Duct Proving and Pull Tape

Purpose

Prove that every duct is clear, round and continuous before the cable crew arrives. A crushed, kinked or silted duct found during the cable pull costs a crew-day and a dig. Proving finds it while the excavation crew is still nearby.

When to Do It

• Trigger: conduit is placed and enclosures are set (UG-07, UG-08, UG-09).
• Prerequisites: duct ends accessible in every enclosure; the owner’s mandrel size and proving requirements.
• Previous step: UG-09 Handholes, Vaults and Pedestals.
• Next step: UG-11 Cable Placement Underground.

Roles

• Foreman: decides how to clear or repair failures, and signs off the proving results.
• Duct proving crew: runs the mandrel or projectile, installs pull tape and plugs ducts.
• Air-blowing or pressure-test technician: pressure-tests microduct per the manufacturer.

Equipment and Materials

• Duct mandrel or test rod sized to the duct: per owner spec (Per owner spec).
• Duct rodder, or air-blowing equipment with rigid proving projectiles sized to the duct: per owner spec (Per owner spec). Foam cleaning plugs clean a duct; they do not prove it.
• Footage-marked pull tape (mule tape).
• Duct plugs for every duct end.
• Microduct pressure test kit per the manufacturer.

Safety

Procedure

Hold Points

Records to Keep

• Proving result for each duct: pass, fail, location of any failure and the repair.
• Pull tape footage at each end.
• Microduct pressure test results.

Common Mistakes

• Skipping proving. The cable crew finds the crush instead, at a much higher cost.
• A mandrel too small to find ovality. A flattened duct passes a small mandrel and still stops the cable.
• Proving with a foam plug. A soft foam plug squeezes through an oval or partly crushed duct, so a pass proves nothing.
• Unplugged ducts filling with silt. Plug them the same day.
• Pull tape tails not secured. They pull back into the duct, and you have to rod it again.

Standards and References

• Owner construction standards for duct proving and mandrel sizes.
• Microduct and air-blowing equipment manufacturer instructions.
• 29 CFR 1926 Subpart AA: confined spaces in construction (1926.1201 to 1926.1213), the rule for construction work.
• 29 CFR 1910.268: telecommunications, including guarding manhole and vault openings and testing the air in manholes and unvented vaults in paragraph (o). Paragraph (a) excludes construction work.
• 29 CFR 1910.146: permit-required confined spaces in general industry, which covers telecom maintenance and service work. Paragraph (a) excludes construction.
• 29 CFR 1926 Subpart M: fall protection in construction, including covers and guardrails at holes such as open enclosures (1926.501(b)(4)).
• MUTCD Part 6: temporary traffic control at enclosures.

On the Map

• HDPE Conduit: the duct proven in this step.
• Innerduct and Microduct: smaller ducts inside a conduit (innerduct), each proven separately.

Related Tools

• Duct Fill: check that the planned cable or innerduct fits the duct before you prove and pull.