Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FMECA of Subsea Control Module
The Field Subsea Control System Architecture
Subsea Control System (SCS) is made up of the electrical
power unit (EPU), hydraulic power unit (HPU) and the master
control station (MCS). An uninterrupted power supply (UPS)
provides and maintains power for the complete SCS units in
redundant configurations (see Fig. 1.0).
Each UPS unit is equipped with inverter, rectifier
and a standard sized battery bank. The SCS
provides a comprehensive power, control and
monitoring starting from the surface interface to
all the subsea installed equipment. Acquired
data is displayed on the topside HMI, allowing
for proper monitoring of the entire system. The
MCS, located topside had a dual redundant
operating system operating. The system is
equipped with dual redundant programmable
logic controllers to allow for the monitoring and
control of the Electrical Power Unit (EPU)
functions including the Emergency System
Distribution (ESD).
The HPU provides the hydraulic supply to the
field routed through a topside umbilical
termination unit (TUTU) to a dynamic umbilical.
The control fluid from the HPU is maintained at a
cleanliness level of SAE AS 4059C Class 6B-F
or better. The HPU supply is regulated and
monitored from the operator's workstation in the
control room.
Dynamic umbilical delivers power, control and
chemical injection functions from the topside
umbilical termination assembly (TUTU) and
electrical junction boxes to a 6-port subsea
distribution unit (SDU) on the seabed.
The umbilical contains 2-off Low Pressure lines
plus a spare, 2-off High Pressures lines plus a
spare, methanol injection and other chemical
injection lines for flow assurance purposes. The
topside tie-in is such that the dynamic umbilical
runs down to an umbilical termination assembly
(UTA) located at the seabed while hydraulic fluids
and electrical flying leads tie-in the UTA to the
SDU.
On the other end also, a hydraulic flying leads
(HFL) in combination with a pair of EFLs in
redundancy connects the SDU to each of the out-
going infield static umbilicals to the trees. Finally,
the HFL at the end of the infield umbilical UTA is
connected to the tree Multi Quick Connector
(MQC) while the EFLs are directly connected to
the SCM.
Fig 1.0
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
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The SCM receives low pressure (LP), high pressure
(HP), multiplexed electrical power and signal via the
umbilical connected to the master control station
(MCS) at the surface. When energized a hydraulic
signal is transmitted to the appropriate hydraulic
valve in the subsea Xmas tree, manifold, downhole
instrumentation or any other subsea equipment. An
electric signal decoded by the SEM operates
solenoid directional control valves (DCVs) and
direct the fluid to the appropriate subsea system or
safety valves. Signals from the subsea sensors are
also encoded through the SEM, analyzed and sent
back to surface facility (see Fig 2). The SCM is
connected to the subsea Xmas tree functions and
monitoring equipment via the Subsea Control
Module Mounting Base (SCMMB).
FMECA of Subsea Control Module
SCM Mode of Operation
Component of SCM
• Electrical Equipment
Subsystem
• Hydraulic Equipment
Subsystem
• Mechanical Parts
• SCM Housing
Fig. 2.0
Bottom - Down method consists of Event Tree Analysis (ETA); FMECA and
Hazard and Operability Study (HAZOP). Bottom Up reliability technique using FMECA was used to determine the reliability of SCM system.
Subsea Control Module (SCM) is made up of
several components (see Appendix A). The main
components can be divided into sub systems
namely;
Reliability Engineering
Reliability is associated with
unexpected failures of
products or services and
understanding why these
failures occur is critical. The
two methods of accessing
system reliability are :
• Top - Down method
• Bottom -Up method
Top - Down method consists
of Fault Tree Analysis (FTA);
Reliability Block Diagram
(RBD) and Markov Analysis.
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
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FMECA of Subsea Control Module
Failure Mode Effect Critical Analysis
FMEA is defined as a structured qualitative analysis
of a system, sub-system, components or function
that highlights potential failure modes, their causes
and the effects of a failure on system operations.
FMEA major objective is to identify potential failure
modes, evaluate and determine what could
eliminate or minimise the chance of failure. The
building block of FMECA analysis is shown in figure
3 below.
