Use of Boolean Algebra in Fault Tree Analysis

Manoj Mishra, Associate Vice President, Chemicals Business, SRF Limited, New Delhi, India mmishra@srf.com

21-10-2010

1

The SRF Problem Solving Process1. Select the theme

2. Understand current circumstances 3. Analyse causes 4. Find solutions 5. Implement the solutions 6. Verify results 7. Standardise and institutionalise

8. Reflect

2

1. Select the theme

Theme Increase HF plant stream capacity from an average of 25 TPD to 32 TPD and maintaining the breakdown hours at the current level of 78 hours per month

3

1. Select the theme

St eam ca ac t (TPD) ca ac ty (TPD) 30.0 25.0 20.0 15.0 No -07 De -07 Ju -07 May-07 26.3 23.9 21.9 18.4 Jun-07 Ap -07 19.9 24.4 23.6 23.2

ril-07 to May-08

28.6 26.7

28.6 26.6

29.0

28.7

Strea

Ma -08

O t-07

eb-08

Month

Inference:Average steam capacity is 25 TPD. Stream Capacity = Total production /running hours x 24

May-08

Jan-08

ep-07

Aug-07

Ap -08

4

Breakdow n hours Breakdown hours (Hrs) 350.0 300.0 250.0 200.0 150.0 100.0 50.0 0.0 Apr-07

April-07 to May-08

316.2 168.1 Average:77.7hrs 42.3 Jul-07 Sep-07 Aug-07 57.3 Nov-07 Oct-07 23.1 11.7 Dec-07 Jan-08 22.5 Mar-08 Feb-08

90.2 28.6 Jun-07 May-07

101.3

112.6 45.4 Apr-08 39.0 29.3 May-08

Month

Inference:Average breakdown hours is 78 hours/month.

5

Backgroundnh drous H drofluoric cid is manufac ured b reac ing Fluoro Spar(CaF2) wi h Sulfuric cid (H2S 4) in ro ar Kiln Gas, which is genera ed, is purified b passing hrough pre scrubbing ower and sulfur separa or and hen i is condensed and s ored in crude ank Crude HF is pumped in o dis illa ion column o fur her purif i from S 2, mois ure and Sulfuric cid

Ins alled capaci of his plan was 16 TP ver he ime demand for HF has increased due o increase of R 22 produc ion, HF requiremen in FSP and new genera ion refrigeran plan (R 134a) Wi h he increase in demand for HF i is imperative to increase capacity of HF plant .Debottlenecking exercise was carried out to increase capacity to 35 TPD in two phases. Phase I debottlenecking exercise was carried out in Feb 05 and Phase ll in ct-06. After debottlenecking exercise average stream capacity that could be achieved in the past one year was 25 TPD. AHF requirement per day is around 30 TPD and there is a gap. AHF is purchased from outside to meet the requirement. The quality of AHF, which is procured, is not upto the specification and it impacts the performance of RG plant. Purchase AHF cannot be used for FSP and R-134a plants as S 2 and moisture contents are high. Indigenous AHF cost is very high ,procurement and transportation is a great challenge. Handling AHF in IS , transporting and unloading into our storage tank call for expertise and it involves great safety risk. Procurement of AHF from China and handling AHF in port and subsequent handling and unloading at our storage tank involves even greater challenge and safety risk. It is very critical to stabilize AHF production at 32 TPD so as to meet the requirement of all the plants. It is even bigger challenge to sustain the quality of AHF at higher capacity. PSP silver project was taken to address this challenge and to stabilized HF plant at 32 TPD keeping the breakdown at the same level.

6

7

Breakdowns phenomenon analysis FMEA FTA Gemba

Quality aspects

8

Analysis of breakdown through Phenomenon Master list of all the breakdowns made from April-08 to October-08. Phenomenon of each breakdown identified and stratified. Phenomenon is stratified based on breakdown hours and number of breakdowns Each phenomenon is further stratified based on equipments. Identified of major phenomenon and carried out a FTA on specific equipment. Identify minimum cut set of events for a failure to happen and took counter measures to prevent the event to happen. Develop a excel sheet module of FTA for simulation. FTA is done after carrying out the FMEA. Most of the potential causes identified in FMEA are are getting captured in FTA.

