Project
NPWTP Fluoridation
Location
NP WTP
Lead by
G POOL
Project No
Scribe
G POOL
Date
19/10/2022
Session
1
HAZOP Team Members
Full Name
Title / Expertise
Team/discipline
Signature
Rachelle Quin
Water Treatment Plant Lead
WTP/Ops
Graeme Olsson
Water Treatment Technician
WTP/Ops
Scott Burgess
Water Treatment Technician
WTP/Ops
Jim Evans
Water Treatment Technician
WTP/Ops
Dylan Bevins
Water Treatment Technician
WTP/Ops
Abby Rawlinson
Water Treatment Technician
WTP/Ops
Jamie Clarges
Mechanical Maintenance Fitter
WTP/Maintenance
Graeme Pool
Principal Operations Engineer
Technical Capablity
Attendance
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Fluoridation HAZOP reviewed 26-6-23.xlsx
Project
NPWTP Fluoridation
Lead by
G POOL
Project No
0
Location
NP WTP
Date
19/10/2022
Plant
NPWTP Fluoridation
DOCUMENTS & DRAWINGS
Number
Title
Revision
Date
W-DAP-0018 rev 5 draft
5 draft
W-DAP-0010
5
Documents
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Fluoridation HAZOP reviewed 26-6-23.xlsx
Project
NPWTP Fluoridation
System Description
Fluoride dosing system complete
Project No
0
System no
1
Location
NP WTP
Drawing
W-DAP-0018 rev 5 draft
Plant
NPWTP Fluoridation
Date
19/10/2022
GUIDEWORD
CAUSES
CONSEQUENCES
SAFEGUARDS
#
RECOMMENDATION
RESPONSIBLE RESPONSE
HIGH FLOW
pipe break
spill - contained by bund
Level switch with alarm in the
bund. Sched 80 pipe
HIGH FLOW
dosing pump not controlled
Overdosing
pump configured to a mximum
final design pump slection has
effectively
flow. Independent monitoring of
maximum capacity of 7.6l/hr.
dose rate by flow meter with
Overdose is only possible at flows
alarms/trips. Independent
less than 27MLD
monitoring of treated water
fluoride concentration by on ine
analyser with alarms/trips
LOW FLOW
equipment failure
low dose - legislative compliance
duty / standby dose pumps
LOW FLOW
loss of sample water to fluoride
loss of fluoride concentration
low flow swith on treated water
analyser
verification (Independent check 3)
sample line to analyser. Note this
sample line goes to ALL treated
water analysers
ZERO FLOW
dosing pump failure
pump damage / low dose
Independent check of dose rate by
flow meter with alarms/trips
ZERO FLOW
transfer pump failure
HFA not transferred to Day tank
transfer pump configured to run for
1 consider using day tank level to
G POOL
Considered rising level. FD includes
reuslting in pump damage and
max time.
ensure rising level while transfer
calcualtion of expected pump run
eventually low dose
pump is running
time based on flow and level and
alarms/ faults if this time is
exceeded
REVERSE FLOW
NA
HIGH LEVEL
High level in dosing skid day tank
spillage of HFA
analogue level instrument with
alarms / trips. Dedicated High level
switch. Overflow pipe to bund.
bund level switch with alarm
LOW LEVEL
transfer pump / valve not
low dose. Possible to run transfer
pump configured to trip if runs too
functioning
pump without pumped media
long and level not achieved.
