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Procedure for Vacuum Box Test of Storage Tank Bottoms
Doc. No.--
Rev. Date Description
Prepared by Approved by Client/Inspection Authority
Procedure for Vacuum Box Test of Storage Tank Bottoms
1.0 Scope
2.0 Reference Code and Specification:
ASME Sec V, Article 10 Appendix-II
3.0 Equipment:
3.1 The vacuum box test shall be performed by using a box with visible window of plastic (e.g.
150mm wide by 750mm long metalic box with a glass acrylic at top 45͒ corner vacuum box shall
be used for shell to bottom annular joints).
3.2 The open bottom scheme shall have suitable connections, necessary valves and calibrated
vacuum gauge.
3.3 The open bottom shall be sealed against the tank surface by suitable gasket.
3.4 Soap solution shall be used as a leak detection medium.
3.5 During testing, illumination shall be adequate for evaluation and interpretation of the test.
3.6 The test scheme shall be demonstrated with sample test block by application of soap solution at
site before conducting the test on job.
4.0 Personnel:
The personnel shall be competent and familiar in performing this method.
5.0 Surface Preparation:
The surface to be examined and all adjacent areas within at least 25mm should be dry and free
from all dirt, grease, scales, welding flux, weld spatters, paint oil and other extraneous matter that could obscure surface opening or otherwise interfere with examination.
6.0 Procedure:
6.1 Visual examination of the bottom and weld shall be done before performing the vacuum box
test.
6.2 Metal surface temperature shall be in between 4 to 52 deg.centigrade.
6.3 The gauge shall be at least register a partial vacuum of 0.304Kg/cm square for inspection of the
joints.Approximately 750mm length of seam under test is applied with the soap solution for
detecting leak. The foaming shall be minimized by means of uniform application of soap
solution. An overlap of 50mm for adjacent placement of the vacuum box shall be used foe each subsequent examination.
7.0 Evaluation:
Bubbles produced by air sucked through the weld seam can detect the presence of defects.Ensure
that there is no quick bubbles or spiting response to large leaks if any. The tested areas are
accepted only when on continuous bubbles formation is absorbed. The require partial vacuum
shall be maintained at least 5 sec, for examination time/until proper inspection is over.
8.0 Repair/Retest:
In case of repair, the position shall be marked and repaired with correct procedure and after
removal of defects that cause the leakage. After repaired, required examination shall also be
carried out, in any case. Liquid Penetrant Examination and retest of vacuum box test shall be
carried out.
Minimum 50mm length of weld or as required by actual weld repair whichever is greater shall be deposited using the same production WPS.
9.0 After test the area shall be cleaned.
10.0 Report/Record:
Upon satisfactory inspection a report shall be prepared as per below format.
Prepared by Approved by Client/Consultant
Vacuum Box Test Report for Vertical Storage Tank Bottom
Cient Report No. Date
Project Company Job Code No.
Consultant Tank description/No.
Sub-Contractor Drawing No./Revision No.
Project Company Job Code No.
Consultant Tank description/No.
Sub-Contractor Drawing No./Revision No.
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1. Test Description --------------------------------------------
2. Partial Vacuum ---------------- MM of Water ------------------- Kg/cm square or psi
3. Partial Vacuum holding duration -------------------------------------------
4. Test Temperature ----------------------------------------------------------------
5. Specific Requirement -----------------------------------------------------------
6. Pressure Gauge details -------------------------------------------------------
Serial No. Range Calibrated Certificate No & Date
Remarks:-
Sub-Contractor Principal Contractor Client/Inspection Authority
2. Partial Vacuum ---------------- MM of Water ------------------- Kg/cm square or psi
3. Partial Vacuum holding duration -------------------------------------------
4. Test Temperature ----------------------------------------------------------------
5. Specific Requirement -----------------------------------------------------------
6. Pressure Gauge details -------------------------------------------------------
Serial No. Range Calibrated Certificate No & Date
Remarks:-
Sub-Contractor Principal Contractor Client/Inspection Authority