9

Phenomenon based breakdown hoursils e ime e 2 ime2 TOT L B Rem rks T g No e ( ( ( ( ( ( ( ( HR To l 12 62 1 29 28 2 2 13 7 2 1 1 1 0 0 0 3 1 1 ll) ll) ll) ll) ll) ll) ll) ll)

Phenomenon based breakdown numberse ils e im e e2 im 2 e T T LB H O R R m rks e T gN o ( ( ( ( ( ( ( ( ll) ll) ll) ll) ll) ll) ll) ll)

HR

Sum of TOT L B Phenomenon choking Broken High lo d Le k ge Slipp ge ccumul ion Knowledge g p Res ric ion Power f ilure B ck up el i ion Shor circui S e m f ilure Loose Closed Gr nd To l

1

0 8 2 4 3 3 9 8 6 2

Cu o P e o e o o n f h n mn n Peo eo h n mn n T l o ch kin o g H h lo d ig S pg lip e L kg e e B ke ro n P w r f ilu o e re ccu u io ml n K o le g g p nw de R s ric io e n B ck u p e l C v io i n S o circu hr i Se mf ilu re Lo o se C se lo d G n T l r d o

8 90 1 0 1 0 120 11 0 90 80 80 20 10 10 10 10 10 10 10 17 60

10

gh a fe ST1

y uptV

spr

yx qpi

B reakdow hours n

C ulative um percentage

A FD G migB E

32

B ad w Hu re k o n o rs

B reakdow hours n

C umulative percentage

A @9 727 BD 7274 427 7270 727Q 7275 72771 Apr-08 to O CT-08

# %

$ ! %

# 1

1

( '1

Breakdown hours (H

Bre ak dow n hours : 351.17

Pareto Diagram Phenomenon wise (breakdown hours)

Apr-08 to Oct-08

Cumulative percentag

1

1

1

1

1

1

1

1

&

" #

)

)

!

Pre pare d by :

B reakdown hours: 124.1

Pareto Diagram Choking Phenom enon in equipm ents (Breakdown hours)

anoj Kum ar

is hra

1

mim mimg mimj mimn miml mimmA pr-08 to O ct-08

A DC@9 A B@9 C 7727 7727 4231 0210 0 77275 772741

1

B reakdown hours: 31.5

Pareto D iagram H load - phenom igh enon in equipm ents (B reakdow hours) n

1

1

C m la e u u tiv p rc n g e e ta e

jihg

mmim mmin mmig mmil mmijg mmimh

1

A CD@9 G lik

625

1

1

str E qr op him s

A FD@9 u u D

PIH

A DF@9 421

A B@9 F 3231

A DF G 128B E

A CCE F 726B

A @9B

B reakdown hours: 62.28

upu upuq uput upuw upuv upuuApr-08 to O ct-08

`T` `T`Y `T`W `T`X `T`S `T``

Pareto Diagram Broken -Phenom enon in equipm ents (Breakdow hours) n

A pr-08 to O ct-08

P repared by : anoj

1

B reakdown hours: 28.58

ishra

Pareto Diagram Leakage- Phenomenon (Breakdown hours)

