By Jim Montague, executive editor
New welds are a lot like babies. They need TENDER, loving care to grow up strong and relatively free from stress.
This might not be too hard to do for a few steel alloy pipe sections or valves, but when youve got hundreds or even thousands of welds to monitor and manage, the solution is obvious. You need a boatload of babysitters.
Companies that build or help to repair oil, gas, petrochemical, or other process plants traditionally bring in dozens of technicians to oversee the many thermocouples and strip-chart recorders used to monitor pre-heating and post-weld procedures in numerous heat-affected zones (HAZs), usually for several hours each. These personnel also document that new welds meet specified hardness requirements, so theyll be durable enough to serve long term in processing heavy flows and withstand often harsh environmental conditions. Good instrumentation and control of welding, and uniform, high-quality welds can add years of service life to a pipeline.
Most post-weld procedures involve baking hydrogen out of a weld, relieving stress, or annealing it. To perform these treatments, users manually attach a ceramic-element heater to the pipe or other structure, insulate it, and apply heat via internal wires. The welder then completes the weld, which usually must be maintained at 1,400 °F for several hours, and undergo controlled cooling (Figure 2). New construction or a major renovation project can require 70-100 people to perform its heat-treating services.SuperheatFGH Canada, Kincardine, Ontario. One power supply can run six to 12 heaters, but the traditional process was so labor-intensive because we needed one operator to read the recorder for each power supply, and we could only respond manually to data outside parameters.
To help it and its clients reduce some of these traditionally high labor costs, SuperheatFGH recently developed and implemented a wireless solution between its 6Wi 460 V, six-HAZ power-units and Site-Access Management (SAM) computing system. This WiFi link allows a technician, who used to monitor only six to12 weld zones, to now oversee and run up to 100 power units, or a total of 600 zones. Lewis says this allows Superheat to run a welding project with 70% fewer staff, which means a site that used to need 100 technicians now needs only 30 or fewer. The level of these labor savings even enables more users to self-perform more of their own welding projects, so Superheat trains them to use its technology.
Superheat acquired U.K.-based FGHs temperature control and instrumentation technology when the company was founded in 2000.
Assisting Aecon at Suncor
Aecon Group Inc. recenty performed a three-month, $3 million chrome-steel pipe installation and distillation tower rebuild project at Suncors new oil-sands processing plant complex in Calgary, Alberta. The project required Aecon to use hundreds of heaters, and so it enlisted Superheat to help monitor them. Aecons facilities include pipe fabrication, refinery module assembly, and site construction services. Heat treating (HT) and stress relief of alloy-steel components and piping play a significant role in all three jobs.
When it comes to pipe and components fabricated from chromium-molybdenum-vanadium (Cr-Mo-V) alloyed steels, such as P91 and P92 grades, as well as heavier, thicker carbon steels, heat treating is mandated, says Diego Carducci, construction operations manager for Aecons western operations. Codes specify the HT cycles during and after welding to yield the proper strength and ductility and to markedly reduce the chance of weld cracking. This is where we use SuperheatFGHs services. He adds that governing authorities wouldnt allow Aecon to perform such welds without proper HT. In performing a welded joint for chrome, for example, the material has to be stress-relieved after welding and receive post-weld heat-treating (PWHT). Non-destructive testing procedures are carried out on these alloy steels. Weld hardness is checked by using either Brinnell or Vickers scales, and final post-weld hardness must be certified to be within a certain range, depending on the welding procedure.
A welder completes the joining of two pipe sections, which typically must be maintained at 1,400 °F for several hours, and undergo controlled cooling to ensure required hardness and long-term durability.