Leak detection techniques
Helium Leak Testing Techniques for Industry.
September 2009
Leak detection techniques
If a system is leaking.......
....... you are in trouble!
September 2009
Leak detection techniques
Finding a leak......
.......can also cause problems!
September 2009
Leak detection techniques
Reasons for Leak Testing:
„
Environmental
„
Safety ISO 9000
„
Product life
„
Reliability
„
Product specifications
„
Marketing advantage
September 2009
Leak detection techniques
Application list
Analytical
Medicine technology
IT
Mass spectrometer systems
Electron beam microscopes
Pacemaker
Electron microscope
X-ray tubes
Ampulla
Transfer chambers
Load looks
Tubing
Power engineering
Vaccum equipment
Power turbine
Power condensor
High voltage components
Whole vacuum program
Pump housings
Automotive
AC
Brake tubing
Heat exchnanger
Fuel tanks
Compressors
Evaporators
Valves
Thermostat
Process industry
R&D
He bath cooler
3He cooler
Ion beam accelerators
UHV ^/XHV systems
He transfer lines
September 2009
Furnaces
Soldering ovens
High pressure vales
Leak detection techniques
Automotive
Pre-test with He-LD integrated in a
refrigerant filling unit for AC
Cars
„
BMW
„
Mercedes/DC
„
Audi
„
VW
„
Ford
„
Volvo
„
Peugeot
„
etc.
Application
Pressure / Vac
Sub-systems
Supplier
„
Fuel tanks
Walbro etc
„
tubes, hoses
Contitech /
Eaton
„
Valves
Buerkert
„Heat
„air
Air condition
He and refrig.
exchangers
bags
September 2009
Temic /
Dyn.Nobel
high pressure
bellows
„
„injection
Behr
pumps
Witzenman
Bosch
Leak detection techniques
Types of Leaks
„
Leaks at connections
flanges, welding, soldering, grindings ( glass fittings)
„
Permeation leaks
gas transport through materials e.g. elastomeric seals,
glass
„
Porosity leaks
castings
„
Virtual leaks
gaps, small volumes in castings, evaporation of liquids,
sintered metal, plastic parts
„
Hot /cold leaks
cracks open or close due to thermal tensions
September 2009
Leak detection techniques
rise pressure mbar
Definition of mbarl/s
Volume of 1 liter
September 2009
time /s
Leak detection techniques
Examples of well known leaks
1,7x10-1
Water tap 1 drip per second
1x10-3 - 5x10-2
Hair between O-ring and flange
mbarl/s
mbarl/s
Bicycle tube in water
( bubble test, 1 bubble/sec )
1x10-2
mbarl/s
Car wheel loses air
1,8 Ô 1,6 bar in 6 month
4x10-5
mbarl/s
September 2009
Leak detection techniques
Understanding of tightness
understanding
leak rate range
particel size
remarks
for Helium
mbarl/s
for air at 20°C
kg/h
water tight
10-2
10-5
drip
vapour tight
10-3
10-6
sweat
bacteria tight
10-4
10-7
fuel and oil tight
10-5
10-8
virus tight
10-6
10-9
gas tight
10-7
10-10
"absolut tight"
10-10
10-11
September 2009
d~10-6 m
d~0,3x10-6 m
technical
Leak detection techniques
Methods of Leak Tests
medium
limit of leak rate
mbarl/s
pressure range
quantifiable
rise pressure
air & others
10-4
vacuum
limited
pressure drop
air & others
10-4
overpressure
limited
foaming agent
air & others
10-5
overpressure
no
bubble test
air & others
10-4
overpressure
limited
supersonic
air & others
10-2
overpressure /
low pressure
no
thermal conductivity
air & others
10-5
overpressure /
low pressure
no
mass spectrometer
quadrupole
refrigerents;gases
10-7
overpressure
yes
mass spectrometer
magnet. Sector field
Helium
Hydrogen
< 10-7
overpressure
yes
mass spectrometer
magnet. Sector field
Helium
Hydrogen
< 5x10-12
vacuum
yes
Procedure
September 2009
Leak detection techniques
Pressure rise effects in a chamber
a) Leak
b) Desorbtion
c) Leak + Desorbtion
September 2009
Leak detection techniques
Why is Helium a good Test Gas?
