Mandrel testing for sanitary and sewer pipes also known as deflection testing. This type of test is used to determine that the ovality of the sewer pipe meets its specification. In other words, we're just checking to ensure the pipe is still round and not displaced under its current load.
The test starts by pulling the mandrel from one end of the pipe to the other. This insures and verifies that there is an adequate clearance. It's about 5% smaller than the pipe being tested and should glad right though. If it doesn't and gets stuck the pipe has failed the mandrel test.
The light weight metal or aluminum deflection mandrel are utilized in a nine arm configuration to ensure testing accuracy. The open design allows water and other debris to easily pass though.
Proving rings are also used to verify that each deflection gauge is within its tolerance.
What Is a Mandrel Inspection
Cities and states use a mandrel to inspect the inside of the underground pipes and sewer conduits. Normally, after new construction or when maintenance is being preformed. They consist of metal rods with fingers and are designed to stop if and when it encounters and impediment.
This is commonly know as pigging, mandrel inspections test flexible pipes for deflection or out of roundness. This test will show whether or not the pipe has bent under stress and pressure of the soil above.
What Are Proving Rings
Proving rings are used to verify deflection gauge sizes. Nothing to special they simply slide over the gauge and gives you a quick and easy size verification.
New Tech for deflection testing
Many companies have switched to a newer tech approach. Using laser profiling and video pipe inspection instead of metal mandrel tests. Laser profiling mandrels can identify all the problems at once. When the standard metal mandrel, each issue or problem must be fixed before the inspection test can continue.
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Types of Deflection Gauges and Mandrels
We get questions all the time about deflection gauges and mandrel we use. So it this section we would like to break down a few of the mandrels we use and talk about some of the specs.
1. Steel Mandrel Gauges
These steel mandrel gauges are designed to all gravel, water and other debris to pass through easily. This is ideal, other gauges have the tendency to get hung on obstructions and rocks causing a deflection.
This in return causes it to fail the mandrel test even though the pipe is within deflection tolerances. Creating an extra expense for the contractor.
2. Adjustable Fin Deflection Gauges
Using a 9 arm design like the steel mandrel this one can adjust for pipe sizes 4 inches to 15 inches. Saving the need for 4 or 5 standard steel gauges.
These are designed to be field verified without the use of a proving rings.
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