I have written a lot about leak testing and pressure testing our piping systems and those articles all mention using the “bubble test” method. Now lets talk about the actual requirements of this test method.
ASME B31.3, 345.8 Sensitive Leak Test refers us to ASME BPVC, Section V, Article 10, Mandatory Appendix I, for how this leak testing method is to be performed and documented. In this mandatory appendix, we will find the specifics that will produce our WRITTEN PROCEDURE for this safety-critical task.
| ASME B31.3, 345.8.2 Method
The test shall be the Bubble Test – Direct Pressure Technique in accordance with ASME BPVC, Section V, Article 10, Mandatory Appendix I or another leak test method that has a demonstrated sensitivity not less than 10-3 std mL/s under test conditions. When the Bubble Test – Direct Pressure Technique is used (a) the test pressure shall be at least the lesser of 105kPa (15 psi) or 25% of the design pressure. (b) the pressure shall be gradually increased until a gage pressure equal to the lesser of one-half the test pressure or 170 kPa (25 psi) is attained, at which time a preliminary check shall be made. Then the pressure shall be gradually increased in steps until the test pressure is reached, the pressure being held long enough at each step to equalize piping strains. |
T-1020 GENERAL
T-1021 Written Procedure Requirements
T-1021.1 Requirements
Leak testing shall be performed in accordance with a written procedure, which shall, as a minimum, contain the requirements listed in the applicable Appendices, paras. 1-1021 through X-1021 and Tables 1-1021 through X-1021.
The written procedure shall establish a single value, or range of values, for each requirement.
T-1021.2 Modification of Requirements
Article (15) 10 contains test techniques; therefore, there are requirements that cannot be modified by the organization through the demonstration process per T-150.
Only those requirements listed in Tables 1-1021 through X-1021 may be so modified by demonstration.
T-1021.3 Procedure Qualification
When procedure qualification is specified by the referencing Code Section, a change of a requirement in the applicable Appendix Tables 1-1021 through X-1021 identified as an essential variable shall require requalification of the written procedure by demonstration.
A change of a requirement identified as a nonessential variable does not require requalification of the written procedure.
All changes of essential and nonessential elements from those specified within the written procedure shall require revision of, or an addendum to, the written procedure.
T-1030 EQUIPMENT
T-1031 Gages
(a) Gage Range
When dial-indicating and recording pressure gage(s) are used in leak testing, they should preferably have the dial(s) graduated over a range of approximately DOUBLE THE INTENDED MAXIMUM PRESSURE, but IN NO CASE shall the range be less than 1.5 or more than four times that pressure.
These range limits do not apply to dial indicating and recording vacuum gages.
Range requirements for other types of gages given in an applicable Mandatory Appendix shall be as required by that Appendix.
(b) Gage Location
When components are to be pressure/ vacuum leak tested, the dial indicating gage(s) shall be connected to the component or to the component from a remote location, with the gage(s) readily visible to the operator controlling the pressure/vacuum throughout the duration of pressurizing, evacuating, testing, and depressurizing or venting of the component. For large vessels or systems where one or more gages are specified or required, a recording type gage is recommended, and it may be substituted for one of the two or more indicating type gages.
(c) When other types of gage(s) are required by an applicable Mandatory Appendix, they may be used in conjunction with or in place of dial indicating or recording type gages.
T-1041 Cleanliness
The surface areas to be tested shall be free of oil, grease, paint, or other contaminants that might mask a leak.
If liquids are used to clean the component or if a hydrostatic or hydropneumatic test is performed before leak testing, the component shall be dry before leak testing.
T-1042 Openings
All openings shall be sealed using plugs, covers, sealing wax, cement, or other suitable material that can be readily and completely removed after completion of the test.
Sealing materials shall be tracer gas free.
T-1043 Temperature
The minimum metal temperature for all components during a test shall be as specified in the applicable Mandatory Appendix of this Article or in the referencing Code Section for the hydrostatic, hydropneumatic, or pneumatic test of the pressure component or parts.
The minimum or maximum temperature during the test shall not exceed that temperature compatible with the leak testing method or technique used.
T-1044 Pressure/Vacuum (Pressure Limits)
Unless specified in the applicable Mandatory Appendix of this Article or by the referencing Code Section, components that are to be pressure-leak tested shall not be tested at a pressure exceeding 25% of the Design Pressure.
T-1050 PROCEDURE
T-1051 Preliminary Leak Test
Prior to employing a sensitive leak testing method, it may be expedient to perform a preliminary test to detect and eliminate gross leaks.
