By Robert Johnston
Valley Forge, Pa.
One of the duties of the Analytical Services Lab is to assist in investigating quality problems. When a customer complains something is wrong with a batch they’ve received, we act to see what happened. Our customer, a steel mill, had received a shipment of hydraulic fluid in fifty-five gallon drums. They filled their system by transferring the fluid through a funnel equipped with a fine mesh screen. The screen was clean when they started, but after transferring the first drum they found dark colored particles on the screen, and they reported that they had received dirty oil.
We requested samples from the drum, and also the particles they had found in the screen. Retain samples of the batch were also obtained from our plant.
Chemical and physical analysis showed that all the fluid samples were within specification, so the next step was to analyze the particles. Microscopic examination showed that they were a mixture of various types, including flat red sheets, spherical clear grains, white chips, and metal chips. FTIR and X-Ray spectroscopy helped us to identify them as iron oxide, sand, clay, feldspar, limestone, and steel.
I hadn’t ruled out the possibility we had sent our customer dirty fluid, but the chemical makeup of the debris from the funnel screen made it look like the type of dust that is common around steel mills. I contacted our technical representative and asked him if any surfaces around the mill were coated with black dust. His answer was, “Sure, the roof, the parking lot, the cars, everything.” When I asked about our drums, he said they were stored outside, and had a layer of black dust on top. He collected samples of the dust for analysis. As I suspected, it was the same composition as the particles from the filter screen.
The customer believed they had received bad product, and we still couldn’t explain how the debris had gotten into the funnel. I asked our Tech Rep to see whether their drum pump could have been contaminated with mill dust. His investigation revealed that they didn’t use a pump to transfer fluid. Instead, they used a drum lift that raised the drum up to the level of the funnel, and then tilted the drum so fluid could pour out. As the angle of the drum increased, the debris on top began to roll off into the funnel. To quote Robin Williams, “Gravity works.” We were able to convince them the fluid was in good condition when they got it, and they needed to brush off the top of the drums before they began to transfer it. They took our advice, and the problem went away.
Five years after we solved this problem, history repeated itself. The steel mill was under new management with a new name, and most of the old staff had retired. The new workers found particles in the funnel screen after transferring our fluid, and nobody remembered the previous incident. It was much easier to solve the case the second time around.
Robert Johnston is group leader, Analytical Services for Houghton International. Contact Johnston at (610) 666-4114 or via email at RJohnston@houghtonintl.com.