Chilled Water Tank Exterior Insulation and Cladding Method of Statement

The scope of work involves supply and installation of exterior insulation and cladding of chilled water storage tank.

Tools and Equipment:

General insulation hand-tools including insulation cutters, band-tighteners, brushes, etc.

General cladding hand-tools including Sheet metal shears, Rivet guns, caulking guns.

Hand Drilling machines

Fabrication tables

Lock-forming machine

Shearing machine

Rolling machine

PUF injection machine

Health and Safety:

The works to be performed shall be undertaken in compliance with site Safety Procedures in place.

All personnel undertaking the works will be issued and wear all applicable PPE including but not limited to full-sleeved coveralls, safety helmets and safety shoes.

Personnel working at heights shall compulsorily use safety belts or harnesses.

All personnel undertaking the works shall undergo client Safety Induction prior to commencement of any works. All the personnel shall also be briefed on the nature of job and associated hazards prior to site deployment.

Prerequisites:

The work-site shall be inspected and cleared by the Execution Engineer. He shall be accompanied by the insulation supervisor / foreman, who shall check the following:

Tank surfaces shall be fairly clean and dry.

All surface preparation by Contractor is complete.

Tank welding joints have been tested and approved for insulation.

All insulation supports have been installed as per client drawings.

Sufficient accessibility and clearance is available for both the insulation and the space necessary for workmen to install insulation.

Necessary space is available on site for storage of materials and for on  site fabrication works. Such areas are to be dry and kept free from hot work.

All materials shall be also visually inspected for any evidence of physical or weather related damage. Such damaged goods shall be rejected and replaced by material suppliers immediately.

Insulation and Cladding Procedure:

Option 1: Conventional Insulation & Cladding

A. Shell Area

a. Install preformed Poly urethane insulation slabs (35kg/m3 density, 125mm thickness, with Aluminium foil facing, vertical ship-lapped edges) on the bare tank surface. All joints shall be tightly fitted and sealed with 3” wide Aluminium foil tape. FOSTER 30-45 joint sealants shall be used to seal all butt joints.

b. Further secure the insulation with 0.5x19mm SS bands and wing-seals, installed at 450mm spacing or a minimum of two bands per segment. All vertical joints on further courses of installed insulation shall be staggered by a 200mm minimum.

c. Insulate the reinforcement ring provided at the junction of the shell and roof, with 19mm thick rubber foam insulation, installed with the help of a compatible adhesive.

d. Below this provide a 25mm wide circumferential contraction joint. This contraction joint shall consist of tightly packed Fiberglass wool insulation (24kg/m3 density, 50mm thickness), further covered with 100mm wide butyl rubber sheet, secured with two SS bands.

e. Install 40mmx1.2mm SS bands at approx. 2m pitch circumferentially on the insulated shell to support the cladding.

f. Install plain Aluminium cladding sheets (0.8mm thick, stucco -embossed) using SS rivets (4.8x13mm) at 150mm centers onto the installed SS bands. A minimum overlap of 75mm shall be provided on all circumferential joints. Minimum overlap of one corrugation shall be provided for all vertical sheet overlap.

g. Collar plates / flashing shall be fabricated from plane sheets. Cut-outs shall be  provided for all openings / protrusions. Cladding seams shall face downwards and  be sealed with FOSTER 95-44 for a weather-proof finish.

B. Roof Area

a. Install preformed Poly urethane insulation spacer blocks (100kg/m3 density, 150x100x100mm,) on the roof surface at 2m pitch, using FOSTER 81-33 adhesive.

b. Install preformed PIR insulation slabs (35kg/m3 density, 125mm thickness, with Aluminium foil facing) on the balance roof surface. All joints shall be tightly fitted and sealed with 3” wide Aluminium foil tape. FOSTER 81-33 shall be used to  bond the insulation onto the roof surface, while FOSTER 30-45 joint sealants shall  be used to seal all butt joints.

c. Install 30mmx2mm GI flat bars on the insulation spacers located on the roof to  provide radial supports for cladding.

d. Install plain Aluminium cladding sheets (0.8mm thick) using SS rivets (4.8x13mm) at 150mm centers onto the flat bars. A minimum overlap of 50mm shall be provided on all joints.

e. Collar plates / flashing shall be fabricated from plane sheets. Cut-outs shall be  provided for all openings / protrusions. Cladding seams shall face downwards and  be sealed with FOSTER 95-44 for a weather-proof finish.

f. Flashing at the edge of the roof shall be lock-formed for additional strength, and then riveted on to the shell cladding. A minimum overlap of 150mm shall be  provided to prevent moisture ingress.

C. Shell Bottom

a. Install plain Aluminium sheet (0.8mm thick) flashing using SS rivets (4.8x13mm) at 150mm centers onto the base of the tank. A minimum overlap of 150mm shall  be provided on this flashing to prevent moisture ingress.

b. Drill holes of suitable diameter at maximum 600mm intervals along the circumference of this flashing. Now pour a freshly prepared mixture of chemicals to achieve min. 125mm thick Poly urethane insulation.

c. All drilled holes shall be sealed with Aluminium rivets or compatible plugs. Cladding seams shall face downwards and be sealed with FOSTER 95-44 for a weather-proof finish.

Option 2: Cladding and in-situ injected insulation

a. Install preformed Poly urethane insulation spacer blocks (100kg/m3 density, 150x100x100mm) on the shell and roof surface at 1m pitch, using FOSTER 81-33 adhesive.

b. Install floating ring fabricated from 6mm GI round bar over the center of the roof and install GI flat bars (30mm x 3mm) over the insulated spacers and fasten to the floating ring on the roof to provide radial supports for cladding.

c. Install plain Aluminium cladding sheets (0.8mm thick) using SS rivets (4.8x13mm) at 150mm centers onto the Poly urethane spacers and using SS304  bands with wing seals. A minimum overlap of 50mm shall be provided on all  joints.

d. All cut-outs, opening etc. shall be provided for with close fitting collar plates. Cladding seams shall face downwards and be sealed with FOSTER 95-44 for a weather-proof finish. Butyl sealant strip shall be used on the circumferential sheet  joints on roof.

e. Drill holes of suitable diameter at maximum 600mm intervals along the circumference of this flashing. Now inject a freshly prepared mixture of chemicals to achieve min. 125mm thick Poly urethane insulation.

f. All drilled holes shall be sealed with Aluminium rivets or compatible plugs. Cladding seams shall face downwards and be sealed with FOSTER 95-44 for a weather-proof finish.

Insulation Quality Control:

During the course of work, the Execution Engineer shall conduct random weekly inspections to check the following points:

 Conditions of the surface to which the insulation is applied.

 Quality of insulation application and their joints.

 Quality of securement of cladding supports.

 Quality of cladding joints and their sealing.

 Final appearance of finished cladding works.