Thermal expansion fire exposure

In cases where vessels are provided with PR valves for protection against overpressure from fire exposure or an operating failure contingency, additional thermal expansion protection is not required. 

Each input source is protected by a PSV set no higher than the maximum allowable working pressure of the vessel, and a PSV is installed on the vessel for fire exposure and thermal expansion. 

Exposure to Fire If a vessel is exposed to a heat radiation from a fire, internal pressure may rise primarily due to the generation of vapor from the internal liquid or from thermal expansion of the contained commodity. 

Thermal Expansion Contained liquids may be subject to heat input that causes them to expand resulting in a pressure increase. Typical heat sources are direct sunlight and fire exposures. 

For the noncooled specimen NC, during the pre-fire mechanical loading, a linear-elastic load-axial displacement response was observed until the maximum load of 145 kN was achieved. The lateral deflection at this load at midheight remained small 1.4 mm toward the fire side. When fire exposure started (attime t = 0), lateral deflection toward the fire side started to increase owing to the thermal expansion of the inner fire-exposed face sheet and reached a maximum of 8.1 mm after 20 min, see Figure 7.8. From this point on, lateral deflections started to decrease owing to... 

The differences in toughness between the as-fired YAG and N-phase samples are consistent with the predicted differences in the thermal expansion mismatch strains at the whisker/matrix interfaces in the composites. The subsequent loss of toughness after heat treatment may be due to the formation of. strong interfacial bonds after the long-term thermal exposure. Additional analysis is currently underway to identify the specific mechanisms which control the composite properties. 

Hot process lines need to be able to handle thermal expansion even with lines expected to operate at normal temperatures it is desirable to provide sufficient flexibility for expansion and contraction caused by changes in atmospheric temperature, possible fire exposure, steam out, and pump out. Flexible couplings may fail rapidly under fire exposure and should be avoided wherever possible in systems handling hydrocarbons. The use of offsets in welded pipe is much safer. 

In thermally decomposed cement pastes that contain distinct amoimts of residual calcium oxide, this constituent rehydrates readily to calcium hydroxide, if in contact with water or exposed to humid air. This reaction is associated with expansion, which may cause further damage to concrete that has been exposed to fire, even in situations where the concrete stracture has withstood the exposure to lire without disintegration or visible signs of destmction. Because of this, concrete stmctures made with blended cements, in which the amount of free lime present after exposure to fire is significantly reduced, are generally less damaged after being exposed to lire than those made with plain Portland cement. 

Concrete may deteriorate if adequate precautions are not exercised to protect it from adverse effects that could result from exposure to natural or artificial conditions. Several physical, chemical, and electrochemical processes are known to induce cracking of concrete. Concrete can have durability problems as a consequence of its exposure to seawater, sulfates, chlorides, freeze-thaw action, carbon dioxide, etc., or when it is attacked by artificially induced processes such as exposure to acids and salts in chemical plants or to fire. In recent years, a new type of durability problem was encountered that involved use of steam cured concrete products. The distress was caused by the formation of delayed ettringite. If the raw materials in concrete are not carefully controlled, there may be an eventual failure of concrete elements, eg., the presence of excess alkali in concrete that promotes alkali-aggregate expansion reaction, harmful impurities in the aggregates, or the presence of excess amounts of dead-burnt MgO. Thermal techniques in combination with others have been employed with success to examine the raw materials as well as the failed concrete. The knowledge gained from such work has been applied to produce more durable concrete. 

---