Author: Professor, Dr. Dietrich Stein - TrenchlessOnline

TECHNICAL FORUM
Choosing a
Manhole Frame-Chimney Seal
Nearly all SSES and I/I studies conducted
have drawn the same conclusion
— that manhole frame-chimney
inflow is one of the most significant
sources of leakage in the entire sewer
system. Large quantities of clear water
can be prevented from ever entering
the sewer system by sealing the framechimney
joint area of sanitary manholes.
Many different methods have
been tried in an attempt to seal this
area of the manhole and new methods
and technologies are being developed
and proposed all the time.
The frame-chimney joint area in
manholes is one that is difficult to seal
long term due to any number of the
following factors:
Thermal expansion and contraction
of the pavement, freeze-thaw cycles
and ground movement cause the
frame to move vertically, as well as laterally
with respect to the top of the
manhole structure.
Traffic loading subjects the frame to
continuous impact and jarring.
The cast-iron frame and masonry of
the manhole structure have different
thermal coefficients and surface textures,
making it difficult to provide a
watertight bond between the two
surfaces.
Based on these factors,NASSCO states
in its “Specifications Guidelines/
Wastewater Collection Systems
Maintenance and Rehabilitation, SG-12”
that:
CALENDAR
2007
23-26 DSS, Cleveland, Ohio, AWWA, (303) 347-6240; E-mail:
dtrujillo@awwa.org; Web: www.awwa.org
27-28 Pipe and Pipeline Renewal seminar, New York Metro Area (Secaucus,
N.J.), ASCE, (800) 548-2723; E-mail: conted@asce.org; Web:
www.asce.org
OCTOBER
1-5 IPLOCA Convention, Sydney, Australia, Web: www.iploca.com
13-17 WEFTEC 2007 Annual Conference & Expo, San Diego, WEF (800)
666-0206
16-19 ICUEE 2007, Louisville, Ky, (800) 867-6060; Fax: (414) 272-2672;
E-mail: info@icuee.com; Web: www.icuee.com
17-19 DCA-Europe Annual Congress, Dresden, Germany, DCA-Europe,
Web: www.dca-europe.de
NOVEMBER
7-8 Dealing with Challenges of Horizontal Directional Drilling (HDD), GEO-
DELFT, Delft, The Netherlands, E-mail: sales@delftgeoacademy.com.
DECEMBER
4-7 CONEXPO Asia 2007, Guangzhou, China, (414) 298-4167 or +86-10-
8519-1566 in China, E-mail: info@conexpoasia.com
www.trenchlessonline.com
“Manhole frame sealing includes
the sealing of the frame joint area
and the chimney above the cone
of the manhole with either a manufactured
or applied internal or
external flexible seal. The seal shall be
designed to prevent leakage of water
into the manhole through these areas
throughout a minimum 25-year design
life.The installed seal shall remain flexible,
to allow for repeated vertical movements
of the frame due to frost lift,
ground movement or other causes of
not less than 2 in. and/or repeated horizontal
movement of the frame due to
thermal movement of pavement or
other causes of not less than a half inch
throughout the design life.”
All frame-chimney seals, whether
they are manufactured or applied, fall
into four basic categories.
Rigid Seal — This type of seal includes
bolting the frame to the precast cone,
extending cementitious liner material
from the manhole wall up onto the
frame, setting the frame in a bed or mortar,
encasing the frame and entire chimney
area in a poured concrete collar or
the use of any other type of non-flexible
material or liner.
Semi Rigid or Semi Flexible — This type
of seal typically involves the use of some
type of sealing material, such as butyl
rubber mastic, between the frame, grade
adjusting rings and manhole cone joints.
Flexible Membrane — This type of seal is
created by applying a flexible coating or
Other Notable Events
By Lee Haessig
membrane to either
the inside or outside
surfaces of the frame
extending down onto
the manhole chimney
and/or cone. Materials may include epoxies,
urethanes, rubber or heat shrinkable
sleeves.
Manufactured Flexible Rubber — This
type of seal is pre-fabricated from a
high-quality rubber material and is
installed either on the inside or outside
of the frame-chimney joint area by
expanding or tightening corrosion
resistant bands with a mechanical tightening
device.
Therefore, community and/or engineers
have many things to consider
when deciding which frame-chimney
seal to use; they must decide whether
the seal can meet expected design life
and performance requirements, as well
as ease of installation and future maintenance
and replacement needs. Different
methods will have different end results
and a successful manhole rehabilitation
project will depend on how much
emphasis is put into factors such as
design life, material performance and
proven success in actual field conditions.The
bottom line is that the cheapest
method at the time of bid quite often
ends up costing more in the long run.
Lee Haessig is northeast regional manager
with Cretex Specialty Products, which is
headquartered in Waukesha, Wis.
2007
18-19 New OrleansTrenchless Road Show, New Orleans, Benjamin Media Inc.,
Ph: (330) 467-7588; Fax: (330) 468-2289; E-mail: info@benjaminmedia.com;
Web: www.rehabroadshow.com
NOVEMBER
13-14 Miami Trenchless Road Show, Miami, Benjamin Media Inc., Ph: (330)
467-7588; Fax: (330) 468-2289; E-mail: info@benjaminmedia.com;
Web: www.rehabroadshow.com
27-28 Asset Management: Bridging the Gap Between Theory & Practice Atlanta,
Benjamin Media Inc., Ph: (330) 467-7588; Fax: (330) 468-2289; E-mail:
info@benjaminmedia.com; Web: www.uimonline.com
2008
JANUARY
22-24 Digital City EXPO, Phoenix, Benjamin Media Inc., Ph: (330) 467-7588,
Fax: (330) 468-2289, E-mail: info@benjaminmedia.com, Web: www.digitalcityexpo.com.
September 2007 TRENCHLESS TECHNOLOGY 59