13.4 Application of Special Measurement Technology
451
Factors on uncertainty of non vacuum accumulation leak
test method by helium Mass Spectrometer
Linearity
Of
Leak
Detector
Change
Of
Inlet
Pressure
Internal
Bumping
Speed
Of
Leak
Detector
Homogeneity
Of
Helium
Concentration
Air
Tightness
Of
Collection
Chamber
Sampling
Pressure
Standard
Volume
Accumulation
Time
Sampling
Time
Random
Effects
Caused
By
Environment
And etc.
Fig. 13.13 Factors on uncertainty of non-vacuum accumulation leak test method by helium Mass
Spectrometer
Table 13.1 Uncertainty components caused by different factors
Magnitude/(Pa•m3/s) Uncertainty caused by
system effect (%)
Uncertainty caused by
random effect (%)
Synthetic standard
uncertainty (%)
1 × 10 −4 ~1 × 10 −5
7.38
6.86
10.08
1 × 10 −3 ~1 × 10 −4
7.64
16.21
17.92
1 × 10 −2 ~1 × 10 −3
7.64
8.24
11.24
13.4.4 Quick Leak Positioning Technology for Propulsion
Subsystem
1. Requirements
The conventional leak test in system assembly process is to conduct single point
leak test, such as weld, screw connection and etc., so as to ensure that single point
leak meet the requirement and then conduct total leak test. In conventional leak
test, if single point leak test is qualified, the total leakage rate is generally qualified.
However, if there is the leak caused by raw material and parts that is unforeseen
leak in system assembly and it is missed before system assembly, there will be total
leakage rate of the system over requirement level. Specially, when the leakage rate
is close to the total leakage rate of system, it will be very hard to position the leak.
Because propulsion subsystem of the Chang’E-3 lunar lander was complex and it was
difficult to position the leak. However, there was requirement for quick positioning
of the leak point during development of the lunar lander. It was necessary to develop
a quick leak positioning technology. The Flexible Helium Hood method for quick
leak positioning was suitable for complex system that could not be tested by bubble
method.
2. Technical Design and Principle
The flexible helium hood method for quick leak positioning was a technology
between the single point leak test and the total leak test of the spacecraft. It was
suitable for the search and identification of the leak below the 10
−4 Pa•M3/s.
451
Factors on uncertainty of non vacuum accumulation leak
test method by helium Mass Spectrometer
Linearity
Of
Leak
Detector
Change
Of
Inlet
Pressure
Internal
Bumping
Speed
Of
Leak
Detector
Homogeneity
Of
Helium
Concentration
Air
Tightness
Of
Collection
Chamber
Sampling
Pressure
Standard
Volume
Accumulation
Time
Sampling
Time
Random
Effects
Caused
By
Environment
And etc.
Fig. 13.13 Factors on uncertainty of non-vacuum accumulation leak test method by helium Mass
Spectrometer
Table 13.1 Uncertainty components caused by different factors
Magnitude/(Pa•m3/s) Uncertainty caused by
system effect (%)
Uncertainty caused by
random effect (%)
Synthetic standard
uncertainty (%)
1 × 10 −4 ~1 × 10 −5
7.38
6.86
10.08
1 × 10 −3 ~1 × 10 −4
7.64
16.21
17.92
1 × 10 −2 ~1 × 10 −3
7.64
8.24
11.24
13.4.4 Quick Leak Positioning Technology for Propulsion
Subsystem
1. Requirements
The conventional leak test in system assembly process is to conduct single point
leak test, such as weld, screw connection and etc., so as to ensure that single point
leak meet the requirement and then conduct total leak test. In conventional leak
test, if single point leak test is qualified, the total leakage rate is generally qualified.
However, if there is the leak caused by raw material and parts that is unforeseen
leak in system assembly and it is missed before system assembly, there will be total
leakage rate of the system over requirement level. Specially, when the leakage rate
is close to the total leakage rate of system, it will be very hard to position the leak.
Because propulsion subsystem of the Chang’E-3 lunar lander was complex and it was
difficult to position the leak. However, there was requirement for quick positioning
of the leak point during development of the lunar lander. It was necessary to develop
a quick leak positioning technology. The Flexible Helium Hood method for quick
leak positioning was suitable for complex system that could not be tested by bubble
method.
2. Technical Design and Principle
The flexible helium hood method for quick leak positioning was a technology
between the single point leak test and the total leak test of the spacecraft. It was
suitable for the search and identification of the leak below the 10
−4 Pa•M3/s.