„
Low concentration in air , only 5 ppm, so low natural background
„
Inert gas, non toxic, non- explosive, environmentally friendly
Good separation in a mass spectrometer ( no cross sensitivity to
other gases and no mass fragments
„
„
Lighter than air
„
Very small gas molecule, can easily pass through small holes/gaps
September 2009
Leak detection techniques
Principle Methods of Leak Detection
Vacuum method
¾
global detection ( He outside )
¾
global detection ( He inside )
¾
Local detection
Overpressure method
¾
Local detection ( sniffing )
September 2009
Leak detection techniques
Vacuum Method
Global Detection
Lowest detectable leak rate < 5x10-12 mbarl/s
1
Test unit
Helium
( under vacuum)
2
1
Pressure chamber w Helium
2
Test vessel
3
Leak detector
4
Helium
5
Auxiliary Pump System
3
September 2009
Leak detection techniques
Vacuum Method
Global Detection
Lowest detectable leak rate < 5x10-12 mbarl/s
1
Vacuum chamber
2
Test body
3
Leak detector
4
Helium
5
Auxiliary Pump System for huge vessels
3
September 2009
Leak detection techniques
Vacuum Method
Local Detection
Lowest detectable leak rate < 5x10-12 mbarl/s
1
Spray gun
2
Test body
3
Leak detector
4
Helium
5
Auxiliary Pump System
(for large vessels)
3
September 2009
Leak detection techniques
Overpressure Method
Local Detection
(sniffing)
Lowest detectable leak rate < 1x10-7 mbarl/s!!!
1
Sniffer probe
2
Test vessel
3
Leak detector
4
Helium
3
September 2009
y
Leak detection techniques
Worked sample
How long does it takes to rise the pressure in a volume
of 1 l from 1 to 2 mbar if a leak of 1x10-6 mbarl/s is
present?
1x10-6mbarl/s
q L = V /t ∗ Δp
t = V / qL ∗ Δp
= 1l / 1x10-6mbarl/s ∗ 1 mbar
V =1l
Δp = 1mbar
= 100 000s
q L = 1x10-6mbarl/s
= 277,7h
= 11,5d
September 2009
Leak detection techniques
Pressure rise method with vacuum ( no Helium )
Example:
Test volume: V = 1m³
Δp: p = 1 · 10-3 mbar until 8 · 10-3 mbar
Time : t = 5 min
QL = ??
Q=
V
t
· Δ p [mbar · l · s-1]
= 1000 l
300 s
· 7 · 10-3 mbar
= 2,33 · 10-2 mbar · l · s-1
Air leak rate
Δ p = p2 – p1 = 8 · 10-3 – 1 · 10-3 = 7 · 10-3 mbar
September 2009
Leak detection techniques
Partial Flow System
September 2009
Leak detection techniques
Partial Flow Principle
Chamber
Test leak
The Helium flow will be splitted into
2 directions
QHe = 3 · 10-5 mbar · l / s
SLD = 2,5 l / s
QHe=Ssum . p
PhoeniXL300
p
QL=SLD. p
SP = 60 m³ / h = 16,66 l / s
Ssum = SLD + SP
p = QHe/Ssum
QL=QHe . SLD/Sp+SLD
Auxiliary pump
Flow to LD
QL: 3 · 10-5 ·
2,5
2,5 + 16,66
= 3,9 · 10-6 mbar · l / s
Flow to auxiliary pump
QP: 3 · 10-5 ·
16,66
2,5 + 16,66
= 2,6 · 10-5 mbar · l / s
Total = 3 · 10-5 mbar · l / s
Flow ratio γ =
September 2009
display LD
leak rate Test leak
Leak detection techniques
Partial Flow System
September 2009
Leak detection techniques
Conversion of mass flowes-(Leak Rates)
1↓ = ... →
mbar · l/s
mbar · l/s
1
kg·h–1
(20 °C)
kg·h–1
(0 °C)
4.28 · 10–3 4.59 · 10–3
cm3/h
(NTP)
cm3/s
(NTP)
Torr · l/s
3554
0.987
g/a
g/a
m · cfm
lusec
Pa · l/s
slpm
1.54 · 105
1593
7.52 · 102
100
59.2 · 10–3
(F12. 20 °C)
(F12. 25°C)
0.75
1.56 · 105
kg · h–1 (20 °C)
234
1
1.073
8.31 · 105
231
175
–
–
37.2 · 104
1.75 · 105
23.4 · 103
13.86
kg · h–1 (0 °C)
218
0.932
1
7.74 · 105
215
163
–
–
34.6 · 104
1.63 · 105
21.8 · 103
12.91
cm3/h (NTP)
2.81 · 10–4
