First-out alarm

Failure modes and desired response of SIS (e.g., first out alarm)... 

First-out annuneiators are highly desirable and should provide suffieient points to aeeommodate the speeified alarm and shutdown funetions. Standard features should inelude aeknowledge/silenee, lamp/test, and both audible and visible deviees for general alarm indieation. A dry auxiliary eontaet from the shutdown eireuit must be provided for expander inlet trip valve aetuation. Additional sets of eontaets are useful for other alarm requirements. 

Annunciator panels should be in a central location with alarm annunciators and shutdown annunciators grouped separately. The first alarm and the first shut-down normally sound a horn and are annunciated. This is called first-out indication. Subsequent shutdown or alarm signals received by the panel are either not annunciated or are annunciated in a different manner so that the operator can determine the initiating cause of the process upset. 

DEVIATIONS Alarms first-out safety-critical alarms many simultaneous or false alarms... 

The smaller of the two boilers became short of water first, and the low w ater level trip shut it dowm. The operator was so busy trying to get it back on line that he ignored the low water level and other alarms that were sounding on the other boiler. Unfortunately the trips on this boiler did not work, as it had been rewired (incorrectly) since it was last checked. Fifteen to 20 minutes later, someone saw flames corning out of the boiler stack. The boiler was then shut down manually. By this time most of the tubes had melted. 

One of the first observations one is likely to make when carrying out low-temperature voltammetric measurements is that the effects of solution iR drop that may have been scarcely noticeable at room temperature are suddenly alarmingly pronounced. The iR drop, of course, is governed by the cell current and the effective resistance between the working electrode and the Luggin capillary of the reference electrode. For example, the solution resistance for an embedded circular disk electrode of radius r with a distant reference electrode is given by Equation 16.13, where p is the resistivity of the solution. 

Note that the first condition is the familiar Shewhart chart limits. Pattern tests can be used to augment Shewhart charts. This combination enables out-of-control behavior to be detected earlier, but the false-alarm rate is higher than that for Shewhart charts alone. 

Warnings turned out to be more than twice as likely to be true if the first conspicuous source of the public warning was based on a report of scientific research produced at a recognized scientific institution. If the alarm was raised by a government agent or citizen advocacy group it was more likely to be false. 

It follows that it is good practice to separate chemical plant safety systems from control systems, so that the number of components common to both is minimised. Whilst it is quite possible to specify that control systems should raise alarms and trips when measured variables move out of bounds, a likely reason for this is that a part of the control system failed in the first place. So the control system cannot be relied upon to raise alarms reliably. 

A 29-year-old woman with bulimia nervosa and a family history of anxiety was enrolled in a trial of naltrexone (100 mg/day). She had no history of opioid use. Within hours of her first dose she experienced alarm, anxiety, chest discomfort, shortness of breath, a fear of dying, sweating, nausea, and derealization. She was unable to remain at home or to go out alone. For 3 days she continued to take naltrexone, with an increasing frequency of panic attacks. On day 4 she was treated with alprazolam (0.5 mg) but relapsed after further naltrexone. Withdrawal of naltrexone led to complete remission of symptoms. 

Figure 132 gives a scheme of the functioning of the apparatus worked out by North American Rockwell Corp. (Los Angeles) A conveyer belt transports the luggage first past a neutron generator and then past a detector. The radiation detected is amplified, analysed and compared with a preset threshold. If the detected radiation surpasses the threshold, a visual alarm is activated. ... 

When water started to react with MIC, no control of the temperature/pressure started, because it was late at night and the operational staff was reduced to a minimum, and the MIC tank s alarms had not worked for 4 years. The gas leakage followed, for the first 30 min, approximately the inverse route of water entrance (Figure 1.6), except that which reached the atmosphere through the vent collection system (VCS). However, the flare tower and the vent gas scrubber (Figure 1.7) had been out of service for 5 months before the disaster. After the first 30 min, the rupture disk bursts and this increased the rate of release of MIC. 

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