Fig. 3.0: Building block of FMECA analysis
In conducting an FMEA, the first step is to define the
scope of the exercise.
The system design is broken down into sub-
assemblies and components such that key failure
modes and effects are not overlooked. Design
FMEA examines system components and
subsystems failure modes and mechanism.
Manufacturing and assembling is analysed at the
process level. Service FMEA focuses on service
functions of the system.
FMECA extends the FMEA to include criticality
analysis by quantifying failure effects in terms of
probability of occurrence and the severity of any
effects.
There are two key ways of performing
failure modes critical analysis, namely;
• Calculating Criticality Number
(CN)
• Developing a risk priority number (RPN)
In this reliability case study RPN was
used.
The chance of failure mode occurrence is ranked O, the
chance of being undetected D and the severity S. A
numerical scale of 1 to 10 is used for ranking.
Mathematically;
RPN = O * S * D
Appendix A shows SCM components and sub-Systems
with their respective FM ID numbers. Appendix B shows
SCM Components Failures Modes, Causes, Effects,
Risk Factors and RPN Values Evaluation.
Criteria for SCM FMECA RPN Calculation
Severity S ranking = 1 – 10
Chances of being undetected D ranking = 1 – 10
Chance of failure mode occurrence is ranked O = 1 – 10
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Appendix A: SCM components and sub-Systems with their respective FM ID numbers
FM ID 1
2
3
4
5
6
7
8
9
Subsystem
Or Component
SCM
Podlock
Dieelectric chamber
over pressure
relief valve
Seawater
check valve
SCM
Housing
SCM
Dielectric fluid
chamber
Electrical
Connectors/Cabling
(internal)
Electrical
Connectors
(External)
Return line check/dump
valves
HP circuit hydraulic
filters
FM ID
10
11
12
13
14
15
16
17
18
Subsystem
Or Component
LP circuit hydraulic
filters
Return line flowmeter
HP supply flowmeter
LP supply flowmeter
HP circuit pressure
transducers + Return
Line
LP Circuit Pressure
Transducers +
Return line
Baseplate mounted hydraulic couplings
HP
Directional Control Valves (DCV)
Choke
DCV valve
FM ID
19
20
21
22
23
24
25
26
27
Subsystem
Or Component
LP
Directional
Control Valves (DCV)
Hydraulic circuitry
Subsea
Electronic Module (SEM)
HP
Accumulation
System
LP
Accumulator System
HP Manifold
System
LP
Manifold System
HP Shuttle
Valve
LP Shuttle
Valve
FM ID
28
29
Subsystem
Or Component
HP
Selector Valve
LP
Selector Valve
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FMECA of Subsea Control Module Data Analysis
A high RPN value corresponds to SCM components with high
critical failure mode. A further analysis was performed on top
seven (7) SCM components with high RPN values based on their
combined failure mode (see Table 1).
Results from data analysis of the SCM FMECA shows that most
failures result from SCM hydraulic component followed by the
Subsea Electronic Module (SEM) (see Fig 4). Hydraulic
components such as HP Directional Control Valves (DCV), Choke
DCV Valve, Hydraulic Circuitry, HP Shuttle Valve, LP Shuttle
Valve and LP Directional Control Valves (DCV) all have
occurrence (O) level ranges between moderate (5) to very high
(9) with severity (S) levels ranging from moderate (5) to serious
(9). All though the level of detectability (D) is high, more reliability
has to be factored into this component as most failure results to
non productive time (NPT).
Subsea Electronic Module (SEM) is another major critical SCM
component with high vulnerability to failure. SEM failure results often to
loss of control and communication to the topside, loss of power to all
DCV valve solenoids, loss in SCM system redundancy and complete
loss of production. Although its level of detectability (D) fall within the
range of very high to most certain; most of its identified components
failure severity level is extreme if it ever occurs.
Table 1.0: Top seven (7) SCM components with high RPN values
Conclusion
Reliability of SCM systems and sub component is critical for the safe and optimum
performance of subsea production system. Most failures resulting from SCM are related to
internal valve failures, failure of the valve solenoid coils, hydraulic leakage from supply or
block lines i.e. HP Directional Control Valves (DCV), Choke DCV Valve, Hydraulic Circuitry,
HP Shuttle Valve, LP Shuttle Valve and LP Directional Control Valves (DCV). Reliability should
be incorporated in the design of this SCM sub components. The SEM is not an exception.
