Miller ProHeat 35 Induction Heating System

Overview

The Miller ProHeat 35 is an air-cooled induction heating system designed specifically for weld preheating up to 400 °F (204 °C). Its 35 kW power source runs at 100 percent duty cycle and drives flexible induction blankets or air-cooled heating cables that wrap around pipe and plate. Miller lists process piping, refinery, petrochemical, cross-country pipeline, power piping, pressure vessels, structural work and shipbuilding as core applications. The Miller ProHeat 35 replaces open-flame and resistance heating with a cleaner, faster and more uniform method of bringing joints to temperature before welding.

Seven Star LLC supplies the Miller ProHeat 35 and its blankets and accessories to pipeline contractors, refinery maintenance teams and power-plant fabricators across Oman and the GCC. Preheat is a mandatory step in many welding procedures for thick carbon steel and chrome-moly piping, and our Muscat team helps customers specify a complete induction package for projects from Fahud and Qarn Alam to Sohar and Duqm.

Operating Principle

As general background, induction heating passes an alternating current through a coil placed close to a conductive workpiece. The changing magnetic field induces eddy currents inside the metal itself, and the resistance of the metal to those currents generates heat within the part rather than on its surface. Because heat is created in the material and not conducted inward from a hot element, the temperature rises quickly and evenly through the thickness of the heat zone.

Miller describes the practical results for the Miller ProHeat 35: uniform heating is maintained along and through the heat zone, the surface is not marred by localised conducted heat above the specified temperature, and time-to-temperature is faster than with conventional processes, which reduces cycle time. The working environment also improves, because welders are not exposed to open flame, explosive gases or the hot elements associated with fuel-gas and resistance heating. At more than 90 percent efficiency, the power source transfers more energy into the part and reduces operating costs compared with other heating methods.

Engineering Design of the Miller ProHeat 35

The Miller ProHeat 35 power source has a built-in temperature controller for manual or temperature-based programming using up to four control thermocouples. It has two outputs and can run one blanket, two blankets in parallel, or four blankets in a series/parallel arrangement using series cable adapters and output extension cables. Each power source connection identifies the type of heating device to the controller, and this cable identification system prevents over-duty-cycling of the heating tool. The unit measures about 699 mm high, 552 mm wide and 933 mm deep and weighs 103 kg; optional running gear adds four 5-inch swivel casters with brakes.

Flexible induction blankets are made from durable high-temperature materials, conform to circular and flat parts, and install in a matter of seconds. Each blanket is supplied with a replaceable Kevlar sleeve that protects against abrasion, cuts and tears. Air-cooled cables in 30, 50 and 80 ft lengths offer the same flexibility as liquid-cooled cables for preheat, and can be wrapped into coils of different shapes without a cooler or coolant. Preheat insulation, 1/2 inch thick, holds coils at the correct coupling distance and can be cut to length.

Temperature feedback on the Miller ProHeat 35 comes from a contact thermocouple sensor placed between the blanket and the part, rated for preheat use up to 500 °F (260 °C). An armoured 25 ft thermocouple extension connects the sensor to the power source, and a thermocouple extension cable with a terminal connection allows six thermocouples to be used, avoiding a clutter of individual wires across the work area. Preheat cable covers protect heating cables from slag and molten metal during welding.

Key Features

The main features of the Miller ProHeat 35 air-cooled system are:

• The power source delivers 35 kW at 100 percent duty cycle for continuous preheat on long welding shifts.
• A built-in temperature controller supports manual or programmed heating with up to four control thermocouples.
• Efficiency above 90 percent transfers more energy into the part than other heating methods.
• Two outputs can drive one, two or four blankets or air-cooled cables at a time.
• Air-cooled blankets fit pipe from 8 to 60 inches and plate lengths from 1 to 5 m.
• Air-cooled cables in 30, 50 and 80 ft lengths heat irregular shapes without coolant.
• Cable identification prevents over-duty-cycling of the connected heating device.
• Remote contactor and RHC-14 hand controls allow heat to be started, stopped or adjusted remotely.

Industrial Applications

In Oman and the wider GCC, the Miller ProHeat 35 is suited to preheating girth welds on cross-country oil, gas and water pipelines, tie-ins at gathering stations, and thick-wall process piping in refineries and petrochemical plants. Power and desalination plants use induction preheat on steam, feedwater and header piping where chrome-moly and thick carbon steels require controlled minimum preheat and interpass temperatures. Because the heat is generated inside the pipe, the blanket can stay in place while the welder works, maintaining temperature throughout the pass sequence.

Fabrication yards using the Miller ProHeat 35 on pressure vessels, structural nodes and ship sections can apply air-cooled cables and preheat insulation on plate and non-standard shapes. Seven Star LLC supplies the ProHeat 35 together with the welding equipment and consumables used on the same joints, such as the LongTeng EL8 submerged arc welding wire and the Lincoln Electric Power Wave S500 MIG system. You can see related equipment in our induction heating and preheating category.

Technical Specifications

The Miller ProHeat 35 specifications below are taken from Miller spec sheet IN/14.0 for the air-cooled system (subject to change without notice).

Call To Action

Send Seven Star LLC an RFQ for the Miller ProHeat 35 listing your site voltage, pipe diameters, wall thickness and required preheat temperature, and we will propose the power source, blankets or cables, extension leads and thermocouple accessories. Download the Miller ProHeat 35 spec sheet from this page and contact our team in Muscat for current availability and engineering support in Oman and the GCC.