Internal lining testing methods against depressurisation: ISO 15741 vs NACE TM0184

Contents ISO 15741, Annex C NACE TM 0185
Coating type Liquid epoxy as internal coating Plastic coating
Objects Steel pipes and fittings Tubular good
Media Non-corrosive gas phase;  nitrogen Corrosive media ( H2S) and /or Chloride solution; hydrocarbon phase
DFT 60~ 100 μm (4.3.3) Not specified
temperature Not specified Elevated temperature required
Pressurizing system Ramping 1 bar/min Continuous monitoring
Depressurizing rate Release pressure rapidly ( no more than 5 min) Cool to 93oC,  and depressurized at a uniform rate to ATM within 15~ 30 mins
Testing panel Type I : 100 mm x 50 mmx 1 mm Type II: 100 mm pipe min. D 80 mm   Area Min. 26 cm2,  min 25% area exposed to each phase
Pre test Test after one-month coating application NA
Duration 10 test cycles up to 100 bar 1 to 4, 6 to 9 cycle; 20 + 4 h 5 and 10 cycles, 68 + 4 h Sufficient length , no less than 16 h at T and P
Pressure cycle test 10 test cycles up to 100 bar 1 to 4, 6 to 9 cycle; 20 + 4 h 5 and 10 cycles, 68 + 4 h Release  pressure rapidly ( no more than 5 min) 4 h in atm for blister Adhesion test  at 0 h; appearance check at 0, 24h and 48 h   (ANNEX C)     Not specified
Decompression blistering test At MAOP  24 h Release gas quickly  < 5min Examine appearance at 0 h, 24h and 48 h Adhesion test at 0 h   (ANNEX C)   Not specified
Examination Adhesion test  at 0 h; appearance check at 0, 24h and 48 h   (ANNEX C)   Appearance check at 0 h for exposure at both phases
Exam items Appearance adhesion BlisteringSofteningCoating thickness changeAdhesion to metal and intercoatsColor changeMetal attackUnderfilm creepIntracoat foam or porosity  
Rating Not specified appearance No changeSlight changeModerate changeSevere change Adhesion No changeSlight loss of adhesionModerate loss of adhesionSevere loss of adhesionDisbondment  

Reference

  1. ISO  15741 2016 Paints and varnishes- friction-reduction coating for the interior of on and offshore steel pipelines for non-corrosive gases
  2. NACE TM0185 2006 Evaluation of internal plastic coatings for corrosion control of tubular goods by autoclave testing
  3. Kaley Stanczyk , High Temperature, High Pressure, Depressurization Testing of Coating Systems Prior to Large Scale Installation, ktauniversity.com

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