Although its level of detectability (D) fall within the range of very high to most certain, reliability
has to be factored in from design as the industry moves into deep and ultra deep waters.
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
Fig 4: Pie chart of the top seven (7) SCM components with high RPN values
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk Profile Number (RPN)
1
SCM Podlock
SCM not correctly locked to SCMMB
• Number of turns is
insufficient
• Inability to function all
LP and HP control functions
3
8
4
96
Inability to unlock the SCM from the mounting base
• Debris (sand,
calcium carbonate) • Worn couplings
during SCM installation
• Corrosion and wear of the base couplings
• Dead Hydraulic lockdown
• Live hydraulic lockdown
• Inability to retrieve the
SCM to the surface for repairs
• Inability to disconnect the SCM from its SCMMB
• Severe loss in production.
• For VXT, Tree assembly retrieval to the surface
• For HXT, Tree and Well Completions retrieval
2
6
4
48
144
Appendix B: SCM Components Failures Modes, Causes, Effects, Risk Factors and RPN Values Evaluation
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
2
Dieelectric chamber over pressure relief valve
Failure of valve to function on demand
• Dynamic Instability • Components of
valve might be worn out.
• Embrittlement of valve components
• Hydraulic components
failure • Electronic components
failure • Total loss of electronic
and hydraulic functions • Total Loss in well
production
3
7
4
84
84
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
3
Seawater check valve
Leakage of seawater check Valve
• Dynamic Instability • Installation damage • Embrittlement of
valve components • Wear
• Seawater migration into
the SCM • Dielectric fluid
contamination • Failure of electrical
components • Total loss of electronic
and hydraulic functions • Total Loss in well
production
5
7
3
105
105
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
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FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
4
SCM Housing
Loss of communication due to Water ingress Sensor
• Internal fault in the
Water Sensor.
• Internal housekeeping
water ingress monitoring loss.
• All DCVs remain in their current positions.
• Partial Loss of subsea monitoring
• Total Loss in well production
2
8
2
32
Loss of SCM pressure compensation.
• Dielectric fluid
leakage from SCM via vent.
• Dielectric fluid leaks
from SCM whilst installed subsea
• Possible water ingress into the SCM.
• Damage to electronic components due to water ingress.
• Total loss in well production.
2
7
2
28
Inability to disconnect SCM assembly from tree.
• Failure due to
hydraulic coupler
• Unable to disconnect
the SCM from the tree. • Effect is Nil under
normal condition. • High Cost Tree retrieval
and replacement • Loss in well production
+ Pull completion.
2
4
7
56
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
Unable to connect SCM assembly to tree.
• Faulty Hydraulic
couplers
• Unable to connect the
SCM to the tree. • Non Productive Time
from retrieval and possible replacement of the SCM assembly
• Loss in well production
3
4
6
72
• Damaged SCM
Baseplate
• Unable to connect the
SCM to the tree. • Non Productive Time
from retrieval and possible replacement of the SCM assembly
• Loss in well production.
3
4
5
60
• Debris (sand,
calcium carbonate)
• Unable to connect the
SCM to the tree. • Non Productive Time
from retrieval and possible replacement of the SCM assembly
• Loss in well production.
3
4
6
72
• Seal carrier
misaligned or damaged
• Unable to connect the
SCM to the tree. • Non Productive Time
from retrieval and possible replacement of the SCM assembly Loss in well production
3
4
6
72
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
Loss off internal temperature sensor
• Temperature sensor
failure
• Partial loss in subsea
monitoring. • No loss in subsea
systems operation
6
4
2
48
Loss off internal pressure sensor
• Pressure sensor
failure
• Partial loss in subsea
monitoring. • No loss in subsea
systems operation
6
4
2
48
488
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk Profile
Number (RPN)
5
SCM Dielectric fluid chamber
Dielectric protection loss to the electrical system
• SCM housing
system leakage • Wrong installation
procedure.
