Control Room Systems

These design criteria include the capability of the system to withstand the effects of earthquakes and missiles shared systems and components prompt shutdown of the reactor from the control room system decay heat heat removal capacity considering a main feedwater line break redundancy reliability in-service inspection and functional testing. 

Control room System-based Operator task-based Operator task-based... 

Where necessary, a supplementary control room, separated and functionally independent from the main control room, shall be provided where the staff could operate in the event of an emergency. Information on important parameters and the radiological conditions in the facility and its surroundings shall be made available in the supplementary control room. Systems designed for this purpose shall be considered safety related systems. 

The design of the control room was poor. That is to say, influx of the hydrocarbon was not recognised until it reached the riser. The control room systems were either outdated or failed. 

Control Room. The control room location can be critical to the efficient operation of a faciHty. One prime concern is to locate it the maximum distance from the most ha2ardous units. These units are usually the units where LPG or other flammables, eg, hydrocarbons that are heavier than air, can be released and accumulate at grade level. Deadly explosions can occur if a pump seal on a light-ends system fails and the heavier-than-air hydrocarbons coUect and are ignited by a flammable source. Also, the sulfur recovery unit area should be kept at a healthy distance away as an upset can cause deadly fumes to accumulate. 

A central location where instmment leads are short is preferred. In modem faciHties with distributed control systems, all units are controUed from a central control room with few operators. Only a few roving operators are available to spot trouble. It is desirable to deep process equipment a minimum of 8 m away from the control room. Any equipment and hydrocarbon-containing equipment should be separated by at least 15 m if possible. Most control rooms are designed with blastproof constmction and have emergency backup power and air conditioning. The room is pressuri2ed to prevent infusion of outside air that may have hydrocarbon content in the explosive range. 

Provide adequate control room ventilation system... 

The main power source is a 2,200 kW rated motor, which drives two high-speed pinions through integral gears. The first stage of the compressor operates at 17,900 rpm, while the second and third stages operate at 21,800 rpm. The unit is controlled by a local control system, but operators can also monitor the operating parameters from the plant control room. 

A typical lubrication oil system is shown in Figure 15-1. Oil is stored in a reservoir to feed the pumps and is then cooled, filtered, distributed to the end users, and returned to the reservoir. The reservoir can be heated for startup purposes and is provided with local temperature indication, a high-tempera-ture alarm and high/low level alarm in the control room, a sight glass, and a controlled dry nitrogen purge blanket to minimize moisture intake. 

Failure of power or controls to the valve (generally related to the seismic capacity of the cable trays, control room, and emergency power). These failure modes are analyzed as failures of separate systems linked to the equipment since they are not related to the specific piece of equipment (i.e., a motor-operated valve) and are common to all active equipment. 

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). 

Room air conditioning (see Fig. 2.1) systems are used to control the main controlled zone. Systems can be divided into subsystems, e.g. ... 

The mere fact that voltage, current, or even both, are at low levels does not guarantee a circuit to be intrinsically safe, even though intrinsically safe circuits do utilize relatively low voltage and current levels. Intrinsically safe systems employ electrical barriers to assure that the system remains intrinsically safe. The barriers limit the voltage and current combinations so as not to present an ignition hazard should a malfunction develop. Typically, devices upstream of barriers are not intrinsically safe and are installed in control rooms or other unclassified locations. All devices and wiring on the downstream side of the barriers are intrinsically safe and can be installed in classified areas. 

The term control panel refers to the instrumentation console in a central control room through which process information is communicated to the process worker and via which the worker changes the state of the process. This category includes display elements such as chart recorders, bar indicators, dials, and modem VDU-based systems together with control elements such as buttons, switches, track balls and mice. The control panel is the human-machine interface (see Chapter 2) that has traditionally received the most attention from human factors specialists. 

Offshore oil platforms are highly automated, requiring little direct operator input to maintain production. In the event of a serious abnormality such as a fire or a gas escape, the control room worker is required to make decisions as to whether to depressurize one or more systems and which systems to blowdown. Other workers have the facility to depressurize some systems at a local control room. 

The human factors audit was part of a hazard analysis which was used to recommend the degree of automation required in blowdown situations. The results of the human factors audit were mainly in terms of major errors which could affect blowdown success likelihood, and causal factors such as procedures, training, control room design, team communications, and aspects of hardware equipment. The major emphasis of the study was on improving the human interaction with the blowdown system, whether manual or automatic. Two specific platform scenarios were investigated. One was a significant gas release in the molecular sieve module (MSM) on a relatively new platform, and the other a release in the separator module (SM) on an older generation platform. 

The major finding of the study was that the manual blowdown philosophy, particularly with respect to gas situations, was not clearly defined. This was most apparent in the offshore attitudes and perceptions regarding the importance of blowdown as a safety system. No decision criteria specifying when blowdown should or should not be activated were provided for the support of control room staff. Blowdown was essentially left to the discretion of the workers. Consequently, the offshore interpretation of this vagueness and ambivalence amounted to a perceived low priority of blowdown. It was concluded that this percephon would probably lead to a significant delay in blowdown or possibly the omission of blowdown when it was actually required. 

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