We buy surplus instrumentation cable

Process measurement cable is bought by the pair. Instrumentation cable runs at 300 V, in 16, 18 and 20 AWG, from single pairs up to 24 pairs or triads, shielded or unshielded, with overall shielding or individual pair shields. The thermocouple extension cable comes in the same lots, with its color-coded conductors.

This is not a volume material. A single reel can carry a whole lot, and its usefulness depends on whether some other project happens to need that exact pair count and shield arrangement. The review runs on identification first, footage second, and condition throughout the lot.

Pairs, triads and what the count tells you

A pair is two conductors, a triad is three, and the count tells you how many loops the cable can carry. A 4-pair cable with an overall shield suits a group of transmitters in one field junction box. A 24-pair cable suits a marshalling cabinet, and rarely anything else.

Triads appear on three-wire resistance temperature detectors and on some analyzers. Because a triad is not interchangeable with a pair, the two are listed apart. Mixed reels of pairs and triads in one pile are sorted before anything is reviewed.

Overall shield against individual pair shields

An overall shield wraps the whole bundle and protects it from outside noise. Individual pair shields separate each pair from its neighbours, which matters when signals of very different levels share a jacket. The two constructions serve different purposes and are never substituted.

We read the shield from the cut end and from the print. A foil shield with a drain wire is common and light. A braid shield is heavier and shows handling damage more clearly. Either way, a shield that has been torn back or a drain wire cut short affects how the reel is read.

Thermocouple extension and changed instrument scope

Thermocouple extension cable uses conductors of the same alloy pair as the thermocouple, and the insulation is color coded to the type. That color is the identification, and it is what a buyer reads. Where the jacket print gives the calibration letter, photograph it. Faded or over-taped extension cable loses most of its standing, not because the copper is worse but because nobody can prove what it is.

Instrument scope changes more than almost anything else on a plant job. A transmitter package is re-specced, a junction box moves, a control philosophy changes, and the cable bought for the old arrangement no longer fits. What is left is a reel of a count nobody needs this year, which is the material we see most, and why a reel is rarely interchangeable with the next project.

Instrument cable in this region comes from water and wastewater plants, from the semiconductor and food processing work along SH-130, and from the smaller process plants east of I-35. A single clarifier or filtration upgrade can produce a dozen unmatched reels.

Panel and integration houses around Round Rock and San Marcos also hold cut-offs from cabinet work. Those lots are usually well labeled, which makes them straightforward. We cover the metro and the plant towns out to Bastrop, Lockhart and Marble Falls.