EMPTY
tank empty out of working hours
disruption to staff
transfer to day tank occurs at 09:00
daily or on low level
HIGH PRESSURE
dosing pumsp generate high
over pressurise pipework causing
dosing pumps have Pressure relief
pressure due to closed valve of
leak or bust - spillage
back to day tank. Blockage or
blocked pipe
closed valve would be identified by
independent check of dose rate by
flow meter
Process Node 1
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Fluoridation HAZOP reviewed 26-6-23.xlsx
LOW PRESSURE
IBC not vented
IBC collapses
Vented cap to be provided and
fitted to IBC as part of changeover
procedure (documented SOP)
HIGH TEMPERATURE
NA
LOW TEMPERATURE
NA
IMPURITIES
Impurities in HFA delivered or
introduction of impurities into
reputable HFA supplier. Assys with
contaminated while on site
drinking water
deliveries. All vents protected from
contamination
CHANGE IN COMPOSITION
NA
CHANGE IN CONCENTRATION change in concentration when IBC's potential for incorrect dose
Assys and direct testing of
are changed over (e.g 1 IBC is 17%
chemical. Ixom confirmed HFA
and the next is 23% the
solution suplied is within range 21 -
concentration in the day tank will
23% Provision in progamming to
be a mix and between 17% &23%
enter chemical strength
2 PHASE FLOW
NA
REACTIONS
Addition of water during IBC
potential for exothermic reaction
Considered unlikely as product is
changeover, or during flushing of
when water is added to acid
already a diluted solution. Water
equipment during maintenance
flow rate during flushing will be
continuous and at a rate such that
the reaction if any does not
accelerate (SOP)
TESTING
samples may need to be collected inadequate testing points
Sample points added to P&ID
to verify assays
TESTING
samples for testing obtained
potential for contact between
2 SOP required for obtaining and
R QUIN
Assays per batch available from
unsafely exposing technicians to
technicians and HFA resulting in
testing sample
supplier
HFA
chemical burns
PLANT ITEMS
seize / corrode if unused for
equipment inoperable when
equipment will be in use at least
3 programme daily changeover of
G POOL
Included as duty change if dosing
periods of time
needed
daily except dosing pumps, and
duty on dosing pumps
pump stops. Else manual
dosing pump PRV's
ELECTRICAL
INSTRUMENTS
Failure of instruments
incorrect dosing
sample low flow swicth, also does
othe rfinal water instrument
OVERVIEW
TOXICITY
Contact between Technicians and
loss of containment of HFA
HFA contained to prevent loss.
HFA
Level switches in containment
bunds to alert to spillage. Dosing
skid, where HFA is presurised is
fully contained in a cabinet
SERVICES REQUIRED
safety shower & Eye wash.
MATERIALS OF
HFA is corrosive to metals
premature failure of equipment
Materials selected to be suitable
CONSTRUCTION
for contact with HFA.
Storage of HFA IBC's is outside
HFA dosing cabinet has forced
ventilation
Process Node 1
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Fluoridation HAZOP reviewed 26-6-23.xlsx
COMMISSIONING
Commissioing issues results in
High or low fluoride dose
Undertake all wet commissioing
incorrect dose
using potable water to verify
operation.
START UP
SHUT DOWN
BREAKDOWN
INFLUENT - RAW WATER
Fluoride present in water entering overdosing fluoride in the treated
testing of source shows steady very
4 routine sampling of Filter backwash R QUIN
Additional fluoride analyser
the WTP from source or via recycle water
low level of fluoride. Recycled filter
recycle and source
ordered 27/7/23. Will be
backwash will contain fluoride. Test
incorporated to continuously
total inflow to verify and option to
monitor incoming water fluoride
enter source fluoride concentration
concentration. Also provides on site
in SCADA calculation
in use analyser which could double
as redundancy in case of failure
EFFLUENT
NA
NOISE
NA
FIRE
NA
EXPLOSION
NA
SEISMIC
NA
CYCLONE
NA
SAFETY EQUIPMENT
loss of water supply to safety
inability to use safety shower/ eye safety shower & eye was supplied
shower / eye wash
was if required
from site water system. To be
plumbed to LP supply as this is fed
by pumps and / or gravity ensuring
constant water supply.
OUTPUT - RELIABILITY &
unavailability of HFA on site
dosing stops due to no product
one IBC in use plus plan to have up
BOTTLENECKS
to 4 IBC's on site (stored on spill
bunds) to provide delivery
flexibility. 4 = min 20 days demand
at peak flow
SIMPLICITY
complexity leads to
incorrect dosing
complexity is inherent in the
misunderstanding and
control to provide safeguards
inappropriate operation
against excessive dosing.
Ensure functional description is
fully documented. Ensure O&M is
documented
ensure training is provided
Process Node 1
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