Traditional heat treating methodology has varied little in the last several decades. As a stress relieving process, the tried-and-true technique utilizing thermocouples, ceramic heaters, insulation, and a power source gets the job done metallurgically. Its purpose is essential: to achieve the strength and toughness that pipe and other major components used in electric power generation plants, chemical manufacturing facilities, and petrochemical plants and refineries require.
In a variety of applications within all these industries, both as new capital improvements or scheduled/unscheduled maintenance, situations occur during which steels must be post-weld heat-treated. The fields of physical metallurgy and welding have proven decades ago that many alloy steels and/or heavy section work pieces are at risk of hydrogen cracking in the presence of residual stresses. As a result, many specification- or code-writing groups, such as AWS, ASME and API, have adopted requirements for the post-weld heating, holding, and cooling to alleviate these stresses. Typical stress relief temperatures range from 600 to 1,150°F.
To create this heating-holding-cooling cycle, traditional technology has utilized rather standard power supplies and controls. Heating cables made from resistance-heating alloys are wrapped through ceramic pieces insulating the cables from the work piece. An on/off controller is also connected to thermocouples, spot-welded to the work piece, and provides on/off control to the heater cables to duplicate the desired temperature-time cycle.
Easy-to-use procedures are designed to accommodate a diversity of industries and applications. They run the gamut from petroleum refineries, fossil and nuclear power generation, pulp and paper, to pipe fabrication plants and offshore drilling operations. Projects range in scope from multi-million dollar heat treating requirements at tar sands sites to small in-house furnace applications, during shutdowns ("turnarounds" at refineries and "outages" at power plants) to scheduled and emergency maintenance, as well as for capital improvements.
As wireless capabilities have empowered the way people use laptops at their local coffee shops and computers at home and the office, new heat treating technology replaces cables and labor-intensive processing with antennas and solid-state computers yielding attendant communications and delivery benefits.
Utilizing Advanced TechnologyEach equipment element within the new heat treating process has unique features that serve quality functions. Temperature data flow seamlessly from thermocouples (T/Cs) welded to each workpiece to the on-site Super 6-W power supply and Site Access Manager (SAM). Thereafter, temperatures move over a secure wireless Wide Area Network (WAN /Internet) to the Quality Management Center (QMC) where readings of actual temperatures are verified and archived.
The customer may be given access with a Data Viewer to real-time temperature data from any office or home computer, Tablet PC, PDA, or digital cell phone. This benefit allows the end-user to have knowledge of data from anywhere at any time. This technology also provides many other capabilities for cost savings and ease of use.
Labor and Cost SavingsIn the traditional on-site heat treating model, extensive numbers of technicians carry out many rudimentary pre-treatment tasks, with passive chart monitoring of long heat treating cycles adding dramatically to billable time.
To reduce typically high labor costs, the wireless paradigm frees users to put their local labor resources to more economic use by carrying out wrapping or other installation procedures. Our training officers instruct the user's labor force within a day or two to become Certified Installers, enabling customers to choose their own degree of involvement in various projects. When applicable, local trade unions support this training for their members. Based on individual needs, the customer can elect to supply only a few people or most of an entire crew, with potential labor savings of up to 45 percent. Our personnel manage the process 24/7 to guarantee successful thermal processing.
The wireless network yields added savings by eliminating the direct and indirect costs for cable/wire installation or facility heat treating cycle disruptions, thus requiring fewer people for on-site monitoring. The system improves scheduling, reducing travel, eliminating administrative costs and lost production time for training and background checks of outside workers. Additionally, economic management of equipment through several purchase or leasing programs can significantly reduce typical equipment fees.
Data SecurityClick-of-a-mouse technology provides instant reporting from SAM to the ‘round-the-clock monitoring team at the QMC. Highly secure communication is assured using proprietary software and a secure Internet link.
The wireless LAN within the customer's plant site is also secure, utilizing a spread-spectrum, channel-hopping algorithm assuring no interference with any other wireless network. Its 902 to 928 MHz unlicensed bandwidth achieves security and performance, irrespective of the presence of buildings or plant units. The system reliably covers all locations within a typical plant site of three square miles.
