The oil chalk test is an NDT method used to find defects in welding. It involves applying chalk powder and low viscosity oil like diesel to the weld. Any leaks will cause the chalk to change color due to wicking of the oil through defects. Welds are inspected after 4 hours for yellow spots indicating failures. Welds without yellow spots pass while defective welds are repaired and retested until passing.

2. CHALK TEST
• Oil chalk test / Penetrating Oil Test is a NDT method used to find out the defects
in welding.
• This NDT method is mainly carried out in
1. Shell to Bottom Joints after the first Run of welding.
2. All the pontoon compartments including the compartment welds(including
bottom deck plates and compartment bulkheads)
3. Roof leg supports to Bottom deck groove welding spots.
4. 100% of the bottom deck welds based on findings.

3. PROCEDURE
• After the first run of Welding, All slag shall be removed from the surface of the weld.
Powder Application:
• Wet chalk powder paste shall be applied uniformly on the weld.
Oil application:
• Once wet chalk get dry then with the help of hand spray cup, low viscosity oil (diesel oil)shall be
applied on the other side of the weld.
Evaluation:
• Once oil application activity completed, leave the joint for 4 hours to identify leaks if any in the
weld. Due to low viscosity diesel oil can penetrate pore holes, minor cracks, and other open

4. discontinuities shall show on the dry chalk powder location due to wicking property of dry chalk
powder.
• After sufficient time (4 hours) for penetration the joint visually inspected for any trace of Wicking on
the welded location.
• Joint shall be visually inspected and if there is an appearance of yellow spot on chalk side of the joint then
spot shall be considered defective. The yellow spot occurs as oil travel through the leak portion on the joint
due to capillary action.
ACCEPTANCE
The weld joint will be accepted if there is no sign of oil leakage developed on chalk powder.

5. REPAIR & RETEST PROCEDURE
➢ If any defect found then the location shall be repaired as per approved Welding procedure
specification.
➢ After completion of rectification re-examine the repair spot additionally minimum 150mm for
repair spot on both directions.
➢ Repeat the process until there is no evidence of leaking.
➢ After completion of the test thoroughly clean the joint from both sides for the further activities.

6. CLEANING
After subject diesel test, the outer surface shall be cleaned with forced air prior to the start further
welding works.
REFERENCE
• API 653 5th Edition, November 2014 : Tank Inspection, Repair, Alteration, and Reconstruction
• API 650 12th Edition, March 2013: Welded Tanks of oil storage
• ASME Section-V Ed. 2019: Non-Destructive Examination