CommScope ConQuest Conduit Construction - Manual (Page 33)

Underground Installation Methods 4.15
Existing Conduit
Existing Conduit Installation
ConQuest products are also designed to be placed into existing conduit systems. An example is the placement of one or
more conduits inside a larger conduit. Multiple conduits should be placed at the same time.
ALWAYS test and ventilate manholes prior to entering into them and follow OSHA confined space
requirements.
An important step that should be taken prior to this type of work is “proofing” the existing conduit. This process will
ensure that all obstructions are cleared and that conduit continuity and alignment is good. It is recommended that a rigid
mandrel roughly 90% of the inner diameter of the conduit be used to perform the proof.
Proofing conduit is typically performed by pushing a fiberglass fish with a rigid mandrel attached through the conduit.
Any problem areas felt by the person pushing the mandrel can be marked on the fish so that the distance to the problem
is recorded, and can be located and repaired with greater ease. If the mandrel makes its way through the conduit
without any difficulties, the conduit has proofed out and no repairs should be necessary.
Specialized equipment is required for existing duct installations. Sheaves, bending shoes, rolling blocks (45 and 90
degrees) and straight pulleys are used for protection of the conduit. It is important that they all meet the proper radius for
the conduit size. The use of a pulling lubrication will greatly reduce the surface tension and stress on the conduit when
pulling conduit into an existing conduit. The use of ball bearing swivels is also required for attaching the winch line to the
conduit harness system.
On long routes and routes with multiple turns it is important to consider mid-
assist locations. There are different ways of providing mid-assist for conduit
pulls. Typically the use of a winch such as a come along or a vehicle winch
is required. The introduction of mid-assist wheels has made conduit pulling
an easier task, requiring less manpower and communication than traditional
winching. Mid-assist wheels also provide greater production capabilities.
The stress of pulling conduit through existing conduit will vary with the length of
the route, the number of turns, the condition of the conduit, and the amount
of lubrication used. The effects of the stress will cause the conduit to elongate
(or stretch) in proportion to the amount of stress, but typically less than 2% of
the total length placed. For this reason, it is important to pull past the conduit
slightly. At least one hour needs to be allowed for the conduit to “relax” before
cutting and trimming.
TECH TIP
Mark the winch line
50 feet before the
attachment to the
conduit, this will
provide advance
notice of the arrival
of the conduit and
prevent injury or
damage to the
equipment.