This shall be done in a manner that will not seal or mask leaks during the specified test.
T-1052 Test Sequence
It is recommended that leak testing be performed before hydrostatic or hydropneumatic testing.
T-1060 CALIBRATION
T-1061 Pressure/Vacuum Gages
(a) All dial indicating and recording type gages used shall be calibrated against a standard deadweight tester, a calibrated master gage, or a mercury column, and recalibrated at least once a year, when in use, unless specified differently by the referencing Code Section or Mandatory Appendix.
All gages used shall provide results accurate to within the Manufacturer’s listed accuracy and shall be recalibrated at any time that there is reason to believe they are in error.
(b) When other than dial indicating or recording type gages are required by an applicable Mandatory Appendix, they shall be calibrated as required by that Mandatory Appendix or referencing Code Section.
T-1062 Temperature Measuring Devices
When temperature measurement is required by the referencing Code Section or Mandatory Appendix, the device(s) shall be calibrated in accordance with the requirements of that Code Section or Mandatory Appendix.
T-1090 DOCUMENTATION
T-1091 Test Report
The test report shall contain, as a minimum, the following information as applicable to the method or technique:
(a) date of test
(b) certified level and name of operator
(c) test procedure (number) and revision number
(d) test method or technique
(e) test results
(f) component identification
(g) test instrument, standard leak, and material identification
(h) test conditions, test pressure, tracer gas, and gas concentration
(i) gage(s) – manufacturer, model, range, and identification number
(J) temperature measuring device(s) and identification number(s)
(k) sketch showing method or technique setup
MANDATORY APPENDIX I – BUBBLE TEST – DIRECT PRESSURE TECHNIQUE
1-1000 INTRODUCTION
1-1010 SCOPE
The objective of the direct pressure technique of bubble leak testing is to locate leaks in a pressurized component by the application of a solution or by immersion in liquid that will form bubbles as leakage gas passes through it.
1-1020 GENERAL
1-1021 Written Procedure Requirements.
1-1021.1 Requirements. The requirements of T-1021.1, Table l-1021, and the following as specified in this Article or referencing Code shall apply.
(a) soak time
(b) pressure gage
(c) test pressure
(d) acceptance criteria
1-1021.2 Procedure Qualification
The requirements of T-1021.3 and Table l-1021 shall apply.
1-1030 EQUIPMENT
1-1031 Gases
Unless otherwise specified, the test gas will normally be air; however inert gases may be used.
NOTE: When inert gas is used, safety aspects of oxygen deficient atmosphere should be considered.
1-1032 Bubble Solution.
(a) The bubble forming solution shall produce a film that does not break away from the area to be tested, and the bubbles formed shall not break rapidly due to air drying or low surface tension. Household soap or detergents are not permitted as substitutes for bubble testing solutions.
(b) The bubble forming solution shall be compatible with the temperature of the test conditions.
1-1070 TEST
1-1071 Soak Time
Prior to examination the test pressure shall be held for a minimum of 15 min.
1-1072 Surface Temperature
As a standard technique, the temperature of the surface of the part to be examined shall not be below 40°F (5°C) nor above 125°F (50°C) throughout the examination. Local heating or cooling is permitted provided temperatures remain within the range of 40°F (5°C) to 125°F
(50°C) during examination. Where it is impractical to comply with the foregoing temperature limitations, other temperatures may be used provided that the procedure is demonstrated.
1-1073 Application of Solution
The bubble forming solution shall be applied to the surface to be tested by flowing, spraying, or brushing the solution over the examination area. The number of bubbles produced in the solution by application should be minimized to reduce the problem of masking bubbles caused by leakage.
1-1074 Immersion in Bath
The area of interest shall be placed below the surface of the bath in an easily observable position.
1-1075 Lighting and Visual Aids
When performing the test, the requirements of Article 9, T-952 and T-953 shall apply.
1-1076 Indication of Leakage
The presence of continuous bubble growth on the surface of the material indicates leakage through an orifice passage(s) in the region under examination.
1-1077 Post test Cleaning
After testing, surface cleaning may be required for product serviceability.
1-1080 EVALUATION
1-1081 Leakage
Unless otherwise specified by the referencing Code Section, the area under test is acceptable when no continuous bubble formation is observed.
1-1082 Repair/Retest
When leakage is observed, the location of the leak(s) shall be marked. The component shall then be depressurized, and the leak(s) repaired as required by the referencing Code Section. After repairs have been made, the repaired area or areas shall be retested in accordance with the requirements of this Appendix.
