Understanding UL651 PVC Conduit: Standards, Performance, and Testing

UL Listed PVC Conduit

The UL651 standard outlines the requirements for Schedule 40 and 80 rigid PVC conduit and fittings, ensuring their safety and performance in various applications. In this article, we will explore the scope of application, dimensions, performance testing, and markings for UL651 PVC conduit.

Scope of Application

UL651 applies to Schedule 40 and 80 rigid PVC conduit and fittings, including elbows, couplings, adapters, expansion, expansion-deflection, deflection joints, and rigid pipe fittings for construction. These conduits can be used for interior and exterior finishing or outdoor use, as long as they are protected from sunlight and inclement weather. They can also be used directly in concrete and withstand temperatures ranging from 50°C (122°F) to 75°C (167°F), with some products suitable for 90°C (194°F) wiring needs.

Dimensions

UL651 specifies the dimensions for Schedule 40 and 80 rigid PVC conduit, including outer, inner, and wall thickness. The tolerance range for outer diameter (OD) is ±0.004 to ±0.011 inch, while inner diameter (ID) and wall thickness have specified minimum values to ensure performance. Type A and EB rigid PVC conduit also have size requirements, with additional requirements added as these sizes are determined to be acceptable.

Performance and Testing

UL651 outlines 19 performance tests to evaluate the safety and performance of PVC conduit. Some key tests include:

a. Tensile Strength: Six samples, including three aged samples, are tested for tensile strength. The minimum requirement is 5,000 psi (34.5 MN/m2) for Schedule 40 and 80 conduit or 4000 lbf/in2 (27.6 MN/m2 or 2.76 kN/cm2 or 2812 gf/mm2) for Type A and EB rigid PVC conduit.

b. Extrusion: This test simulates extruding PVC pipes using anhydrous acetone to observe and test for incomplete fusion.

c. Water Absorption: After soaking in distilled water for 24 hours, the water absorption rate should not exceed 0.50% of the conduit's weight.

d. Resistance to Impact: Ten samples are tested for impact resistance, with at least seven samples not having cracks or fragments above 1/32 inch (0.8mm) on the surface.

e. Resistance to Crushing: The inner diameter of a qualified sample after pressure should not be less than 70% of the standard sample.

f. Flame: The sample is subjected to a flame retardant test, ensuring it does not burn for more than 5s after the fire source is cut off and that drippings cannot ignite cotton at the bottom.

g. Permanence of Printing: The printed characters on the conduit should be clearly visible after testing, including the manufacturer's name, production date, and other relevant information.

Markings

PVC conduit should include the following markings:

With the words 'Rigid PVC conduit'
Trade size
The name of the manufacturer or brand owner
Production date
The information above needs to be printed at least once every 10ft
Printing should be permanent


Accessory products, such as elbows and couplings, should also have clear and permanent markings, including the manufacturer's name, product model, and any specific usage requirements.

Conclusion

Understanding the UL651 standard is crucial for ensuring the safety and performance of Schedule 40 and 80 rigid PVC conduit and fittings. By adhering to the size specifications, performance testing requirements, and proper markings, the electrical conduit manufacturers can produce high-quality PVC conduit that meets the needs of various applications.