Material Failures in Fire Protection Systems March 4, 2014 University of Central Florida (UCF), Orlando, FL Jeff Pfaendtner Materials/Metallurgical Engineer Crane Engineering Inc., Plymouth, MN Crane Engineering 2014
PROFESSIONAL DISCIPLINES Mechanical Engineering Metallurgical & Materials Eng. Chemical Engineering Electrical Engineering Forensic Architecture Structural Engineering Fire Protection Engineering Civil Engineering Geotechnical Engineering Forensic Engineering FORENSIC ENGINEERING & CONSULTING SERVICES Fire and Explosion Investigation Propane & Natural Gas Investigation Materials & Process Engineering Industrial Accident Investigation Slip and Fall Investigations Standards and Code Consulting Building Science Investigations Automotive System and Component Analysis Accident Investigation and Crash Reconstruction Crane Engineering 2014 2
Failure Modes Relate to: Design Manufacture Installation Service Environment Water chemistry Introduction A flaw becomes a defect when it prevents the part/system from functioning as designed. Nominal Operating Temp & Temp extremes Service & Maintenance Age Geographic location etc. Crane Engineering 2014 3
Case Studies 1. CPVC Spider Lines (M) 2. CPVC Environmental Stress Cracking (I&E) 3. CPVC Environmental Stress Cracking (I&E) 4. CPVC Other Incompatible Materials (I&E) 5. Sprinkler head: Crack in Frangible Bulb (M) 6. Sprinkler head: Casting defect (M) 7. Sprinkler head: Galvanic/Crevice Corrosion (D&M) 8. Steel pipe: Microbiologically Induced Corrosion (I&E) 9. Steel pipe: Pitting Corrosion (I&E) 10. Brass Fittings: Stress Corrosion Cracking (D, M, E) 11. Steel pipe: Light wall Pipe (D) 12. Freeze failures (I & E) 13. Rube Goldberg type failures (E) Key: D Design M Manufacture I Installation E Environment Crane Engineering 2014 4
Case 1 - Spider Lines in PVC Pipes Straight fracture observed in CPVC pipe after less than one year of service. Crane Engineering 2014 5
Case 1 - Spider Lines in PVC Pipes Outer Surface of Pipe Scanning Electron Microscope (SEM) images of fracture Fracture Surface Spider lines are virtual cracks in pipe From manufacture process Crane Engineering 2014 6
Failure after 10 years in service. Case 2 CPVC & Glycol System was a glycerin filled system, but testing revealed the presence of glycol. Environmental Stress Cracking (ESC) from residual glycol Crane Engineering 2014 7
Case 3 CPVC & Alkane Oils Wet system in condo building Heated garage is Allied XL steel Steel to CPVC transition (living space) Water leaks in CPVC after ~3 years Crane Engineering 2014 8
Case 3 CPVC & Alkane Oils External view of CPVC pipe Throughthickness cracks Crane Engineering 2014 9
Case 3 CPVC & Alkane Oils Internal view of CPVC pipe Multiple cracks developing on ID surface Crane Engineering 2014 10
Case 3 CPVC & Alkane Oils Internal view of CPVC pipe Cracks developing around cement drip Crane Engineering 2014 11
Case 3 CPVC & Alkane Oils Crane Engineering 2014 12
Case 3 CPVC & Alkane Oils Environmental Stress Cracking (ESC) from residual thread cutting oil Crane Engineering 2014 13
Summary: Environmental Stress Cracking Environmental Stress Cracking (ESC) is a time dependent (slow) cracking mechanism ESC has three main requirements: Susceptible material (e.g., CPVC pipe) Stress (either residual in the material, or applied stress) Incompatible chemical species (certain oils, plasticizers, glycols, etc.) Failures are usually manifested as slow leaks, but sometimes as catastrophic breaks. Crane Engineering 2014 14
Case 4 Incompatible Materials CPVC potable hot water line to irrigate trash chute in high rise condo. Pipe failure occurred after several years in service at location of contact with grommet. Crane Engineering 2014 15
Case 4 Incompatible Materials Plasticizer diffuse from one plastic into another Pipe weakens & ruptures Crane Engineering 2014 16