Three-Step ImplementationIt is a relatively simple matter to initiate wireless heat treating services into a customer's plant. The first step is for our training officers to come in and instruct local staff to become Certified Installers, usually within one or two days. Certified installers handle standard applications in accord with specification sheets provided. For unique or specialized applications, assistance is available at all hours.
The second step is to initiate execution of the heat treatment process, which begins by establishing the wireless LAN to assure total coverage of the plant site with no fringe areas or interference with other operations.
Following installation of all heating and related equipment and qualification of wireless connections, the customer's staff is free to carry on other work. Our Quality Management Center monitors and manages all heat treating applications remotely.
System ComponentsThe Super 6-W power supply manages up to six heated zones. Thermocouples transmit temperatures from each location, providing data to the power supply unit. Power cables are hard-wired to the heaters, while a mobile diesel generator or standard in-plant unit provides 480/550 VAC electric power to the unit.
Temperature data are sampled four times per second to facilitate "on/off" decisions about electric power to the heaters, while each power supply continuously monitors the accuracy and quality of the heat treatment process. Binary-coded data are sent over the LAN to SAM every five seconds.
In the event of a communications disruption, the power supply is still able to run the job, ensuring continuity and process integrity. It also manages alarm functions, which signal conditions such as broken thermocouple wires, disconnected cables, and temperature errors, assuring quality and accuracy to specification.
A portable, solid-state computer, the Site Access Manager (SAM), utilizes three data transfer networks to serve as an information hub among three major components: the power supply(ies), the QMC, and the Data Viewer(s). Packaged within a rugged container, SAM logs up to five days of data, in addition to the power supply's own six-month data storage, for extra protection. Its minimal power demand permits a 12-Volt automobile battery to continually function for up to 24 hours.
SAM's three antennas are connected to the wireless network hub, transmitting data to and from all components. The robust wireless connection permits up to a four-mile separation without a line-of-sight requirement from each power supply to the SAM in a typical industrial setting.
The QMC is connected to the system via a secure Internet link for handling binary-coded data using proprietary software via cable modem, DSL, EVDO cards, or similar cell network availability. Only minimal bandwidth is required for this secure connection. For example, a 56K fax line is sufficient to operate 26 Super 6-W power supplies. Should any connection be interrupted, the system automatically retrieves stored backup data, synchronizing all devices and data within a few seconds.
The Data Viewer offers customers unique flexibility, allowing access to real-time temperature data. Utilizing a local 802 wireless LAN or a WAN connection, the customer can view live data using a digital cell phone, PDA, or Tablet PC.
It's All in the SoftwareAt the heart of this heat treating system is our proprietary SuperManager software that assures total quality. Comparing actual and pre-loaded data, it instantly recognizes deviations, rectifies them, and notifies designated personnel, to avert any process failure and the subsequent need for costly rework.
Control and automatic adjustment capabilities include unit shutdown in the event of over-temperature, alarm/hold protection for over/under temperature, open/shorted thermocouple, equipment temperature alarm with shutdown protection, circuit-breaker protection, and manual emergency shutdown buttons on all units. Should the need arise, monitoring personnel can communicate with the customer's on-site personnel.
As a preventive measure, redundancy exists in operations plans and communications systems. During heat treating, full operation control exists within each power supply if communication links are lost. Power supplies have external, manual emergency shutdown buttons, and data are stored within each unit.
Multiple Internet providers, direct telephone connections, remote shutdown capability, and multiple locations in the United States and Canada provide additional back-up.
Heat Treating Changes, After AllThough traditional heat treating methodology may have changed little over the years, the application of wireless control technology has transformed the process. It's fired up, ready to meet the advancing needs of an assortment of industries in the 21st Century.
Additional related material may be found by searching for these (and other) key words/terms via BNP Media LINX at www.industrialheating.com: heat treating, stress relief.