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Chairs: 6 Essential Quality Assurance Tests and Checks

by John Niggl

How much of your life is spent sitting down?

Vincent’s Chair, a 1888 painting by Vincent van GoghAccording to one study, the average adult spends more than 90 percent of their leisure time sitting – 90 percent! That figure doesn't even include the time you might be sitting at work or, as most of us in the Western world tend to do when nature calls, sitting on the toilet.

As long as you’re spending so much time sitting, wouldn’t you like to be sure that the chair you’re sitting in is one that’s not only comfortable and durable, but safe and stable as well? That’s why Quality Wars is bringing you the 6 ESSENTIAL quality assurance tests and checks for chairs that you can perform anywhere – even on-site at the factory – to make sure your chair is a quality one.

So pull up a chair and take a load off. But before you do, make sure you’re sitting in a chair you can trust!

1. Seat static load test

The static load test is one of the most basic of quality tests performed on chairs, and there are several different standards used (see the below chart for standards). The static load test consists of placing a fixed weight on the center of the seat of the chair for an extended period of time and then checking for permanent deformation and structural damage. If the height of the chair being tested can be adjusted it should be set to its highest, for this and other tests, as this is the position at which the chair is most structurally vulnerable. As a general rule, if a chair exhibits permanent deformation in excess of 1/4 inch it fails this test.

StandardWeightTime
American – Indoor500lbs1min
European – Indoor130kg10min
American – Outdoor180kg30min
European – Outdoor160kg30min

 

2. Impact drop test

The impact drop test is helpful in assessing a chair’s ability to resist the sudden impact of a weight load. To perform this test, fix a load of 200 pounds 6 inches above the seat of the chair and allow the weight to free-fall onto the center of the seat. As with the static load test, any chair that shows structural breakage or permanent deformation over 1/4 inch fails the impact drop test.

 

Back pull durability test3. Back pull durability test

The back pull durability test is a reliable test used for checking structural integrity of a chair’s back. This test involves exerting a force of 100 pounds on the back of the chair for 1 minute. The force should be evenly distributed and applied 16 inches above the seat and at a 90 degree angle against the back. Form-fitting blocks can be used to ensure even load distribution and clamps secured to the legs can hold the base of the chair in place. If the chair sustains structural failure or loss of serviceability under the test load, then it fails the back pull durability test.

 

Arm strength test4. Vertical/horizontal arm strength test

Although the arms of a chair are, typically, not intended to be sat on, if a chair has arms, the arms should be tested to a certain load both vertically and horizontally. For the vertical arm strength test, set a load of 300 pounds on both arms, evenly distributed, and hold the weight for 1 minute.

For the horizontal arm strength test, first secure the chair firmly so that it will not slide from side-to-side. Subject each side of each arm of the chair to 75 pounds of force for one minute. If the arms show structural failure, including arm fracture, or loss of serviceability following either test the chair fails that test.

Leg strength test5. Leg strength test

The phrase “a chain is only as strong as its weakest link” might aptly apply to chairs as “a chair is only as strong as its weakest leg”. Test the strength of a chair’s legs by setting the chair down on its back and hanging a load of 75 pounds 1 inch from the end of each front leg for 1 minute. Then set the chair on its front and hang the same weight 1 inch from the end of each back leg for 1 minute. Finally, turn the chair on either side and repeat the process so that force is applied at all four directions – forward, backward and side-to-side. If there is any permanent deformation or structural damage to the chair or its legs afterward, then the chair fails the leg strength test.

6. Chair drop test 

This last test is a stability test that can identify a weakness in any component of the chair. Drop the chair at a slight angle and from a height of 8 inches so that its rear legs impact first with the floor. Continue this test a minimum of 10 times and repeat so that the front legs impact first. The chair fails the drop test if there is component malfunction or permanent deformation exceeding 1/4 inch.


John Niggl is a Client Manager at InTouch Manufacturing Services, a QC firm that performs product inspections and factory audits in China for US and EU clients. John also writes for the QC-related blog, Quality Wars.

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