Case 5 Crack in Frangible Bulb Sprinkler head deployed unexpectedly causing water damage. Purple staining observed on frame arms & body. Crane Engineering 2014 17
Case 5 Crack in Frangible Bulb Crack develops & propagates Fluid leaks from bulb over time Bulb breaks; water flows Crane Engineering 2014 18
Case 6 Casting Defect in Sprinkler Head 200 F Attic head Unexpected deployment of attic sprinkler head Deformed load screw Crane Engineering 2014 19
Case 6 Casting Defect in Sprinkler Head SEM & X-ray imaging shows evidence of cracks in one frame arm Crane Engineering 2014 20
Case 6 Casting Defect in Sprinkler Head Difference in compliance between frame arms creates mechanical imbalance Frangible bulb walks off set screw w/ thermal cycling Crane Engineering 2014 21
Case 7 Galvanic/Crevice Corrosion Sprinkler head leaked after 3 years in service. Water damage to condo. Crane Engineering 2014 22
Case 7 Galvanic/Crevice Corrosion Pinhole leak in Belleville spring (under seal) Corrosion over months/years Crane Engineering 2014 23
Case 7 Galvanic/Crevice Corrosion Area C O F Na Al Si S Cl Ca Ti Mn Fe Ni Cu Zn A 3.65 2.06 0.38 0.43 93.47 B 9.68 23.53 0.62 0.78 0.48 1.50 0.32 0.30 0.78 8.01 48.98 2.17 2.83 C 7.75 42.56 0.18 1.07 0.44 0.16 0.18 0.38 42.52 3.27 1.49 D 9.55 29.86 1.46 0.21 0.47 11.00 0.48 20.54 0.96 2.16 18.71 1.72 2.88 E 7.19 50.96 0.54 0.88 1.37 0.58 11.70 0.24 8.68 14.11 0.75 3.00 Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) Crane Engineering 2014 24
Case 8 Microbiologically Induced Corrosion (MIC) Dry system developed pinhole leaks 5 years after installation. Tubercles observed on pipe ID. Water supply not corrosive. High levels of aerobic bacteria, low nutrient bacteria, and acid producing bacteria found Crane Engineering 2014 25
Case 9 Pitting Corrosion A wet system developed pinhole leaks after 25 years. Water testing showed high levels of dissolved oxygen, high hardness, and high levels of dissolved solids. Bacterial cultures showed low or undetectable levels of bacteria Crane Engineering 2014 26
Case 10 Stress Corrosion Cracking (SCC) Catastrophic failure of brass hose valve $1M+ water damage to large commercial building Crane Engineering 2014 27
Case 10 Stress Corrosion Cracking (SCC) Catastrophic failure of brass hose valve Multiple cracks Raw material costs: Copper: $3.32/lb. Zinc: $0.85/lb. C37700 Forging Brass Copper: 58.0 62.0 wt.% Lead: 1.5 2.5 wt.% Iron: 0.3wt% max Other impurities: 0.5% max Zinc: Balance Crane Engineering 2014 28
Case 10 Stress Corrosion Cracking (SCC) Brass alloy defective Zinc too high; Iron impurity too high Crane Engineering 2014 29
Case 11 Light wall Pipe Leaking NPT joints in factory producing printed circuit boards Crane Engineering 2014 30
Case 11 Light wall Pipe 0.5mm = 0.02 inch Crane Engineering 2014 31
Torque (ft-lb) 350 300 250 200 2" Pipe Case 11 Light wall Pipe R 2 = 0.8983 Schedule 40 2in. BLT Linear (Schedule 40) Linear (2in. BLT) R 2 = 0.6746 150 100 50 0 1 2 3 4 5 # wrench turns Crane Engineering 2014 32
Case 12 Freeze Damage Component failure due to volumetric expansion of freezing water (~9 vol%) Crane Engineering 2014 33
Case 12 Freeze Damage Freeze failures often yield multiple cracks Crane Engineering 2014 34
Case 12 Freeze Damage Freeze failures often yield multiple cracks Crane Engineering 2014 35
Case 12 Freeze Damage Freeze-up can induce large scale deformation Crane Engineering 2014 36
Case 12 Freeze Damage Freeze-up can induce large scale deformation Crane Engineering 2014 37
Case 13 Special Environmental Effects Crane Engineering 2014 38
Summary & Final Thoughts All materials have their own vulnerabilities, and therefore their own application issues. No component is immune to failure. A variety of failure modes are operable in fire protection systems. Failures can occur in all stages of life of the system. Failure prevention involves good system design, material choice, good installation & maintenance taking local environments into account Crane Engineering 2014 39