Shutdown normal

If operating procedures need to be developed from scratch, this could account for a considerable portion of the pre-startup work. If current, valid standard operating procedures exist, and the toll is only introducing a new set of batch instructions, the task becomes simpler. However, it is recommended that the new batch instructions are reviewed simultaneously with the existing startup, shutdown, normal and emergency operating procedures for the equipment to help ensure potential process deviations are examined and addressed. 

Sfart-up/shutdown Provide for safe start-up, including purging if necessary Provide for safe shutdown Normal By a trip On standby In various emergency situations, etc. 

Mechanically withstands a wide range of operating conditions, including start-up, shutdown, normal operation, and upset conditions... 

Is there a potential for overtemperature during startup, shutdown, normal... 

Normal Shutdown Normal shutdown circumstances are those where the reactor is shut down and maintained in that state under controlled conditions ... 

Emergency operation and shutdown Normal shutdowns Sample log sheets... 

The results of tiie midtidimensional core analyses are summarized in TaUe I. Comparison of tiie multiplication factor for the cdd shutdown, normal-core base case with those for the tiftee disrupted c< e models led to the following condiisions for tiiis heavily borated stem ... 

In general, the control subsystem with an appropriate architecture is designed to manage various control tasks (e.g., startup, shutdown and emergency shutdown, normal operation, and other modes such as maintenance, idle, and power off)... 

Other scheme Startup/shutdown/normal operation, timing issue, synchronization,... 

Power operation Start-up and shutdown Normal operation... 

The second step is to make the reactor subcritical by diluting the fuel. This type of shutdown normally requires 3 to 5 hr, since it is desirable to have the reactor subcritical at the storage temperature of approximately 25°C when the reactor is emptied. The rate at which the temperature can be reduced is again determined by the permissible cooling rate of the system components. 

The results of over 1 year of continuous, on-line acoustic emission (AE) structural surveillance of high temperature / high pressure steam headers, gained on 2 M-scale 600MW supercritical multifuel ENEL power units in normal operation, are presented in the paper. The influence of background noise, the correlation between plant operating conditions (steady load, load variations, startup / shutdown transients) and AE activity and the diagnostic evaluation of recorded AE events are also discussed. 

The RCCA s (32 to 52 assemblies in the core), regulate the neutron flux in the reactor, and are used for emergency shutdown of the reactor activity. In normal working conditions, the RCCA s are suspended above the fuel elements. 

Normal Operation. The designer of a chemical plant must provide an adequate interface between the process and the operating employees. This is usually accompHshed by providing instmments to sense pressures, temperatures, flows, etc, and automatic or remote-operated valves to control the process and utility streams. Alarms and interlock systems provide warnings of process upsets and automatic shutdown for excessive deviations from the desired ranges of control, respectively. Periodic intermption of operations is necessary to ensure that instmments are properly caUbrated and that emergency devices would operate if needed (see Flow measurement Temperaturemeasurement). 

Shutdown. Written procedures for normal, as well as for emergency, shutdowns should be prepared, rehearsed, and kept up-to-date. Operating supervisors must be responsible for leaving the process equipment in a safe condition or preparing plant equipment for maintenance work. 

Internal Regenerator Bed Colls. Internal cods generate high overall heat-transfer coefficients [550 W / (m -K)] and typically produce saturated steam up to 4.6 MPa (667 psi). Lower heat fluxes are attained when producing superheated steam. The tube banks are normally arranged horizontally in rows of three or four, but because of their location in a continuously active bubbling or turbulent bed, they offer limited duty flexibdity with no shutdown or start-up potential. 

In selec ting the machines of choice, the use of specific speed and diameter best describe the flow. Figure 10-67 shows the characteristics of the three types of compressors. Other considerations in chemical plant service such as problems with gases which may be corrosive or have abrasive solids in suspension must be dealt with. Gases at elevated temperatures may create a potential explosion hazard, while air at the same temperatures may be handled qmte normally minute amounts of lubricating oil or water may contaminate the process gas and so may not be permissible, and for continuous-process use, a high degree of equipment rehability is required, since frequent shutdowns for inspec tion or maintenance cannot be tolerated. 

S/, = S from Table 10-49 at maximum (hot) metal temperature normally expected during operation or shutdown... 

Gas Distrihutor The gas distributor has a considerable effect on proper operation of the flmdized bed. Basically there are two types (1) For use when the inlet gas contains solids and (2) for use when the inlet gas is clean. In the latter case, the distributor is designed to prevent Back flow of sohds during normal operation, and in many cases it is designed to prevent back flow during shutdown. In order to provide distribution, it is necessary to restrict the gas or gas and solids flow so that pressure drops across the restriction amount to from 0.5 kPa (2 in of water) to 20 kPa (3 Ibf/iu ). 

Shutdown This includes all procedures preparing for, completing and following up a planned normal shutdown. 

Emergency operations Process changes initiated by the operations staff to place the process into a safe condition (back to normal operations or shutdown) in response to any abnormal situation that could cause a release, explosion, or other significant event. 

Normal operations Any process operations intended to be performed between startup and shutdown to support continued operation within safe upper and lower operating limits. 

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