Pre-heating of pipe to 150°C before welding on a transmission pipeline

proheat-35-app1-150x150Air-cooled induction blankets are perfect for this application. The induction coil is sewn into a durable 3-D woven silica material with preheat insulation on the bottom. The entire blanket can be moved from joint-to-joint with minimal change over time. Induction blank ets can be used to heat the target material up to 400° F. Note also that Miller’s Induction power sources can be powered from a portable generator set.

 

 

Pre-heating of a valve body to 260°C before welding on a repair

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Water-cooled induction coils are flexible and easy to apply to a variety of geometries. Here a “pancake” style coil has been wrapped around a repair area. Typical heat time for this application is 10-15 minutes for both the inside and outside of the body to be at temperature. Note also that this coil is protected with pre-heat covers to protect the coil from hot weld slag and abrasive wheels. Because the heat is in the valve and not the coil, rope, plastic tie wraps and tape can be used to hold the coil into place.

 

 

Post Weld Heat Treating (PWHT) a P91 header to 760°C after welding

proheat-35-app3-150x150Water-cooled induction coils wrap around PWHT insulation that is applied to the header. The 1” thick silica needle mat insulation traps the heat in the header while protecting the coil from the high PWHT temperatures. The insulation is re-usable and does not emit dangerous particulate into the environment. Thermocouples are attached to the weld joint to provide temperature feedback to the power source. The integrated temperature controller on the ProHeat 35 has a standard PWHT program that will execute a controlled heating profile that will ramp up to a set temperature, dwell there for a set time, and then cool down at a controlled ramp rate. The unit also has a custom program feature that will allow parts to be heated with multiple steps, ramps and dwells in a single cycle.

 

Pre-heating of a Feed Water Heater to 150°C before welding on a repair.

proheat-35-app4a-150x150proheat-35-app4b-150x150Liquid-cooled induction coils are flexible and easy to apply to a variety of geometries. Since the coil remains cool, common materials can be used to support the coil. Here a “pancake” style coil is wrapped to the size of the needed heat zone on the water heater. A plywood form is cut to size and the coil is fitted to the wood with common strapping tape. The coil is held to the part using the studs on the water heater. The repair area is now set-up and heated in a fraction of the time it used to take, and the heat is uniform, no hot spots.

 

 

Post Weld Heat Treating (PWHT) a carbon steel pipe to 676°C after welding

proheat-35-app5-150x150Water-cooled induction coils wrap around insulation that is applied to the pipe. The heat zone on this weld needs to be wider than the 13 wraps of the coil, so the coil is widened some by spreading the coils apart slightly. This set-up also illustrates how to properly 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 of the coil.

 

 

Post Weld Heat Treating (PWHT) of a 12

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Liquid-cooled induction coils wrap around insulation that is applied to the pipe. The valve body has a heavier wall thickness than the 12″ pipe, so extra turns of the coil are applied to the valve to heat the extra mass.

 

 

 

Pre-heating two joints to 150°C before welding, with a single coil

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Liquid-cooled induction coils are flexible and can be placed in multiple locations. Here a single coil is used to wrap around both ends of the pipe where weld joints are prepped. As long as the dimensions of the pipe are similar from joint to joint, the applied induction field will heat both joints relatively the same.

 

 

 

Pre-heating of structural steel tube to 150°C.

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Air-cooled induction blankets are used for this application. The induction coil is sewn into a durable 3-D woven silica material with preheat insulation on the bottom. The entire blanket can be moved from joint-to-joint with minimal change over time. Induction blankets can be used to heat the target material up to 400°F.

 

 

 

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

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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. Since the material is taking heat away from the joint, a second unit is used to apply extra power to achieve the desired heat in the joint. This also allows each side of the joint to have independent temperature control.

 

 

 

Pre-heating of structural steel I-Beam to 150°C

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Liquid-cooled induction coils are used for this application. The induction coil is wound in a “pancake” style layout and secured to a piece of plywood to hold its shape. There is a layer of preheat insulation placed between the plywood and I-Beam to prevent overheating the wood. Note the ability of the magnetic fields to pass through wood and insulation to induce eddy currents into the I-Beam for the desired heating.

 

 

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

proheat-35-app11-150x150Liquid-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. This operation is called a “hot tap”. Material flowing in 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. Note the use of common inexpensive materials to hold the coil into place while welding. Hours were driven out of the set up time and cycle time using the Miller ProHeat 35 Induction system.

 

 

Pre-heating, from the I.D. of a Flange to Pipe assembly, to 150°C before welding

proheat-35-app12b-150x150proheat-35-app12a-150x150Liquid-cooled induction coils are flexible and easy to apply to a variety of geometries. Since the coil remains cool, common materials can be used to support the coil. Here an “internal diameter” style coil is wrapped onto a common piece of corrugated plastic sewer pipe. The pre-heat temperature is cool enough that it does not affect the coil or plastic pipe. Insulation can be used to protect the coil and pipe if higher temperatures are desired. The coil is slid into the I.D. of the target work piece. The weld area is now set-up and heated in a fraction of the time it used to take, and the heat is uniform, no hot spots. Similar set-ups can be used for shrink fit applications.

 

Pre-heating of an 8” o-let to a 20” manifold to 200°C before welding.

proheat-35-app13-150x150Water-cooled induction coils are flexible and easy to apply to a variety of geometries.  One coil can be used to wrap around multiple heat areas.  Here a coil is wound 4 turns “pancake” style onto the larger 20” manifold, then a 3’ long loop is formed so the coil is clear of the weld area for the welder, and finally a 4 turn “solenoid” style coil is wound around the 8” pipe.  Because the heat is in the pipe and not the coil, rope, plastic tie wraps and tape can be used to hold the coil into place.  This set-up was applied in less than 15 minutes and in another 15 minutes the temperature at the root was 400°F, ready to weld.  The control system automatically regulates the power output to maintain the 400°F temperature, so the pipe stays at temperature during breaks, between shifts, or all week if you want.