Cumulative percentage

1

upu upu upuq1

eyx wp

ff x vp1

dyx e upq1

spq

Breakdown hours

1 1

h a fe YTY

ccb a fe XTW

dcg a fe TV

UTSR

`T` `T` `T`Y `T`R `T`W `T`V `T`X

1

1

1

111 B E 1 11

dcb a

1 1

L

B

B

L

r-08 to Oct-08

Pareto iagram Phenomenon wise Break own numbersBreak ow n Nos: 1

150 100 50 15 0 15 12 11 8 8 2 1 1y

8

1

1

1

1

1

100.0 0.0 80.0 0.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0

S

S

Pre are b : M anoj Kum ar M ishrar -08 to OCT-

S

Break ow n nos: 89

Break

w bers

80.0 35 60.0 30 40.0

10 5 0 1 1 1

40

153

E 304

S

S

S

223

S

S

S

150

200

151

152

300

0

0.0

Pre are b : Ma

jK

ar Mishra

S 204

S 300

E 304

3

2

1

1

1

20.0

li

age - h e

e s

req e c

Bre ak

C la ive erce age

60.0 40.0 20.0E 304

5.00 0.00

4.0

40.0 2.0 2.0 1.0E 304 204 300 151

Break

1.0152

20.0 0.0

S

S

S

S

C

0.0

0.0

Break

10.00

5.0

60.0

80.0

15.00

100.0

8.0

80.0

w

w

bers

bers

100.0

la ive erce age

Break

w

s : 15

15.0

Pare e

iagra i eq i

r -08

Oc - 08

Pare Leakage- Phes : 11

iagra e

r -08

Oc - 08

req e c

w

C la ive erce age

80

~ z } |y{ zwz xywwvz

100.0

Cumulative ercentage

Break own numbers

15

Break

Pare iagra Choki g Phe o me o n in eq i ments

08

req enc

High l a -Phe

Pare iagra e i eq i

r-08

Oc -08

e s

req e c

w

s : 15

12

100.0 80.0 60.0 40.0 20.0 0.0

Cumulative ercentage

Break own numbers

12

Major breakdown phenomenonPHE ME REAKD W UM ERS 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 REAKD W

Chokin

i h load

Slippa e

eaka e reak

Po er failure Accumulation

no led e ap

Restriction

ack up elay

Ca itation Short circuit Steam failure

oose

Closed

H URS 1 3 5 4 2 9 6 7 8 10 11 12 13 14 15 16

13

BREA

W PHE

E

EQUIPME

WISE

PHEME

EQUIPME T SC-151

.

REAKD W H URS 3 1 6 2

FREQUE CY 1 2 3 4

REMARKS Choking is a common phenomenon which takes place in spar feeding system from SC-151 to pre-reactor. High load phenomenon is observed in gypsum handling system only in SC-300. Slippage phenomenon is exclusively seen in E304. ucket elevator chain slippage is a chronicle problem. eakage phenomenon is observed in gland sealing and they happen when the system get pressurized due to accumulation. reak phenomenon is observed in Gypsum handling system.

Chokin

SC-152 SC-153 SC-200

Hi h load

SC-300

1

1

Slippa e

BE 304 SC-200

1 1 2 3 1 2 3

1 1 5 7 1 3 2

eaka e

SC-153 SC-300 E-304

Break

SC-300 SC-204

14

FTA SC-152 CHOKING PHENOMENON SC-151 CHOKING PHENOMENON SC-200 CHOKING PHENOMENON

15

What is a Fault Tree? Fault Tree Analysis (FTA) is a method for discovering the root causes of failures or potential failures. FTA is a top-down approach that helps you understands how to fix or prevent a failure. FTA starts with a top-level event like a service outage. Then one goes down to detailing all the contributing faults and the causes of faults for that failure. You use the resulting FTA diagram to establish countermeasures to eliminate the causes of the outage.16

Fault Tree GatesA gate is used to describe the relationship between the input and output events in a fault tree. Fault trees can have several different kinds of gates. Two kinds of gates are described and shown below: Description AND Gate. The AND gate indicates that the output occurs if and only if all of the input events occur. Picture Input A Truth Table Input B Output

T T F F OR Gate. The OR gate indicates that the output occurs if and only if at least one of the input events occur.

T F T F

T F F F

Input A T T F F

Input B T F T F

Output T T T F

17

Boolean algebra: Boolean algebra can be used in FTA to simplify the complex logical expression to simple expression. The simpler expression can be used to understand the events and the relationship which can cause the top event to happen. It is easy to find solution and implement. The English mathematician George Boole (1815-1864) sought to give symbolic form to Aristotle's system of logic. Boole wrote a treatise on the subject in 1854, titled An Investigation of the Laws of Thought, on Which Are Founded the Mathematical Theories of Logic and Probabilities, which codified several rules of relationship between mathematical quantities limited to one of two possible values: true or false, 1 or 0. His mathematical system became known as Boolean algebra.

18

Boolean arithmetic If we add numbers together:

The first three sums is elementary addition. The last sum, contradicts principles of addition for real numbers, but not for Boolean numbers. In Boolean algebra, there are only two possible values for any quantity and for any arithmetic operation: 1 or 0. Since the sum "1 + 1" certainly isn't 0, it must be 1 by process of elimination.

