HAZOP (NA62 CEDAR EXPERIMENT)
Reference drawings:
Participants:
Node:
GUIDEWORD
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DEVIATION
POSSIBLE CAUSES
07 February 2016
CONSEQUENCES
ACTION REQUIRED
Node: Purging the N2 line plus detector
GUIDEWORD
DEVIATION
POSSIBLE CAUSES
CONSEQUENCES
ACTION REQUIRED
NONE
FLOW
Hand valve closed
Power cut
No N2 flow to the detector
Downtime. Have to open hand valves
1.
NONE
LEVEL
Not relevant
Not relevant
Not relevant
NONE
MAINTENANCE
Human error
Can lead to problems
2.
Establish a maintenance schedule of for all relevant
equipment items.
REVERSE
FLOW
False manipulation could cause gas flow
from the pumping system
REVERSE
EQUIPMENT
Wrong mounting of equipment
Slow pressure increase through CEDAR
and all other gas lines. Pump out gas and
refill with N2 again
Bad behaviour detected at
commissioning and repair done
MORE OF
MORE FLOW
Mass flow controller does not see
forward flow
gas sent through CEDAR to the vent
line.
Opening one of the entrance valves or
change the pressure set point.
Mass flow controller has to have a well
chosen maximum setting.
MORE OF
PRESSURE
Human error, allowing gas coming from
the pump line
More gas released through vent line
Safety release valve will switch to the
vent line
MORE OF
TIME
Computer crash
3.
Define minimum time for purging with N2 and
include in procedure.
PART OF
COMPOSITION
Human error
Watchdog will notice and switch off all
input and outputs
Does not matter really
Wrong gas mixture, possibility to get
flammable gas into the detector
PART OF
OPERATION
Control by-passed in part by human
error
Wrong gas mixture, possibility to get
flammable gas into the detector
4. Password protection.Write a record in log-files of bypassing. .Follow-up and avoid in the future
Page 2 of 7
07 February 2016
Put contacts on input valves that give an alarm via
the computer. Put mixer in stop mode.
See Action No. 1.
Node: Filling procedure (as pure as possible, 1 permille) to a pressure precision of 0.5 mbar
GUIDEWORD
DEVIATION
POSSIBLE CAUSES
CONSEQUENCES
NONE
FLOW
Hand valves closed
Procedure does not work
REVERSE
FLOW
False manipulation could cause gas flow
from the pumping system
MORE OF
PRESSURE
Pressure safety valve broken or set point
pressure gauge broken
Slow pressure increase through CEDAR
and all other gas lines. Pump out gas and
refill with H2 again
Spotted by set point (or safety valve)
detector and stop Issue an alarm and stop
MORE OF
TEMPERATURE
(External) fire
MORE OF
TIME
PART OF
COMPOSITION
Wrong valve position
Interlocked
FLOW
Failure or unlikely leak of pneumatic
valves and leaking non-return valves.
Wrong manipulation
H2 into N2 or vacuum lines. Does not
matter too much
OTHER THAN
Page 3 of 7
Risk of explosion
Level 3 fire alarm in building and/or
mixer region Level 3 interlock shuts off
H2 supply.
ACTION REQUIRED
5. Set pressure relief of PSV-6074 to below safety limit
for windows.
6. Consider the need for local smoke detection and/or
temperature sensors in Cedar region (contact HSE Unit,
Fire Prevention).
7. Limit presence of combustible materials, e.g.
insulating material of CEDAR.
Procedure stops. Have to investigate and
start again.
07 February 2016
8. Pumps, flow meters, valves etc. will be ATEX rated.
Check with HSE Unit, Electrical Safety when ordering
equipment.
9. Consider safe locations for venting.
Node: Empty the CEDAR to a pressure of 0.1 mbar
GUIDEWORD
DEVIATION
NONE
FLOW
REVERSE
POSSIBLE CAUSES
CONSEQUENCES
No pumping, Loss of time.
Need to repair problem
FLOW
Pump not working
Power cut
Pneumatic valve closed
Pump connected wrong (unlikely)
MORE OF
PRESSURE
Leak
Fix leak and pump longer
PART OF
OPERATION
No vacuum in beam line
Risk of window rupture
FLOW
Nitrogen safety valve in wrong position
N2 wasted
OTHER THAN
Page 4 of 7
07 February 2016
ACTION REQUIRED
Seen in commissioning
10. Interlock emptying with vacuum pressure in blue
tube
Node: Pressure scan , i.e. lower H2 pressure stepwise to a lower value within 0.1 mbar
GUIDEWORD
DEVIATION
NONE
FLOW
REVERSE
FLOW
LESS
PRESSURE
POSSIBLE CAUSES
CONSEQUENCES
ACTION REQUIRED
Pump or valve or mass flow controller
broken.
Hand valve closed.
When in vacuum, valve from exhaust
opened.
Scan does not work.
Need to identify and fix causes
11. Consider removing manual/hand valve HV-5035
from vent line.
Could suck in air into Cedar.
Several valves prevent this
12. Add non-return valve from vent line to pump
Two valves failing at the same time
Too low pressure, Get warnings
13. General remark: update P&ID with modifications to
system and to reflect the instrumentation in place (e.g.
indicate which instruments give alarms, actual position
of PSV-6074 directly on CEDAR Vessel, position of
manual/hand valve HV-6005)
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07 February 2016
GUIDEWORD
PARAMETER
MEANING
NONE
FLOW
LEVEL
MAINTENANCE
NO FLOW
VESSEL EMPTY
NOT CARRIED OUT
REVERSE
FLOW
EQUIPMENT
REVERSE FLOW
INSTALLED WRONG WAY ROUND
MORE OF AND
LESS OF
FLOW
TEMPERATURE
PRESSURE
LEVEL
TIME
WRONG FLOW
WRONG TEMPERATURE
WRONG PRESSURE
WRONG LEVEL
WRONG TIME
PART OF
COMPOSITION
OPERATION
MISSING COMPONENT
NOT COMPLETED PROPERLY
OTHER THAN
FLOW
OPERATION
FLOW MISDIRECTED
DIFFERENT PROCEDURE USED
WHERE ELSE
FLOW
COMPOSITION
FLOW DIRECTED ELSEWHERE AS WELL
CONTAMINANT PRESENT
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07 February 2016
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07 February 2016