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Helium Leak Detection Method
  • Integral test of parts under vacuum in helium
  • Sniffing Test
  • Integral test of helium-filled parts in vacuum
  • Integral test at atmospheric pressure
  • Spraying test
  • Bombing test
  • Micro-Flow (overpressure test)
  • Mass Extraction(vacuum test)
Advantage :-
  • A part is put under a certain pressure condition.
  • A pressure Variation is observed over time.
  • The detected pressure variation is directly proportional to the leak rate.
Disadvantage :-
  • A very slow method.
  • Sensitive to temperature variations.
  • Desired sensitivity range out of reach.
  • Only suitable for containers that do not “flex”.
  • Leak pin-pointing not possible.
Advantage :-
  • The Bubble method is an inside out method, where the part is pressurized.
  • Observation of bubbles is made over time.
  • The part can be submerged into water.
  • The part can be wetted with a soap solution.
  • Unimportant leaks can be ignored.
  • Positive identification of the leak location.
Disadvantage :-
  • Product being wetted.
  • No total leak measurement possible.
  • Sensitivity depends on fluid surface tension.
Advantage :-
  • Inexpensive.
  • Same vacuum system for any part size.
  • Pin-Pointing a leak is easy.
  • No wetting to the parts.
Disadvantage :-
  • Leak to probe distance affects sensitivity.
  • Efficiency related to operator.
  • Efficiency related to operator.
Advantage :-
  • High sensitivity.
  • True leak rate measurement.
  • Short cycle time possible.
  • Background Problems eliminated.
  • No temperature influence.
Disadvantage :-
  • More expensive (more complex).
  • Only total leak measurement.

Helium Leak Detection Method

  • Integral test of parts under vacuum in helium
  • Sniffing Test
  • Integral test of helium-filled parts in vacuum
  • Integral test at atmospheric pressure
  • Spraying test
  • Bombing test
  • Micro-Flow (overpressure test)
  • Mass Extraction(vacuum test)

Dacay Method

Advantage :-
  • A part is put under a certain pressure condition.
  • A pressure Variation is observed over time.
  • The detected pressure variation is directly proportional
    to the leak rate.
Disadvantage :-
  • A very slow method.
  • Sensitive to temperature variations.
  • Desired sensitivity range out of reach.
  • Only suitable for containers that do not “flex”.
  • Leak pin-pointing not possible.

Water Immersion Test

Advantage :-
  • The Bubble method is an inside out method, where the part is pressurized.
  • Observation of bubbles is made over time.
  • The part can be submerged into water.
  • The part can be wetted with a soap solution.
  • Unimportant leaks can be ignored.
  • Positive identification of the leak location.
Disadvantage :-
  • Product being wetted.
  • No total leak measurement possible.
  • Sensitivity depends on fluid surface tension.

Sniffing Method

Advantage :-
  • Inexpensive.
  • Same vacuum system for any part size.
  • Pin-Pointing a leak is easy.
  • No wetting to the parts.
Disadvantage :-
  • Leak to probe distance affects sensitivity.
  • Efficiency related to operator.
  • Efficiency related to operator.

Spray Method

Advantage :-
  • High sensitivity.
  • True leak rate measurement.
  • Short cycle time possible.
  • Background Problems eliminated.
  • No temperature influence.
Disadvantage :-
  • More expensive (more complex).
  • Only total leak measurement.

Vaccum Pump Comparison Chart
DRY TYPE VACUUM PUMP SYSTEM
STEAM EJETOR SYSTEM
OIL ROTARY VACUUM PUMP SYSTEM
WATER SEALED VACUUM PUMP SYSTEM
Ultimate Pressure
Available until high vacuum (100-10-Torr), No chance of ultimate pressure at high temperature in Summer
As water temperature. rises at summer, ultimate pressure falis.
Emulsifying water and oil, ultimate pressure falls
It's limited for use under low vacuum (60-500 Torr)
Environment
Sewage problem is eliminated
Sewage
Waste oil
Sewage
Processing capacity (Pump capacity)
Capacity from small to high is used for specific application
For high capacity
The capacity is limited. For small capacity mostly
High capacity is available but with big expenses of power and investment
Utility
Only Little space needed for installation, Easy to utilize free space
Wide space is needed for installation
The space for installation is quite small so some free space is available.
Wide space is needed for installation
Operation cost
At same capa, 50% of operating cost can be saved.
Huge operating cost is spent due to excess utility
More electric power is needed compared to processing capacity
As capacity is getting bigger. power cost and operating cost are needed more.
Maintenance
Simple manipulation and maintenance at processing.
Difficult maintenance because of many individual facilities
Vacuum oil is needed to change often. Difficult maintenance
Difficult maintenance because of many individual facilities
Water Vapor Pressure Table

For this subsection, the following units conversions are applicable.

