Fire proofing

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I.            SCOPE

     This procedure covers the general requirements of materials and the method of application for external protection of structural steel members, vessels/columns skirts, saddles and supports against fire by shotcreting, in-situ concrete or vermiculite cementitious coatings.

II.           MATERIAL

All materials to be used shall conform to the requirements of respective BIS Codes. Sample and test results for all materials shall be submitted to the Engineer in-charge and got approved by him in writing before execution work. Acceptance criteria of commonly used materials is given below:

1)           Cement

The cement used shall conform to either of the following BIS Codes:

33 Grade ordinary Portland cement conforming to IS:269.
Portland slag cement conforming to IS:455.
Portland pozzaoland cement (fly ash based) conforming to IS:1489 ( Part-I).
43 Grade ordinary Portland cement conforming to IS:8112.

Fire proofing for all structures in and around Sulpur handling units shall necessary be using sulphate resisting Portland cement conforming to IS:12330.

2)           Aggregate

a) Sand:

Sand shall comply with the requirements of IS:383 and graded evenly from fine to coarse as per Zone II and zone III. Sand of zone IV shall not be used.

b) Coarse Aggregate:

Coarse aggregate shall comply with the requirements of IS:383. Maximum size of aggregate shell be 10mm. the grading of aggregate shall be as per IS:383.


c) Water:

Water used shall conform to IS:9103.

d) Admixture

Admixture shall to IS:9103. This shall be mixed with concrete strictly as per manufacturer’s recommendations and shall also meet the requirements of IS:456.

              e) Vermiculite Cementitious Coating:

Branded product with base as Vermiculite and mixed with ordinary Portland cement shall have a maximum loose density of 400Kg/m3: while in moulded conditions, density shall not exceed 800 Kg/m3. sulphate content in the branded product shall not exceed 1% when the sulphate content is expressed as sulphar trioxide.

f) Expanded Metal Steel Sheet:

Expanded metal sheets shall conform to IS:412 and shall be of an approved type. Size of the mesh shall be 10mm x40mm with standard of 2.5 mm 


              g) Reinforcement:

Welded wire to fabric to be used as reinforcement, shall conform to IS :1566 and shall be of approved type. Mesh size shall be 50mmx50mm and thickness of wire shall be 3mm.

              h) Attachments:

a)     Tie Wire:
Tie wire shall be of mild steel, not thinner than 16 SWG.

b)     Nuts:
Nuts shall be made of mild steel and shall conform to IS:1367 and IS:2585.

c)      Cover Plates:
Cover Plates shall conform to IS:2062 Grade-A.

d)     Bitumen mastic flashing:
     Bitumen mastic flashing shall conform to IS:3037.


III.          SURFACE PREPARATION:

1)           Surface Cleaning:

All steel surfaces to be in contact with fire proofing coating material, shall be cleaned of all oil, grease, loose rust, scales and dust by using wire brush and washing using detergents.

2)           Welding of nuts and application of primer:

Nuts of M16 bolts shall be welded with all the steel members to be fire proofed. Maximum spacing of nuts shall be 400mm center to center in both directions. Nuts shall not be welded to the vessel supports/skirts ( to b welded by fabricator ): unless directed by Engineer in-charge. Primer paint shall be applied to the MS nuts and affected surfaces of the members due to welding after proper cleaning. Primer paint shall be compatible with the primer already applied to the steel members.

3)           Fixing of expanded metal steel sheet.

Expanded metal steel sheet shall only be used for built up sections, consisting of two members spaced apart. This shall be kept in position true to line and face, and shall be attached firmly to structural steel member by tack welding or with the help of clips and 16 SWG tying wire at 30mm center to center. Minimum lap of 75mm shall be provided wherever required, however laps shall be avoided at bends. Strands of the expanded metal steel sheet shall slope inwards & downwards.

4)           Placement of reinforcement:

Reinforcement shall be placed in the middle of coated material thickness. It shall be bent confirming with outlines of finished encasement rigidly secured in place by tie wire with all the nuts. Minimum lap at ends and sides shall be 100mm and lapped wire fabric shall be tied firmly.

Cover Plate:

Cover Plates shall be welded to the top flange of the beams if top edges of fire proofing are not protected with bitumen mastic flashing.



