Composite Corded Strapping Specifications: What to Put in Your RFQ

A specification for composite corded strappings is only useful if it is unambiguous to someone who cannot see your project. Most disputes on this product do not come from bad manufacturing — they come from a drawing that could reasonably be read two ways, where the supplier read it the cheap way and the buyer read it the expensive way.

This is a practical specification checklist, written around what the standards actually require.

The three specification families you will meet

Suppliers will quote against whichever family your market uses, and the part can usually be built to any of them:

• ASTM D3950 — nonmetallic strapping specification.
• ASTM D7269 reference — aramid/cord tensile test method context.

The mistake is to specify a standard reference without specifying the class or grade within it. If you write only the standard number, the supplier will quote the lowest class that satisfies it. Write the standard and the level you want.

Dimensional data that has to be on the drawing

For this product the critical dimensions are: width 13–25 mm; breaking loads 400–1100 kg (system rating strap + wire buckle); coils 250–500 m.

Three rules that prevent most dimensional disputes:

1. Give tolerances on every functional dimension, not just the nominal values. A nominal dimension with no tolerance is legally “as the supplier chooses”.
2. Say which dimensions are functional and which are cosmetic. Suppliers prioritise what you prioritise, and they cannot guess.
3. State the gauge or measuring method where a dimension is critical. Two inspectors with different methods will disagree about the same part.

Material and grade

The base specification is high-tenacity polyester yarn bundle in a PU coating. Grades commonly offered include:

• 13 mm / 400 kg
• 16 mm / 550 kg
• 19 mm / 750 kg
• 25 mm / 1100 kg (system ratings with matching buckle)

Ask the supplier to state the grade on the quotation, not on an assumption. Grade substitution is the single most common silent cost reduction, and it is usually invisible in the finished part — a 201 stainless component looks exactly like a 304 one until the second winter.

Surface treatment

The usual finish for this product is white PU-coated cord; buckle-coated or uncoated ends.

Two points worth writing into the order:

• A measured requirement, not a process name. “Hot-dip galvanised” is a process; “70 µm minimum, tested by coating mass on three parts per batch” is a requirement.
• What happens at cut edges and drilled holes, if any. These are where coatings are habitually broken and where corrosion starts.

Type tests and routine tests

These are different things and are frequently confused in quotations:

• Type tests qualify the design once. On this product: system breaking load with the matched wire buckle; elongation and tension-retention after 24 h; coating adhesion and abrasion on the buckle edge.
• Routine tests are run on every batch: UV ageing 1000 h.

Specify which type-test reports you want supplied as documents, and which routine test results must accompany each shipment. On a first order, ask for the type-test report before you place it.

The failure modes your specification should be closing

• Strap cutting on the buckle edge — buckle wire gauge too light or corners not radiused; the cord parts at the buckle under load — always rate strap and buckle as a pair
• Tension loss on shifting loads — under-tensioned because the tool could not reach spec; cord strapping needs a proper tensioner, not hand muscle
• Coating wear in transit — coating abraded on rough cargo edges; corner boards or sleeve protection fix what thinner coating cannot

Each of these can be turned into one line in the specification. That is the real purpose of writing it out: not bureaucracy, but making the specific failure you are worried about somebody’s explicit responsibility.

A specification skeleton you can reuse

1. Scope: Composite Corded Strapping to be supplied as composite strapping, cord strapping, woven polyester strap, fibreglass strapping band.
2. Dimensions and tolerances: width 13–25 mm; breaking loads 400–1100 kg (system rating strap + wire buckle); coils 250–500 m.
3. Material: high-tenacity polyester yarn bundle in a PU coating; grade 13 mm / 400 kg or better.
4. Standard: ASTM D3950 — nonmetallic strapping specification; ASTM D7269 reference — aramid/cord tensile test method context.
5. Finish: white PU-coated cord; buckle-coated or uncoated ends.
6. Tests: system breaking load with the matched wire buckle; elongation and tension-retention after 24 h; coating adhesion and abrasion on the buckle edge; UV ageing 1000 h.
7. Marking and packing: coils in cartons, buckles boxed separately but quoted as a system.
8. Inspection: pre-shipment, against this specification, with photo evidence and test records.

Related: the composite corded strapping quality inspection checklist turns this specification into an inspection plan you can hand to a third-party inspector.