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environmental failure analysis & prevention health technology development A leading engineering & scientific consulting firm dedicated to helping our clients solve their technical problems 40th Annual Engineering Insurance Conference October 10, 2013, Toronto, Canada Ali Reza, P.E., CFI
What is an Explosion? Does an explosion require a fire? What is a fire? Why is this relevant?
A pressure vessel in natural gas processing failed in service. Head separated from vessel because attachment pins failed. Extensive damage and very large fire Gas processing company had insurance coverage for mechanical failures but not for fire and explosion Mechanical failure of head pins caused by gasket failure and subsequent uneven gas pressure against head The gasket failure before the head failure caused a small gas leak. Did that leak ignite? Although the fire (if it did occur) from this small leak could not cause the blow out, could it trigger the fire exclusion for the property insurer? Does the blow-out of the head qualify as an explosion? Should the damage that occurred due to the fire after the blow-out be excluded from coverage? Coverage disputes: First case study
Case study 1: Overview of gas processing facility
Case study 1: Clamp push-out initiated by gasket failure Vessel filters dust and water droplets from gas as it is pumped out of the ground m diameter, 5 m length, 140 bars internal pressure Removable closures at each end Two gasket leaks before accident: one 3 days earlier, the other on day before accident Replacement O-rings may have been too large in cross-section. O-ring ruptured under clamp (pushed out during accident) Draw-bolt retaining pin broke and nut stripped from safety bolt Head ejected 500 m, extensive mechanical damage and fire to facility
Gasket rupturePressure failure Case study 1: Details of head-cover failure Clamping mechanism Normal forces on clamp
Subject vessel, failed head at top567 kg steel head launched at high speed Case study 1: Ejected head
Case study 1: Post incident damage
The head cover for a hydroelectric turbine separated from the main turbine body, permitting a substantial amount of water and oil to escape from the confined chamber. Significant property loss damage Property insurance covered certain listed perils, including loss caused by explosion. However, mechanical breakdowns were excluded Investigation concluded that studs securing the head cover failed because they had not been properly heat treated Hydroelectric company employees reported a loud initial blast followed by a series of resonating thunder-like explosions Lawsuit between hydroelectric company and insurer after insurer denied coverage Did an explosion occur after the mechanical breakdown? Coverage disputes: Second case study
Case study 2: Typical turbine arrangement
Institute of Engineering and Technology (UK, 2011) 2009 Hydroelectric turbine failure Sayano–Shushenskaya Power plant (Siberia) Case study 2: Damage from similar incident
Turbine approximately 142 vertical feet below water level (penstock head) Hydraulic pressure of 62 psig Investigation revealed head cover assembly had been violently lifted away from main turbine body All retaining studs had failed Significant momentum transfer from the escaping water Flooding and mechanical damage caused loss of 452 MW generating capacity for several months No gas involved in incident Case study 2: Violent incident. Large loss
Mechanical problem caused misalignment of the output shaft of large chiller, such that it rubbed against the cast iron housing. Subsequent sustained exothermic reaction between the aluminum and the decomposition products of the refrigerant. Failure of rupture disk and elbow caused extensive damage Dispute between Property insurer and Boiler and Machinery reinsurer on who should cover this loss Property insurance covered fire and explosion but excluded mechanical breakdown Boiler and Machinery insurance covered mechanical breakdown Did a fire or explosion occur in this incident? Coverage disputes: Third case study
Frictional heat from the spinning impeller (8, ,000 rpm) rubbing against the cast iron housing sufficient to melt the impeller (650°C). R-11 refrigerant decomposition occurs at 1100 F (593.3 C), releasing chlorine. Chlorine is an aggressive oxidizer similar to oxygen The molten aluminum reacted with the chlorine, creating aluminum chloride The heat released sustained the reaction, further melting layers of aluminum and decomposing additional amounts of R-11 The gases pressurized the system and ruptured an elbow and a stainless steel hose The reaction also produced copious amounts of Carbon (soot) Case study 3: A vigorous chemical reaction
Heated distorted turning vanes Damage around ruptured hose Ruptured hose Suction vanes Case study 3: Heat damage was obvious
The terms fire or explosion was not clarified or defined in any of the disputed policies Some but not all policies clarified fire (but not explosion) coverage after mechanical breakdown: Loss or damage caused by or resulting from any of the following causes of loss: (1) Fire (including fire resulting from an Equipment Breakdown Loss); or water or other means used to extinguish a fire. (2) Explosion of gas or unconsumed fuel within the furnace of any boiler or fired vessel or within the passages from that furnace to the atmosphere. ( 3) Any explosion (except for explosion of steam boilers, steam piping, steam engines or steam turbines. Which brings us back to our questions: What is an explosion? What is a fire? Each matter had policy language challenges
From a colloquial perspective (Webster, McGraw Hill) explosions share distinct characteristics Suddenness Noise Release of internal energy Bursting or fragmentation Expansion of gases? Combustion and fire science require elements of fire Fast chemical reaction that convert potential (chemical or nuclear) energy to thermal energy Rapid pressure rise Explosion investigators highlight the effects but not the causes Rupturing, fragmentation, bursting What is an explosion? -1
Safety standards concerned with both effect (bursting, rupture) and cause (deflagration, combustion, overpressure) Required element is the rapid expansion of gases NFPA : The sudden conversion of potential energy (chemical or mechanical) into kinetic energy with the production or release of gases under pressure, or the release of gas under pressure. These high pressure gases then do mechanical work such as moving, changing, or shattering nearby materials NFPA /NFPA : The bursting or rupturing of an enclosure or a container due to the development of internal pressure from a deflagration FM Global Data Sheet FMDS0700 (September, 2006): An explosion is a rapid transformation of potential physical or chemical energy into mechanical energy and involves the violent expansion of gases What is an explosion? -2
Martin, Reza, and Anderson, Journal of Loss Prevention in the Process Industries, vol. 13, , (2000): Explosions, in the broadest sense must do significant pV work on the environment. Significant pV work can only occur if a gas is involved. In chemical explosions, exothermic chemical reactions provide the energy for the pV work, while in mechanical explosions, the expansion of a compressed gas provides this energy.