• Ingress of seawater into
the SCM • Contamination of the
dielectric fluid. • Electrical component of
the SCM failure. • Total Loss in well
production
2
6
8
96
96
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
6
Electrical Connectors/Cabling (internal)
Power loss from the SEM to the valve units
• Short circuit / open
circuit.
• Loss of power to the
associated valve solenoid
• DCV valve remains in its last latched position
• Control and communication loss to the topside
• Power loss to all the associated subsea/well Instrument
• Partial Loss of subsea monitoring
4
6
2
48
• Faulty Electrical
cable or connector
• Loss of power to the
associated valve solenoid
• DCV valve remains in its last latched position
• Control and communication loss to the topside
• Power loss to all the associated subsea/well Instrument
• Partial Loss of subsea monitoring
48
96
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
7
Electrical Connectors (External)
Loss of power from the SCM electrical connectors
• Internal fault in
the electrical connectors
• Loss of power to one SEM channel in
the SCM • Loss of DHPT signal from the SEM
channel • Control and communication loss to
the topside • Loss of power to all associated valve
solenoid • DCV valve remains in its last latched
position • Power loss to all the associated
subsea/well Instrument
• Total loss in well production
6
4
2
48
• Leakage in the
connector system
• Loss of power to one SEM channel in
the SCM • Loss of DHPT signal from the SEM
channel • Loss in SCM system redundancy. • Control and communication loss to
the topside • Loss of power to the associated valve
solenoid • DCV valve remains in its last latched
position • Total loss in well production
6 6 2 72
120
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
8
Return line check/dump valves
Reduction in LP hydraulic dump capability.
• Blocked dump
return lines.
• Unable to completely "dump" LP hydraulic
supply pressure to compensation circuit. • All DCVs remain hydraulically latched with
tree valves remaining in last position. • Production flow is not shut in. • No Loss in Production
4
3
2
24
LP Dump Valve fails to operate on demand.
• Internal fault in
the dump valve system
• Unable to completely "dump" LP hydraulic
supply pressure to compensation circuit. • All DCVs remain hydraulically latched with
tree valves remaining in last position. • Production flow is not shut in. • No Loss in Production
4 4 2 32
56
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk Profile
Number (RPN)
9
HP circuit hydraulic filters
Clogging Blockage
• Unfiltered
contaminated Hydraulics
• Unfiltered contaminated
hydraulics - Blockage and Wearing of SCM components
• Stop or slow slowly moving of actuators.
• Malfunction of subsea components
• Complete Loss in well production
4
4
4
64
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
Loss of HP hydraulic fltration
• Filter element missing • Rupture of filter element • Wear filter element
components • Holed or filter by-pass
spuriously operates. • Inadequate filter elements. • Design error in the filter
porosity
• Dormant failure in normal
operation • Clogging or binding of
mobile parts of the DCV valves
• Unfiltered contaminated hydraulics - Blockage and Wearing of SCM components
• Stop or slow slowly moving of actuators.
• Malfunction of subsea components
• Complete Loss in well production
4
4
4
64
128
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
10
LP circuit hydraulic filters
Loss of LP hydraulic fltration
• Inadequate filter
elements. • Design error in the
filter porosity
• Clogging or binding of
mobile parts of the DCV valves and other components,
• Stop or slow slowly moving of actuators.
• Complete Loss in well production
4
5
4
80
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
• Filter element missing • Rupture of filter element • Wear filter element
components • Holed or filter by-pass
spuriously operates.
• Dormant failure in normal
operation • Clogging or binding of
mobile parts of the DCV valves
• Unfiltered contaminated hydraulics - Blockage and Wearing of SCM components
• Stop or slow slowly moving of actuators.
• Malfunction of subsea components
• Complete Loss in well production
4
5
4
80
• Clogging Blockage due to
fluid contamination
• Clogging or binding of
mobile parts of the DCV valves and other components,
• Wearing of SCM components
• Stop or slow slowly moving of actuators.
• Complete Loss in well production
4
5
4
80
240
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
11
Return line flowmeter
Loss of electronic monitoring of the Return line flow.
