Steel rack broken when loaded less than the withstand load
A consumer bought a steel rack through an online shopping site. Soon after placing an object on the rack, although its weight was lighter than the withstand load indicated on the shopping site, the rack was broken. This article describes details of the case.
Details of the inquiry
I found and bought a steel rack sold through an online shopping mall. It was a two-layered collapsible steel rack on casters (hereinafter called "rack"). The shopping site indicated the total movable load (average static load) 120 kg. I assembled the rack and placed a 38 kg fax machine on it. Within 20 minutes, the rack was broken and the wall nearby was damaged by the falling machine.
The instructions for assembling the rack indicated the "withstand load 100 kg", which was different from "120 kg" shown on the online shopping site. At any rate, the rack broke down when I placed an object lighter than 40 kg on it, so it appears that the rack had bad quality.
I informed the rack manufacturer of the incident. Later they brought an alternative product and said, "We consider that the withstand load of the product is 50 kg per layer. This time the product broke down when loaded less than 50 kg, so we will change the representations of the products". The manufacturer didn't care about product safety. I am dissatisfied with the irresponsible attitude.
After hearing the details from the inquirer, the National Consumer Affairs Center of Japan (hereinafter called "NCAC") asked the inquirer to send the instruction manual and a photo image of the rack. Then, NCAC asked the manufacturer for a detailed explanation.
The manufacturer said, "After taking back the broken product, we visually checked and disposed of it. We conducted product tests to investigate the cause of collapse, using the same type products". NCAC asked the manufacturer to send the report on results of the withstand load test. NCAC received and read the report. According to the report, there was no sample which fell down due to a dent or deflection in shelf boards or a load applied.
The manufacturer measured a dent or deflection when shelf boards were evenly loaded. However, it is not always the case in everyday life that boards are evenly loaded. The test results appeared insufficient to support that the racks had no quality problem. Therefore, NCAC's Product Test Department conducted a series of product tests with use of the same type products.
Stiffness of the whole rack is influenced by "tightening torque" * of bolts fixing uprights and mounting hardware. Therefore, NCAC applied different levels of tightening torque in the product tests. The test results showed that the strength of the rack was very sensitive to tightening torque of screws fixing uprights and mounting hardware and that insufficient tightening torque caused deformation or collapse of the rack even when loaded 100 kg or less. Then it was found out that the collapse incident could have been caused by insufficient tightening torque.
Later, NCAC informed the manufacturer of the product test results and asked the manufacturer to consider measures for improvement. NCAC also requested the manufacturer to describe on the instruction manual how to properly tighten screws with specific values and illustrations. NCAC proposed to change the specification to strengthen the structure. The manufacturer replied that they would consider whether or not to change the specification, or to decrease the withstand load to be indicated.
At a later date, the manufacturer informed NCAC of the results of reviewing the instruction manual. The manufacturer sold two types of racks: two-layered racks and three-layered racks. The manufacturer provided same instruction manuals for these two types. The manufacturer told that they would replace representations of the withstand load "two-layered rack: 100 kg (50 kg per layer); three-layered rack: 120 kg (50 kg per layer)" with "40 kg per layer (total load: up to 80 kg)" and that they would change the text in the instruction manuals.
The manufacturer also said, "We stopped manufacturing two-layered racks. We have not received any complaint about three-layered racks. The three layered rack has more screwed positions than the two-layered rack, so the three layered rack is stronger. Considering product safety, we decided to indicate the withstand load as 40 kg per layer. Drastic specification change costs too much, so we won't change the specification at this time".
NCAC pointed out as follows: "If there will be no change in the specification of the joint parts, there will be no change in vulnerability of the three-layered racks as well. We concern that the three-layered racks are as vulnerable as the two-layered racks and might break down when loaded, so it is necessary to alert consumers to risk. It is also necessary to change the description about the withstand load on the online shop".
The manufacturer replied as follows: "We understand the necessity for improvement. In light of the status of complaints received, we will take measures as appropriate". However, the manufacturer didn't accept to improve design of three-layered racks, saying "We have not received any complaint about three-layered racks manufactured and sold to this date". NCAC repeatedly tried to persuade the manufacturer, but they did not change their stance.
The outcome was not satisfactory, so NCAC needs to pay attention to the future inquiries and complaints concerned. Since the manufacturer made a certain improvement in their products, the consultation was concluded.
* A twisting force when a screw is tightened
The manufacturer insisted that there was no problem with strength of the products based on their product test results. NCAC informed the manufacturer of the outcome of the product tests conducted by the Product Test Department and repeated negotiations with them. As a result, the manufacturer improved the instruction manual, but did not change the specification of the existing three-layered racks.
The rack is made of steel. If it breaks down with a heavy load on it, it could cause serious damage to persons and objects nearby. The manufacturer, however, did not seem to have any sense of danger.
If a serious accident occurs due to the use of a product, the product manufacturer would be blamed by the general public and would suffer a heavy loss. NCAC hopes that manufacturers keep it in mind when making and selling their products.