“F=9/5°C+32

To convert milimeters of mercury to pounds-force per square inch, multiply by 0.01934

VAPOR PRESSURE OF WATER ICE FORM -15 TO 0 °C
1°C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
-14
1.361
1.348
1.336
1.324
1.312
1.3
1.288
1.276
1.264
1.253
-13
1.49
1.477
1.464
1.45
1.437
1.424
1.411
1.399
1.386
1.373
-12
1.632
1.617
1.602
1.588
1.574
1.559
1.546
1.532
1.518
1.504
-11
1.785
1.769
1.753
1.787
1.722
1.707
1.691
1.676
1.661
1.646
-10
1.95
1.934
1.916
1.899
1.883
1.866
1.849
1.833
1.817
1.8
-9
2.131
2.112
2.093
2.075
2.057
2.039
2.021
2.003
1.985
1.968
-8
2.326
2.306
2.285
2.266
2.246
2.226
2.207
2.187
2.168
2.149
-7
2.537
2.515
2.493
2.472
2.45
2.429
2.408
2.387
2.367
2.346
-6
2.765
2.742
2.718
2.695
2.672
2.649
2.626
2.603
2.581
2.559
-5
3.013
2.987
2.967
2.937
2.912
2.887
2.862
2.838
2.813
2.79
-4
3.28
3.252
3.225
2.198
3.171
3.144
3.117
3.091
3.065
3.039
-3
3.568
3.539
3.509
3.48
3.451
3.422
3.393
3.364
3.336
3.308
-2
3.88
3.848
3.816
3.785
3.753
3.722
3.691
3.66
3.63
3.599
-1
4.217
4.182
4.147
4.113
4.079
4.045
4.012
3.979
3.946
3.913
0
4.579
4.542
4.504
4.467
4.431
4.395
4.359
4.323
4.587
4.252
VAPOR PRESSURE OF WATER ICE FORM -16 TO 0 °C
t°C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
-15
1.436
1.425
1.414
1.402
1.39
1.379
1.368
1.356
1.345
1.334
-14
1.56
1.547
1.534
1.522
1.511
1.407
1.485
1.472
1.46
1.449
-13
1.691
1.678
1.665
1.651
1.637
1.624
1.611
1.599
1.585
1.575
-12
1.834
1.819
1.804
1.79
1.776
1.761
1.748
1.734
1.72
1.705
-11
1.987
1.971
1.955
1.939
1.924
1.909
1.893
1.878
1.863
1.848
-10
2.149
2.134
2.116
2.099
2.084
2.067
2.05
2.034
2.018
2.001
-9
2.326
2.307
2.289
2.271
2.254
2.236
2.219
2.201
2.184
2.167
-8
2.514
2.495
2.475
2.456
2.437
2.418
2.399
2.38
2.362
2.343
-7
2.715
2.695
2.674
2.654
2.633
2.613
2.593
2.572
2.553
2.533
-6
2.931
2.909
2.887
2.866
2.843
2.822
2.8
2.778
2.757
2.736
-5
3.163
3.139
3.002
3.092
3.069
3.046
3.022
3
2.976
2.955
-4
3.41
3.384
3.334
3.334
3,309
3.284
3,259
3.234
3.211
3.187
-3
3.673
3.647
3.593
3.593
3.567
3.54
3.512
3.487
3.461
2.436
-2
3.956
3.927
3.871
3.871
3.841
3.813
3.785
3.757
3.73
3.702
-1
4.258
4.227
4.165
4.165
4.135
4.105
4.075
4.045
4.016
3.986
0
4.579
4.546
4.48
4.48
4.448
4.416
4.385
4.353
4.32
4.289

Computed form the above table with the aid of the thermodynamic quation.
log10 pw-1.1489t pi 273.1+t -5/2 -8/2 –1.330×10 +9.084×10

