2010年10月5日星期二

Fire Protection and Corrosion Protection System for Structural Steel

Structural steel shall be protected against fire and corrosion.

Fire Protection System

Fire protection system shall include surface preparation, application of primer, fixing details, etc.

There are mainly two type of fire protection system, the sprayed fire protection system and intumescent coating system.

(i) Sprayed Fire Protection System

  • For interior structural steelwork.

  • For dry environment, the steel surface shall be blast cleaned (e.g. to Swedish Standard SIS055900 Sa2) and shall be thoroughly cleared of oil, grease, dirt or other foreign substrances which may impair the propoer adhesion of the fire protection to the substrate.

  • For high humidity location, the steel surface shall be:
    (1) blast cleaned (e.g. to Swedish Standard SIS055900 Sa 2.5);
    (2) provided with corrosion protection system using two pack epoxy based zinc rich primer (say, to BS4652) with a dry film thickness of 80μm.
    (3) apply a bond coat to the primed surface
    (4) apply sprayed mineral fire coating to the surface

(ii) Intumescent Coating System


  • For both interior and exterior condition.

  • For Interior condition, all interior structural steelwork (including fasteners and welded connections) shall be blast cleaned to Swedish Standard SIS 055900 Sa 2 ½ and with:
    (1) Primer: 2-pack epoxy based zinc rich primer with dry film thickness = 80μm
    (2) Basement: protective fire coating with thickness depends on Hp/A and fire rating.
    (3) Finishing Coat: Compatible finishing coat with dry file thickness = 80μm

  • For Exterior condition, all structural steelwork (including fasteners and welded connections) shall hot-dip galvanized to BSEN ISO 1461 with:
    (1) Pretreatment: Degrease and rinse, apply British Rail T-Wash.
    (2) Primer: Thickness and type to be recommended by the fire protection coating manufacturer.
    (3) Basement: protective fire coating with thickness depends on Hp/A and fire rating.
    (4) Finishing Coat: Compatible finishing coat with dry file thickness = 50μm


Corrosion Protection System

(i) For Interior Environment (without FRP Requirement), either
  • Hot-dip galvanized to BS EN ISO 1461 and receive the protective coating below:

  • (1) Pre-treatment: Degrease and rinse, apply British Rail T-Wash.
    (2) Finishing coat: 2-packed recoatable polyurethane finishing paint applied in 2 coats recommended as suitable by paint manufacturer for direct application to etched surface. Etched surface shall be overcoated within 24 hours or the time limit by the manufacturer. Dry film thickness = 80μm

    OR

  • Blast cleaned to Sa 2 ½ and shall receive the protective coating as follows:

  • (1) Primer: 2-pack epoxy based zinc rich primer to BS 4652, dry film thickness = 80μm
    (2) Undercoat: 2-pack epoxy based micaceous iron oxide paint, dry film thickness = 100μm
    (3) Finishing coat: 2-pack recoatable polyurethane coat, applied in two coats, dry film thickness = 100μm
    (4) Minimum overall dry film thickness = 280μm



(ii) For External Environment (without FRP Requirement),
  • Hot-dip galvanized to BS EN ISO 1461 and receive the protective coating below:

  • (1) Pre-treatment: Degrease and rinse, apply British Rail T-Wash.
    (2) Primer: 2-pack epoxy based zinc phosphate primer to BS4652 with dry film thickness = 40μm
    (3) Undercoat: 2-pack epoxy based micaceous iron oxide paint, dry film thickness = 80μm
    (4) Finishing coat: 2-packed recoatable polyurethane coat, applied in two coat with dry film thickness = 100μm
    (5) Minimum overall dry film thickness = 220μm

    2010年4月19日星期一

    Piezometer Vs Standpipe

    Piezometer and standpipe are both used to measure the ground water level.

    A piezometer is a small-diameter observation well used to measure the hydraulic head of groundwater. Typical configuration of piezometer consists of filter tip surrounded by sand filter zone at the bottom. Above the tilter tip is bentonite seal and bentonite-cement grout.



    As piezometer is used to measure the water pressure at the tip, long response time is required.

    Contrast to piezometer, standpipe is used to measure the water level directly and hence shorter response time is expected. The configuration of standpipe is similar to that of piezometer, except that the bentonite seal/ grout are replaced by sand/ gravel. Typical standpipe arrangement is as follow:

    2010年4月18日星期日

    Standard Penetration Test (SPT)

    SPT is a simple tool to check for the strength/ stiffness of soil.

    Number of blows to penentrate 75mm underground (total 6 segments with total length of 400mm) is measured.

    The 1st set and 2nd set of readings (i.e. from 0mm to 150mm) will not be used. The total number of blows for the sampler to penetrate each 75mm is the SPT value for the soil.

    The test in the 1st segment and 2nd segment will be stopped if the number of blows reaches 50. The counting of blows for other segments (for 3rd segment to 6th segment) will also be stopped if number of blows reaches 100.

    Attached is a video of SPT testing procedure: