How to Match Thermit Portions and Sand Moulds to Rail Profiles
A thermit portion and a sand mould for the specified rail profilemust be selected as parts of the same approved rail-welding system. Rail Profile is essential, but it is not the only input. The supplier also needs the rail grade, specified weld gap or repair condition, rail condition, approved process and project requirements. Matching by approximate rail size or by a product photograph is not a reliable procurement method.
Reviewing thermit portion selection together with mould fit helps prevent incompatible component ordering.
The safest RFQ gives the supplier enough information to identify what can be offered, what requires engineering review and what remains outside the standard product range.
Why the portion and mould cannot be purchased independently
The portion provides the reaction charge and weld metal for the process. The sand mould forms the cavity around the joint and directs the metal according to the system design. The crucible and tapping arrangement deliver the molten metal to that mould. Because these elements interact, selecting one item without confirming the others can create a compatibility gap.
A technically complete offer should identify a compatible rail welding system, including the matched portion, mould and crucible arrangement for the stated rail and joint condition. If a buyer intends to combine new consumables with existing equipment, the existing system designation should be included in the enquiry.
1. Confirm the exact rail profile
Rail profile defines the cross-sectional geometry that the mould must fit. Provide the full profile designation rather than a broad weight category. Where different naming systems are used, attach a dimensioned rail drawing or the project Rail Specification.
For worn rail, do not assume that a mould intended for new rail will automatically provide the required fit. State the measured condition and ask whether the proposed process covers it. Different profiles at the same joint require separate technical review.
2. Confirm the rail steel grade
Rail grade is relevant to the selected welding process and portion. Give the exact grade shown in the contract, rail certificate or marking. Avoid descriptions such as "normal rail" or "high-strength rail," which are not sufficient for selection.
If the two rails have different grades, highlight this at the beginning of the enquiry. Do not assume that a standard portion for one grade can be used for a mixed-grade joint.
3. State the weld gap and joint condition
The specified gap is part of the process definition. State whether the work is a standard new-Rail Joint, wide-gap weld, repair, closure weld or another condition defined by the project. Include the actual project terminology and drawing where available.
Special gaps can change material and mould requirements. They should not be handled by adding material, combining portions or modifying a mould in the field unless an approved process explicitly requires it.
4. Verify the mould designation and interface
For the offered mould, confirm the rail profile, side designation where relevant, mould code, clamping arrangement and sealing method. Ask how the mould is packaged and identified and what storage conditions apply.
Before use, the project team should follow the approved inspection and fitting instructions. A cracked, damaged, wet or incorrectly labelled mould should be controlled under the quality procedure, not repaired through an unapproved site improvisation.
5. Verify portion identity and traceability
The commercial offer should state the portion designation and its intended system application. The buyer should define which batch, packing or certificate information the project requires. On site, the issued portion should be checked against the work order and matched mould/system.
Storage and shelf-life statements must come from the exact product documentation. Do not copy a value from another supplier or another portion type.
6. Check the existing crucible and tools
If the buyer already has a one-shot or reusable crucible system, provide its manufacturer, model or process designation and associated equipment information. Physical fit alone does not demonstrate process compatibility. The same applies to clamps, stands, preheating equipment and ignition items.
Matching-data hierarchy
| Priority | Data | Why it matters |
|---|---|---|
| 1 | Project specification and approved process | Controls acceptance and the permitted welding system |
| 2 | Exact rail profile and dimensioned drawing | Defines the mould geometry and joint interface |
| 3 | Rail Steel grade | Supports portion/process selection |
| 4 | Gap, rail condition and special joint details | Identifies whether a standard or special process review is needed |
| 5 | Existing crucible, clamps and tools | Prevents incompatible mixing of systems |
| 6 | Quantity, schedule, storage and work fronts | Supports packing, allocation and project supply planning |
Twelve questions to answer before placing an order
- What is the exact rail profile?
- Is a dimensioned rail drawing available?
- What is the rail steel grade?
- Are both rails the same profile and grade?
- Are the rails new, worn or repaired?
- What weld gap or joint condition is specified?
- Which standard, process or owner approval applies?
- Which crucible technology will be used?
- Which clamps, stands and preheating equipment are already available?
- What product and batch documents are required?
- How many welds and work fronts are planned?
- What storage, delivery and technical-support conditions apply?
Common procurement mistakes
- Ordering by rail weight without confirming the exact profile.
- Using the term "standard gap" without stating the required dimension or process.
- Assuming moulds for visually similar rails are interchangeable.
- Requesting portions without naming the rail grade and crucible system.
- Mixing items from different systems without technical approval.
- Leaving document and traceability requirements until after shipment.
- Failing to identify worn rail, mixed rail or wide-gap conditions.
Frequently asked questions
Can a supplier identify a sand mould from a rail photo?
A photograph can support discussion but should not replace the exact profile designation and dimensions. Perspective and wear can make visual identification unreliable.
Does the same rail profile always use the same portion?
Not necessarily. Rail grade, gap, joint condition and approved process also matter.
Can a thermit portion be divided for a smaller rail?
Do not divide, combine or alter a portion unless the approved process and manufacturer explicitly require it.
What information should appear on the RFQ?
At minimum: project country, rail profile and drawing, rail grade, gap or joint condition, applicable process or standard, quantity, schedule, existing equipment, documents and support needs.
What if the project uses worn or different rails?
Mark the enquiry for technical review and provide measurements, drawings, photographs and the project repair or welding specification. Do not assume a standard new-Rail System applies.
Send RMTS the rail profile and drawing, rail grade, weld gap or repair condition, approved process or project standard, existing crucible system, quantity, schedule and required documents. Clear input allows a faster and more reliable compatibility review.