IV.          APPLICATION:

1)     Application of fireproofing material coating shall be carried out by skilled and experienced operators.
2)     Before start of application, pipes and equipments in the vicinity shall be covered with polythene / tarpaulin to protect them against damage. Open end of pipes shall be covered with wooden plugs or with wooden plugs or with other suitable shielding material.
3)     Steel sections up to and including 300mm depth, shall be coated by solid fill while sections more than 300m shall be coated in the shape of profile of sections as shown in sketches. For vessel skirts, columns and saddles of horizontal vessels, The coating material shall be applied in horizontal bands working upwards from the bottom of the skirt or column/ saddle base plate. All outside edges of the fire proofing shall be champhered by 20mm except for shortcreting, corners shall be rounded.
4)     Thickness of fire coating shall be established by providing ground wires both in vertical and horizontal directions. Ground wires shall be tight and true to line, and placed in such a manner that they can be further tightened if required.
5)     The fire proofing material, after application, shall be cured by keeping it in moist condition for a period of at least 14 days of else the surface shall be coated with a membrane of approved curing compound. Brand name of manufacturer, test results and method of applications shall be submitted to and got approved from the Engineer  in-charge prior to procurement of curing compound.

V.    APPROACH, WORKING PLATFORM, SCAFFOLDING & FORM WORK

Form work wherever required shall be of plywood sheeting. It shall be adequately supported and braced to protect against deformation on account of vibration during the application.

VI.        SPECIFIC REQUIREMENTS

1)     Fireproofing by shortcreting:
      
            Thickness of concrete coating over the steel shall be 50mm.

2)     Fire Proofing by in-situ concrete:

a.     Concrete for fireproofing shall be of M20 grade ( nominal mix)

b.     Thickness of concrete coating over the steel shall be minimum 50mm.

c.      Concrete shall be poured into well made form properly oiled and made to correct dimensions. Concrete shall be vibrated as necessary to ensure smooth surface, free from voids and irregularities. Any defects, honeycomb etc shall be made good.

3)     Vermiculite cementitious Coatings:

            i) Design requirement:

a)     Vermiculite cementitious coating shall restrict the temperature of a vessel / structure, below the maximum permissible temperature of 4270C for vessel support & skirts and 5500C for structural steel member respectively, for a minimum time period of 2 hours. The material shall not fail till end of the specified period.
b)     The coating shall be on non corrosive to the steel members & shall not be affected by environmental conditions, whether natural or from local leaks, spillage or pollution. It shall also be asbestos free.
c)      The coating shall be able to withstand both thermal shocks and impingement of water from fire hose and monitors.
d)     The coating material shall be durable and easily repairable.
e)      Application procedure of the coating shall be easy, non hazardous and also shall not interfere with the working of the adjoining areas.

ii) Application:

a)     Vermiculite cementitious coatings shall be mixed with water on a clean platform or in a clean mixing box or in a suitable mixer as per manufacturer specifications. Water cement ratio shall be adjusted so that vermiculite cementitious coating adheres properly to steel surface and does not sag or slide upon application.
b)     Primer compatible with the Vermiculite cement coating as recommended by the manufacturer shall be applied over the steel surface after cleaning the shop primer if required as per manufacturer specifications.
c)      Mixed vermiculite cementitious coatings shall generally be applied, over the steel surface, with the help of spray gun expect for small areas and inaccessible location, where application with convectional hand tools shall be permitted. Mixed vermiculite shall be used with in the pot life specified by the manufacturer. Under no circumstance rebound material shell be used.
d)     The full specified thickness shall be developed in three successive coats.

-Rendering Coat             thickness between 8 to 12mm.

-Floating Coat                thickness between 18 to 22mm to give
                                     a total thickness of 30mm upto the
                                     floating coat.

-Finishing coat               Not less than 8mm thick.

Each successive layer shall only be applied after the preceding layer has developed its initial set and is also properly scratched with steel brush to developed proper bond. If the application is interrupted and does not satisfy criteria, the coating shall be cut back to the steel surface/proceeding layer with a trowel at an inclined angle. Exposed surface of his coating shall be thoroughly wetted before resuming the work.

e)      Application of mixed vermiculite shall not be carried out if the air temperature or the temperature of the surface to be fire proofed is 40C or less. Provision shall be made for adequate ventilation during and after application, until the coating is dry.


VII.       FINSIHING AND JOINT SEALING:

a)     Fire proof coating shall be finished with 2 coats of micro-porous exterior top coat, compatible to cement surfaces, of approved make & colour conforming to IS specifications.
b)     All exposed joints between fire proofing material coating & steel shall be sealed with min. 10mm thick bitumen mastic flashing, when not otherwise shielded.



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