19

AdditionIt is the same pattern of 1's and 0's as seen in the truth table for an OR gate. In other words, Boolean addition corresponds to the logical function of an "OR" gate, as well as to parallel switch contacts:

20

MultiplicationMultiplication is valid in Boolean algebra, and is the same as in realnumber algebra: anything multiplied by 0 is 0, and anything multiplied by 1 remains unchanged:

21

Boolean multiplication corresponds to the logical function of an "AND" gate, as well as to series switch contacts:

22

23

Based on Boolean Algebra models were developed in excel to test these simplified logical expression for all the three screws in the plant E.g. SC-151, SC-152 and SC-200

24

FTA OF SC-152 CHOKING

25

Solving equation using Boolean

26

Solution implemented in SC-152 to prevent events to happen

27

Design change- SC-153 plug length provide and SC-152 outlet size increasedBEFORE AFTER

From SC-152

From SC-152

SC-153 To re-reactorSC-15 fl i t isc ti s. On kiln kil ss is ti n s ill y ck t SC-152 t Sc-15 . F ts c find fi its condensed nd s c s ets et nd ets deposited t Sc-152 ts t ts sit c outlet. This leads to choking phenomenon. tl t. is l s t c ki .

SC-153 To re-reactor olug l l length provide in SC-15 . On kil pressurisation gas ill t i i kiln ss is ti s not fi its ay ack t SC-152 t t find y ck to through Sc-15 . Spar ill not c t get et and there y choking at Sc-152 outlet ill not t k t t t c ki t c tl t t take l c . place.

S -15210 1 8

i

Avg: .5 :

5

2 1 0 8 Apr-08 y 8 May-08 8 Jun-08 l 8 Jul-08 8 Aug-08

Avg: 1. : 1.2

8 Sep-08

ct 8 Oct-08 8 Nov-08

SC-15 plug length provided.V 15 l l t i .V . Inspection f sleeve removed. I s cti of SCsl 152 st t . V C sheet ell 15 started. s t llow i i 151 tl t. provided in SC-151 outlet.

c 8 Dec-08

28

32

8

No of reakdowns

5

'%Normal

' % &Normal

" ! t I % r % t fr t t t t . tt tt t

Design change- SC-300 flight redesigned

rrent

amps

$#

$#

f r

r

r f rt t r

t

ft

t

t

t

t t r

t

tt .

t

C 300 reakdown trend(Hi h load phenomenon)

1

0

)

(

6

7 6

5

0 1 2 3 4 5 7 8 Avg: 2.8 BEFORE tr t ft tt t rf r t t r ft t rVGP leeve removed. New modified crew inst lled. Screw profile modified. urrent came dow n from 20 amps to amps

Apr-08

M

-08

Jun-08

Jul-08

Aug-08 r

r f

Sep-08 rrent AFTER

Avg: 0.2

0 amps

Oct-08 . t

Nov-08 t r.

Dec-08 f r .

29

4

FMEA detailsBefore FMEA was carried out on 31-July-08. Whole HF plant was covered. Total failure mode identified: 56 nos Total potential causes identified: 140 nos. Total number of points whose RPN number is more then 100 is 43 nos. Total number of points whose severity is 8 - 25 nos. Total number of points whose severity is 9 - 6 nos. All points with RPN number more than 100 is addressed to bring it below 100. All points with severity more than 8 and RPN more than 100 is addressed (14 nos). Three month (April-08 to Jun-08) breakdowns was studied to find out the actual occurrences. Actual occurrence was use in RPN calculation. Existing system for control and detection was taken for evaluation of RPN.

AfterFMEA was carried out on 1-Dec-08. Whole HF plant was covered. Total failure mode identified: 56 nos Total potential caused identified: 140 nos. Total number of points whose RPN number is more then 100 is zero. Total number of points whose severity is 8 - 13 nos. Total number of points whose severity is 9 - 6 nos Total design change: 6 nos Total SOP revised: 8 nos QCPC revised Troubleshooting chart revised Inspection schedule revised.