VAPOR PRESSURE OF LIQUID WATER FORM 0 TO 100 °C
t°C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0
4.579
4.613
4.647
4.681
4.715
4.75
4.785
4.82
4.855
4.89
1
4.926
4.962
4.998
5.034
5.07
5.107
5.144
5.181
5.219
5.256
2
5.294
5.332
5.37
5.408
5.447
5.486
5.525
5.565
5.605
5.645
3
5,685
5.725
5.766
5,807
5.848
5.889
5.931
5.973
6.015
6.058
4
6.101
6.144
6.187
6.23
6.274
6.318
6.363
6.408
6.453
6.498
5
6.543
6.589
6.635
6,681
6.728
6.775
6.822
6.869
6.917
6,965
6
7.013
7.062
7.111
7.16
7.209
7.259
7.309
7.36
7.411
7.462
7
7.513
7.565
7.617
7,669
7.722
7.775
7.828
7.882
7.936
7.99
8
8.045
81
8.155
8.211
8.267
8323
8.38
8.437
8.494
8.551
9
8.609
8.668
8.727
8.786
8.845
8.905
8.965
9,025
9.086
9.147
VAPOR PRESSURE OF LIQUID WATER FORM 0 TO 100 °C
t°C 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
109.2099.2119.3339.3659.4689.5219.5959.6499.7149.779
119.8449.9319.97610.04210.10910.17610.24410.31210.38010.449
1210.51810.58810.65810.72810.79910.87010.94111.01311.08511.158
1311.23111.30511.37911.45311.52811.60211.67811.75411.83111.908
1411.98712.06512.14412.22312.30212.38212.46212.54312.62412.706
1512.78812.87112.95313.03713.12113.20513.29013.37513.46113.547
1613.63413.72113.80913.89813.98714.07614.16614.25614.34714.438
1714.53014.62214.71514.80914.90314.99715.09215.18815.28415.380
1815.47715.57515.67315.77215.87115.97116.07116.17116.27216.374
1916.47716.58116.68516.78916.89416.99917.10517.21217.31917.427
2017.53517.64417.75317.86317.97418.08518.19718.30918.42218.536
2118.65118.76718.88319.00019.11819.23619.35519.47519.59519.716
2219.83719.95920.08120.20420.32820.45220.57720.70320.82920.956
2321.08421.21321.34221.47221.60321.73421.86621.99922.13222.266
2422.40122.53722.67422.81122.94923.08823.22723.36823.50923.651
2523.79423.93724.08124.22624.37224.51824.66524.81324.96225.112
2625.26325.41425.56625.71925.87326.02726.18226.33826.49526.653
2726.81226.97127.13127.29227.45427.61727.78127.94628.11128.278
2828.44628.61428.78328.95329.12429.29629.46929.64329.81829.994
2930.17130.34930.52830.70830.88931.07131.25431.43831.62331.809
3031.99632.18532.37532.56632.75832.95133.14533.34033.53633.733
3133.93134.13034.33034.53234.73434.93735.14135.34635.55235.759
3235.96736.17636.38636.59736.80937.02237.23637.45137.66737.884
3338.10238.32138.54138.76238.98439.20739.43139.65639.88240.109
3440.33740.56640.79641.02741.25941.49241.72641.96142.19742.434
3542.67242.91143.15143.39243.63443.87744.12144.36644.61244.859
3645.10745.35645.60645.85746.10946.36246.61646.87147.12747.384
3747.64247.90148.16148.42248.68448.94749.21149.47649.74250.009
3850.27750.54650.81651.08751.35951.63251.90652.18152.45752.734
3953.01253.29153.57153.85254.13454.41754.70154.98655.27255.559
4055.84756.13656.42656.71757.00957.30257.59657.89158.18758.484
4158.78259.08159.38159.68259.98460.28760.59160.89661.20261.509
4261.81762.12662.43662.74763.05963.37263.68664.00164.31764.634
4364.95265.27165.59165.91266.23466.55766.88167.20667.53267.859
4468.18768.51668.84669.17769.50969.84270.17670.51170.84771.184
4571.52271.86172.20172.54272.88473.22773.57173.91674.26274.609
4674.95775.30675.65676.00776.35976.71277.06677.42177.77778.134
4778.49278.85179.21179.57279.93480.29780.66181.02681.39281.759
4882.12782.49682.86683.23783.60983.98284.35684.73185.10785.484
4985.86286.24186.62187.00287.38487.76788.15188.53688.92289.309
5089.69790.08690.47690.86791.25991.65292.04692.44192.83793.234
60149.38150.43151.77153.38155.31157.54159.95162.47165.17168.01
70223.7226.9230.4234.1238.0242.1246.3250.6255.0259.6
80335.1340.7346.9353.5360.6368.2376.3384.9394.0403.7
90525.76527.76529.77531.78533.80535.82537.86539.9541.95544.0
91546.05548.11550.18552.26554.35556.44558.53560.64562.75564.87
92566.99569.12571.26573.4575.55577.71579.87582.04584.22586.41
93588.6590.8593.0595.21597.43599.66601.89604.13606.38608.64
94610.90613.17615.44617.72620.01622.31624.61626.92629.24631.57
95633.90636.24638.59640.94643.3645.67648.05650.43652.82655.22
96657.62660.03662.45664.88667.31669.75672.2674.66677.12679.69
97682.7684.85687.04689.04692.05694.57697.1699.63702.17704.71
98707.27709.83712.4714.98717.56720.15722.75725.36727.98730.61
99733.24735.88738.53741.18743.85746.52749.20751.89754.58757.29
100760.0762.72765.45768.19770.93773.68776.44779.22782.0784.78
101787.57790.37793.18796.0798.82801.66804.5807.35810.21813.08

Pressure Unit Converter

to
Pressure unit Conversion Table
FROM/TO
Pa
Torr
atm
mbar
psi
kg/cm
mmAq
Pascal(N/㎡)
1
7.5 X 10
9.87 X 10
10
1.45 X 10
1.02 X 105
0.10197
Torr(mmHg)
13
1
1.316 X 10
1.333
1.934 X 10
1.359 X 10
13.59
atm(atmosphere)
1.013 X 10
760
1
1.013 X 10
14.695
1.033
10332
mbar(millibar)
100
0.75
9.87 X 10
1
1.45 X 10
1.02 X 10
10.197
psi(lb/
6.89 X 10
51.71
6.8 X 102
6.89
1
7.031 X 10
703.1
kg/cm
9.81 X 10
7.536 X 102
0.968
9.81 X 10
14.223
1
10000
mmAq(水柱)
9.806
0.0736
9.68 X 10
0.098
1.42 X 10
1 X 10
1