October 19, 2009

JEAN SORENSEN

Four decades of looking through the lens of a microscope has given forensic engineer Vic Baker a volume of information on why materials fail.

Building materials

Quality control testing increases with imports: forensic engineer

JEAN SORENSEN

correspondent

Materials testing is becoming more important today as offshore imports impact the construction industry and quality control becomes an issue, says forensic engineer Vic Baker, P.Eng.

Five years ago, a contractor arrived at Baker’s lab with copper pipe from a failed installation project at an air-conditioning plant in Eastern Canada.

“They thought it was the installation,” said Baker who founded Baker Materials Engineering Ltd., Vancouver’s first forensic engineering firm in 1970.

But, when Baker turned his microscope onto the pipe, he discovered something unusual.

“Copper is usually very ductible,” said Baker. But, this particular pipe, which carried Canadian testing company Warnock Hersey’s stamp, was found to be have been very unusual. Long brittle cracks developed when it was handled.

“It was splitting like rotten wood,” he said.

The pipe was linked to a specific Chinese manufacturer and further analysis found it lacked the critical element phosphorous in its make-up.

The results were disastrous; some pipe started leaking even during the pressure tests. It sparked a major recall of pipe, but not before other condo installations came to light.

In Vancouver, Global News carried reports of at least four condominiums in 2004 that were experiencing leaky problems to the extent the insurance company in one was refusing to cover damages. (YouTube still has a video showing condo damage).

Baker said his company is not sure how the standards stamps got onto the pipe, whether it was an over-sight in testing or whether the Chinese supplier replicated the “WH” without the proper authority.

What is known is that as more offshore imports arrive in the construction industry, quality control is an issue. Recently, Baker investigated failed bolts holding a critical clutch element on a large B.C. Ferries engine. Crews had noticed a rattling and dismantled the clutch to find several broken bolts.

“The manufacturer was a traditional German maker of bolts,” said Baker, adding that bolts carry the manufacturer’s code name and such info on the head.

However, when Baker began probing, he found something else. A company in China had bought the German company. “They now owned the coding on the head,” he said, adding it now could be used for coding for bolts outside of Germany, including jobbed out orders from smaller manufacturers in China. “There is really a lack of quality control,” he said.

Baker does quality control testing before a project for clients who want to ensure that the materials that they install in projects meet the standards. The Baker laboratory tries to duplicate the importer’s performance standards under real performance tests.

For example, Baker points to his web site which shows pictures of stacks of particle board that has undergone miles of test cuts with sample tools.

Baker also is called onto accident sites, such as when a sling carrying glass panels on a construction site failed and crashed to the ground. Luckily no one was injured. The question was why did the webbing on the sling fail?

Material testing found that even a small and seemingly insignificant nick or tear in the strap’s edge of a sling can cause failure. The results were surprising, as construction crews can be casual in their treatment of slings on sites.

“Of course, the regulators (such as WorkSafeBC) were interested in our findings,” said Baker, who is often retained by construction companies, developer’s lawyers and insurance companies.

Baker’s role is to find out what happened by looking into all aspects of the accident. When a leased crane was lowering two men into a foundation excavation on the SkyTrain project a few years ago, the cable suddenly released and the bucket dropped, killing both.

A professional engineer had certified the crane but WorkSafeBC held the company responsible, as it had not done the required load test prior to the lift.

Baker arrived, gathered evidence, and reached a different conclusion.

“The wrong (shaped) wedge was used,” he said. It held the line onto the drum. The light bucket load of two crewmembers plus the cable’s stiffness kicked out the wedge, causing the drum to spin out dropping them.

The required load test (several times the men’s weight) with more wraps and tension on the drum would have kept the line and wedge in place only to fail later when it was spooled out.

Such sleuthing at accident sites or places where buildings have failed has taught Baker to separate out events and damages and determine what is root cause and what is “secondary” damage.

For example, a steel support may corrode shifting the load onto others, deforming them. While they are visually graphic, they are not the root cause of the failure.

“About 95 per cent of what you see is often secondary damage,” said Baker. “The challenge is really to sort that out.”

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