Internal fault in the Return line flowmeter
• Loss of flow monitoring in
the Return Line • No direct impact on a
normally operating tree. • Partial Loss in subsea
monitoring
4
4
2
32
32
12
HP supply flowmeter
Loss of electronic monitoring of the HP Supply flow.
Internal fault in the HP flowmeter
• Loss of flow monitoring of
the HP supply. • No direct impact on a
normally operating tree. • Partial Loss in subsea
monitoring
4
4
2
32
32
13
LP supply flowmeter
Loss of electronic monitoring of the LP Supply flow.
Internal fault in the LP flowmeter
• Loss of flow monitoring of
the LP supply. • No direct impact on a
normally operating tree. • Partial Loss in subsea
monitoring
4
4
2
32
32
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
14
HP circuit pressure transducers + Return Line
Loss of electronic monitoring of a single hydro quad function.
• Loss of DCV Output
Pressure Transducer.
• All associated DCV's
remain latched in their last position
• Loss of monitoring and positional status of a single DCV.
• No direct impact on a normally operating tree.
• Partial Loss in subsea monitoring
4
3
2
24
Loss of electronic monitoring of the HP Supply Pressure.
• Loss of HP Pressure
Transducer.
• All associated DCV's
remain latched in their last position
• Loss of monitoring and positional status of a single DCV.
• No direct impact on a normally operating tree.
• Partial Loss in subsea monitoring
4
2
2
32
56
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
15
LP Circuit Pressure Transducers + Return line
Loss of electronic monitoring of a single hydro quad function.
• Loss of DCV Output
Pressure Transducer.
• All associated DCV's
remain latched in their last position
• Loss of monitoring and positional status of a single DCV.
• No direct impact on a normally operating tree.
• Partial Loss in subsea monitoring
4
2
2
16
Loss of electronic monitoring of the LP line Pressure.
• LP Pressure
Transducer is Faulty
• All associated DCV's
remain latched in their last position
• Loss of monitoring and positional status of a single DCV.
• No direct impact on a normally operating tree.
• Partial Loss in subsea monitoring
6
4
2
48
64
16
Baseplate mounted hydraulic couplings
Inability to connect the SCM to the Xmas tree
• Couplings worn out
during SCM • Installation
Corrosion and wear of the base couplings
• Inability to makeup the
SCM to the Xmas tree • Complete Loss of
Production
2
4
2
32
32
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
17
HP Directional Control Valves (DCVs)
SCSSV DCV fails to open on demand from the closed position.
• Failure of the valve
solenoid coils
• SCSSV fails to open. • Unable to start
production from the well.
• Complete Loss in Production
5
6
4
120
• DCV internal fault of
the latching mechanism
• SCSSV fails to open. • Unable to start
production from the well.
• Complete Loss in Production
5
6
4
120
SSCSV shuts spuriously from the open position.
• DCV internal fault of
the latching mechanism.
• SCSSV spuriously
closes. • Unscheduled loss of
production. • Complete Loss in
Production
5
6
4
120
SCSSV fails to shut on demand from the open position.
• Failure of the valve
solenoid system
• Loss of SCSSV
protection • Reduced well barrier for
the SPS • Partial Loss in Well
Control
6
6
3
108
• DCV internal fault of
the latching mechanism to latch.
• Loss of SCSSV
protection • Reduced well barrier for
the SPS • Partial Loss in Well
Control
6
6
2
72
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
540
18
Choke DCV valve
Choke DCV fails to open on demand.
• Failure of the valve
solenoid coils
• Unable to set required
choke valve position • Reduction in flow of oil
from the well. • Partial Loss of
Production
4
4
2
32
• DCV internal valve
failure.
• Unable to set required
choke valve position • Reduction in flow of oil
from the well. • Partial Loss of
Production
6
4
2
48
Choke DCV fails to shut on demand.
• Solenoid valve
sticks in energized position.
• Production Choke
Valve Close actuator (PCVC) fails to extend to required position.
• Reduction in flow of oil from the well.
• Partial Loss of Production
4
4
2
32
• DCV internal valve
failure.
• Production Choke
Valve Close actuator (PCVC) fails to extend to required position.