30

baIHFfrd u

Fa`d efF bhFj

B C B C B C B C B C B C B C B @ XGbt @ e:

Y D p Y D p

fedHFaFcbac Haecba saFaei sbdaaFG hb eac Hfbhe cbs FHfe dae X P P P UTRSR t fd bHFaecaeGfd saFsfFH bI X R S UU U R UQ I z , , , b

C

t u w v p/

Y D p

t u Y D p/

w v pt u Y D p cbv

x1

HGb b bH I b H Iba Gb Y X ` ii F PF g P USR R hb H Hfbhb chd fedHI e sbffF c ` P P P fe rfdfdFaH fedHIPe Ied e HfbhbPch X US RV U U RW RSW b Isb G fedHFHfbhb chd fedHFHfbhdabc b P ` hb H bbaGP fedHIPe bHFabfbw X ` f US hb H HbH bIFG ` b eac fe bdb`Hec` bIFG PFdGbcu X P F RT RS fedHFGdidHFaH fedHFdfFraeba FHFs HFc gfedHFabe gfedHGbPPeG FHFt X RT UW T T U RT URy fedHFhaei hFbH gfedHFaFcbac abHaF`Y X RW RV U RV U UTRSRQ HddHGDIx I , b & , , & , , , b b

w v pt u

@ XHG3/ /

@ Xcb

u

@ XrID

@ X I P

9 @9 9 D XbfI / 1

rz} zr} z}z s uwz} ry rzw zr} } sw| ~uv}| {zwywxw svut srq: : :

lg l ponk f h ik ji g h h

swvw uz u y }zzw| sru } sw| ~uv}| srxr| aFb fedHFaFcbac e bH t i F3 /1 / : : :3

dsFd g Y gt q v ` u

Exec

i

/ PSP a d ai

crease ai i g e

Ac ivi y sc ed le

a s rea reakd w

capaci y r a rs a a evel

PLA VS ACTUAL

r P S P a d Exec

3 W

average TPD rs per

W1 W

W3 W

i

W1 W

e

es

W3 W

TPD

W1 W

W3 W

W1 W

W3 W

W1 W

W3 W

W1 W

W3 W

A

A

A

A

A

A

A

e u

l m l g g fe d

3

:

sbeaccD sbaFcbab b

IH G D PF F E sbffF c P:

/

/

31sfbrbq

Stream capacity monthly basisSt it ( PD) 35.0 30.0 25.0 20.0 15. St 26. v 23. 18. 1 . t 25TP 24.4 21. 28.6 26. 23.6 23.2 28.6 26.6 All luti ns i ple ented 29. 28. it t l i ( PD)

ilt 2TPD 27.2 26.1 27.9

t D

33.7 28.9 27.1 26.6

t

Average stream capacity after implementation of all solutions (26th Nov. 09) is 33.7 TPD in the month of Dec. 09 which exceeds the target of 32 TPD. Average stream capacity has increased from 25 TPD to 28.2 TPD.

32

Stream capacity on daily basisS tre am ca pac ity of HF pl ant a fter Impl ementa ti onDa ta : 26-N ov- 08 to 31- De c- 08 (36 nos)40

215/4 L/R line blockage

BE-304 chain slipped

UC L = 39.76

Ind iv id ual V alue

35

_ X = 33.15

30 L C L = 26.54 251 1

26- Nov -08

3 0-N ov - 08

4- De c -0 8

8- D ec - 08

12- Dec -08 D a te

16 -D ec - 08

20- Dec - 08

24- Dec - 08

28- Dec - 08

1

UC L = 8.118 7.5 M ov in g R an ge

5.0 __ M R = 2.48 5

2.5

0.0 26- Nov -08 3 0-N ov - 08 4- De c -0 8 8- D ec - 08 12- Dec -08 D a te 16 -D ec - 08 20- Dec - 08 24- Dec - 08 28- Dec - 08

LC L=0

Pre pa re d by: M a noj M is hra

Plant capacity was increased to 35 TPD after correcting the VGP. Average stream capacity is 33.15 TPD. Plant was operated at 36 TPD without any problem33

Breakdown hoursBreakdow n hours 350.0 300.0 250.0 200.0 150.0 100.0 50.0 0.0 Apr-07

