Slipform Chimney Construction!!

This "Slipform" assembly,  pictured at the start of construction,  is an extremely
complicated form!  A lot of controlled functions are especially designed to adjust
this form's diameter, taper and the poured shell thickness,  as this fancy form
rides the jackrod supports embedded in the pre-placed concrete voids in the shell
of the chimney!   Below is a summary of some key construction features:

1. The form rises non-stop (continuously) at a rate of approx 1 foot/hour.

2. Each Jack is mounted to a yoke, to which is secured the inside and outside
    form sheets and the working platforms.

3. Each Jackrod is removed upon completion of the shell. This leaves
    typically 32 nominally 32" diameter holes internal to the wall, extending
    for the fill height of the concrete shaft (Most chimneys built this way are
    between 1000 and 1250 feet tall!).  To protect from water entrainment
    after the chimney is completed, the jack rod voids are capped top and
    bottom with grout.

3. Radiused walers extend between the yoke frames on both the outside
    and the inside surfaces of the concrete wall, and additional form sheets
    (which lap the sheets fixed to the yokes) will be attached to these walers.

4. The diameter of the slipform assembly is controlled by a radial adjustment
     fitted to each yoke frame, and the taper of the column or slope of the wall
     is set by an adjustment at the top of each yoke frame. 

     See the cross-section!

5.  The thickness of the concrete wall will be controlled by adjustments that
     are secured to the inside form sheets and the yoke frames.

6.  The construction of the shaft, that is the slipping of the form, is usually
     carried out continuously on a 24-hour day, 5-day week basis, with a
     temporary shutdown each weekend.

7.  Cast-in inserts are not installed due to great difficulty experienced in the
     industry when a slipform is used.  The practice is to anchor all interior
     and exterior securements (For balconies, fixtures, and accessory items)
     using Bulldog (or equal) self-drilling expansion shields.

8.  It is the usual practice of the slipform construction team to require the
     customer to provide centerline markings for starting the chimney, such
     as lines to demarcate the orientation of chimney centerpoint, flue, access,
     or other openings, as well as foundation slab elevation data.

9.  Hoisting the work personnel to the top platform of the slipform is based on the
     utilization of a "man-cage" rigged with cable grabbers and two guide cables, so
     that in the event of a hoist line cable breakage, the grabbers would actuate and
     suspend the cage from the guide cables. This man-cage is typically operated by
     a safety hoist, equipped with limit switches and operated under power in both
     directions.  The customer supplies the hoist, if there is no acceptance of this
     lifting system.

I have no detail drawings or bill-of-materials of the Custodis Construction
slipform system.  These are proprietary (protected by patents), and were
owned and stored at a facility near the Chicago office of Custodis Construction Co.
Div of Hamon-Cottrell.

Slipform Designers-Manufacturers:

Scanada Slipform
Some of the most talked about slipform and heavy-lift projects in the world were accomplished by
the people now working for SCANADA.  Every CANDU reactor in the world, every coal preparation
plant in Alberta and British Columbia since 1981, as well as the hundreds of grain elevators, stacks,
towers, bridge columns, and high-rise buildings constructed with SCANADA's expertise are more
examples of why SCANADA has earned the respect of the construction industry around the world.

In serving the world over the course of over 25 years (formerly known as Heede) as designers, manufacturers,
developers and implementers of almost every imaginable application of slipform and heavy-lift equipment
for almost every imaginable kind of construction project, the SCANADA group has become a repository
of immense experience.

Gleitschnellbau GmbH (No Web itself):
Gleitschnellbau is a recognized leader in slipform construction and the use of heavy lifting equipment. 
This partnership has enabled Custodis to maintain efficiency and cost-effectiveness throughout the
most challenging construction jobs and has stimulated the development of new construction methods.
The shared slipform expertise has resulted in the development of hydraulic jacking systems to safely
and efficiently lift chimney liners weighing 500,000 to 1,000,000 pounds or more. In fact, most of the
tall chimneys (700 feet) in North America were built by the partnership of Gleitschnellbau and 
Hamon Custodis.
  User Partnerships:   Custodis    Ting Tai    Strabag

GBG Gleitbau Salzburg

Balanced Engineering and Construction

Structural Systems, Limited

Slipform Systems Austria

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