SH5204 – Safety Engineering Project on Process Plant of a FPSO

8th April 2014Group 09

Stuthi Raghavan A0108001EDinesh Shanmugam A0107905H

Ng Chun Wee A0116972YShaukat Ali A0096176U

Contents

1. Introduction 2. Process unit under study 3. Safety Studies4. Reliability Studies 5. Recommendations 6. Conclusions

Introduction

• Process unit part of Floating Production Storage and Offloading unit (FPSO) operating on Bualuang field in Gulf of Thailand.

FPSO General Layout of Process Modules

Process Flow Diagram

2 Stage Separation Train System to obtain Crude within acceptable BS&W

1

2

3

4

5

6

3a

3b

1st Stage Separator

Bafflers – Structured Packing Bridles for Level Transmitters

Jet wash pipesFor Sand Jetting Crude Oil Outlet

With Vortex Breaker

Produced Water OutletWith Vortex Breaker

Adjustable Oil Spillover Weir Plate

Inlet Diverter Device

Vane Pack Demister1st Stage Separator InternalsGas Outlet To HP Flare

1st Stage Separator Controls Systems Overview

• PCS – Allen Bradley RS Logix• LTs, PTs, FTs• PCVs, FCVs, LCVs, BDV• SDVs, PSVs

Safety Studies - Outline

• HAZOP• Fault Tree Analysis (FTA)• Event Tree Analysis (ETA)

Safety Studies - HAZOP

• Why ?• Analyze the system• Identify shortcoming in Design and Operation & Maintenance• How to improve the System –> Inherently Safer Design• Measure the effectiveness/severity

• Existing Design/Safeguards• After Recommendations

Safety Studies - HAZOP

• How ?• Node Selection in P&ID and PFD• Choose Deviations/Scenarios• Causes for Deviations• Consequences• Existing Safeguards• Recommendations• Severity Rankings

OperationMaintenance

CorrosionFeed Composition Changes

Utility Systems

Other Deviations

FlowPressure

TemperatureLevel

Low & High

Flow

No & Reverse

Safety Studies - HAZOP

• Applications? • Recommendations

• Safety issues• Design/Process issues

• Measure Severity of Risk• Evaluate consequences

• Engineer an Inherently Safer Design• Prepare Fault Tree

Fau

lt T

ree A

naly

sis

Design Pressure: 17.5 bargPSV101A/B: 16.9 bargPAHH102: 16.55 bargPAH101: 13.8 bargOperating Pressure: 6.9 – 10.3 barg

Protection layers:1. Pressure relief2. ESD Shutdown3. Pressure alarm for

operator’s action

Safety Studies – FTAMCS derivation from fault tree:• Basic events: {B,I, A,E,G,H,F,C,D,K,O,J,L,N,M)• Release of HC ‘T’= {{(A+G+H+E+F+C). I.(K+D+O+J+L)} . B}+N+M = {B.I.(AK+AD+AL+AO+AJ+GK+GD+GL+GO+GJ+HK+HD+HO+HJ+HL

+EK+ED+EL+EJ+EO+FK+FD+FO+FL+FJ+CK+CD+CL+CO+CJ)} +N+ M• MCS of ‘T’ = {IBAK, IBAD, IBAL, IBAO, IBAJ, IBGK, IBGD, IBGL, IBGO, IBGJ, IBHK,

IBHD, IBHO, IBHJ, IBHL, IBEK, IBED, IBEL, IBEJ, IBEO, IBFK, IBFD, IBFO, IBFL, IBFJ, IBCK, IBCD, IBCL, IBCO, IBCJ, N,M}

• Uses: -Further used in deriving Failure/Unreliability of system ’Q’-Birnbaum, structural & criticality importance of each component-Assess RRW and RAW -Conclude how reliability of system can be increased

Safety Studies – FTA Q derivation

Qs=(qB.qI.qX.qY)+ (qN+qM-qNqM)

= (qBqIqXqY +qN+qM-qNqM- qBqIqXqYqN-qBqIqXqYqM+ qBqIqXqYqNqM) where:

X=A+E+G+H+F+C; Y=K+O+D+L+J;

qX= q(A+E+G)+ q(H+F+C) -{q(A+E+G). q(H+F+C)};

qY= q(K+D+O) + q(J+L) -{q(K+D+O).q(J+L) };

q(A+E+G) = qA +qE- qA.qE+qG-qAqG-qEqG+ qAqEqG;

q(H+F+C)= qH+qF-qHqF+qC-qHqC-qFqC+qHqCqF

Event Tree Analysis

Gas detector

Decrease in:1. Severity of Fire 2. Damage to eq.

