UL 5128 Mica Wire — 450°C / 300V, Stainless Steel Braid Option — High Temp Instrumentation México
Style 5128 addresses a specific gap in the high-temperature wire specification landscape — the need for mica-insulated wire rated at 450°C for instrumentation, signal, and low-voltage control circuits where a 300V insulation rating is sufficient and the thinner mica insulation wall of the 300V construction delivers a more compact wire profile than the heavier 600V-rated alternatives. Rated 450°C and 300 Vac with non-extruded mica tape or mica composite insulation and treated glass braid, Style 5128 covers the thermocouple lead, temperature sensor signal, and low-voltage control circuit wiring applications in industrial furnaces, petrochemical fired heaters, and process heating equipment across México’s heavy industrial sectors.
The optional stainless steel alloy 304 braid over the treated glass braid — a construction feature unique to Style 5128 within this mica wire group — extends the wire’s suitability to chemically aggressive environments where acid vapors, sulfur compounds, or aggressive industrial atmospheres contact the wire surface alongside extreme temperatures. For Mexican petrochemical instrumentation contractors and industrial process control equipment importers, this combination of 450°C thermal rating, 300V insulation, and optional stainless steel braid mechanical and chemical protection defines the premium instrumentation wire specification for México’s most demanding process industry applications.
Technical Specifications — UL Style 5128
| Parameter | Value |
|---|---|
| UL Style | 5128 |
| UL Subject | 758, Section 5 |
| Temperature Rating | 450°C |
| Voltage Rating | 300 Vac |
| Flame Rating | Horizontal flame |
| AWG Range | 24 AWG – 4 AWG, solid or stranded |
| Conductor | Solid or stranded copper |
| Insulation System | Non-extruded mica tape or mica composite |
| Insulation — 24–12 AWG | Mica 15 mils min avg + Glass braid treated with silicone varnish or TFE finish 7 mils min avg |
| Insulation — 11–4 AWG | Mica 20 mils min avg + Glass braid treated with silicone varnish or TFE finish 15 mils min avg |
| Optional Shield | Stainless steel alloy 304 braid over treated glass braid |
| Optional Assembly | Multi-conductor cabled, max OD 1.500 inches; mica glass binder and/or fiberglass fillers; optional overall treated glass braid |
| Typical Use | Internal wiring of high-temperature equipment — not subjected to repeated flexing or mechanical abuse (instrumentación de alta temperatura — sin flexión repetida) |
| Available Colors | Natural mica/glass (standard); custom on request |
| Standard Spool Length | 50 m / 100 m |
| MOQ | Contact for quote — consultar cotización |
Instrumentation Applications — Alta Temperatura e Instrumentación en México
Style 5128’s 450°C / 300V construction with optional stainless steel braid serves the instrumentation and signal wiring needs of México’s petrochemical, glass, and ceramic processing industries where extreme temperatures and chemical exposure coexist:
- Petrochemical fired heater tube skin thermocouple wiring — thermocouple head connection leads and temperature transmitter signal wiring in direct-fired process heaters across Veracruz’s petrochemical processing complex, where tube skin temperature monitoring systems require 450°C-rated wire for sensor leads routed in proximity to furnace tube banks operating at 400–450°C surface temperature, and where sulfur compounds in the process fuel atmosphere make the optional stainless steel 304 braid essential for long-term wire integrity in the corrosive furnace environment.
- Glass furnace temperature control signal circuits — low-voltage control circuit wiring between temperature controllers, thermocouple transmitters, and SCR power controller signal inputs in float glass and container glass furnace control systems across Tamaulipas and Nuevo León’s glass manufacturing facilities, where the 300V rating of Style 5128 is fully adequate for 24V and 120V control circuit voltages and the thinner insulation wall compared to 600V-rated mica styles allows cleaner routing through the conduit and wireway systems serving the furnace control room interface.
- Industrial ceramics kiln atmosphere control wiring — internal signal wiring for kiln atmosphere sensors, oxygen probe leads, and combustion control system signal circuits in tunnel kilns used for advanced technical ceramics manufacturing across Guanajuato’s ceramics and refractory materials industry, where kiln atmosphere monitoring system wiring must survive sustained 400°C+ ambient temperatures in the kiln tunnel measurement zone while carrying only low-voltage analog and digital signal currents well within the 300V insulation rating.