• Reduction in flow of oil from the well.
• Partial Loss of Production
6
4
2
48
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
• Failure of the valve
solenoid coils
• Production Choke
Valve Close actuator (PCVC) fails to extend to required position.
• Reduction in flow of oil from the well.
• Partial Loss of Production
4
4
2
32
192
19
LP Directional Control Valves (DCV)
LP tree valves DCV fails to open on demand
• Failure of the valve
solenoid coils
• Selected Xmas tree
valve fails to open on demand
• DCV remains in the last latched and shut position.
• Well remains in the shut-in position
• Complete Loss of Production
6
6
3
108
• Internal fault in the
DCV latching mechanism
• Selected Xmas tree
valve fails to open on demand
• DCV remains in the last latched and shut position.
• Well remains in the shut-in position
• Complete Loss of Production
6
6
3
108
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
LP Tree valves DCV shuts spuriously from the open position.
• Internal fault in the
DCV latching mechanism
• Associated tree valve
spuriously closes • Unscheduled Loss of
production • Complete Loss of
Production
4
6
3
72
LP Tree DCV fails to close on demand
• Failure of the valve
solenoid coils
• Unable to shutoff
production • Partial Loss in well
control
7
5
3
105
393
20
Hydraulic circuitry
Loss of single LP hydraulic supply
• Solenoid valve
spuriously operates
• Loss of single LP
channel in the tree SCM.
• Pressure drop in the shuttle valves
• Total loss of Tree controls
• Complete Loss of Production
4
6
3
72
• Leakage from LP
hydraulic Lines / connectors
• Loss of single LP
channel in the SCM. • Leakage of hydraulic
fluid into the sea. • Loss of Production
6
6
3
108
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
• Single LP hydraulic
line blocked
• Loss of LP pressure in
the affected channel. • Loss of Xmas Tree
controls • Loss of Production
5
6
2
60
Loss of single HP hydraulic supply
• Loss in HP hydraulic
line/connector in a single channel.
• Loss of single HP
channel to all the Xmas tree.
• Severe leakage of hydraulic fluid into the sea.
• Eventual drop of all the HP DCVs
• Loss of Production
6
6
2
72
• Leakage from HP
hydraulic lines
• Gradual loss of single
HP channel to all the Xmas tree/Well.
• Leakage of hydraulic fluid into the sea.
• Loss of Production
6
5
3
90
• Single HP hydraulic
line blocked
• Loss of HP pressure in
the affected channel. • Loss in SCSSV and
FCV Controls • Loss of Production
4
6
2
48
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
Loss of both LP hydraulic supplies
• Line/connector
Leakage in the LP supply Lines
• Loss of hydraulic
suplies to the LP DCVs • Loss of Xmas Tree
controls • Complete Loss of
Production
5
8
2
80
• Blocked LP
hydraulic lines
• Loss of hydraulic
suplies to the LP DCVs • Loss of Xmas Tree
controls • Complete Loss of
Production
5
8
2
80
Loss of both HP hydraulic supplies
• Leakage in the HP
supply lines
• Loss of hydraulic
suplies to the HP DCVs • Loss of SCSSV and
IWCV controls • Complete Loss of
Production
5
8
2
80
• Blocked HP
hydraulic lines
• Loss of hydraulic
suplies to the HP DCVs • Loss of SCSSV and
IWCV controls • Complete Loss of
Production
5
8
2
80
770
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
21
Subsea Electronic Module (SEM)
Complete Loss of Power supply from the SEM
• Internal fault
with the SEM power supply units
• Water ingress into the SCM unit
• Loss of DHPT signal from
the SEM channel • Loss of control and
communication to the topside
• Loss of power to all DCV valve solenoids
• Loss in SCM system redundancy
• Complete Loss of Production
6
8
2
96
Loss of Controller board functionality
• Failure of
controller board
• Loss of single LP channel in
the tree SCM. • Loss of Tree Controls • Loss of control and
communication to the topside
• Loss of Production
6
8
2
96
Loss of Signal from one SEM
• I/O card failure
in SEM, Corrupt software
• Loss of single LP channel in
the tree SCM. • Loss of Tree Controls • Complete Loss of
Production
5
8
2
96
Complete Loss of signal from both SEM
• I/O card failure
in SEM, Corrupt software
• Loss of DCV Valve controls • Loss of all associated
subsea instrumentation. • Loss of Xmas Tree controls • Complete Loss of
Production
5
8
2
96
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
Loss of I/O Interface Board
• I/O Board
Internal fault.
