Thermit Weld Inspection
Thermit welding — also called aluminothermic welding — joins two rail ends by pouring superheated molten steel into a mould around the joint. It is the standard method for joining continuously welded rail in the field, and because the weld is cast rather than rolled, its internal structure cannot be judged from the outside. Radiographic inspection passes gamma radiation through the completed weld and records the result on film or a digital detector, showing the internal condition of the joint through its full cross-section.
Why thermit weld inspection matters
A thermit weld sits in the running rail, carrying the full dynamic load of every axle that passes over it. Internal porosity, shrinkage cavities or lack of fusion concentrate stress and can grow into a complete rail break under traffic — one of the most serious failures on a railway. Because these defects are entirely internal, radiography is the only practical way to see them before the joint is put into service. Inspection at the point of welding is far cheaper than a possession to cut out and replace a failed weld later.
What it detects
Where it is applied
- ●Continuously welded rail (CWR) field joints
- ●Turnout and crossing welds
- ●Rail renewal and re-railing campaigns
- ●Emergency and closure welds
DELIVERED USING RADIOGRAPHIC TESTING (RT)
Applicable Standards
TFR BBB Specification, ASME B31.3, SNT-TC-1A Level III Certifications
Professional Equipment
Ir-192 Gamma Sources, Digital Capture Systems, Mobile Field Units, 100XD Film
Common questions
Does the rail have to be cut out or removed for inspection?
No. Thermit weld radiography is carried out in place on the track. The equipment is brought to the weld, the exposure is made within a controlled exclusion zone, and the rail is left undisturbed. That is the central advantage of a non-destructive method — the joint is examined without being damaged or removed.
How soon after welding can the joint be radiographed?
Inspection takes place once the weld has cooled and been trimmed and ground to profile. Sequencing is normally agreed with the welding team so the inspection fits the possession rather than extending it.
What happens if a weld is rejected?
The weld is reported against the applicable specification with its defect type and classification, so the asset owner can decide whether it is cut out and re-welded or accepted with monitoring. The report is the formal record that the joint was assessed.
Where we deliver it
MPIA Services is based in Durban (also known as eMkhomazi), KwaZulu-Natal, and carries out thermit weld inspection on site across all nine South African provinces. Mobile field units travel to the asset, so the work happens in place — on live rail corridors, in yards and depots, and at industrial sites — rather than requiring components to be sent away. See where we work.
Need thermit weld inspection?
Tell us the asset, the standard you need to satisfy and where the work is. We will come back with scope, timing and a quotation.
REQUEST A QUOTE