OH&S practices as a cause of corrosion under insulation?

Transcription

1 OH&S practices as a cause of corrosion under insulation? Graham Carlisle Principal Corrosion and Coating Engineer

2 TOPICS 1. THERMAL PROPERTIES OF MATERIALS 2. WHY INSULATE 3. TYPES OF INSULATION 8. THERMAL INSULATION COATINGS 9. TESTING 10. CASE HISTORY MEG VSESSELS 11. CONCLUSION 4. OH&S SAFE TO TOUCH specs 5. ISSUES WITH INSULATION 7. MAINTAINING COMPLIANCE 6. MITIGATION OF CUI

3 Heat transfer Conduction Radiation Convection www. coolcosmos.ipac.caltech.edu

4 Thermal conductance

5 Thermal conductance Q heat flow = k ΔT difference in temperature L material thickness k = thermal conductivity, where k = k l + k e Q is measured in W/m 2 and k in W/m-K Normal lattice positions for atoms Positions displaced because of vibrations Therefore, in a time rate of steady state heat flow through a unit area of a material Conductance = k L W.D. Callister, Chapt. 19- Materials Science and Engineering

6 Thermal inertia Silica fibre insulation Internal temperature = C (white-hot) Photograph courtesy of Lockheed Missiles & Space Company, Inc.

7 Why insulate? Thermal energy conservation To provide: Operational stability Energy efficiency Equipment reliability Use materials with low thermal conductivities Limit transfer of thermal energy Insulate hot process from heat loss Isolate cold process from heat gain

8 Personal protection Time in secs 1. No Burn 2. Burn Threshold 3. Burn ISO B o s c h u n d s i e m e n s h a u s g e r ä t e g r u p p e

9 Types of insulation-inorganic Calcium Silicate Aerogel Mineral wool Foam glass Vermiculite Perlite

10 Types of insulation-organic Polyisocyanurate Rigid phenolic foam Polyethylene Various Elastomers Polyurethane

11 OH&S Specifications for Safe to Touch Surfaces operating at temperatures in excess of 60ºC (140ºF) shall be fitted with personnel protection, consisting of SS 316 metal mesh guard. Operating above C Any area that is accessible 2.1m vertically above grade or from platforms 0.9m horizontally from periphery of platforms, walkways or ladders.

12 Alternative personal protection Bound wire HDG mesh Expanded diamond SS mesh Physical hard barriers Perforated SS mesh (S) Perforated SS mesh (L)

13 Corrosion associated with insulation-general & Localised Chloride (Sulphide) induced stress corrosion cracking General & localised corrosion from moisture ingress due to damaged cladding and failed joint M. Chauviere, MoniCorr Inc.

14 Corrosion associated with insulation-galvanic Corrosion Galvanic corrosion from dissimilar metals due to no isolation between cathode and anode M. Chauviere, MoniCorr Inc.

15 Corrosion associated with insulation-crevice Corrosion

16 Mitigation of CUI Insulation specification Closed cell foams/aerogels (hydrophobic) Low chloride Low moisture Dry construction Dry storage during shipment and storage Protection during construction Design detail to prevent water ingress Top hats to shed water Arrange cladding to shed water Drain points at the base of long vertical sections Waterproof seals on pipe hangers and supports Avoid joints in steam tracing lines

17 Mitigation of CUI Protect the substrate Organic coatings (carbon and stainless steels) Aluminium foil (austenitic stainless steel) Inhibited insulation (silicates for the SCC of austenitic S.S.) Prompt maintenance/repair of damaged cladding Warm air drying (recent development - limited application) Review the need for insulation: Lower temperatures later in life Use guards rather than insulation for personnel protection But, beware the possibility of introducing internal dew-point corrosion risks

18 Mitigation of CUI- Inspection With insulation in place: Neutron back-scatter Other novel NDE techniques Thermal imaging Detects insulation breakdown (implies water present) Radiography Detects corrosion thinning of pipe/vessel wall Removable windows in cladding/insulation Remove insulation (common practice)

19 Maintaining compliance-pp Removing insulation or SS mesh 1. OH&S to consider thermal inertia properties of various materials in specifications 2. Use thermal insulation coatings to protect and modify surface

20 Thermal insulation coatings Binders Acrylic Pigments Hollow glass microspheres Water Based Epoxy Hybrid Acrylic/Epoxy Silica aerogels Polyurethane

21 Testing of thermal insulation coatings Acrylic Coating Insulation Technology Approximate Thermal Conductivity (mw/m-k) Average Application Thickness- one coat (mm) Thermal Resistance per Pass (x10 3 m 2 K/W) A Aerogel B C D Ceramic microspheres Ceramic microspheres Ceramic microspheres E None P. Pescatore et. al., PCI Journal, 03/07/2013

