Condenser cooling failure

the dynamic response of pressure is slowed down by both the thermal capacitance of the condenser and the rigorous handling of heat transfer in the reboiler. 

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Thus, the system must be kept open to allow vapor to condense and escape. Since the gas is toxic, a scrubber, which works in the case of cooling failure, must be provided. The condenser must also work after a cooling failure, such as an independent coolant. In order to check the feasibility of these measures, it is important to assess the controllability of the mnaway at MTT The objective is to control the reaction course by providing evaporative cooling. 

This is a very particular application where we have the potential for overpressure due to loss of overhead condensing or reflux failure. In the event the cooling medium in the condenser is lost, additional vapour may be present at the top of the column. This additional vapour may require pressure relief. In a typical distillation system, a cooling failure also results in a loss of reflux within a short period of time (typically about 15 minutes). API RP 521 states that the required relief rates before and after loss of reflux should be considered. The Berwanger audit method encompassed both of these calculations, as it was not intuitive, which case would require the larger required relief rate. 

By far the most (about 96 per cent) of the heat generated In the reactor is removed ffom the reactor by the primary coolant system, transferred to the boiling water secondary system and dissipated to the Columbia River via condenser cooling water streams, failure of the primary coolant system to remove heat from the reactorat design power level will result In certain fuel melting unless the last-ditch backup cooling system functions. 

This may cause greater contingency in a particular relief scenario. For example, in a distillation system, the cooling water may stop from loss of high-pressure steam (loss of condenser cooling), whereas the reboiler can still use low-pressure steam as a source of energy. This will result in maximum contingency in the event of partial steam failure. 

Direct water spray cooling must be carried out with care. The spray chamber must be designed to ensure complete evaporation of all Hquid droplets before the gas enters the baghouse. Spray impinging on the chamber walls can result ia a dust mud iaside the chamber and any increase ia gas dewpoint may result in baghouse problems or atmospheric plume condensation. Spray nozzle wear can result in coarse or distorted spray and wetted bags, and water pressure failure can cause high temperature bag deterioration. 

This analysis underscores the importance of examining failed components before they are cleaned or in any way altered. It also demonstrates the potential complexity of failure analysis and the need that exists to discard explanations that do not adequately account for all relevant observations. Important also to note is the potential connectedness of environmental factors, such that the seasonal development of seed hairs in a field of grass near a cooling tower would eventually contribute to perforations of tubes in a condenser. 

The condensing steam turbine has a relatively low thermal efficiency because about two-thirds of the steam enthalpy is lost to cooling water in the condenser. Expensive boiler feedwater treatment is required to remove chlorides, salts, and silicates, which can be deposited on the blades causing premature failure. The blades are already under erosion conditions because of water drops present in the condensing steam. Even with these disadvantages, the condensing turbine is still selected, especially in a process that requires very large compressor drivers and relatively low amounts of process steam. 

There is also a general failure to recognize that cooling water quality can be very dynamic. Do not, for example, make the mistake of installing a new tower, placing it into operation, and ignoring the water treatment for a few days. Some closely coupled systems with small water volumes (evaporative condensers and fluid coolers lending the best examples) can be scaled in a matter of hours. 

Failure is considered both on a local basis i.e., loss of utihty supply to one item of equipment (e.g., electric power to a pump motor) and on a general basis i.e., loss of supply to all consuming equipment in a process unit (e.g., cooling water to all coolers and condensers). For the purpose of these pressure rehef design considerations, a process unit is defined as one which meets all the following criteria ... 

Tube failure in a water-cooled or steam-heated exchanger used in hydrocarbon service can result in the contamination of the effluent cooling water or the condensate by the process stream, especially if the latter is at a higher pressure. Such effluents must be disposed of in such a maimer that the hydrocarbon contaminations can be safely contained. The following are some safe design practices ... 

LOCA, is presented in Table 3.4.5-1. In preparing the event tree, reference to the reactor s design determines the effect of the failure of the various systems. Following the pipe break, the system should scram (Figure 3.4.5-2, node 1). If scram is successful, the line following the node goes up. Successful initial steam condensation (node 2 up) protects the containment from initial overpressure. Continuing success in these events traverses the upper line of the event tree to state 1 core cooled. Any failures cause a traversal of other paths in the evL-nl tree. 

FIC8 = No Flow (new) Conditions are as specified. It must be inadequate cooling of column Top reflux pump failure (confirmed) Alternative goals Reduce heating in reboiler Reduce flow rate of input Increase cooling in condenser ... 

In early times 70/30 brass condenser tubes failed by dezincification and Admiralty brass (70Cu-29Zn-lSn) was brought into use. This proved little better, but some time later the addition of arsenic was found to inhibit dezincification. Failures of Admiralty brass by impingement attack became a serious problem, particularly as cooling water speeds increased with the development of the steam turbine. The introduction of alloys resistant to this type of attack was a great step forward and immediately reduced the incidences of failure. 

Cooling system failure could occur due to failure of pumps or controls supplying cooling media to the reactor vessel jacket, coils, or overhead reflux condensers. Piping to or from the condensers could become plugged or any of the heat exchange surfaces could become excessively fouled. 

Many subtleties associated with ED, for instance, accompanying thermodynamic cooling issues, failure processes, and effects of localized stresses, are discussed in detail in the extensive review on this topic by Briscoe et al. Other workers have observed similar fracture effects arising from rapid temperature increases while maintaining pressure the connection with ED is via Henry s law linking dissolved gas concentration and solubility coefficient, and the fact that solubility coefficient decreases (in an Arrhenius fashion, as it happens) for readily condensable (i.e., less volatile) gases when temperature increases. 

Failure of the Cooling Water Supply A reduction in cooling water flow to condense vapors in a vessel may lead to an increased pressure drop through the condensers resulting in an increased pressure in the vessel. 

Catalytic reduction of aromatic nitro compounds to the amines is highly exothermic (AH = —548 12 kJ/mol) and has high potential for hazard in the event of cooling- or other process-failure. The total reaction proceeds via nitroso and hydroxylamino intermediates, both of which are reactive and may undergo undesired condensation or disproportionation reactions, and the thermochemistry of all these possibilities was investigated. The reduction or disproportionation of the hydroxylamino intermediate (which is of low thermal stability) is identified as the fastest and most exothermic step (despite which it can frequently be concentrated or trapped) implications for process safety are considered in detail and verified by experiment with typical compounds and intermediates [1]. A calorimetric study of the hazards inherent in hydrogenation of nitroaromatics was made, using nitrobenzene as model compound [2]. Individual incidents of this type are ... 

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