Pipeline construction glossary
The jargon you hear on your first day on a spread and quietly look up that night. Plain definitions, no assumed background.
These are standard, widely-used terms in Canadian pipeline construction, not company-specific or disputed claims. Checked 2026-09-08.
The one-page jargon sheet
The compiled artifact for this cluster: every term below in one printable table, alphabetical.
| Term | What it means |
|---|---|
| Bending (field bend / mandrel bend) | Cold-bending straight pipe sections on-site with a hydraulic bending machine so the line follows the terrain's actual curves, instead of using a pre-fabricated fitting at every direction change. |
| Coating | The corrosion-protection layer applied to the outside of the pipe -- factory-applied fusion bonded epoxy (FBE) on the mill-coated joints, with a separate coating (sometimes called a 'yellow jacket' on site) applied over each girth weld after it's made, since that one spot arrives on-site bare steel. |
| Girth weld | The circumferential weld that joins two lengths of pipe end-to-end, all the way around the pipe's circumference -- the weld a welder makes to connect one joint of pipe to the next as the line is strung together. |
| HDD (horizontal directional drilling) | A trenchless method for getting a pipeline under an obstacle -- a river, a road, a rail line -- by drilling a curved bore from the surface, then pulling a pre-welded pipe section back through it, instead of digging an open trench across the crossing. |
| Hydrotest (hydrostatic test) | Proof-testing a finished section of pipeline by filling it with water and pressurizing it above its normal operating pressure for a set period, to confirm the pipe and its welds can hold before the line goes into service. |
| Mainline | The main pipeline itself, running continuously along the right-of-way -- as distinct from station piping, tie-ins, or the shorter connecting lines that feed into or branch off it. |
| Pigging | Running a 'pig' -- a device sized to fit inside the pipe -- through the completed line, either to clean it, dry it after a hydrotest, or (for a 'smart pig') inspect the pipe wall for defects from the inside. |
| Right-of-way (ROW) | The strip of land the pipeline is built and buried under, cleared and graded before construction starts and reclaimed afterward -- the workspace the whole spread physically moves along as it advances. |
| Sideboom | A tracked machine with a boom and counterweight mounted on the side rather than the front -- used to lift and lower long, heavy sections of welded pipe (a 'string') into the ditch without the machine tipping toward the load. |
| Skid | A prefabricated equipment assembly -- valves, piping, instrumentation -- built and mostly assembled off-site on a steel frame ('skid'), then set in place at a station rather than built piece-by-piece on location. |
| Spread | The whole mobile construction crew and equipment set working a defined section of pipeline route at one time -- clearing, ditching, stringing, welding, coating, lowering-in, and backfilling as one coordinated operation that moves down the right-of-way together. |
| Station | A fixed facility along the pipeline -- a pump station, compressor station, or metering/valve station -- as distinct from the buried mainline itself; station work is generally more like conventional industrial construction than spread work. |
| Stringing | Laying out individual joints of pipe end-to-end along the right-of-way, in position and in order, ahead of the welding crew -- the step that turns individual pipe joints into a line ready to be welded together. |
| Tie-in | The final weld (or set of welds) that connects two already-completed sections of pipeline together -- often the last piece of a spread's work, or the connection between a new segment and an existing operating line. |
Sources
- Pipeline Safety Trust -- Glossary — accessed 2026-09-08. Source for the hydrostatic-testing and "pig" definitions above; does not define the other terms on this page, which are standard industry usage.
Frequently asked questions
What's the difference between a spread and a mainline?
A spread is the crew and equipment -- the whole moving construction operation working a section of route. The mainline is the pipe itself, the thing the spread is building. You work on a spread; you're building a mainline.
What does a sideboom actually do?
It lifts and lowers welded pipe -- often a long, heavy string of joints already welded together -- into the ditch. The boom and counterweight sit off to the side of the tracked base rather than the front, which is what lets it hold a heavy suspended load without tipping toward the ditch the way a front-boom machine would.
What is a tie-in, and why does it matter so much on a spread?
It's the weld (or set of welds) that connects two already-built sections of line together -- often the very last piece of work joining a new spread's segment to an existing line, or joining two spreads that started from opposite ends and met in the middle. It's frequently treated as a milestone because everything upstream of it -- stringing, welding, coating, lowering-in -- has to already be finished and correct before a tie-in crew can close the gap.
Why does a pipeline need to be hydrotested if it's already welded and coated?
Because a hydrotest is the check that the pipe and every weld can actually hold pressure above normal operating levels before the line goes into service -- filling the finished section with water and pressurizing it is how a defect gets caught on a test bench of water, not after the line is carrying product.
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