Transcript Slide 1
Corrosion Under Fire Protection - Ian Bradley, International Paint Saudi Arabia Limited (IPSAL) Presentation to NACE Middle East & African Branch Contents • Types of passive fireproofing (PFP) • Commonly found corrosion problems • Corrosion testing for PFP systems – UL exterior listing – Norsok – Comparison • Guidance for specifying PFP systems in corrosive environments • Summary • 20 – 25 minutes • Questions & Answers session Types of passive fire protection • Dense Concrete • Lightweight Cementitious • Solvent based and solvent free Epoxy intumescents • Subliming materials • Mineral Wool (and other insulations) ISO 12944 – C5 • • • • • • • ISO 12944 developed to assist engineers Global standard Designates environments according corrosivity Based upon corrosion of steel < 120ºC C5 - M superseded by ISO 20340 Addresses corrosion aspect but not fire performance A typical plant may encompass several environments – Jetty – Areas around cooling water towers etc Some examples of corrosion beneath passive fire protection Examples of corrosion behind PFP Corrosion beneath concrete fireproofing – C5 I environment (Southern Europe) Vessel support structure Corrosion cycle Loss of passivation effect • Acidic industrial atmosphere • Decrease in pH • Leads to loss of passivity • Active corrosion beneath cementitious materials Examples of corrosion behind PFP Corrosion beneath concrete fireproofing – C5I environment (Southern Europe) Note significant thinning of section flange Examples of corrosion behind PFP Pitting corrosion behind lightweight cementitious fireproofing C5I Pitting corrosion caused by ingress of calcium chloride during maintenance on vessel LPG drier in refinery Examples of corrosion behind PFP General corrosion behind delaminated fireproofing material C5 - M Structural steel offshore Examples of corrosion behind PFP Delamination of topcoat and subsequent deteoriation of passive fire protection material C5-M Structural steel offshore Examples of corrosion behind PFP Severe corrosion of structural I sections beneath fireproofing Chemical Plant USA (C5-I) Examples of corrosion behind PFP Gas pipe-work support structure Structural steel onshore C4 / C5-I Examples of corrosion behind PFP Process vessel and structural steel offshore Structural steel offshore C5 -M Examples of corrosion behind PFP LPG Sphere Leg Structural steel onshore C5 - M Some contributing factors • No coating or inadequate coating beneath • Testing of fire monitors containing water or worse seawater • Lack of flashing plates / sealing caps • No stand off • But no bond to surface either • Non destructive NDT difficult / impossible When specifying fire protection materials What do engineers concentrate on? • • • • • Fire performance Fire duration Critical core temperature Type of fire (hydrocarbon, cellulosic, jet fire) Cost (Fire protection is a major cost item on new plant) • Still too little emphasis on durability and weatherability For fire protection to be effective it must be present and intact at the time of the fire How do we define intact? Many ways you could define “intact” • • • • • Unaltered from as built condition Free from significant amounts of water Bonded to the substrate Whole (i.e. free from cracks, corrosion paths etc) But we need something subjective!! – i.e. test standard • High impact if wrong decision is made Early attempts to measure weathering DiBt • • • • • German standard for fireproofing Requires non-accelerated weathering samples Fire tested at regular periods Cellulosic fire protection (buildings) Long time periods involved GASAFE • • • • LPG fire protection program 1990’s Tried to address weathering aspect Limited success More Recent Attempts UL1709 • • • • • UL 1709 addresses fire performance “Exterior listing” addresses weathering Accelerated weathering Will then list complete system Follow up service – compliance with as tested material NORSOK • • • • • Numerous revisions (covered later) Designed for offshore (C5-M) Accelerated weathering Generic type based Two categories UL 1709 Exterior Listing Test Standard Comments Aging Circulating oven Humidity - 97-100% humidity, 180 days Industrial atmosphere - 1% SO2 / 1% CO2 in chamber + water. 95F for 30 days Salt spray ASTM B117 Wet Freeze Dry Cycling - Fire testing UL 1709 70ºC for 170 days 90 days salt fog testing 0.05 mm/ s water for 72 hours,-40ºC for 24 hours,60ºC for 24 hours repeated for 12 cycles Must meet original acceptance criteria Norsok M501 Revision 5 Test Standard Ageing resistance ISO 20340 See below Salt Spray ASTM B117 Artificial seawater, 35ºC, 72 hours Low temperature Comments -20ºC 24 hours 168 hours UVA/Condensation Σ 4200 hrs ASTM G53 Adhesion ISO 4624 Scribe Creep - UVA exposure followed by 100% condensation Adhesion < 50% reduction from, > original > 3MPa < 3mm Norsok M501 Revision 5 - continued Test Standard Comments Blistering, rusting cracking, ISO 4628 Water absorption - Shall be reported Fire testing - Fire testing to 400ºC critical core temperature for 60 minutes within 10% or original unexposed test Rating 0 for all Norsok M-501 Revision 5 versus Revision 4 • Salt spray and freeze/dry is now a combined cycle • Revision 4 – Salt spray/drying (ISO 7253) + UV-A (G-53) 4200 hours – Water / freezing / drying / humidity ISO 2812-2 4200 hours • Evaluation of scribe creep has changed • Tested without top-coats Corrosion Issues with major generic types Dense concrete • Prone to damage • No bond to substrate (undercutting) • Can retain significant amounts of water (spalling) • Passivation lost with time in marine / industrial environments • Needs weather cap / sealing Lightweight cementitious • Prone to damage • No bond to substrate (undercutting) • Application must be correct • Similar to dense concrete • Needs Weather cap / sealing Corrosion Issues with major generic types Mineral Fibre / Cladding • Prone to damage • Very absorbent once cladding damaged • Salts in mineral wool may contribute • Needs weather cap / sealing Epoxy • Offer many performance advantages, however, • Generally fire performance / weatherability is a balance • Number of materials where balance is incorrect • More sensitive to application • Careful (and detailed) specification is necessary Some general trends • Cement based and mineral fibre systems no longer used in C5-M • Cannot exclude problems in C5-I • More awareness of extent of C5-M environment – Jetties – Coastal Refineries + other locations • Awareness of these corrosion issues • Not translated into action in many parts of industry • Corrosivity of project location remains un-established (Quantitatively) Guidance for specifying PFP performance • • • Be aware of the problem Know your environment Question existing practises – Materials – Construction details • • • Consider key areas and potential for upgrade Consider suitable weatherability criteria – UL / Norsok In conjunction with fire performance These are safety critical decisions Demonstrated performance by case history • Applied in 1976 • Inspected and analysed • BAM - 1992 • No chemical changes in material detected • Intumescent chemicals unaffected • C5-M Refinery (The Netherlands) Conclusions • Corrosion behind some types of passive fire protection is a real risk • Durability is as important as initial fire performance • Test procedures exist which can distinguish materials performance • Recognised and workable standards • Available to use Questions [email protected]