RAL Template

1
MICE Hydrogen System Implementation
Tom Bradshaw Elwyn Baynham Iouri
Ivaniouchenkov Jim Rochford
HydrogenSystemImplementationBrekleyDec2003 V8.ppt
2
Talk Contents

• Design Criteria the conceptual basis for the
  design
• Baseline layout - operating modes
• Choice of hydride bed storage option
• Safety containment / Hydrogen Zones
• Pipework and implementation
• Interlocks
• Thermal issues

3
Design Criteria 1/3

• Independent hydrogen systems on each of the MICE
  absorbers to eliminate consequential and
  interactive effects
• Easier to isolate faults
• Smaller systems are easier to deal with
• This will also ease the staging of MICE and
  reduce the need for extra testing

4
Design Criteria 2/3

• Minimise venting and purging
• Most incidents have happened during venting
  operations
• Sealed system is safer
• Minimise amount of hydrogen

5
Design Criteria 3/3

• Must be safe in the event of a power loss or
  system shut-down
• No surfaces on the absorber vacuum vessel below
  the BPt of Oxygen this is to prevent
  cryopumping of oxygen on any surface that may
  come into contact with hydrogen in the event of a
  failure
• Relief valves to vent to buffer volume and to air
  through a flame arrester in case of major release
• Prove the basis of a system for a neutrino factory

6
Absorber parameters

• Liquid-hydrogen volume (at 20K), litres 21
• Hydrogen volume (at STP), m3 17
• LH2 operating temperature at load, K 18
• LH2 operating pressure, bar abs
  1
• LH2 max pressure, bar abs - relief valve set
  point 1.6
• Max. heat removal, W - this is the design
  figure 100
• Refrigerant mass flow, g/s lt5
• Refrigerant inlet (outlet) temperature, K 14
  (18)
• (at max heat removal)
• Refrigerant inlet (outlet) pressure, bar
  18(14)
• Absorber vacuum volume (within the module),
  litres 265

7
Hydrogen Storage
Options for hydrogen storage 1. Low pressure
tank Pros - truly passive system
Cons - size (about 30 m3), 3 tanks are required
- dispersed system with long
pipes - difficult to collect hydrogen in
case of leak - hardly
feasible for neutrino factory - many systems

2. Metal hydride
bed Pros - very compact system
(lt1 m3) - easier to collect hydrogen in case
of leak - hydrogen is
stored as a solid compound
- more feasible for neutrino factory.
Cons - not a truly passive system -
requires active heater/cooler
8
Hydride Bed Parameters

• Hydrogen storage capacity (at STP), m3 20
• Absorber filling/empting time, hours 5
• Preferable size 1 m3
• Environment temperature 15-25 C
• Max. pressure in the system, bar abs 1.6

Hydride bed will be procured and certified to
relevant safety standard
9
Cross section of Absorber

1. Windows are mounted off RT interface see
   thermal model later
2. Space for change in pipe dimension close to
   magnet
3. Large bucket at base to contain any rupture

