GB/T 15823-2009 PDF English
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Non-destructive testing -- Test methods for helium leak testing
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| GB/T 15823-1995 | English | 439 |
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Examination for helium leak detecting
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GB/T 15823-2009: PDF in English (GBT 15823-2009) GB/T 15823-2009
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 19.100
J 04
Replacing GB/T 15823-1995
Non-destructive testing - Test methods for helium leak
testing
ISSUED ON: MAY 26, 2009
IMPLEMENTED ON: DECEMBER 01, 2009
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of the PRC;
Standardization Administration of the PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 General requirements ... 5
5 Testing ... 7
6 Documentation ... 9
7 Report ... 9
Appendix A (Normative) Suction gun technique ... 11
Appendix B (Normative) Tracer probe technique ... 16
Appendix C (Normative) Shield technique ... 20
Non-destructive testing - Test methods for helium leak
testing
1 Scope
This Standard specifies the methods and requirements for helium leak testing.
These testing methods or techniques can be used to determine the leak position
or measure the leak rate. See Appendix A ~ Appendix C for specific testing
techniques.
2 Normative references
The following documents contain provisions which, through reference in this
Standard, constitute provisions of this Standard. For the dated references, their
subsequent amendments (excluding corrections) or revisions do not apply to
this Standard. However, the parties who enter into agreement based on this
Standard are encouraged to investigate whether the latest editions of these
documents are applicable. For undated reference documents, the latest
editions apply to this Standard.
GB/T 5616 Non-destructive testing - Guidelines for application
GB/T 9445 Non-destructive testing - Qualification and certification of
personnel (GB/T 9445-2008, ISO 9712:2005, IDT)
GB/T 12604.7 Non-destructive testing - Terminology - Leak testing
GB/T 20737 Non-destructive testing - General terms and definitions (GB/T
20737-2006, ISO/TS 18173:2005, IDT)
3 Terms and definitions
The terms and definitions established in GB/T 12604.7 and GB/T 20737 apply
to this Standard.
4 General requirements
4.1 Pre-leak testing
Before adopting a more sensitive testing method, a pre-leak testing can be
When performing pressure/vacuum leak testing, the indicating-type pressure
gauge shall be directly connected to the tested part, or connected to the tested
part from the remote end; so that the tester can easily observe these pressure
gauges/vacuum gauges during the whole process of testing.
For large vessels or systems under test that require one or more pressure
gauges/vacuum gauges, it is recommended to use a recording-type pressure
gauge/vacuum gauge, to replace one of the two or more indicating-type
pressure gauges/vacuum gauges.
4.3.1.4 Application
When Appendix A ~ Appendix C require the use of other types of pressure
gauges/vacuum gauges, they can be used separately instead of the
corresponding number of indicating-type or recording-type pressure gauges; or
can be used in combination.
4.3.2 Temperature measuring device
When Appendix A ~ Appendix C require temperature measurement, the
temperature measuring device shall pass the verification.
4.3.3 Standard leak
The standard leaks used for helium mass spectrometer leak testing can be
divided into the following two categories:
a) Permeable standard leak - It shall be a permeable leak of glass or quartz
that has been melted and calibrated. It has a helium leak rate of 1×10-11
Pa · m3/s ~ 1×10-7 Pa · m3/s; shall pass the verification.
b) Channel-type standard leak - It shall be a channel-type leak calibrated
with helium that allows the tracer gas to pass through a tube. It shall have
a leak rate equal to or less than the product of the required testing
sensitivity and the actual percentage concentration of tracer gas. It shall
pass the verification.
5 Testing
5.1 Preparation for testing
5.1.1 Surface preparation
The surface of the tested part shall be free of oil, grease, paint and other dirt
that may hinder the testing. When liquids are used to clean the parts, or the
water pressure test or hydro-pneumatic test is performed before the leak testing,
the tested parts shall be fully dried before the testing.
5.1.2 Seal
Before testing, plugs, cover plates, sealing grease, glue, or other suitable
materials that can be easily removed after leak testing shall be used to seal all
holes. The sealing material shall not contain tracer gas.
5.1.3 Testing temperature
The minimum temperature of the tested parts during the testing shall be in
accordance with the requirements of each appendix; or in accordance with the
provisions of relevant product design documents and of procurement technical
conditions for hydraulic, hydro-pneumatic or pneumatic tests of the tested parts.
