Localized PWHT Services: Electrical Resistance Heat Treating

Localized post weld heat treatment (PWHT) applies controlled heat to a specific weld zone — a pipe spool, nozzle weld, flange face, or repair area — without heating the full assembly. Gulf Coast Combustion performs localized PWHT services using electrical resistance flexible ceramic heater pads (FCPs), on-site at your facility or in-house at our Spring, TX shop, to ASME Section VIII, B31.1, and B31.3 requirements.

When Localized PWHT Is the Right Call

Not every job requires heating an entire vessel. When code requires PWHT after welding but the work is confined to a specific weld seam, connection point, or repaired section, localized PWHT is the correct approach. It’s precise, it’s efficient, and it keeps your project moving without staging equipment for a full heat cycle.

How Electrical Resistance PWHT Works

Electrical resistance PWHT uses flexible ceramic heater pads (FCPs) placed directly on and around the weld zone. The pads are wired to a portable 6-zone power console, which ramps the temperature at a controlled rate, holds it at soak, and controls the cool-down — all recorded continuously on a strip chart recorder.

Insulation blankets wrap over the FCPs to retain heat and minimize gradient temperatures. Thermocouples are attached directly to the workpiece surface using a TAU capacitor discharge spot welder — the same attachment method GCC uses on full vessel jobs. No clips, no bands, no welded nuts. The steel surface becomes the measurement point.

Per ASME B31.1 and B31.3, heater pads must extend past each edge of the weld by a minimum of 3T (three times the wall thickness). Thermocouple count is determined by pipe diameter. Every job produces a complete documentation package before GCC leaves the site.

Heat Cycle Specifications — Carbon Steel (as of May 2026)

Thermocouple Requirements by Pipe Diameter

Common Applications

Documentation on Every Job

Every localized PWHT job produces a complete documentation package. GCC management and quality control approve all heat cycles and setups before work begins. Nothing starts without a signed-off execution plan.

• Heat Treatment Record (HTR) — signed by GCC representative and client
• Strip chart recorder trace — identifies thermocouple placement, FCP locations, job number, date, and recorder serial number
• Calibration certificate — NIST traceable, recorders calibrated annually by third-party vendor
• Execution plan — submitted for client approval before work begins

On-Site or In-House — Your Call

Most localized PWHT work happens on-site at your facility. Keeping components in place reduces handling, protects schedule on larger projects, and eliminates transportation cost and risk entirely. GCC mobilizes anywhere in the U.S.

For smaller jobs, GCC also handles work in-house at our Spring, TX facility. Our in-house furnace handles vessels and components up to 25,000 lbs (30′ x 10′ x 10′). For full vessel pressure vessel PWHT, see: Pressure Vessel Heat Treating.