Six broad definitions now accepted. All involve gas expansion Physical (Overpressure, BLEVE) Chemical (Reaction, Thermal, Deflagration, Detonation) Four well characterized phenomena serve as benchmarks Detonation of a high explosive (e.g. TNT or ANFO) Deflagration or rapid, subsonic combustion (e.g. fuel air mixture) Rupture of a gas pressurized vessel (e.g. steam boiler) All three produce gas expansion, rapid release of energy. Significant pV work Hydrostatic forced displacement (e.g. fatigue failure of a blind flange) Incompressible fluid. No pV work What is an explosion? -3
From a colloquial perspective (Webster), Fire is the phenomenon of combustion manifested in light, flame and heat In scientific literature, combustion is defined as Any chemical reaction accompanied by liberation of heat and emission of light (Demidov, 1965) A self-sustained, high-temperature oxidation reaction (Babrauskas, 2003) In Industry, combustion is defined as An exothermic chemical reaction usually (emphasis added) involving oxidation of a fuel by atmospheric oxygen. Glowing combustion involves direct oxidation of a solid or liquid fuel, such as charcoal or magnesium. Flaming combustion involves a gas phase or volatile matter driven off by heat (FM Global, 2006) What is a fire?
The fire tetrahedron requires a supply of fuel, a supply of an oxidizer, an ignition source, and a sustained chain reaction What does the NFPA state?
There can be an implicit perception that fires only involve air or oxygen For most fire protection purposes, fire is: the combination of fuel and oxygen in blazing combustion Fire begins when an ignition source connects with a combustible material in the presence of oxygen. Rapid oxidation, usually with the evolution of heat and light; heat fuel, oxygen and interaction of the three Coverage disputes can occur if insurer contends that only fires involving atmospheric oxygen are covered What is a fire? -2
1.Gas storage vessel Coverage for mechanical failures/breakdowns but not explosions Does the blow-out of the head after the mechanical failure qualify as an explosion? Should the subsequent fire damage be excluded from coverage? 2.Hydroelectric turbine Coverage for explosion but not mechanical failures/breakdowns Significant damage but did an explosion occur? 3.Exothermic reaction in compressor Coverage for explosions and fires but not mechanical breakdowns/failures Significant heat but no oxygen. Did a fire occur? Did an explosion occur? Case studies: A recap
Mechanical failure caused the head to be violently ejected Was this an explosion? Sudden release of high-pressure gas, but there was no increase in pressure inside the vessel and no combustion or chemical reaction prior to the incident However, there was significant pV work due to the depressurization of the vessel Qualifies as an explosion based on definitions we just discussed: Rupture of a gas pressurized vessel Fire damage due to ignition of natural gas after explosion Case settled by insurance company No explicit language in policy stating that fire or explosion exclusion applied after a mechanical failure Case study 1: Should this be a covered loss?
Mechanical failure of bolts holding head to turbine body No combustion or chemical reaction. No expansion of gases. No rapid pressure rise Water is essentially incompressible. No pV work Does not qualify as explosion: Hydrostatic forced displacement Bulk of observed mechanical damage due to the momentum of the water jet imparted by the 144-foot head Analogous to a high pressure fire house knocking down a screen door Case settled after expert reports because policy language did not define explosion Case study 2: Should this be a covered loss?
As defined by the NFPA, the fire tetrahedron requires Fuel, oxidizer, ignition source and a sustained chain reaction Investigation confirmed all four components were present The oxidizer was not oxygen, rather chlorine from the decomposition products of the R-11 Some insurance companies call this event a Freon Fire The heat build-up from the fire and the decomposition of the refrigerant was accompanied by an increase in pressure. This is a requirement of the equation of state pV=nRT The overpressure ultimately caused the rupture of an explosion relief disc, failed a connected stainless vent hose and a cast iron elbow Combustion products vented into room causing electrical damage Split verdict during arbitration because definition of fire and explosion not included in policy Case study 3: Should this be a covered loss?
We have always understood that the everyday definition of explosion and fire should apply An explosion is a large scale, rapid and spectacular expansion, outbreak, or other upheaval The definition for fire is one that's commonly accepted, one that is understood by the insurance underwriting and buying public, and one that requires that fuel [be] ignited and combined with oxygen to produce heat, light and flame Precise definitions of fires and explosions and the sequence of mechanical failures vis-à-vis a fire or explosion should be included in policy language Some common refrains during coverage disputes