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This is the material collected from the personnel website of a foreign slipform company whose slipform

system is similar to ours.

Slipform Chimney Construction

This Slipform assembly for chimney is an extremely complicated form! A lot of controlled functions are

specially designed to adjust this form's diameter, taper and the poured shell thickness, as this fancy form

rides the jack rod supports embedded in the pre-placed concrete voids in the shell of the chimney!

Below is a summary of some key construction features:

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

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

the working platforms.

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.

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.

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. The thickness of the concrete wall will be controlled by adjustments that are secured to

the inside form sheets and the yoke frames.

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.

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.

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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

center point, flue, access, or other openings, as well as foundation slab elevation data.

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.

Some foreign Slipform experts:

Interform (The parent company from whom we bought our slipform engineering)

BYGGIN-Uddeman

Gleitschnellbau GmbH:

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