Protection layers:1. Fire detection

system2. Active fire Fighting

system3. Passive fire

protection

Safety Studies – Layers of Protection

PAH

ESD

PSV

PFP

13.8 barg 16.55 barg 16.9 barg

17.5 bargBPCS

10.3 barg Vessel design

Release of HC

AFP

FDS

Fire detectedAutomatic

SIFs

8 Protection layers

Above 16.9 barg

Below 16.9 barg

Safety Studies – Key SHE recommendations• Pressure alarm at 13.8 barg for operator to be automated.• Monitoring and redundant unit for the N2 supply system need to be added• Test separator should be installed upstream for monitoring composition of

well fluid • NRVs are to provided on the individual line to flare header to prevent

flashback• Addition of isolation valves for V-101 (inlet and outlet lines) for quick restart

and maintenance of the system• Consider operating both PSVs online • Also consider adding a spare PSV while maintaining either one• Gas detectors to be added as an extra Layer of protection

Safety Studies – Key SHE recommendations• Siphon breakers should be provided for V-101• Pumps should trip on detecting flow fluctuations• Ensure Corrosion prevention using UT gauging along with frequent NDT

for piping• Ensure Planned flushing and steam blowing of equipment during

shutdown• Consider adding one more demister pad nozzle on V-101• Ensure Flow meters, temperature and pressure transmitters are installed

in the locations specified in HAZOP

Reliability Studies

Fault Tree

A E G F H C

I

K D L O J

B

N M

Reliability Block Diagram

T = N + B.(K+D+L+O+J).I.(A+E+G+F+H+C) + M

PAH

ESD

PSV

Reliability Studies

i Description p q Q IBi IB

φi Icri RAW RRW

O Control System 0.999 0.001

0.0002316

0.00012 0.004 0.001 1.520 0.998J BDV104 fails 0.959 0.041 0.00013 0.004 0.022 1.520 1.020D IA supply 0.950 0.050 0.00013 0.004 0.027 1.520 1.025K PT102 fails 0.955 0.045 0.00013 0.004 0.025 1.520 1.025L Stuck open ESDV 0.571 0.429 0.00021 0.004 0.391 1.520 1.643A Accumulation of Sediments 0.997 0.003 0.00094 0.002 0.013 5.039 1.011E NRV fail (V-101 to V-201 line) 0.997 0.003 0.00094 0.002 0.013 5.039 1.011F NRV flare header fail 0.997 0.003 0.00094 0.002 0.013 5.039 1.011G SDV 102 Mech failure 0.969 0.031 0.00096 0.002 0.129 5.039 1.145H SDV 103 Mech failure 0.969 0.031 0.00096 0.002 0.129 5.039 1.145C N2 supply failure 0.950 0.050 0.00098 0.002 0.212 5.039 1.266I Operator error 0.900 0.100 0.00123 0.119 0.532 5.786 2.125B PSV 101A/B 0.979 0.021 0.00584 0.119 0.530 25.691 2.125M Leak from flanges 1.000 0.000 0.99978 0.381 0.038 4317.789 1.039N Corrosion 1.000 0.000 0.99987 0.381 0.432 4317.789 1.755

Failure probability, q = 1-e-μt

Failure frequency per year, μ is derived from various sources e.g. OREDA, Lees’ Loss Prevention in Process Industries

Birnbaum Reliability Importance, IBi

Birnbaum Structural Importance, IBφi

Criticality Importance, Icri

Risk Achievement Worth, RAW

Risk Reduction Worth, RRW

High

Low

Reliability StudiesRAW

Low High

RRW

Low

Not a candidate for both reliability growth and PM maintenance

Candidate for PM maintenance

High

Candidate for reliability growth Candidate for both reliability growth and PM maintenance

M

B NI L

JODK

A E FG H

C

i DescriptionA Accumulation of SedimentsB PSV 101A/BC N2 supply failureD IA supply E NRV fail (V-101 to V-201 line)F NRV flare header fail G SDV 102 Mech failureH SDV 103 Mech failureI Operator errorJ BDV104 failsK PT102 failsL Stuck open ESDVM Leak from flangesN CorrosionO Control System

Key Reliability Study Findings

• PSV 101A/B needs undergo Preventive Maintenance• Corrosion mitigation, periodic UT testing• Currently Operator error contributes to high failure probability,

recommended to be automated by triggering PSD• Replace ESDV for it to be capable of being partially stroked• Flange leaks can be checked visually for damage and online corrosion

monitoring should be done• BDV104 has low RRW and RAW, but considering the fact that it is not

always under operation, we suggest preventive maintenance• IA supply - Corrective Maintenance

Conclusions

• A safety and reliability studies had been carried out for the process node onboard an FPSO

• Preventive maintenance is usually preferred for all the components to work effectively in the system

• However, this could lead to ineffective cost and time management • Hence, Reliability Importance, RRW, and RAW can help to prioritize

the effective utilization of critical components and resources

Questions?Thank you