22 Test Procedure Average Values Obtained Comparative Bench Mark Values Corrosion resistance: Cyclic wet/dry test (Prohesion)- G85-11 and D No visible corrosion or coating defects after 500 hours of exposure. Rating of: 9 for plate 1 9 for plate 2 9 for plate 3 No visible corrosion or coating defects after 500 hours of exposure. 9 for epoxies References The Effect of Four Commercially Available Steel Decontamination Processes on the Performance of External Coatings NACE corrosion paper, San Antonia Conference, Performance of Dry Film-Moisture vapour transmission rate- D g/m 2 /24hr Low < 15g (m 2 d) -1 EN ISO :2001 Flexibility of cured film- D522-93a(2008) 500 mm Pass (cold) 50 mm Pass (hot) No published values Flexibility and Toughness, John Fletcher and Joseph Walker in Paint and Coating Testing Manual-15th. Edition of the Gardner-Sward Handbook

23 Test Procedure Average Values Obtained Comparative Bench Mark Values Adhesion of cured 2.53 MPa Un-exposed film- D e1 4.6 MPa Cyclic wet/dry 350 psi (2.4 MPa) 2.47 MPa thermal cycling 4.4 MPa EPX4 to various substrates 8.2 MPa NanoPrime to Various substrates (all cohesive failures) 5 MPa Resistance to thermal cycling- D Thermal resistivity of cured film- C335/C335M-10e1 No checking No blistering No cracking W/m.K (thermal conductivity) No checking No blistering No cracking ~0.060 W/m.K at 70% PVC (thermal conductivity) References Nansulate EPX4 data sheet Norsok M-501 The Effect of Four Commercially Available Steel Decontamination Processes on the Performance of External Coatings NACE corrosion paper, San Antonia Conference, Quantitative analysis of silica aerogel-based thermal insulation coatings, Søren Kiil in Progress in Organic Coatings, 2014

24 Validation of safe-to-touch H. Mitschke & G. More, Mascoat, NACE PP paper

25 Validation of safe-to-touch H. Mitschke & G. More, Mascoat, NACE PP paper

26 Validation of safe-to-touch

27 Case study: thermal insulation coatings OVERVIEW The client had a number of process vessels and piping that operated above the safe to touch temperature, in accessible locations. Previous strategies using traditional insulation/cladding and metallic shields had led to either CUI or bi-metallic corrosion. SOLUTION IAS employed the use of a patented formulation of a thermal insulation coating Conducted a thermal survey to establish hot-spots and high risk areas Specified the appropriate thickness in order to achieve the required temperature reduction Applied the Nansulate coating system and ensured hot surfaces complied with HSE policy Structure Application Type Operating Environment Surface Preparation Glycol regeneration package Texture sprayer 3 vessels Diameter 1.1m Operating Temperature Safe to Touch Temperature Corrosion Type Proven Technology Power tool cleaning C 68 C Corrosion under insulation (CUI) Nansulate Heatshield EPX4 NanoPrime Removes the need for traditional insulation Live system application & 30% quicker to apply Small footprint for equipment & reduced logistics

28 Case study: Thermal insulation coatings Test points Glycol Flash Vessel 38-VD-002 (3 coats) Glycol Surge Vessel 38-VL-005 (3 coats) Cold Glycol Heat Exchanger 38-HF-003 (6 coats) Vessel shell Day 1 Day 30 Vessel shell Day 1 Day 30 Vessel shell Day 1 Day 30 Aft 66 0 C 46 0 C 59 0 C 68 0 C 51 0 C 55 0 C 84 0 C 62 0 C 75 0 C Centre 57 0 C 51 0 C 60 0 C 69 0 C 48 0 C 65 0 C 88 0 C 63 0 C 72 0 C Forward 63 0 C 38 0 C 54 0 C 71 0 C 45 0 C 73 0 C 84 0 C 56 0 C 51 0 C Operating temp ~70 0 C ~70 0 C ~90 0 C ~74 0 C ~74 0 C ~94 0 C ~90 0 C ~90 0 C ~110 0 C Day 1 Vessel 38 HF 003 (aft end mid level) Thermocouple reading 62 0 C Day 30 Vessel 38 HF 003 (aft end mid level) Magnetic thermometer reading 80 0 C Infrared reading C

29 Conclusion Traditional insulation materials for high/low temperature applications, critical processes requiring thermal energy conservation Liquid TIC can be used for uninsulated systems requiring improved efficiencies and operating at -10 to C Liquid TIC for insulated systems are ideally for use where insulation was predominantly installed for personal protection TIC s reduce incidence of CUI and as well as protecting the asset Overall cost of installation is lower for TIC compared to traditional insulation and the ease of insulation of irregular geometries is significantly better TIC s OH&S complaint???

30 Thank you! Questions? Graham Carlisle Principal Corrosion and Coating Engineer