ASTM E908 – 98(2004), Standard Practice for Calibrating Gaseous Reference Leaks.
ASTM E1002 – 05, Standard Test Method for Leaks Using Ultrasonics.
ASTM E1003 – 05, Standard Test Method for Hydrostatic Leak Testing.
ASTM E1066 – 95(2006) Standard Test Method for Ammonia Colorimetric Leak Testing.
ASTM E1211 – 07 Standard Practice for Leak Detection and Location Using Surface-Mounted Acoustic Emission Sensors.
ASTM E1603 – 99(2006) Standard Test Methods for Leakage Measurement Using the Mass Spectrometer Leak Detector or Residual Gas Analyzer in the Hood Mode.
BS EN 1518 (1998) Non-destructive testing – Leak testing – Characterization of mass spectrometer leak detectors.
BS EN 1593 (1999) Non-destructive testing – Leak testing – Bubble emission techniques.
BS EN 1779 (1999) Leak tightness by indication or measurement of gas leakage.
BS EN 13184 (2001) Non-destructive testing – Leak testing – Pressure change method.
BS EN 13185 (2001) Non-destructive testing. Leak testing. Tracer gas method.
5.1.3. Standards related to specific product forms
In addition to the many standards that relate to the testing techniques and their applications, it should be recognized that the manufacturers and users of specific equipment may include in their standards some requirements for leak testing. Some typical such product standards are listed in this section. There has been no attempt to list all such standards and it is incumbent on the user to be familiar with the technology related to the specific product being examined.
ISO 27895 (2009) Vacuum technology - Valves – Leak test.
BS EN 12298 (1998) Biotechnology - Equipment - Guidance on testing procedures for leak tightness
ASTM A1047 – 05(2009) Standard Test Method for Pneumatic Leak Testing of Tubing.
ASTM D4991 – 07 Standard Test Method for Leakage Testing of Empty Rigid Containers by Vacuum Method.
ASTM F2338 – 09 Standard Test Method for Nondestructive Detection of Leaks in Packages by Vacuum Decay Method.
ASTM F2786 – 10 Standard Practice for Field Leak Testing of Polyethylene (PE) Pressure Piping Systems Using Gaseous Media under Pressure (Pneumatic Leak Testing).
5.1.4. Materials for the test
Test materials are covered in the individual procedural or recommended practice standards.
For liquid penetrant testing, standard coloured or fluorescent dyes are used. For bubble
testing, there are a range of commercial solutions available, but the important criteria is the ability for escaping gas to form bubbles.
Specialized helium, halogen and radioactive tracers use available, safe and economical materials.
One of the critical conditions is that the tracer or other leak testing working materials must not react in any way with the working fluid in the component being tested. The test materials should not leave traces after the test that can react with the working fluids.
5.1.5. ASME code
The ASME Boiler and Pressure Vessel Code is comprised of several sections related specifically to pressure equipment. Section V of the Code lists non-destructive test methods and in this Leak Testing is included. Equally important are the provisions within the product codes, such as Section I for Boilers, and Section VIII Division 1 for Pressure Vessels, providing guidance for when and where to apply leak testing .
Section I calls for hydrostatic testing as an acceptance test for new installations in Paragraph PG-99, as follows:
5.1.5.1. PG-99 hydrostatic test
Hydrostatic testing of the completed boiler unit shall be conducted in accordance with the following requirements:
After a boiler has been completed (see PG-104), it shall be subjected to pressure tests using water at not less than ambient temperature, but in no case less than 70°F (20°C). Where required test pressures are specified in this paragraph, whether minimum or maximum pressures, they apply to the highest point of the boiler system. When the boiler is completed in the Manufacturer’s shop without boiler external piping, subsequent hydrostatic testing of the boiler external piping shall be the responsibility of any holder of a valid “S,” “A,” or “PP”
stamp. The pressure relief valves need not be included in the hydrostatic test. The tests shall be made in two stages in the following sequence:
5.1.5.2. PG-99.1
Hydrostatic pressure tests shall be applied by raising the pressure gradually to not less than 11⁄2 times the maximum allowable working pressure as shown on the data report to be stamped on the boiler. No part of the boiler shall be subjected to a general membrane stress greater than 90% of its yield strength (0.2% offset) at test temperature. The primary membrane stress to which boiler components are subjected during hydrostatic test shall be taken into account when designing the components. Close visual inspection for leakage is not required during this stage.”