10
Baseline layout
Version 21/11/2003
Vent outside flame arrester
He Purge system
Metal Hydride storage unit (20m3 capacity)
1 bar
Chiller/Heater Unit
18 K He
14 K He from Cold box
Fill valve
X 2
X 2
1.6 bar
2.0 bar
Purge valve
Liquid level gauge
Vent outside flame arrester
Vacuum
Ventilation system
Internal Window
LH2 Absorber
Safety window
LHe Heat exchanger
Purge valve
Vent outside flame arrester
Evacuated vent buffer tank
2.0 bar
Vacuum vessel
1.6 bar
1.4 bar
Pressure relief valve
Pressure regulator
Pressure gauge
Non-return valve
Vacuum pump
Bursting disk
Valve
11
Activate Hydride Bed
Vent outside flame arrester
He Purge system
Metal Hydride storage unit (20m3 capacity)
Chiller/Heater Unit
Fill valve
1 bar
This is required only once to activate the
hydride beds prior to use. Beds are heated to 80C
and pumped.
12
Purge Process
Vent outside flame arrester
He Purge system
Metal Hydride storage unit (20m3 capacity)
Chiller/Heater Unit
18 K He
14 K He from Cold box
Fill valve
1 bar
X 2
X 2
1.6 bar
2.0 bar
Purge valve
Liquid level gauge
Vacuum
Internal Window
LH2 Absorber
Safety window
LHe Heat exchanger
Purge valve
Vent outside flame arrester
Evacuated vent buffer tank
2.0 bar
Vacuum vessel
1.6 bar
1.4 bar
13
Hydrogen Fill
Heat applied to Hydride to fill Heat removed/
cooled to empty
Vent outside flame arrester
He Purge system
Metal Hydride storage unit (20m3 capacity)
Chiller/Heater Unit
18 K He
14 K He from Cold box
Fill valve
1 bar
X 2
X 2
1.6 bar
2.0 bar
Purge valve
Liquid level gauge
Vacuum
Internal Window
LH2 Absorber
Safety window
LHe Heat exchanger
Purge valve
Vent outside flame arrester
Evacuated vent buffer tank
2.0 bar
Vacuum vessel
1.6 bar
1.4 bar
14
Normal Operation
Vent outside flame arrester
He Purge system
Metal Hydride storage unit (20m3 capacity)
Cold
Chiller/Heater Unit
18 K He
14 K He from Cold box
1 bar
Fill valve
X 2
X 2
1.6 bar
2.0 bar
Purge valve
Liquid level gauge
Vacuum
Internal Window
LH2 Absorber
Safety window
LHe Heat exchanger
Purge valve
Vent outside flame arrester
Evacuated vent buffer tank
2.0 bar
Vacuum vessel
1.6 bar
1.4 bar
15
Hydrogen Empty
Heat applied to Hydride to fill Heat removed/
cooled to empty
Vent outside flame arrester
He Purge system
Metal Hydride storage unit (20m3 capacity)
Chiller/Heater Unit
18 K He
14 K He from Cold box
Fill valve
1 bar
X 2
X 2
1.6 bar
2.0 bar
Purge valve
Liquid level gauge
Vacuum
Internal Window
LH2 Absorber
Safety window
LHe Heat exchanger
Purge valve
Vent outside flame arrester
Evacuated vent buffer tank
2.0 bar
Vacuum vessel
1.6 bar
1.4 bar
16
Purge Process
Vent outside flame arrester
He Purge system
Metal Hydride storage unit (20m3 capacity)
Chiller/Heater Unit
18 K He
14 K He from Cold box
Fill valve
1 bar
X 2
X 2
1.6 bar
2.0 bar
Purge valve
Liquid level gauge
Vacuum
Internal Window
LH2 Absorber
Safety window
LHe Heat exchanger
Purge valve
Vent outside flame arrester
Evacuated vent buffer tank
2.0 bar
Vacuum vessel
1.6 bar
1.4 bar
17
Hydrogen Zones
Hydrogen zones definition according to RAL Safety
Code No.1 Zone 0 An area or enclosed space
within which any flammable or explosive
substance, whether gas, vapour, or volatile
liquid, is continuously present in concentrations
within the lower and upper limits of
flammability. Zone 1 An area within which any
flammable or explosive substance, whether gas,
vapour, or volatile liquid is processed, handled
or stored and where during normal operations an
explosive or ignitable concentration is likely to
occur in sufficient quantity to produce a hazard.
Zone 2 An area within which any flammable or
explosive substance whether gas, vapour or
volatile liquid, although processed or stored, is
so well under conditions of control that the
production (or release) of an explosive or
ignitable concentration in sufficient quantity to
constitute a hazard is only likely under abnormal
conditions.
18
Hydrogen Containment/Zones
Ventilated Hood
Vent outside flame arrester
He Purge system
Metal Hydride storage unit (20m3 capacity)
Chiller/Heater Unit
18 K He
14 K He from Cold box
1 bar
Fill valve
X 2
X 2
1.6 bar
2.0 bar
Purge valve
Liquid level gauge
Vacuum
Internal Window
LH2 Absorber
Safety window
LHe Heat exchanger
Purge valve
Vent outside flame arrester
2.0 bar
Evacuated vent buffer tank
Vacuum vessel
1.6 bar
Instrument Vacuum
1.4 bar
Lab
Outside
19
Safety Containment