April-07 to Dec-08

Breakdown hours (Hrs)

316.2 Average:50.3hrs Average:77.7hrs 90.2 28.6 Jul-07 Jun-07 May-07 Aug-07 101.3 42.3 57.3 Oct-07 Sep-07 23.1 11.7 Jan-08 Nov-07 Dec-07 22.5 Feb-08 Mar-08 168.1 112.6 45.4 Apr-08 39.029.3 Jul-08 Jun-08 May-08 59.6 74.8 66.2 40.5 27.7 Nov-08 Dec-08

30.9 52.6 Aug-08 Sep-08 Oct-08

Month

Average breakdown has come down from 77.7 hours to 50.3 hours. Breakdown in the last three months is in decreasing trend.34

Breakdown hours/stream capacityBreakdow n hours/stream capacity 20.000 Breakdown hours (Hrs) 17.18 15.000 10.000 5.000 0.000 May-07 Apr-07 Average:3.386 3.43 1.20 Jul-07 Jun-07 Aug-07 5.09 1.93 2.35 Oct-07 Nov-07 Sep-07 5.88 0.980.50 Jan-08 Dec-07 0.84 Mar-08 Feb-08 3.94 Average:1.819 2.192.86 1.02 Jul-08 Jun-08 Aug-08 1.11 Oct-08 Nov-08 Sep-08 2.291.94

April-07 to Dec-08

1.71 1.34 May-08 Apr-08

1.52 0.82 Dec-08

Month

Breakdown hours per stream capacity has come down from 3.386 to 1.819 and it is at 0.82 for the month of December .35

Breakdown hours 3 months moving averageBreakdow n hours 3 months moving average 200 Breakdown hours (Hrs) 150 100 50 0 Jul-07 Oct-07 Jun-07 Nov-07 Dec-07 May-07 Sep-07 Apr-07 Aug-07 145.0 153.3 148.7 89.2 82.8 67.0 67.6 19.1 Jan-08 48.9 60.2 Mar-08 Apr-08 65.7 37.9 May-08 Target:< 77.7hrs 42.6 54.6 57.3 53.1 40.2 55.1 49.9 Jul-08 Oct-08 Nov-08 Aug-08 Dec-08 Sep-08

April-07 to Dec-08

Month

3 months moving average of breakdown hours is less than 77.7 hours. After PSP , HF plant capacity increased from 25 TPD to 33.7 TPD without increase in breakdown hours.36

Feb-08

Jun-08

Feed acid moisture (Quality)

Before70 60 50 Frequency 40 30 20 10 0 0.0

Histogram of FA moisture-BeforeData: 01/04/08 to 28/07/08 Mean: 8.66 N : 303 St. Dev: 2.739 USL

3.6

7.2

Prepared by : Manoj Mishra

10.8 FA moisture

14.4

18.0

21.6

After90 80 70 Frequency 60 50 40 30 20 10 0 0 3

Histogram of FA moisture-After

USL

Data: 28/07/08 to 19/01/09 Mean: 7.25 N: 451 St. Dev: 1.364

After installation of dip pipe in oleum reactor and mass flow meter in PSA system to measure density , feed acid moisture came down from an average of 8.7% to 7.3%. Feed acid moisture variation also came down significantly from a St. dev of 2.739 to 1.364. 1% reduction in feed acid moisture will reduce 7% energy consumption.37

6

9

Prepared by: Manoj Mishra

12 FA m oisture

15

18

21

6. Verify results

PSA moisture (Quality)i tograUCL

80 70 60 Frequency 50 40 30 20 10 0 0 9

Prepared by : Manoj Mishra

After80 70 60 Frequency 50 40 30 20 10 0 -0.0 8.8

Histogram of PSA moisture afterUCL

17.6

26.4 35.2 44.0 PSA moisture after

Prepared by : Manoj Mi ra

Before

of PSA

oi ture before

Data: 1/4/08 to 28/7/08 Mean:19.6 N:317 St. Dev:7.35

18

27 36 PSA oi ture before

45

54

63

Data: 29/7/08 to 19/1/09 Mean: 16.4 N:455 St. Dev: 2.71

After installation of dip pipe in oleum reactor and mass flow meter in PSA system to measure density , PSA moisture came down from an average of 19.6% to 16.4%. Feed acid moisture variation also came down significantly from a St. dev of 7.35 to 2.71.

