Instrument and signal cable · Georgia
We buy instrumentation cable for Georgia process plants
Pair and triad cable for analogue and thermocouple signals, individually and overall shielded. Reviewed on pair count, gauge, shield arrangement and the length left on the reel.
- 1 to 24 pairs
- 16 to 24 AWG
- Individual and overall shields
01Overview
Pairs, triads and shields
Instrumentation cable carries a measurement rather than a command. It is built in pairs, or in triads for thermocouple circuits, with each pair twisted to reject induced noise and the whole assembly wrapped, shielded and jacketed. Some constructions shield each pair individually; others shield only the assembly; some do both.
That arrangement is the identity of the product, and it is what a review has to establish. Two reels of sixteen-pair cable, one with individual pair shields and one without, serve different loops in the same plant and are not interchangeable. Both arrive as surplus when a process unit is cancelled or an instrument upgrade is descoped.
02Specification
What an instrument cable reel declares
- Construction
- Pairs or triads, 1 through 24 pair, twisted and laid up
- Sizes
- 16, 18, 20, 22 and 24 AWG, stranded or solid
- Voltage
- 300 V and 600 V; PLTC and ITC listings on process cable
- Shield
- Individual pair foil, overall foil or braid, with drain wires
- Insulation
- PVC or PE, with a colour-coded or numbered pair identification
- Jacket
- PVC or CPE overall jacket, sunlight and oil resistant where rated
- Reels
- 500 and 1,000 ft reels; 250 ft on the heavier pair counts
- Marking
- Type, pair count, AWG, voltage and shield arrangement on the print
The print on instrument cable is long and often crowded. Photograph it in two overlapping frames rather than one, so the pair count and the shield arrangement are both readable.
03Instrument cable we review
Instrument cable we review
Individual and overall shielded pairs
The highest-specification construction in the family: foil around each pair, a drain wire per pair, and an overall shield or braid on top. Used on analogue loops in electrically noisy plants, and reviewed on shield integrity at the cut end.
Overall-shielded only
Pairs twisted together under a single foil and drain. Common on process work where the noise environment is milder. A coil of this construction cannot be described as individually shielded, and the difference is a review point.
Thermocouple triads and extension cable
Three-conductor constructions with the alloy or compensating conductor specified for a thermocouple type. Worth identifying by the print, because the conductor alloy is part of the product and cannot be seen.
Cut lengths from loop pulls
The remainder of a reel after a unit was wired. Instrument cable is pulled in single loops, so remainders are large and often well documented on the reel tag. These are the best lots in the family when the tag survives.
04Evaluation
How an instrument cable lot is reviewed
Pair count and shield arrangement first, then gauge, then length. The first two decide which loops a reel can serve, and neither can be inferred from the outside diameter with any confidence — a fourteen-pair unshielded cable and a twelve-pair individually shielded one are close in size and unrelated in use.
Shield condition is the main technical deduction. Foil that has been crushed where a reel was stacked, or a drain wire cut back beyond reach at the end, changes what the cable will do. Neither is visible in a photograph of a wrapped reel, so a seller who opens one end and photographs the layup is doing the most useful thing possible.
Then length and storage. Instrument cable is light for its volume and travels cheaply, but it is easily crushed and it does not like being coiled tightly. A reel stored on its flange for years takes a set, and a reel stored in a plant with solvent vapours can go hard at the jacket. Give the reel tag, the length and where it has been kept.
Instrument circuits are frequently intrinsically safe, and a cable that has been used in a classified area carries requirements about what may be reconnected to it. Cable removed from a process unit is not returned to service on a buyer’s assumption; the loop documentation decides that.
05Seller terms
Before you sell: how it works
Four things a seller should be able to pin down before a truck is booked.
Verification
Footage is checked against the reel tag, the sequential marks on the jacket, the wrap count against the barrel, or a published weight per 1,000 ft — whichever the reel actually supports.
Payment
Payment method and timing are agreed in writing for the specific lot before anything is loaded or moved. No verbal number is treated as an agreement.
Paperwork
A bill of sale for the lot, and for utility material the owning utility’s release reference. Neither is optional and neither is created after the fact.
Freight
Collection is arranged as part of the terms. Say what can lift the reels and whether a 53-foot trailer can reach them, and the pickup is planned around that.
Sending a reel list and photographs costs nothing. A review is not a purchase, and nothing is bought, moved or scheduled until written lot terms are agreed for that material. Request a pickup when the lot is ready.
07Questions
Instrument cable questions
What is the difference between a pair and a triad?
A pair is two twisted conductors for a two-wire signal; a triad is three, used for thermocouple and resistance circuits. The count and the grouping are both printed on the jacket.
Does individual shielding matter?
It decides which loops the cable can serve in a noisy plant. Individually shielded and overall-shielded coils are reviewed as different products, not as grades of one.
Do you buy instrument cable with the shield cut back?
Yes. A cut-back drain wire is normal on a part reel and is recovered at termination. Foil torn along the length is a deduction and should be described.
How is pair count confirmed?
By counting at the cut end and by reading the print, which states the pair count and the AWG together. Both should agree before a lot is described.
Two photographs of the print
Pair count, gauge, shield arrangement and the reel tag. Overlapping photographs of the jacket print cover the rest without unrolling anything.