• Loss of the channel I/O
Board. • Inability to monitor one set
of external instrumentation. • All DCVs will remain latched
to their current positions.
• Complete Loss of Production
8
8
2
128
Loss of DHPT Board
• DHPT Board
Internal fault.
• Loss of Communication to
the Tree DHPT instruments from the Channel.
• All DCVs remain in their last positions.
• The redundant DHPT board provides the service
• Complete loss of monitoring
6
8
2
96
Loss of Modem Functionality - Interface to topside
• Modem Failure.
• Loss of one communication
channel to the topside • Loss of control and
communication to the topside
• The control function of the SCM is unaffected.
• Complete loss of monitoring
6
8
2
96
• Modem
Freezes - produces steady output
• Partial Loss of monitoring • Loss of control and
communication to the topside
• Complete loss of monitoring
6
8
2
96
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
Critical Loss of Electronic Control
• Combinational
loss of power supply, modem and control board
• Inability to monitor subsea
instrumentation or command Inability to open or close any valve from the topside
• All hydraulically actuated valves remain in last positions
• Inability to shut in the tree in a controlled manner through the integrated system
• Complete loss of subsea monitoring
• Complete Loss of Production
6
8
2
96
896
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
22
HP Accumulation System
Reduction in HP Accumulation.
• Single HP
accumulator loss of precharge.
• Reduction in HP
accumulation • Excessive drop in
supply during valve operation
• All DCVs delatch/All tree valves close
• Loss of Production
4
7
3
84
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
• Reduction in
HP accumulation
• Reduction in HP
accumulation • Excessive drop in supply
during valve operation • All DCVs delatch/All tree
valves close • Loss of Production
4
7
3
84
Loss of HP Accumulation.
• Loss all HP
accumulator pre-charge.
• Loss/reduction in HP
accumulation • All DCVs delatch • Complete Loss of
Production
4
7
3
84
Loss / reduction of HP supply pressure.
• HP supply line
plugged with particulate.
• Loss/reduction in HP
accumulation • Excessive drop in supply
during valve operation • All HP DCVs delatch • Complete Loss of
Production
4
7
3
84
336
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
23
LP Accumulator System
Loss/reduction in LP Accumulation.
• Loss all LP
accumulator pre-charge.
• Loss of common LP supply
pressure • All DCVs eventually unlatch • Complete Loss of
Production
6
7
3
126
• Severe leak
from the LP Common Header Pressure Transmitter.
• Reduction in LP
accumulation • Excessive drop in supply
during valve operation • All DCVs delatch/All tree
valves close • Complete Loss of
Production
5
7
3
105
• Single LP
bladder failure.
• Reduction in LP
accumulation • Excessive drop in supply
during valve operation • All DCVs delatch/All tree
valves close • Complete Loss of
Production
5
7
3
105
336
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
24
HP Manifold System
Severe Leak in the HP Manifold (E.G. Seals etc)
• Faulty seals
and other system malfunction.
• Loss of common HP supply
pressure • All HP DCVs eventually
unlatch and Well shutting. • Loss of Production
3
5
3
45
45
25
LP Manifold System
Severe Leak in the LP Manifold
• Faulty seals
and other system malfunction
• Loss of common LP supply
pressure • All LP DCVs eventually
unlatch and Well shutting. • Complete Loss of
Production
3
5
4
60
60
26
HP Shuttle Valve
Shuttle Valve fails to change over to the next HP supply line.
• HP Shuttle
valve internal fault.
• Inability to select/change
over to an HP supply on demand.
• No direct effect if both lines remain serviceable
• All DCVs unlatch and Well shutting if 2nd line is not available
• Complete Loss of Production
6
7
2
84
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
Severe Leak in the Common HP Hydraulic Header.
