

Permissives for MOV Switching• Analyzer sample valves closed

• HC feed isolated

• Quench oil isolated

• Decoke air isolated

• In “Decoke” mode

• DMDS isolated

• Steam flow rates above minimum (Administrative)

Permissive failure after decoking commences causes alarm


21/31

CONFIDENTIAL

MOV Switching - From Transfer Line to Decoke Line

• Control room operator activates local panel

• Field operator begins transfer line valve (TLV) closure

– High Transfer line pressure alarm active

• Operator stops TLV movement based on furnace pressure and/or TLV ∆P

• Field operator begins opening of decoke line valve (DLV).

– Low Transfer line pressure alarm active

• Operator stops DLV movement based on transfer line pressure and/or TLV ∆P

• If Transfer Line Low DP or High Pressure Occurs valve movement stopsuntil corrected

• Close TLV - Low TLV ∆P alarm disabled

• Open DLV - High transfer line pressure alarm disabled.

MOV Switching Sequence From Decoke Line to Transfer Line


22/31

CONFIDENTIAL

MOV Switching Sequence - From Decoke Line to Transfer Line

• Control room operator activates local panel

• Field operator begins DLV closure

– High Transfer line pressure alarm active

• Operator stops DLV movement based on transfer line pressureand/or TLV ∆P

• Field operator begins opening of TLV – Low Transfer line pressure alarm active

• If Transfer Line Low DP or High Pressure Occurs valve movement stops

until corrected

• Close DLV - Low TLV ∆P alarm disabled

• Open TLV - High transfer line pressure alarm disabled.


23/31

CONFIDENTIAL

Interlocks for Hydrocarbon Service

• Decoke line MOV 100% closed

• Decoke air isolated

• Transfer line MOV 100% open

• Decoke/Cracking Mode Switch in Cracking position


Permissive failure after cracking commences causes an alarm

I l k O D k Ai (SAD)


24/31

CONFIDENTIAL

Interlocks to Open Decoke Air (SAD)

• Transfer line MOV 100% closed

• Decoke line MOV 100% open

• HC feed isolated

• Quench oil isolated

• Decoke/Cracking Mode Switch in Decoke position

• Chromatograph isolated


Permissive failure after decoking commences causes an alarm


25/31

CONFIDENTIAL

Burner Lightoff System

• Checks permissives

• Purges firebox

• Checks for burner fuel gas cock closure

• Includes temporary bypasses for:

– High fuel gas pressure

– Low fuel gas pressure

• Firebox purge & fuel gas cock closure tests run in

parallel to save time

• Includes bypass switch for pilots usage

I t l k / P d f B Li ht ff


26/31

CONFIDENTIAL

Interlocks / Procedure for Burner Light-off

Burner Purge Panels:

• ESD Console Panel

• Outside Burner Panel• DCS Switches, Lights

F l G C t l


27/31

CONFIDENTIAL

Fuel Gas Control

QIC

AI

ATM @ SAFE

LOCATION

Burner Header

PIC

FO

Burner Light Off Sequences


28/31

CONFIDENTIAL

Burner Light-Off Sequences

There are four separate burner light-off sequences

1. Pilot, Main, and Decoke Burner Light-Off

1. Furnace is cold or Complete Trip with Pilot Trip

2. Pilots lit first then Main and Decoke burners can be tested and lit

2. Main & Decoke Burner Light-Off

1. Furnace has had Complete Trip but Pilots remain lit

2. Main and Decoke burners tested together and enabled

3. Main Burner Light-Off 1. Furnace has had Low Fire Trip but Pilots and Decoke burners remain lit

2. Main burners are tested and enabled

4. Main & Decoke Burner Light-Off – Pilots Bypassed

1. Furnace has had Complete Trip or is Cold

2. Main and Decoke burners tested together and enabled

All three sequences follow a similar pattern

Burner Light Off Sequence Firebox Purge


29/31

CONFIDENTIAL

Burner Light-Off Sequence – Firebox Purge

• If furnace is hot and permissives satisfied, firebox purge

starts automatically.

• If furnace is cold, operator must initiate firebox purge.

• Must satisfy all permissives for 15 minutes.

• Purge complete light illuminates.

Burner Light Off Sequence Cock Closure Test


30/31

CONFIDENTIAL

Burner Light-Off Sequence – Cock Closure Test

• Field operator closes all burner fuel gas cocks

• Check that burner fuel gas header pressure is low

• Operator starts 5 minute timer: – Fuel gas commissioned to spring loaded valve

– Open isolation valve upstream of spring loaded valve

– Operator holds spring loaded valve open

– Fuel gas flows through RO into burner fuel gas header

– Fuel gas header pressure rises to set point?

– Close isolation valve upstream of spring loaded valve

Burner Light Off Sequence Light Burners


31/31

CONFIDENTIAL

Burner Light-Off Sequence – Light Burners

• Firebox purge & cock closure tests successful• 5 minute timer starts automatically

– Low & High fuel gas pressure trips bypassed for 5 minutes

– Fuel gas commissioned to fuel gas header

– Operator adjusts fuel gas vent to stabilize pressure between Low

& High fuel gas pressure trip set points (PCV-1082

recommended setpoint ~ 0.4 kg/cm2g)

– Light burners as required

– Close vent valve when sufficient burners are lit to allow CV to

control

Section 04 Shutdowns & Interlocks CAPC

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