Work Procedure:

1. Objective

Objective of this procedure is to provide a guideline for sequence of operations pertaining to Slip form Works for Silo Construction, so as to ensure that the works are carried out in a systematic manner and to ensure that the works conform to the Owner’s specification and drawings.

2. Scope

This procedure is applicable for Construction of Clinker Silo at Lafarge Sonadih Cement Plant.

3. Reference

This Procedure is based on the requirements of the Owner’s Technical Specification for Civil/Structural works for Silo package works and Simplex Experience in Construction of Silo by Slipform.

4. Resource Deployment

The Contractor shall deploy any or all of the following resources as dictated by the volume and nature of work.

a) Tools & tackles

 Spade.  Shovel  Basket  Wheel Barrow  Steel Wire Rope  Spanner

b) Plant & Machinery

 Batching Plant.  Transit Mixer.  Concrete Pump with pipeline.  Builder Hoist Winch.  High Frequency Vibrator with Needle   High lift curing pump.  Boom Placer.

In addition to the above, the Contractor shall deploy a specialist agency for slip forming having experience for carrying out such work.

5. Slipform Technique:

We propose that we shall erect the slipform shuttering right from F.F.L. of R.C.C. Shell of Outer Wall. The shuttering plates and other various components of Interform type slipform equipment shall be erected as per line and level required for Clinker Silo. The jack rod for 6 / 3 T Hydraulic Jacks shall rest on steel shoe placed at the top of already cast shell. Some of the salient features of the various components to be used for the slipform technique as shown in SKETCH NO.: 012 / DD / LAFARGE S / SILO / SDS / 002 Rev – 0 are explained below.

5.1 Yokes:

A set of yoke leg placed at required alignment and connected by means of yoke beams at the top wherein climbing jack mounted, provides key members for fixing the Form Panel for inner and outer faces. Requirements of total number of yoke sets depend on the sizes of the structure and the capacity of hydraulic jack. Spacing of the jack would be around 1.25 m for this Clinker Silo.

5.2 Slipform Hydraulic Jacks:

We shall be using 75 nos. 6 T capacities “Interform” type hydraulic jacks which climbs on bright steel rod of 32 mm dia and operates with two sets of ball grip. Jacks can only move upward direction when hydraulic pressure is applied. The upper movement of the slipform will be as per set criteria provided by the manufacturers of the Jacks or minimum of 100 mm / 150 mm per hour.

5.3 Consoles:

Consoles shall be provided on to the yokes meant for support of the working platform both inside and outside. This working platform shall be used for concreting, reinforcement binding and operation of the hydraulic pumps. Consoles will be fabricated members in combination with structural angles and tubular pipes / reinforcement rod with structural channel, angles & tubular pipes.

5.4 Hanging Scaffolding:

These members are suspended from consoles both inside and outside for the purpose of inspection and finishing work of the exposed concrete after slipping. These hanging scaffolds will be of rigid frame structural members.

5.5 Waler:

These member spans within the two yokes and provide support for the Form Panel against Lateral Force due to green concrete.

6. Support For Reinforcement Steel:

Arrangements made from the top of yoke beams with reinforcement guide, supports reinforcement to maintain its aligned position.

7. Guard Railings:

For the safety arrangement guard railings with post placed at the working platform both inside and outside and reinforcement type rails also provided for the hanging scaffolds.

8. High Pressure Hydraulic Pumps Pipelines & Fittings:

Circuit oil lines of high-pressure rubber hoses inter-connect all vertical jacks and plug in unit with one or more centrally positioned electrically powered high-pressure pump. Connections to the jacks and pump are carried out through valves and male and female fittings ‘as required’.

9. Illumination:

Illumination is essentially required as the work normally carried out 24 hours a day non- stop. Accordingly both on working platform, at the hanging scaffolds, stairways and working areas are illuminated properly.

10. Operation:

For smooth operation of slipform, jack readings and plumb readings are to be monitored once in every two hours.

11. Access Tower:

Access tower is to be installed for concrete lifting and climbing of personnel through temporary stairs, made of ISMC & ISA..

12. Special Arrangements:

1. Minimum 10% extra jacks are required as standby. Adequate jack rods should also be available at site.
2. 75 nos jack of 6 T capacity each to be put on the job i.e. with a spacing of around 1.25 m c/c.
3. Slow and uniform concrete pouring is to be maintained. Empty height of shutters
should be maintained 150-200mm from top/ deck level. Lifting of the shutters should be limited to 10mm –15mm per lift i.e. in 10minutes interval, (60-90 mm per hour) to avoid bulging of concrete surfaces, rate of slippages will also depend on the concrete quality (i.e. on setting time)
4. To maintain verticality of shell wall, plumb bobs (minimum) are to be hanged at equal intervals at outer side of shell wall from deck through the gap between shutter and masons’ platform (hanging platform), however the plumb points should be avoided in front of openings. Verticality shall be checked at least 2 times in every shift jointly. On the entire jack rod horizontal level is to be marked at 300mm height from top of the jack by means of water level tube and Jack rod rings are to be put at this level on the entire jack rod. During lifting when the entire jack touches the ring then horizontality of the system will be ensured. At this time dia & plumb checking will be done and readings are to be noted in a register. If any discrepancy is found that is to be brought to the knowledge of the Owner’s Site In-charge immediately for necessary remedial measures. Same procedure will continue till successful completion of slip form concreting of shell wall.
5. All axis to be marked on the deck slab by means of triangular shaped GI sheet /Ply.
6. One standby hydraulic pump of same capacity in OK condition must the there on the deck slab.