1.20 · 10–6
1.29 · 10–6
1
44
–
44.7 · 10–2
2.11 · 10–1
2.81 · 10–2
1.66 · 10–5
cm3/s (NTP)
1.013
4.33 · 10–3
4.65 · 10–3
3600
1
0.760
1.58 · 105
–
1611
760
101
6 · 10–2
Torr · l/s
1.33
5.70 · 10–3
6.12 · 10–3
4727
1.32
1
2.08 · 105
2.05 · 105
2119
1 · 103
133
78.8 · 10–3
g/a (F12. 20 °C) 6.39 · 10–6
–
–
2.27 · 10–2 6.31 · 10–6 4.80 · 10–6
1
–
10.2 · 10–3
4.8 · 10–3
6.39 · 10–4
37.9 · 10–8
g/a (F12. 25 °C) 6.50 · 10–6
–
–
–
4.88 · 10–6
–
1
10.4 · 10–3
4.89 · 10–3
6.5 · 10–4
38.5 · 10–8
98.16
96.58
1
0.472
6.28 · 10–2
37.2 · 10–6
208
205
2.12
1
13.3 · 10–2
78.8 · 10–6
1.54 · 103
15.93
7.50
1
59.2 · 10–5
12.7 · 103
16.9 · 102
1
2.78 · 10–4 2.11 · 10–4
–
m · cfm
6.28 · 10–4
2.69 · 10–6
2.89 · 10–6
2.24
6.21 · 10–4 4.72 · 10–4
lusec
1.33 · 10–3
5.70 · 10–6
6.12 · 10–6
4.737
1.32 · 10–3 1 · 10–3
1 · 10–2
4.28 · 10–5
4.59 · 10–5
35.54
9.87 · 10–3 7.5 · 10–3 1.56 · 103
Pa · l/s
slpm
16.88
72.15 · 10–3 77.45 · 10–3 60.08 · 103
16.67
12.69
2.64 · 106
2.60 · 106 26.9 · 103
1 cm3 (NTP) = 1 cm3 under normal condition (T = 273.15 K; p = 1013.25 mbar)
NTP = normal temperature and pressure (1 atm; 0 °C) R = 83.14 mbar · l · mol–1 · K–1
1 cm3 (NTP) · h–1 = 1 atm · cm3 · h–1 = 1 Ncm3 · h–1 = 1 std cch
1 sccm = 10–3 slpm = 10–3 N · l · min–1 = 60 sccs
SI-System kohärent: 1 Pa · m3 · s–1 = 10 mbar · l · s–1; R = 8.314 Pa · m3 · mol–1 · K–1; M in kg / mol
1 cm3 (NTP) · s–1 = 1 sccs = 60 cm3 (NTP) · min–1 60 sccm = 60 std ccm = 60 Ncm3 · min–1
1 lusec = 1 l · μ · s–1 1 · μ = 1 micron = 10–3 Torr 1 lusec = 10–3 Torr · l · s–1
Freon F 12 (CCl2F2) M = 120.92 g · mol–1; Luft M = 28.96 g · mol–1
Achtung: Anglo-amerikanische Einheiten werden uneinheitlich abgekürzt! Beispiel: Standard cubic centimeter per minute → sccm = sccpm = std ccm = std ccpm
September 2009
Leak detection techniques
Technical Data
PhoeniXL 300
Lowest detectable He leak rate ( vacuum mode )
mbarl/s
<5x10
-12
PhoeniXL 300 Dry
<3x10
-7
-11
-7
PhoeniXL 300Modul
<5x10
-12
/ <8x10
-12
-8
Lowest detectable leak rate ( sniffer mode )
mbarl/s
<1x10
Max. detectable He leak rate ( vacuum mode )
mbarl/s
> 0,1
> 0,1
> 0,1
Max. permissable inlet pressure
mbar
15
15
15
Max. permeissable inlet pressure w partial flow set
mbar
1000
-
-
2,5 ( 50 Hz )
3 ( 60 Hz )
1,6 ( 50 Hz )
1,8 ( 60 Hz )
> 2,5
16/20 ( 50 / 60 Hz ) D16B
25/30 ( 50 / 60 Hz )D25B
30/36 ( 50 / 60 Hz )Scroll
> 2,5
3
<1x10
<1x10
Pumping speed during pump down
m
Pumping speed for Helium
l/s
> 2,5
Pumping speed with partial flow set and D16B
l/s
16 ( 50Hz)
Pumping speed with partial flow set and D25B
l/s
25 ( 50 Hz )
Time constant for leak rate signal
s
<1
<1
<1
min
<2
<2
<2
Time until ready for operation
180° magn. Sector field
Mass spectrometer
4
He; 3 He ; H 2
4; 3 ; 2
4; 3 ; 2
4; 3 ; 2
Relay outputs
4
4
4
SPS inputs
6
6
6
Detectable masses
amu
DN 25 KF
Test port connection
Length of hand unit cable ( option )
m
4 ( max. 32 )
4 ( max. 32 )
4 ( max. 32 )
420 VA
350 VA
350 VA
mm
495 x 456 x 314
495 x 456 x 314
495 x 456 x 314
kg
40
37,5
29
Power consumption
Dimensions
Weight
(LxHxD)
PhoeniXL300Modul pump connection flange size DN25KF
September 2009
Leak detection techniques
Customised test stations
(Customized by OLV)
LD work station for serial
production of small parts
„
PhoeniXL340
September 2009
September 2009
September 2009