52.8

61.6

38

6. Verify results

SO2 in Crude tank (Quality)of SO2 in rude FforDat : 06/04/08 to 07/06/08 N: 8 Mean: 1.01 St. Dev: 0.

istogr

USL 3.0 2.5 Fr quency 2.0 1.5 1.0 0.5 0.0 0.0 Prepared by : Manoj Mis ra

0.5

1.0 SO2 in r ude F

1.5

i togra

of SO2 in rude

USL 9 8 7 Frequency 6 5 4 3 2 1 0 0.00 0.32 0.64 0.96 SO2 in rude 1.28 F_1

Prepared by : Manoj Mishra

After

F-AfterData: 19/06/08 to 18/01/09 0.76 N: 24 Mean: 7.25 St. Dev: 0.091

1.60

2.0

Before

After installation of dip pipe in oleum reactor SO2 in crude tank came down from a level of 1% to 0.76%. As per specification SO2 should be less than 1%. Reduction in SO2 in crude tank will have less load on distillation column and it is easier to get a quality product with SO2 less than 10 ppm.

1.92

39

7. Standardise and institutionaliseSTA DARDISATI

S.

STA DARDISATI

D CUME T

.

1

SC-151 out bellow inspection added in check list

HF-C -02

2

SC-152 outlet cleaning to be done during any plant stoppage

HF-C -02

3

S P for stopping feed to pre-reactor to avoid choking.

HF-WI-01

4

Pre-reactor feed acid blockage incorporated in troubleshooting chart.

HF-WI-01

5

Mix acid flow calculation formula changed.

SCADA

6

Density reading incorporated in control room log sheet.

HF-F-04

7

leum addition procedure changed to control feed acid moisture around 7 .

HF QCPC 01

8

Inspection schedule changed.

HF-T-03

9

Feed acid and PSA moisture troubleshooting.

HF-WI-01

10

QCPC revised to control PSA moisture.

HF QCPC 01

40

7. Standardise and institutionalise

FIELD CHECK LIST

41

7. Standardise and institutionalise

CONTROL ROOM LOG SHEET

42

7. Standardise and institutionalise

INSPECTION SCHEDULE

43

8. Reflect

REFLECTION FTA tool was used for the first time in CB and it was found to be very useful in bring significant improvement in the system. It makes the system robust. From FMEA many points immersed out having high severity but low RPN numbers. They can be studied further to improve the system. Study to be made to find out the limitation of HF plant beyond 36 TPD. Installation of Pre-heater in feed line to distillation column to be carried out. FTA & FMEA can be implemented in other plants to bring significant improvement. Simulation module of FTA in Excel can be used as training tool. PSP silver can bring dramatic change in the System and can improve Q C D S M by many folds. Boolean Algebra can be used effectively in solving complex equation in FTA.

44

BENEFITS HF plant is stabilized at 36 TPD. This has helped to meet the HF requirements of RG, HFC and FSP plat at the same time at full capacity. HF Stock has increased to a maximum level i.e. 190 MT. This excess stock will help to carry out maintenance jobs if required without affecting RG,HFC&FSP capacity. AHF quality has improved significantly. S02 has come down below 10 ppm which helped to remove Smell problem in R-134 a. Feed acid moisture has comedown from a level of 9% to 7%. This has improved the process stability. This has reduced the corrosion of kiln. Lot of energy saving. 1% moisture reduction will reduce 7% energy consumption. Breakdown has comedown significantly. This will improve yields, steam and power norms. HF purchase from outside has stopped completely. This has saved about 860 lakhs. He ISO unloading was stopped completely. This has improved the safely significantly. People capability has improved. Morale his gone up. Environment his improved. No kiln pressurization. Choking phenomenon in spar feed section reduced significantly. Leaned the importance of FTA. Its a tool to bring improvement in system. Productively has improved by 30%. It has changed the mind set of people. They have become more positive. Team wonk can brings a see charge. 45

46