• All external hydrogen pipes between the
  instrument and ventilation hood will be coaxial
  with an Argon jacket
• Hydrides and gas handling system will be situated
  under a hood

20
Layouts Pipework

• Use co-axial lines to prevent hydrogen escaping
  into the hall
• Storage and buffer tanks located in a vented
  enclosure
• Hydrogen pipes are at a high level so that any
  flames or escaping gas does not pass any personnel

21
Hydrogen Zones
Hydrogen system
Ventilation duct
H2 Buffer Tank
H2 Hydride unit
22
Pipe sizes - hydrogen vent
Massive loss of absorber vacuum ingress of air
or argon
40K 80K 300K Length m 0.3 0.5 10 Diameter
mm 15 25 40 Velocity m/s 109 154 227 Press
drop Bar 0.0165 0.0104 0.0989 Total 0.1258
300K
80K
40K
Magnet
Specific load (W/cm2) 3.6 Heat Load (W)
10kW Mass flow 23
g/sec
Mice vacuum space
23
Window rupture pipe sizes
Mike Green calculations on pipe sizes
Pipe from interspace vacuum 60mm Pipe connecting
buffer to flame arrester 100mm
1.6 bar
2.0 bar
Purge valve
Liquid level gauge
Vacuum
Internal Window
LH2 Absorber
Safety window
LHe Heat exchanger
Purge valve
Vent outside flame arrester
2.0 bar
Evacuated vent buffer tank
Vacuum vessel
1.6 bar
Instrument Vacuum
1.4 bar
Lab
Outside
24
Interlocks preliminary list
Alarm Possible Causes Actions
H2 Detector (any of three) Leak RF off, Beam off Empty absorber Purge
Pressure in interspace gt 1 x 104 mbar Air leak/H2 leak RF off, Beam off Empty absorber
Pressure in absorber gt 1.5 bar Plug or blockage RF off, Beam off Attempt to Empty absorber
Helium in gt 16K (TBC) Helium in lt 12K (TBC) Refrigerator problem note that we dont want to solidify hydrogen RF off, Beam off Empty absorber
25
Thermal Modelling for Safety
Thermal balance between radiation to inner
window at 18K and conduction to 300K
Particular concern is that the centre of the
outer window will fall below condensation point
of Oxygen
26
Implementation

• Absorbers will be tested prior to installation
  (see accompanying presentation)
• When in place helium leak detection will be used
  to check the leak tightness of the system prior
  to filling with hydrogen

27
Implementation

• Hydrogen sensors will be fitted in appropriate
  areas in the laboratory
• Intrinsically safe electrical connections will be
  made to all parts of the hydrogen system
• A stage testing and fault simulation plan will be
  implemented
• User and operating manual, procedures will be
  developed for the safe operation.
• A training plan will be followed

28
Summary

• We have well defined criteria for the current
  design of the hydrogen system
• Areas of risk have been identified and
  removed/minimised in the design
• System that will passively vent to a safe state
  without operator intervention

29

• END

30
Hydrogen Vapour Pressure
31
H2 Zones Electrical Safety
RAL Safety Code No.1 says The conditions
described as Zone 0 normally require the total
exclusion of any electrical equipment. Where this
proves to be impracticable special measures such
as pressurisation or the use of intrinsically
safe equipment may be used. A risk of the nature
described under Zone 1 can usually be met by the
use of flameproof or intrinsically safe
equipment. An alternative is to segregate,
ventilate or pressurise the electrical equipment
or room. In Zone 2 areas specially designed
electrical equipment is necessary. Intrinsic
Safety A circuit or piece of electrical
apparatus is said to be intrinsically safe when
the energy produced by a spark is insufficient to
ignite a flammable concentration. The minimum
ignition energy for hydrogen is 0.019mJ.
Pressurisation


Uncontaminated air or an inert gas such as
nitrogen shall be supplied to the apparatus. The
internal pressure must be maintained above the
ambient pressure. Segregation


It may be
possible to locate switches, control equipment,
motors etc. in a separate room within a high risk
area (Zone 0 or 1). The room should be kept under
slight positive air pressure using an
uncontaminated air supply the air pressure
should be monitored and the signal connected to
an alarm.