Pull Tester Info
Pull testers, also called fastener testers, were originally designed to test the pull-out resistance strength of roofing fasteners used on commercial buildings. As the pull tester extracts the fastener, it reads and captures the maximum force required.
Analog Pull Tester with Roofing Screw Fixture
All pull testers use fixtures or lifter feet to attach the pull tester to the fastener. Roofing screws Analog Pull Tester with Lightweight Concrete Fixture and drive-in light weight concrete fasteners are the most commonly tested fasteners. Roofing screws typically offer a high pull out resistance strength and require pull testers with higher capacities ranging from 1,000 to 2,000 lbs. Drive-in lightweight concrete fasteners typically require a capacity of 300 lbs or less. Adhesion fixtures can also be used to test the adhesion strengths of bonded materials and surfaces with glues and epoxies. Specialty fixtures can enable pull testers to test adhesion samples as large as 2’ x 2’.
How To Choose A Pull Tester
Pull Testers and Fixtures Because many different capacities and types of pull testers are available, choosing the right pull tester for your application can be confusing. The two most common types are analog and digital. Both the analog and digital pull tester’s accuracies are based on percentages of their full scale capacity, or gauge size. The larger the gauge size, the larger the inaccuracy.
A typical test standard may require the gauge to be within plus or minus 5% of the reading. 5% of the reading should not to be confused with 5% of capacity; they are not the same. We have derived an easy formula to calculate the minimum force a tester can test while maintaining a reading accuracy of 5%. Simply multiply the tester’s capacity in pounds by its % accuracy, and divide by 5. For example, if we look at a 2,000 lbs capacity tester with an accuracy of plus or minus 3%, we can calculate its minimum usable reading to be: (2000 x 3)/5 = 1,200 lbs. This means a 2,000 lbs capacity tester with an accuracy of 3%, can test all the way down to 1,200 lbs, and still be within the parameters of the test standard. Below that, the accuracy diminishes.
Our analog pull testers have a rated accuracy of plus or minus 3% of their gauge size. This is fairly accurate for a portable device, but the equation above must be used to specify the correct size. A quick rule of thumb is to choose an analog pull tester with a capacity of 100-200 lbs above the force you will be testing, and not test below half its capacity. The particular test standard you will be adhering to should state the allowable accuracy. Call or email us if you have any questions. We will be happy to help you.
Digital pull testers are typically several times more accurate than the same capacity analog pull testers. Take our 2,000 pound capacity digital pull tester for example. It has an accuracy of plus or minus 0.5%. Using the equation above, it can test as low as 200 lbs, and adhere to most standards. This makes the digital tester much more versatile. Unfortunately, the high cost of the digital gauge makes them much more expensive than analog models.