The Lofty Tank Specialist

When it comes to storage tank construction, respective experts in design, fabrication, and inspection collaborate to deliver a final product.  The conception of a design usually begins with a qualified engineer, his drawings eventually reaching a foreman who supervises fabrication, the baton then passing to an inspector who grades the final product.  And this production flow, where each task is supervised by different parties, can function well when communication is crystal clear. In contrast to those who fill only a single role, experts familiar with all facets of tanks are called tank specialists.  They are experienced in tank design and fabrication, also possessing the knowledge to perform inspections.  Tank specialists are invaluable because they have both theoretical knowledge and hands-on construction experience, training and practical know-how that affords a complete view of a project.  Equally deft with AutoCAD or welding torch, these specialists, on any given day, can be seen donning a white collared long sleeve or a pair of Nomex coveralls. Incorporating a tank specialist into the construction process provides insight that transcend the typical divisions of labour.  The specialist ensures unity between theory and practical application, and often has the last word when designers and fabricators butt heads.  A specialist’s participation from project start to finish, with his tremendous knowledge, pays enormous dividends—-both in terms of economic benefits, and also keeping peace between the white collars and the Nomex crowd.  ...

A Near Miss: A Narrowly Averted Catastrophic Explosion

Recently, a senior project manager at ASI recounted an experience that took place nearly thirty years ago. The short tale underscores the importance of QC and safety procedures, and having the courage to follow protocol. As a young welder with limited experience, my colleague was called to a job in southern Saskatchewan.  His task was to perform a hot tap (installing a nozzle on an in-service tank) on a tank with highly volatile contents.  An old and surly maintenance supervisor, head of maintenance on the Saskatchewan site, was more interested in lost production than safety, and pressured our young welder to start up immediately.  Ron was in a quandary: perform mandatory NDE testing as he’d been trained, and incur the wrath of the much more experienced site sup, or relent and start work. Ron ultimately decided to defy the unscrupulous sup and wait for the results of ultrasonic thickness testing before striking an arc.  Indeed, the UT confirmed a serious delamination precisely at the location of the hot tap. Had my colleague surrendered to the more senior maintenance foreman, he would have burned a hole through the shell.  The high current would have certainly ignited the tank contents, and he wouldn’t be alive today to tell the story. Let this cautionary tale remind us of the importance of trusting in ourselves and following proven safety...

Alberta Stretched Thin

Alberta has been an economic hotbed for nearly ten years.  $100 oil has made unconventional plays in the Athabasca Oilsands more than attractive and foreign investment dollars are flowing in almost as fast the bitumen is flowing out.  Newspapers report daily on the labour shortage and industry does everything possible to lure skilled workers to the wild rose province. Regular announcements of major capital projects have precipitated a steady flow of prosperity seeking migrants to Alberta.  All in all, the pace of life in Alberta is reaching breakneck speed. What does all this mean? For one, Alberta trade schools are pumping out more welders than any other jurisdiction in North America—5000 annually.  Industry is demanding more and more welders and schools are happily obliging.  But is this a positive development?.  Yes and no.  More welders to accommodate the needs of economic growth is an undeniably good news story.  But what’s less comforting is the speed at which students are rushed through trade programs. To clarify, Alberta’s trade schools and the calibre of tradespeople they produce are excellent.  However, due to the urgent demands of industry, more advanced techniques (like multi-pass welds) are being ignored for the sake of expediency.  The alarming trend seems to be quantity over quality, and new welders are rushed into work they aren’t always ready to undertake.  For instance, freshly minted journeryman can attain their tickets with very limited, repetitive welding experience.  But because welders are in high demand, a rookie with flat groove experience only is suddenly hired to lay flawless overhead fillets.  The result is poor workmanship that leads to failures and potential loss of life. Unfortunately, heavy duty fabrication is not child’s play. Tacking a muffler onto an exhaust pipe...

Post Weld Heat Treatment

We receive a lot of questions regarding post weld heat treatment (PWHT).  Confusion seems to stem from a lack of metallurgical understanding, and how heat alters the microstructure of iron at given temperatures. So firstly, some background… The atomic arrangement of iron—when it remains under transformation temperature— is called body centered cubic (BCC).  The BCC structure is unwelcoming to carbon, accepting very little carbon into it’s microstructure, severely limiting BCC’s strength ratings. However, when iron is brought to a specific temperature and mixed with carbon (and/or other alloys), iron’s BCC structure has a change of heart.  BCC becomes face centered cubic (FCC), an atomic structure that accepts carbon with open arms.  The result is called austenitic steel, and this transformation, and the subsequent rate of cooling, greatly alters the properties of the metal. In some cases, the austenitic steel is cooled very quickly (quenched) in water, a process which results in very strong steel. Unfortunately, increased strength comes at the expense of ductility. And so, when extremely strong but moderately ductile steel is sought, pre or post weld heat treatment may be utilized to ‘temper’ the steel.   When steel is rolled, the grain structure is subjected to significant stress, detrimentally distorting the microstructure.  PWHT is effective in relieving the internal stress, refining the grains and improving overall strength. PWHT is also very useful for ‘baking out’ excess hydrogen that may exist in weld metal, a defect that can cause hydrogen induced cracking. And finally, in addition to tempering the parent metal, PWHT tempers the heat affected zones (HAZ) caused by the welding arc, adding ductility to all areas of brittleness. Ultimately, PWHT is highly effective if conducted properly.  Excessive temperatures or holding...

RIP SMAW: Is stick welding passe?

In a quiet battle that wages in the inner sanctum of many fab shops, a welding debate pits the Old Guard against the next generation of welders.  Though most trade schools have given the nod to semi-auto welding processes, seasoned veterans who’ve finessed their hard-earned technique by burning truckloads of rod aren’t necessarily convinced. So which is better, SMAW or hard wire? Well, regardless of where you stand on the issue, the fab industry is undergoing a paradigm shift.  Out with stick and in with MIG and FCAW.  Whether this shift is motivated by the more operator friendly nature of MIG/FCAW or semi-auto’s higher weld deposition is debatable. What is clear is that the bias against stick welding is wide spread. But wait, the stick artisans argue, MIG is useless outdoors and FCAW chokes with fumes.  The roll drives that feed wire are finicky and more problem prone than the simpler shielded arc setup. Plus, semi-autos are less forgiving to incorrect volt/current settings, the CV welding units more temperamental than their CC counterparts. However, when MIG setups are dialed in and utilized in controlled environments, there’s no denying their supremacy.  The auto feed wire eliminates the need to constantly change rods and gas shielding negates slag removal.  FCAW, with its slag system, adds outdoor capability with much greater deposition rates than stick.  Also, the shorter electrode stick out is easier to manipulate and requires less talent to master. Does this mean stick is dead? Hardly. Those fabricators and weekend warriors that work outside will probably never abandon stick, especially if simplicity, affordability, and portability are preferred.  SMAW is incredibly versatile, well suited to a wide range of metals and thicknesses.  Moreover, the longer rod- –a bane to...