Emergency depressuring

Install depressurizing system Install emergency relief device Develop emergency response plan... 

The AP600 passive safety system includes subsystems for safety injection, residual heat removal, containment cooling, and control room habitability under emergency conditions. Several of these aspects are in existing nuclear plants such as accumulators, isolation condensers as natural-circulation closed loop heat removal systems (in early BWRs), automatic depressurization systems (ADS - in BWRs) and spargers (in BWRs). 

Fit an emergency depressuring valve so that the pressure in the vessel can be reduced to one fifth of design in ten minutes to reduce the strain on the metal [13]. The time can be increased to 30 minutes if the vessel is insulated and to one hour if, in addition, the ground is sloped. 

The costs of a wrong decision are loss of production, on the one hand, and failure to respond to a real emergency on the other. In order to improve his or her decision basis, the control room worker will usually dispatch others to the source of the emergency signal to declare whether it is spurious (false alarm) or whether it is real, but it is containable without need for depressurizing. This takes up valuable time, during which the situation could escalate dangerously. 

Train all personnel in the functioning and value of blowdown during an emergency. This may be achieved by safety specialists explaining the various hazards and relative risks of blowing down and failing to depressurize. 

The time required to stop the leak is a function of isolating points, emergency valves, depressuring systems, and other mitigation systems as appropriate. 

Process system emergency safety features (i.e. ESD, isolation, depressurization and blowdown) should be considered the prime safeguards for loss prevention over fire protection measures (i.e. fireproofing or barriers, firewater systems, manual fire fighting). 

Survivability of Safety Systems - An estimation of the ability for safety systems to maintain integrity from the effects of explosions and fires. (Safety systems may include ESD, depressurization, fire protection - active and passive, communication, emergency power, evacuation mechanism, etc.). 

Hydrocarbon processing facilities pose severe risks with respect to fire, explosions and vessel ruptures. Among the prime methods to prevent and limit the loss potential from such incidents are the provisions of hydrocarbon inventory isolation and removal system. These systems are commonly referred to in the petroleum industry as ESD (emergency shutdown) and depressuring or blowdown. Although most standards and practices acknowledge the need for depressuring capabilities the exact determination of their requirement is not wholly defined. NFPA fire codes and standards rarely mention the subject. 

The apparatus incorporates a fibre optic interface for the spectrofluorimetric measurement on the supercritical carbon dioxide emerging from the extraction cell of a supercritical fluid extractor, prior to depressurization from up to 350 bar. Recoveries of polyaromatic hydrocarbons are between 89 and 107%, and measurements can be carried on with a relative standard deviation of less than 5%. 

The in-line safety valve [45] as shown in Fig. 4.2-7 is used in LDPE plants during emergency situations in order to depressurize the system by the outlet (2). The valve is directly included in the tubular reactor train (1) in a manner to avoid dead spaces where harmful decomposition of the polymer could take place. The control of the safety valve is effected again by a special... 

NFPA 57 recommends that LNG dispensers be protected from collisions with vehicles and that they incorporate an emergency shut-down system. The maximum delivery pressure of the dispenser shall not exceed the operating pressure of the LNG tanks on the vehicle being refueled, and the LNG delivery hoses must have a shut-off valve at the end and a breakaway valve in the event a vehicle drives off with the refueling hoses attached. Bleed and vent valve must be incorporated into the dispensing lines to allow them to be drained and depressurized prior to disconnection if necessary. 

This measure is different from emergency pressure relief. A controlled depressurization is activated in the early stages of the runaway, while the temperature increase rate and the heat release rate are slow. 

In the examples given above, we see how important an early intervention is in case of runaway. Whatever the measure considered, the sooner it becomes active the better. An exothermal reaction is obviously easier to control at its beginning, before the heat release rate becomes too great. This is true for emergency cooling as well as for controlled depressurization. Thus, the idea arose to detect a runaway situation by an alarm system. The first attempt in this direction stems from Hub [15, 16], who proposed evaluating the second time derivatives of the reactor temperature and the first derivative of the temperature difference between reactor and jacket, giving a criteria for a mnaway ... 

A transfer vessel is a device that receives the contents of another vessel for emergency or nonemergency purposes. It can be as simple as a vacuum truck or as complex as a hard-piped, dedicated system. For liquids, the system typically consists of a container or containment system located below the protected vessel where gravity will promote a rapid transfer. In the few instances where a transfer vessel is used with gases, it assists in the depressurization of a process. In other instances, it may consist of a spare vessel capable of accepting the contents of a nearby vessel (in case of fire or leak) so that the damaged vessel s entire contents are not destroyed or released (Lees, 1980). In this case, a pump may be used to make the transfer between vessels. 

Marked items marked are considered minimum data required for a HAZOP or What-If review to occur. This data basically contains the layout (plot plan) of the facility, the process design (P ID and process description) and how it will be controlled during an emergency (SAFE chart and fire protection plant). With this information the "experts" can understand the design and operating principles of the facility. Since the emergency isolation, depressurization and fire protection features are provided, it can be readily deduced how the facility will fare from a catastrophic incident. 

Similar emergency situation with partial depressurization of SFA canisters and the primary circuit occurred at NS 541. Based on the results of radiation and engineering... 

The catalyst emerging from the bottom of the reactor passes through a depressuring pot, and the steam that escapes from the catalyst is removed by a small jet condenser. Completeness of the purge is checked by inspecting the steam condensate for traces of oil. The temperature of the catalyst leaving the reactor is of the order of 875 F. (with a catalyst inlet temperature of 1000°F.), and carbon content is of the order to 2 to 4 wt. %. 

The effectiveness of the different ways in which the depressurized mixture emerging from the restrictor can be collected depends on the characteristics of the particular extractant and analytes. When the extractant is a gas under atmospheric conditions (e.g. COj), the three collection modes described in Section 7.3 are applicable. 

Jets of a boiling-up liquid may originate in an emergency in various thermal-power and chemical machines. The consequences of an accident with local depressurization of a high-pressure pipeline (vessel) are affected by diverse factors, for instance, the flow rate of a heat-transfer agent, the jet form and its dynamic reaction to the construction elements. 

Thermistor and carbon resistor sensors performed satisfactorily, in that no false indication was noted even during the dewar filling operation and during pressurization or depressurization. Recorded response times on emergence were relatively fast. Some manufacturers have installed a separate heater w ire winding around the sensing element to speed up the temperature rise and thereby improve the recovery time. 

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