Cable Duct Seal Specifications: What to Put in Your RFQ

A specification for cable duct seals 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:

• IEC 60529 — Enclosure IP ratings.
• EN 1366 — Fire resistance tests for service installations.

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: duct diameter 50–200 mm, cable range 10–120 mm per port, single and multi-cable versions.

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 moulded elastomer seal with a mechanical compression plate, or a resin-based system. Grades commonly offered include:

• EPDM seal
• silicone for wide temperature range
• polyurethane resin
• intumescent variants for fire-rated entries

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 UV and ozone stabilised elastomer; metal plates galvanised or stainless.

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: water tightness at pressure head; gas tightness; fire resistance where rated.
• Routine tests are run on every batch: temperature cycling.

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

• Seal leaking around an oversized duct — the seal is sized for the duct nominal but the installed duct is outside tolerance, which is common with concrete ducts
• Cables migrating through the seal — no mechanical anchoring of the cable on the inner side; the seal is not a cable clamp

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: Cable Duct Seal to be supplied as duct seal, cable gland seal, cable entry seal.
2. Dimensions and tolerances: duct diameter 50–200 mm, cable range 10–120 mm per port, single and multi-cable versions.
3. Material: moulded elastomer seal with a mechanical compression plate, or a resin-based system; grade EPDM seal or better.
4. Standard: IEC 60529 — Enclosure IP ratings; EN 1366 — Fire resistance tests for service installations.
5. Finish: UV and ozone stabilised elastomer; metal plates galvanised or stainless.
6. Tests: water tightness at pressure head; gas tightness; fire resistance where rated; temperature cycling.
7. Marking and packing: 10 sets per carton with installation instructions.
8. Inspection: pre-shipment, against this specification, with photo evidence and test records.

Related: the cable duct seal quality inspection checklist turns this specification into an inspection plan you can hand to a third-party inspector.