The minimum or maximum temperature during testing shall not exceed the
temperature allowed by the leak testing method or technique used.
5.1.4 Pressure/vacuum (pressure limit)
Unless otherwise specified in the relevant design documents and procurement
technical conditions, components, which need to be subjected to pressure leak
testing, shall not be tested at a pressure exceeding 25% of the design pressure.
5.2 Testing timing
Leak testing should be performed before hydraulic or hydro-pneumatic testing.
If the acceptance party considers it necessary, a leak testing can be performed
again after the hydraulic or hydro-pneumatic testing. The pressure vessel shall
not be evacuated unless it is confirmed by design calculation.
5.3 Testing methods and techniques
Common helium leak testing methods and techniques are shown in Table 1.
The specific requirements of various helium leak testing methods and
techniques listed in Table 1 are shown in Appendix A ~ Appendix C.
m) Post cleaning method;
n) Personnel qualifications.
A.2.2 Equipment and apparatus
A.2.2.1 Instruments
A helium mass spectrometer capable of sensing and measuring trace amounts
of helium shall be used. One or more of the following signal devices shall be
used to indicate leak:
a) Meter - A meter on or attached to an instrument;
b) Audible device - Loudspeaker or earphone capable of emitting audible
signals;
c) Indicator lamp - An indicator lamp that can emit visible light.
A.2.2.2 Auxiliary equipment
When needed, the following auxiliary equipment can be used:
a) Voltage stabilizer - When there is voltage fluctuation in the power supply
line, a voltage stabilizer shall be connected to the instrument;
b) Suction gun - All parts that need to be inspected shall be scanned with a
suction gun. The suction gun is connected to the instrument with a section
of bellows. In order to shorten the response time and purification time,
unless the testing device is specially designed to obtain a short response
time and purification time with a longer hose, the length of the hose shall
be about 4570 mm.
A.2.2.3 Calibrated standard leak
The calibrated standard leak can be a permeable or channel-type standard leak
according to 4.3.3 of this Standard. The type of standard leak used shall be
determined according to the sensitivity requirements of the instrument or
equipment, or according to relevant design specifications.
A.3 Calibration
A.3.1 Instrument calibration
A.3.1.1 Preheating
Before calibrating with the verified standard leak, the instrument shall be
energized to preheat. The minimum time for preheating shall be in accordance
l) Scan distance, speed and method;
m) Acceptance criteria;
n) Personnel qualifications.
B.2.2 Equipment and apparatus
B.2.2.1 Instruments
A helium mass spectrometer capable of sensing and measuring trace amounts
of tracer helium shall be used. One or more of the following signal devices shall
be used to indicate leak:
a) Meter - A meter on or attached to an instrument;
b) Audible device - Loudspeaker or earphone capable of emitting audible
signals;
c) Indicator lamp - An indicator lamp that can emit visible light.
B.2.2.2 Auxiliary equipment
When needed, the following auxiliary equipment can be used:
a) Voltage stabilizer - When there is voltage fluctuation in the power supply
line, a voltage stabilizer shall be connected to the instrument;
b) Auxiliary pump system - When the testing equipment needs to use the
auxiliary vacuum pump system, the absolute pressure and pump speed
of the system shall enable the testing sensitivity and response time to
meet the requirements;
c) Multi-directional joints - Pipes and valves that can correctly connect the
instrument vacuum gauge, auxiliary pump, standard leaks and tested
parts;
d) Tracer probe - Connected to a 100% helium source; a valve with a small
opening is used at the other end to adjust the helium flow;
e) Vacuum gauge - The range of the vacuum gauge shall be able to measure
the absolute pressure when the evacuated system is tested. The location
of the vacuum gauge used in large systems shall be as far away as
possible from the inlet of the pump system.
B.2.2.3 Calibrated standard leak
The calibrated standard leak can be a permeable or channel-type standard leak.
The type of standard leaks shall be selected according to the instrument or
sensitivity requirements, or according to design specifications.
B.3 Calibration
B.3.1 Instrument calibration
B.3.1.1 Preheating
Before calibrating with the verified standard leak, the instrument shall be
energized to preheat. The minimum time for preheating shall be in accordance
with the regulations of the instrument manufacturer.