Section VIII of the ASME Boiler and Pressure Vessel Code covers hydrostatic testing of new pressure vessels and components in paragraph UG-130 (d) (2):
5.1.5.3. UG-136(d)(2) hydrostatic pressure test
(a) Hydrostatic testing shall be performed on the pressure containing parts of the shell of each valve at a pressure at least 1.5 times the design pressure of the parts. The valve
shell is defined as parts, such as the body, bonnet, and cap, which isolate primary or secondary pressure from atmosphere.
Parts meeting the following criteria shall be exempt from hydrostatic testing:
(1) the applied stress under hydrostatic test conditions does not exceed 50% of the allowable stress; and
(2) the part is not cast or welded.
(b) Testing may be performed pneumatically at a pressure of 1.25 times the design pressure of the part. Pneumatic testing can be hazardous; it is therefore recommended that special precautions be taken when conducting a pneumatic test.
(c) Testing may be done in the component or assembled condition.
(d) These tests shall be conducted after all machining and welding operations on the parts have been completed.
(e) There shall be no visible sign of leakage.
These particular instructions are common to all of the ASME product codes; ASME relies on the ability of the manufactured component or device to hold pressure—the visual observation for leaking coupled with observation of pressure drop has served well for many years.
Test specifications and procedures 5.2.
5.2.1. Definition of testing and instructions, considering field of application, equipment and technique
Leak testing techniques are based on widely differing technologies. It follows that each technique has its own set of rules and instructions, its own dedicated equipment and its own safety rules. The selection of the correct technique can only be made with a good knowledge of the application and the possible test parameters, i.e. static or dynamic, additive, tracer or working fluid, and detection technique, particularly for those techniques which require chemical analysis.
5.2.2. Interpretation and evaluation
Interpretation must be based on knowledge of the working system and its performance characteristics, as well as the testing technique, and how it is affected by the presence of a leak.
5.2.3. Formulation of instructions for the test
Instructions for any test are prepared by or on behalf of a Level 3 expert. Generally these will be based on a published standard, on product information provided by the manufacturer, or on performance requirements detailed in the specification. Instructions or performance standards that are unachievable serve no one.
5.2.4. Contents of codes, standards, specifications and guidelines
Documented test instructions may be in the form of codes (referenced in legislation), standards (industry consensus), purchaser’s specifications or guidelines. It is the latter category that provide the most challenge for the service provider – he must not only prove
that the test is appropriate and that the acceptance criteria are achievable, but that the results are a true indication of the integrity of the system tested.
National standards for leak testing and testing personnel 5.3.
5.3.1. Quality control of the test and procedure for its administration
The qualification of personnel for leak testing is covered in ISO 9712:2005 and BS EN 73:2008. These standards provide guidance for third party certification of personnel at three levels in any NDT method, and specifically include leak testing.
Most national standards for personnel qualifications are based on one of the two international documents listed above.
5.3.2. Quality assurance requirements
General quality assurance requirements are detailed in Chapter 1 of this book.
Problems of industrial safety in the use of chemical and inflammable products 6.1.
6.1.1. Applicable safety standards
Materials used in leak testing may be radioactive or reactive. Where such materials are used, the appropriate safety standards and plant practices shall apply.
6.1.2. Drafting of safety instructions for the personnel involved
Safety is the concern of every worker, with the supervisor bearing special responsibility to ensure that the worker has been properly instructed or trained. The role of safety instructions is to communicate those precautions which are common sense, those which are passed down by the manufacturer, and those which might arise with the specific application, to the worker.
6.1.3. Safety factors applicable to the test
Aside from any hazards which might arise from the materials being used in the test, the technician must be constantly aware of the function of the object under test. The consequences of a failure in service emphasize the importance of the test. For pressure tests, particularly pneumatic tests, the requirement to overpressure creates a hazard in itself.
Investigating leaks in an operating system can be hazardous. If the system is known to be leaking, there is a possibility that the leak is growing, and full failure could result. If the working contents are explosive, combustible or toxic, leaks must be approached with a great deal of caution.
Control of hazards from toxic and radioactive liquids, vapours and particles of 6.2.
flammable liquids and vapours
Hazards can be associated with the working fluids in the systems being tested or with the testing fluids. Some specific precautions for handling chemicals are listed below.
6.2.1. Chemical handling
Use bottle carriers to transport chemicals. Close caps securely. Pour all chemicals carefully.
Add acid to water, not water to acid.
6.2.2. Labels
Be sure all labels are securely attached and legible. Keep chemicals in their original containers if possible. Label all secondary containers to avoid unknown chemicals and/or inadvertent reaction. Date all chemicals, which may become unstable over time or are peroxidizable.
6.2.3. Shelves
Do not store chemicals on hard-to-reach shelves. Labels on stored chemicals should be able to be read easily. Shelves should be made of a chemically resistant material and should have a 2-inch lip or side rails.