A seal that proves the drum arrived as it left

In air, for the whole of the argument

A drum end sits in air from the hour it is closed at the works to the hour it is broken open on site. It is never buried and it is seldom splashed: a lorry bed, a yard, a quay, a sheet thrown over it. At that depth a closed cap has an easy job, and almost anything that stays on will keep weather off. Depth, then, is not the reason to choose this particular cap.

The reason is that the end has to arrive provably untouched. Cable is bought by the metre and paid for by the metre, and a drum passes through a haulier, a port, a store and a subcontractor before anybody puts a wheel on it. When the measured length comes up short, the argument runs backwards through every one of those hands and none of them can be excluded. A printed permanent end seal turns that into a question with an answer: either your own mark is whole on both ends, or it is not.

Be honest about what the mark is worth, because the product name oversells it slightly. It is tamper-evident. It will not stop a determined person cutting a cap off, and it records no date, no time and no identity. What it removes is deniability. An end opened between the works and the site cannot be put back the way it left, because the cap that came off cannot go back on.

The sealing itself is done by the hot-melt lining rather than by the grip of the cap. On the four jackets you meet on 36 kV joints — XLPE, PVC, PILC and rubber-sheathed — that lining flows into the scores and ridges of the sheath as the cap recovers, and the closed end is held to IP68 on that bond. Read the rating as a statement about the adhesive and not about the polymer; what an end-cap datasheet proves takes the wording apart properly.

When a printed end seal is the wrong call

Five situations where specifying this cap wastes the print, and what to reach for instead.

• The drum will be cut down before delivery. Re-drumming leaves your mark on an offcut and the customer's end unmarked, which is worse than not marking at all.
• The end has to be opened and closed in store. Recovery is one-way; a cap taken off is scrap. Where a store needs repeated access, a push-on PVC cap covers the end without pretending to seal it.
• The cable is 33 kV or above and heading somewhere hot. A plain sealed end traps the gas the insulation gives off. Specify the relief-valved build and keep the printing.
• No hot work is permitted where the cap will be fitted. Read the no-flame page before you commit a torch-fitted part to a refinery or a magazine.
• The end is buried or immersed for months rather than in transit. The seal holds, but corrosion at a long-term buried end is a different specification; see corrosion barriers and sealed ends.