B.3.1.2 Calibration
In accordance with the operation and maintenance manual of the instrument
manufacturer, the instrument shall be calibrated with the permeable standard
leak described in 4.3.3 a) of this Standard, so that it is at the best or adequate
sensitivity. The sensitivity of the instrument is at least 1×10-10 Pa · m3/s.
B.3.2 System calibration
B.3.2.1 Standard leak size
Connect the verified channel-type standard leak described in B.2.2.3 to the
component; and as far as possible away from the connection between the leak
detector and the component. When calibrating the testing system, the verified
standard leak shall be opened.
B.3.2.2 Scan rate
When the evacuated parts reach sufficient vacuum, connect the helium mass
spectrometer to the system. Calibrate the system by tracing the probe nozzle
across the standard leak. The probe nozzle shall be within 6 mm from the
standard leak. For the known flow rate of the 100% helium tracer probe, the
scan rate for the testing system shall not exceed the rate at which leak from the
standard leak can be detected.
B.3.2.3 Response time
During system calibration, it shall observe the time required for the appearance
of an indicator signal and for the instrument output to stabilize. It is generally
desirable that this time be as short as possible, to reduce the time required to
determine the leak position.
B.3.2.4 Calibration frequency and sensitivity
l) Acceptance criteria;
m) Personnel qualifications.
C.2.2 Equipment and apparatus
C.2.2.1 Instruments
A helium mass spectrometer capable of sensing and measuring trace amounts
of tracer helium shall be used. The leak shall be indicated by the meter on or
attached to the test instrument.
C.2.2.2 Auxiliary equipment
When needed, the following auxiliary equipment can be used:
a) Voltage stabilizer - When there is voltage fluctuation in the power supply
line, a voltage stabilizer shall be connected to the instrument;
b) Auxiliary pump system - When the testing equipment needs to use the
auxiliary vacuum pump system, the absolute pressure and pump speed
of the system shall enable the testing sensitivity and response time to
meet the requirements;
c) Multi-directional joints - Pipes and valves that can correctly connect the
instrument vacuum gauge, auxiliary pump, standard leaks and tested
parts;
d) Shield - Any suitable cover or container, such as a plastic bag, with an
intake pipe used as multiple nozzles;
e) Vacuum gauge - The range of the vacuum gauge shall be able to measure
the absolute pressure when the evacuated system is tested. The location
of the vacuum gauge used in large systems shall be as far away as
possible from the inlet of the pump system.
C.2.2.3 Calibrated standard leak
The permeable standard leak described in 4.3.3 of this Standard shall be used.
Unless otherwise specified in the relevant design specifications, its maximum
helium leak rate is 1×10-7 Pa · m3/s.
C.3 Calibration
C.3.1 Instrument calibration
C.3.1.1 Preheating
Before calibrating with the verified standard leak, the instrument shall be
energized to preheat. The minimum time for preheating shall be in accordance
with the regulations of the instrument manufacturer.
C.3.1.2 Calibration
According to the operation and maintenance manual of the instrument
manufacturer, use the permeable standard leak described in 4.3.3 a) of this
Standard, to confirm whether the instrument is in the best condition or has
sufficient sensitivity. The sensitivity of instrument to helium is at least 1×10-10
Pa · m3/s.
C.3.2 System calibration
C.3.2.1 Standard leak size
Connect the calibrated standard leak with 100% helium as described in 4.3.3 to
the component; and keep it as far away as possible from the connection
between the leak detector and the component.
C.3.2.2 Response time
The components are evacuated to an absolute pressure sufficient to allow the
helium mass spectrometer to be connected to the system. The verified standard
leak shall be opened to the system.
The standard leak shall remain open until the instrument signal becomes stable.
The time when the verified standard leak opens to the component and the time
when the output signal increases to stabilize shall be recorded. The time
elapsed between the two readings is the response time. Record the stable
instrument reading M1.
C.3.2.3 Background reading
The background reading M2 is determined after measuring the response time.
The calibrated standard leak closes the testing system. When the instrument
reading reaches a stable level, record the instrument reading M2.
C.3.2.4 Initial calibration
The initial system sensitivity S1 shall be calculated according to formula (C.1):
Where:
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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