Understanding What Dimensional Inspection Services is All About

08 June 2018

Dimensional inspections, as carried out on structures, have been mentioned in past posts. There was talk about structural features, about spatial coordinate systems, and specialist measurement tools. This time, the welding inspection is going to receive that same level of appraisal. And, importantly, these checks begin before the weld is applied. Down in the joint site, we’re looking to see if the area is prepped for the job at hand.

Weld Preparation Inspections 

The project is tricky because of the calculated loading factors. Or maybe it’s the newest codes and regulations that insist on this pre-check step. Whatever the reason, the welding inspector is on-site with his bag of tools. A flashlight and portable microscope are pulled from the toolkit. The joint zone is inspected. The area is assessed to see if the metal is clean. A wire scrubber is the welder’s tool of choice here, with the wiry brush scouring away patches of corrosion and old paint.

Carrying Out the Dimensional Groundwork

The joint area is now plainly visible. According to the principles and methods that direct the procedure, all member edges or root openings must be aligned correctly. The inspector pulls out calipers and measuring aids and really assesses this key part of the weld site. After all, if the various overlapping surfaces and root openings aren’t spaced just-so, then the fused materials won’t penetrate the surface faces properly. Poorly aligned surface gaps are likely to hinder the fusion process and impede the operation’s deeply penetrating liquefied materials.

By-The-Book Spatial Checks 

Granted, the inspector’s mind is full of allowable tolerance values, as determined by some professional engineering authority, but there’s a second set of measurements to satisfy. This is where the dimensional specs on the design drawings enter. Opening his journal, the welding inspector looks up the engineer’s design drawings and allowable joint error margins. This phase is carried out after the preparation check but before the painters arrive to coat everything in a protective layer of urethane. Remember, even if the welder is certified, there are always moments when a weld could shrink or deform because of some material defect or an unforeseen environmental factor.

A visual inspection is one thing, but a dimensional inspection, one that assesses numerous pre-weld areas and post-welded joints, is something else entirely. The metal surfaces are recorded on paper as clean and dirt free. Root edges are measured with calipers and specialised gauges. Last of all, the geometry of the entire weld is inspected to make sure no material shrinkage or deformation has occurred.

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