- Forging and heat treatment furnace instrumentation — thermocouple multiplexer wiring, PID controller signal leads, and safety thermostat circuit connections in industrial heat treatment and forging furnace control systems across Guanajuato’s automotive parts heat treatment sector, where instrumentation wire routed inside furnace enclosures between temperature sensing points and control panel interface terminals experiences sustained 300–400°C ambient temperatures requiring 450°C-rated mica insulation for reliable long-term signal circuit integrity.
Engineering Notes — 300V Mica vs. 600V Mica: Compact Profile for Instrumentation
Thinner insulation wall compared to Style 5107 at equivalent AWG: At 24–12 AWG, Style 5128 specifies 15 mils minimum average mica layer plus 7 mils glass braid — compared to Style 5107’s 25 mils mica plus 7 mils glass braid at the same AWG range. The 10-mil reduction in mica layer thickness produces a meaningfully smaller overall wire outer diameter at equivalent AWG. In instrumentation applications where multiple thermocouple and signal wires are bundled and routed through conduit runs in high-temperature furnace zones, this compact profile allows higher wire count per conduit fill — a practical installation advantage when conduit routing in high-temperature zones is constrained by available space in furnace structure penetration points.
Optional stainless steel 304 braid — chemical resistance in aggressive atmospheres: The optional stainless steel alloy 304 braid over the treated glass braid provides a metallic outer covering that resists chemical attack from acid vapors, sulfur compounds, chlorine-containing atmospheres, and aggressive industrial cleaning agents — all common in petrochemical process environments and certain ceramic and glass manufacturing atmospheres. Glass fiber, while thermally stable, is susceptible to acid attack and alkali degradation in certain industrial chemical environments. The stainless steel braid encapsulates the glass fiber layer, protecting it from chemical exposure while providing additional mechanical protection against abrasion from furnace structure contact. Specify the stainless steel braid option for all petrochemical and chemical process applications where the wire routing environment includes corrosive vapor exposure.
300V adequacy for instrumentation signal circuits: Industrial instrumentation signal circuits — 4–20 mA analog loops, 0–10 Vdc analog signals, Modbus RS-485 data circuits, and 24 Vdc digital I/O — all operate well within the 300V insulation rating of Style 5128. Even 120 Vac control voltage circuits provide adequate margin within the 300V rating. The only instrumentation application category where 300V rating may be insufficient is high-voltage measurement circuits — such as 480 Vac motor voltage sensing inputs to power monitors — where 600V-rated Style 5107 should be specified instead. For the vast majority of process instrumentation wiring in industrial furnace and kiln environments, Style 5128 at 300V is the appropriate and more compact specification.
Multi-conductor assembly for instrumentation cable: The optional multi-conductor assembly configuration — up to 1.500 inch maximum OD with mica glass binder and fiberglass fillers and optional overall treated glass braid — enables Style 5128 conductors to be assembled into multi-pair or multi-conductor high-temperature instrumentation cables. This is particularly relevant for thermocouple multi-point measurement systems in industrial furnaces where a single cable assembly carrying multiple thermocouple pairs through a single furnace wall penetration point simplifies installation and reduces the number of high-temperature penetration seals required.
Related UL Styles for Comparison
UL 5128 buyers commonly cross-reference: UL 5107 (200–450°C / 600V mica tape, higher voltage class with thicker insulation wall for power circuit wiring at same temperature rating), UL 5334 (450°C / 300V mica composite with glass braid, alternative 300V mica construction for high-temperature instrumentation), UL 5360 (200–450°C / 300V mica tape, single conductor alternative at same voltage class), and UL 1659 (250°C / 600V PTFE, for applications where 250°C thermal rating is sufficient and fluoropolymer insulation is preferred).
Request a Quote — Solicitar Cotización
Submit your AWG, stainless steel braid requirement, optional assembly configuration, spool format, and annual volume estimate below. Our bilingual team responds with a formal cotización within 24 business hours. Wire samples available for high-temperature qualification testing upon request.
