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Will you cave under pressure? A psi blog

Altro manufactures flooring products that are extremely durable and long lasting.  But how can durability be quantified?  One way is through PSI testing.  PSI testing (called static load limit testing) is a way of measuring flooring to see if it will indent under pressure.

psi.jpgWhat is PSI?

PSI stands for pounds per square inch.  It is one of the most important measurements for determining a floor’s durability.  Something can weigh a lot but have a low PSI.  PSI is calculated by dividing the weight in pounds divided by the surface area in square inches.

What exerts the greater potential of pressure-per-square inch when walking?   A 100 lb. woman in high heels or a 6,000 lb. elephant in bare feet?

Stiletto heels have an area of about 1/16 of a square inch. So at the point in walking when she stands solely on the heel, the woman exerts more than 1,500 psi.  Elephants, unlike humans, walk with two feet on the ground at a time. Each foot is about 40 square inches. Thus, the elephant only exerts 75 psi.
This is a big problem with vct, laminate and hardwood floor coverings as the heels can leave indentation  marks throughout the floor.  This is also particularly important in industries such as healthcare, where a single bariatric bed with a patient can weigh as much as 1,500 lbs. and is solely supported by four castor wheels. 

Testing for PSI

How is a floor covering tested for PSI indentation resistance?  ASTM F-970 is the Standard Test Method of Static Load Limit testing.  This test method is a meaningful test for determining the indentation recovery properties of resilient floor covering. 
The way the test method works is that first the thickness of the material is measure by a dial micrometer.  Then a weight is applied to the surface.  This is done by a measure amount of weight being applied to 2” square stainless steel, round head indenter.  The specified load is used, 75, 125, 175, or 250 pounds per square inch as per the standard.  Anything above that is considered to be modified.  The weight is left on the sample for 24 hours.  The weight is then removed and the sample is allowed a recovery period of 24 hours.  After which time the sample is again measured by the dial micrometer.  If the final indentation is less than or equal to of 0.005 in. (0.125 mm), the material passes.  If it is greater it fails. 
While the standard only calls for tests up to 250 pounds per square inch, Altro tests beyond that.  As with the examples above, we understand that 250 lbs is insufficient and the demands of today’s facilities call for products that can withstand greater amounts of weight. 
As such many Altro products have been tested and proven to withstand weights of over 2,000 psi.  Altro Suprema has been tested to withstand as much as 2500 psi.  Now that’s a lot of weight!

Posted: 7/2/2014 7:15:13 PM by Lea Charnley | with 0 comments
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