 |
|||
|
|
|||
Pipeline Equipment - Induction heating in welding applications
Bas Valk Pipeline Equipment - Rapid Heat - ; Our induction heating systems for welding applications, has proven its technology on a number of projects, including oil and gas pipelines, heavy equipment construction and maintenance and repair of mining equipment. Summaries of various projects are presented below.
Oil Pipeline A North American oil pipeline maintenance operation had used a combination of propane torches and electrical resistance to heat pipe before welding encirclement repair sleeves or STOPPLE fittings to the pipeline's 48-inch girth. While many repairs could be made without having to stop oil flow or drain it from the pipe, the presence of the crude itself hampered welding efficiency due to the heat sink effect of the flowing oil. Propane torches required constant interruption of welding to maintain heat, and resistance heating - while providing continuous heat - often couldn't meet required weld temperatures. The maintenance company turned to induction heating as a solution. On encirclement sleeve repairs, two 25kW systems were employed with parallel blankets to obtain a preheat temperature of 125 degrees F. As a result, cycle time was reduced from 8-12 hours to 4 hours per girth weld. Preheating for a STOPPLE fitting (a "T" junction with valve) repair had been even more challenging due to the fitting's greater wall thickness. With induction heating however, the company used four 25kW systems with a paralleled blanket set-up. Two systems were used on each side of the "T". One system was used on the mainline to preheat the oil and the second was used to preheat the "T" at the circumferential weld joint. The preheat temperature was 125 degrees F. The weld time was reduced from 12-18 hours to seven hours per girth weld. Natural Gas Pipeline A natural gas pipeline construction project entailed building a 36 in. diameter, .633 in. pipeline from Alberta, Canada to Chicago. On one spread of this pipeline, the welding contractor used two 25kW power sources mounted on a tractor with the induction blankets attached to booms for speed and convenience. The power sources were used to preheat both sides of the pipe joint. Critical to this process was speed and reliable temperature control. As alloy content increases in materials to reduce weight and weld time, and to increase part life, controlling preheat temperatures becomes more critical. In this induction heating application, it required less than three minutes to obtain the 250 degrees F preheat temperature, versus approximately five minutes using traditional preheating methods. In addition, temperature uniformity and operator safety were improved. Heavy Equipment A heavy equipment manufacturer often welds adapter teeth onto its loader bucket edges. Previously, the tack welded assembly was moved back and forth to a large furnace, requiring the welding operator to wait while the part was reheated repeatedly. The manufacturer opted to try induction heating to preheat the assembly to prevent movement of the product. The material is 4 in. thick with a high required preheat temperature due to alloy content. RHS worked with the customer to develop customized induction blankets to meet the application requirements. The insulation and coil design provided the added benefit of shielding the operator from the part's radiant heat. Overall, operations were considerably more efficient, reducing welding time and maintaining temperature throughout the welding process. Mining Equipment A mine had been experiencing cold cracking problems and preheating inefficiency using propane heaters in its repair operations of mining equipment. Welding operators had to remove a conventional insulating blanket from the thick part frequently to apply heat and keep the part at the correct temperature. The mine opted to try induction heating using flat, air-cooled blankets to preheat the parts before welding. The induction process applied heat to the part quickly. It also could be used continuously during the welding process. Weld repair time was reduced by 50 percent. In addition, the power source was equipped with a temperature controller to keep the part at the target temperature. This virtually eliminated rework due to cold cracking. The customer reported an annual savings of $80,000. Power Plant A power plant builder was constructing a natural gas power facility in California. Boilermakers and pipefitters had been experiencing construction delays due to the preheating and stress relieving methods they were employing on the plant's steam lines. One of the biggest problems on this job was reliability of the electrical resistance equipment, which suffered from contactor and connector failures and broken wires on the heating pads during stress relieving. Extensive rework as a result, combined with long heating cycles, was delaying construction significantly. The company brought in induction heating technology in an attempt to increase efficiency, particularly for work on medium to large steam lines, as these pieces take the most heat treating time required on a job site. |
|||
|
