PWHT Equipment List

PWHT (Post Weld Heat Treatment) refers to a series of processes used to ensure welds and joints will function effectively under their intended service conditions. This may involve stress relieving, preheating, postweld and interpass.

There is an array of PWHT equipment available, and this article will outline some of the more frequently utilized types.

1. Heat Treating Machines

Induction heat treating machines offer multiple services, including hardening (case/surface and through), softening, tempering, stress relieving and normalizing. PWHT equipment is widely utilized across applications like automotive manufacturing, rail cars, nuclear power plants and mining; with precise localized heating limiting heat loss and distortion in order to increase production rates.

Byington Steel can offer solutions for preheat, interpass, postweld, or stress relief applications of up to 2,150 degrees F with four inches of firebrick insulation backed up by thermal barriers – no matter the temperature requirements of your application. Our machines feature full temperature control up to 2,150 degrees F while being protected with thermal barriers for added insulation.

Byington Steel offers a portable refractory-lined high-temperature furnace designed for tool room and precision casting of carbon steel, cast iron and aluminum at temperatures up to 2,150 degrees F. Equipped with digital controls and an overheat safety system for maximum operating temperature, its maximum operating temperature can reach 2,150 degrees Fahrenheit; further information about this machine can be found in its specifications sheet here. We currently have stock available of our FireBox-HT product so contact us now about your PWHT needs! Byington Steel is an industry leader when it comes to industrial equipment and supplies!

2. Preheaters

Preheaters are essential components of many industrial processes that involve heating liquids, gases, or solids. By increasing the temperature before entering the processing unit, preheaters reduce thermal stress on equipment while increasing efficiency and output. Preheaters are used in oil refineries to improve separation and conversion processes while chemical plants use them to ensure reactants reach an ideal temperature before an reaction takes place.

These units consist of serpentine coils of finned pipe inside a steel shell, heated thermal fluid flowing through them to heat liquid surrounding them. This serpentine configuration increases surface area by around 800% compared with bare pipes for much more effective heat transfer than can be achieved using traditional tube bundles; modulating controls also allow precise temperature regulation that falls within degrees of your desired set point.

Air preheaters come in either tubular or cast-tube designs. Once built in their shop environment, these modules are thoroughly shop assembled and leak tested to ensure leak free performance at project site. Having modular construction reduces installation time at plant and allows for on-line removal of scaling or buildup within modules without disrupting production. Preheaters also include large discharge plungers powered by hydraulic power units with redundant pumps for high system availability and reliability.

3. Postwelding

Post-weld heat treatment (PWHT) involves heating all welds to temperatures higher than their base materials in order to decrease residual stresses and avoid severe distortion or collapse of structures if performed incorrectly. PWHT is required by many welding codes for metals like high-grade carbon steel, work-hardened steel and stainless steel.

Hydrogen Induced Cracking (HIC) can be an enormously disruptive threat for long-distance pipelines and large pressure vessels transporting liquid and gaseous hydrocarbons. HIC occurs when hydrogen permeates into welds and causes stress build-up that eventually results in fractured welds. Post Heating can minimize HIC by dispersing hydrogen away from weld areas before cooling to ambient temperatures sets in.

For this task, the weld and its surrounding base material must be heated to a specific temperature and held there for an amount of time determined by its thickness. This process typically involves locally applied heating elements placed around its circumference or HAZs; thermal insulation helps ensure heat doesn’t escape to areas that do not need heating; code and service requirements dictate a time and temperature range for soaking.