Induction Heating Applications

Preheating of an in-service pipeline to 100° C before welding on a sleeve

Liquid-cooled induction coils are flexible and easy to apply to a variety of geometries.

Here, a sleeve is being welded onto a pipe that has material flowing through it - an

operation known as a "hot tap". The material flowing through the pipe is taking heat away

from the joint, but here a single 35 kW unit is able to maintain the desired temperature at

the joint. Common, inexpensive materials are used to hold the coil in place. The set-up time

and cycle-time hours were reduced as a result of using the ProHeat 35 Induction System


Post Weld Heat Treating (PWHT) of a drill pipe to 1350° F after welding

Two PWHT joints are being processed with one water-cooled induction coil. As long as the

dimensions of the two pipe joints are similar, the applied induction field will heat both

relatively the same. This also shows the proper way to terminate any unused portion of the

coil. The ends of the coil should be twisted together or tied together with tie-wraps, tape,

rope or string in order to reduce the amount of losses in the unused portion. These

common, inexpensive materials can be used to secure the excess coil ends as the coil itself

does not heat during the process.


Preheating of structural I-Beam to 300° F

Liquid-cooled induction coils are wound "pancake" style and secured to a section of

plywood to hold the desired shape. A layer of preheat insulation is placed between the

plywood and the I-Beam to prevent the overheating of the wood. The magnetic field passes

through the plywood and the insulation to induce the desired heating of the I-Beam.


Post Weld Heat Treating (PWHT) of a P91 header to 1400° F after welding

Liquid-cooled coils wrap around PWHT insulation that is applied to the header. The

insulation is a 1" thick silica needle mat which traps the heat in the header while protecting

the coil from the high temperatures. Thermocouples are attached to the weld joint to provide

temperature data back to the power source. The integrated temperature controller on the

ProHeat 35 has a standard PWHT program that will execute the controlled heating profile,

that will ramp up to the set temperature, dwell there for a set time, then cool down at a

controlled ramp rate. Custom programs can be created within the controller with multiple

steps, ramps and dwells in a single cycle.