Underground Construction - April 2022 - 31

EDITION 73 | APR 2022 | NASSCO.ORG
Commonly used pipe cleaning methods for slip lining
and CIPP are Drag Scraping, Rack and Bore, and
Water Jet cleaning. It should be noted that care must
be used with Rack and Bore cleaning, as it can reduce
the diameter and shape of brass service connections
and may result is service damage in highly deteriorated
host pipes. The service diameter reduction may or may
not impact flow through the service connection. Since
the rehabilitation liner is not bonded to the host pipe,
an annular space will exist between the liner and host
pipe. To ensure no pressurized water is transferred
through this annular space, special considerations may
be required at liner termination points and at service
connections.
In contrast to Cement Mortar, SIPP linings can be
Class I or Class II. SIPP prevents internal metallic pipe
corrosion by creating an impermeable barrier that
prevents water from being in contact with the pipe wall.
Common SIPP pipe cleaning methods are Rack and
Bore and Airborne Abrasives.
Below are additional factors that can be
considered to select an appropriate cleaning
method for your project:
1) Time to complete the cleaning and the quality of
pipe cleaning. Airborne abrasives have shown that it
produces a higher quality level of pipe cleaning and
preparation is quicker than other cleaning methods.
2) Water consumption. Rack and bore and water jet
cleaning can use a significant amount of water for
required removal and disposal from the cleaning pit.
3) Targeted cleaning at services, joints, and specific
pipe locations. Airborne abrasives can provide
targeted cleaning at specialized locations which is
difficult using other methods.
4) The condition of the pipe and joints after cleaning
is complete. Some methods will leave the pipe and
services dry while other methods will leave the pipe
surface wet.
Abrasive airborne pipe cleaning
For AWWA Class I and Class II liner systems, the
rehabilitation liner is not considered to have sufficient
ring stiffness to be self-supporting. Thus, the liner must
rely on adhesion to the pipe wall. Cement mortar and
Spray-in-Place-Pipe (SIPP) liners are common AWWA
Class I and Class II systems. The host pipe must be
clean and prepared for the liner to adhere. Thus, the
level of pipe cleaning and pipe preparation is much
higher for AWWA Class I and Class II.
Cement Mortar is deemed to be a Class I and is
a permeable liner system that stops metal pipe
internal pipe wall corrosion by the passivation of
metal corrosion in the presence of water. Common
pipe cleaning methods for Cement Mortar are Drag
Scraping and Rack and Bore.
5) Ease to complete the post cleaning CCTV
inspection, a pipe condition rating, and to determine
if services are leaking prior to the liner installation.
6) Contractor and equipment availability and cost.
The cleaning of pressure pipes is much more complex
than the cleaning of gravity pipelines and requires
specialized contractors. The type of pipe cleaning also
depends on the type of rehabilitation liner systems
being installed. It is recommended that you consult
the liner's manufacturer to determine appropriate pipe
cleaning and pipe preparation requirements for the
product to be installed.
-
1
AWWA Committee Report " Structural Classifications of Pressure
Pipe Linings - Suggested Protocol for Product Classification "
2019.
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Underground Construction - April 2022

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