Preformed Dead End Specifications: What to Put in Your RFQ

A specification for preformed dead ends 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 A475 — Zinc coated steel wire strand.
• IEC 61395 — General requirements for overhead line fittings.

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: conductor 25–400 mm², strand diameter 6–25 mm, leg lengths 300–1500 mm.

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 galvanised steel or stainless steel wire, preformed to a matched helix. Grades commonly offered include:

• galvanised steel strand
• AISI 304 stainless
• AISI 316 for coastal and chemical exposure
• aluminium alloy clad for aluminium conductor

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 hot-dip galvanised or bright stainless; colour coded by conductor size to prevent mis-installation.

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: hold test to rated tension; helix pitch check; salt spray 480 h.
• Routine tests are run on every batch: rod end inspection.

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

• Grip slipping on the conductor — a set made for the wrong conductor construction; both aluminium and ACSR exist at the same nominal area
• Mix-ups on site — no colour coding, so a set for one size gets fitted to another and fails at first tensioning

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: Preformed Dead End to be supplied as helical dead end, preformed dead end grip, wire grip.
2. Dimensions and tolerances: conductor 25–400 mm², strand diameter 6–25 mm, leg lengths 300–1500 mm.
3. Material: galvanised steel or stainless steel wire, preformed to a matched helix; grade galvanised steel strand or better.
4. Standard: ASTM A475 — Zinc coated steel wire strand; IEC 61395 — General requirements for overhead line fittings.
5. Finish: hot-dip galvanised or bright stainless; colour coded by conductor size to prevent mis-installation.
6. Tests: hold test to rated tension; helix pitch check; salt spray 480 h; rod end inspection.
7. Marking and packing: 25 sets per bundle, colour coded and labelled.
8. Inspection: pre-shipment, against this specification, with photo evidence and test records.

Related: the preformed dead end quality inspection checklist turns this specification into an inspection plan you can hand to a third-party inspector.