• Severe leak
from the HP Shuttle valve.
• Loss of common HP supply
pressure • All DCVs eventually unlatch • Loss of Production
6
7
2
84
• Severe leak
from the HP manifold (seals etc).
• Loss of common HP supply
pressure • All DCVs eventually unlatch • Loss of Production
6
7
2
84
• Severe leak
from the HP Common Header Pressure Transmitter.
• Loss of common HP supply
pressure • All DCVs eventually unlatch • Loss of Production
6
7
2
84
• Severe leak
from the HP Common Header Pressure Transmitter.
• Loss of common HP supply
pressure • All DCVs eventually unlatch • Loss of Production
6
7
2
84
• Severe leak
from the HP Common Header Flow Meter.
• Loss of common HP supply
pressure • All DCVs eventually unlatch • Loss of Production
6
7
2
84
504
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
27
LP Shuttle Valve
Shuttle Valve fails to change over to the next LP supply line.
• Shuttle valve
internal fault.
• Inability to select/change
over to an LP supply on demand.
• No direct effect if 2nd line is serviceable
4
7
3
84
Severe Leak in the Common LP Hydraulic Header.
• Severe leak
from the LP Shuttle valve.
• Loss of common LP supply
pressure • All DCVs eventually unlatch • Loss of Production
4
7
3
84
• Severe leak
from a LP Accumulator.
• Loss of common LP supply
pressure • All DCVs eventually unlatch • Loss of Production
5
7
3
105
• Severe leak
from the LP Common Header Pressure Transmitter.
• Loss of common LP supply
pressure • All DCVs eventually unlatch • Loss of Production
5
7
3
105
• Severe leak
from the LP Common Header Flow Meter.
• Loss of common LP supply
pressure • All DCVs eventually unlatch • Loss of Production
5
7
3
105
483
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
28
HP Selector Valve
HP selector valve spuriously closes..
• HP selector
valve internal fault of the latching mechanism.
• Selector Valve spuriously
isolates and vent down an incoming supply
• Loss of a single HP hydraulic supply to the SCM.
• No Effect on normal operation
• Loss of HP hydraulic supply redundancy
4
6
2
48
HP selector valve fails to open.
• Failure of the
valve solenoid system.
• Loss of a single HP
hydraulic supply to the SCM.
• No Effect on normal operation
• Loss of hydraulic supply redundancy
6
4
2
48
• HP selector
valve internal fault of the latching mechanism
• Loss of a single HP
hydraulic supply to the SCM.
• No direct Effect on normal operation
• Loss of hydraulic supply redundancy
4
4
2
48
144
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
29
LP Selector Valve
LP selector valve spuriously closes.
• LP selector
valve internal fault of the latching mechanism.
• Selector Valve spuriously
isolates and vent down an incoming supply
• Loss of a single LP hydraulic supply to the SCM.
• No Effect on normal operation
• Loss of hydraulic supply redundancy
4
6
2
48
LP selector valve fails to open.
• Failure of the
valve solenoid system.
• Loss of a single LP
hydraulic supply to the SCM.
• No Effect on normal operation
• Loss of hydraulic supply redundancy
6
6
2
72
• LP selector
valve internal fault of the latching mechanism
• Loss of a single LP
hydraulic supply to the SCM.
• No direct Effect on normal operation
• Loss of hydraulic supply redundancy
4
6
2
48
Chess Subsea Engineering (UK) Limited is registered in England (registration number 9616564) and having its registered office at London, Erith, Kenth, DZDA18, United Kingdom.
Tel: +447903310642, +447419706555, +2348139340494. Email: [email protected]
FM ID
Component
Failure Mode
Failure Cause
Failure Effects
O
S
D
Risk
Profile Number (RPN)
LP selector valve fails to close.
• Complete
failure of the selector valve solenoid system
• Unable to select LP channel
as required • No direct Effect on normal
operation • Loss of hydraulic supply
redundancy
4
6
2
48
LP selector valve fails to open.
• LP selector
valve internal fault of the latching mechanism.
• Unable to select LP channel
as required • No direct Effect on normal
operation • Loss of hydraulic supply
redundancy
4
6
2
48
264