General Alarm Requirements

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. 

Most automated SiFs are designed as de-energize to trip. As a result, the PFDavg calculation for these SIFs generally does not take into consideration any utility systems. Operator action inherently requires support systems to compiete the safety function. Display/alarms require power to actuate the light and/or horn for operator response. Therefore, the reliability of the electrical power system directly affects the PFDavg of the credited operator action. 

A variety of instmments are available to analyze carbon monoxide in gas streams from 1 ppm to 90%. One group of analyzers determines the concentration of carbon monoxide by measuring the intensity of its infrared stretching frequency at 2143 cm . Another group measures the oxidation of carbon monoxide to carbon dioxide electrochemically. Such instmments are generally lightweight and weU suited to appHcations requiring portable analyzers. Many analyzers are equipped with alarms and serve as work area monitors. 

The maximum allowable oxygen concentration (MAOC), which is, in general, 2 vol % below the LOC, has to include the following considerations fluc tuatiou in oxygen concentrations due to process and breakdown conditions per time and location, as well as the requirement for protective measures or emergency measures to become effective. In addition, a concentration level for an alarm has to be set below the MAOC. 

It generally is recommended, and often required, that gas dcicciiuii systems be installed in a fail-safe manner. That is, if power is disconnected or otherwise interrupted, alarm and/or process equipment shutdown (or other corrective action) should occur. All specific systems should be carefully reviewed, however, to ensure that non-anticipated equipment shutdowns would not result in a more hazardous condition tlian the lack of shutdown of the equipment. If a more hazardous situation would occur with shutdown, only a warning should be provided. As an example, a more hazardous situation might occur if blowout preventers were automatically actuated during drilling operations upon detection of low levels of gas concentrations than if drilling personnel were only warned. 

The most important hardware items appeared to be the detectors themselves. The gas detection system gave frequent spurious alarms, and on both platforms the ultraviolet (UV) fire detectors were also prone to spurious activation from distant hot work for example, and had a limited ability to detect real fires. The tmreliability of these systems had a general effect on response time and would, overall, lengthen the time to respond. The second aspect which was related to hardware was fimction and performance testing of the emergency blowdown systems. It is critical that the workers believe the systems will work when required, and this can only be achieved by occasional use or at least fimction testing. 

In general practice, the gas detection alarm set points are the settings recommended by the manufacturer of the equipment or by requirements of an operating company to effect an acceptable compromise on any given field of operation. The lower the set points the higher the sensitivity to possible leakage emissions. 

In general, the tracking procedure starts with an association process to combine the established track parameter with the radar sensor or radar network measurements. Errors in the association process will always lead to ghost targets. But the general requirement for automotive applications is to keep the false alarm probability as low as possible, which underlines the importance of the association process for radar networks. 

A pharmacy, like any other business entity, needs to protect itself, its employees, and its customers from physical and financial harm. No matter how careful a pharmacy is about preventing risks, it is practically impossible to eliminate accidents, such as when a customer or employee slips on the pharmacy s floor. At the same time, insuring for these risks does not eliminate the need for pharmacies to take effective risk prevention measures. Indeed, insurers commonly require that pharmacies have risk prevention measures in place to keep insurance policies in good standing for these risks or to reduce premiums. For instance, insurance for fire damage generally requires a sprinkler system or smoke detectors or alarms. 

A satisfactory facility emergency alarm system must meet three additional requirements. It must, at a minimum, immediately alert all the people on the site. (A single signaling device should be adequate for small sites however, large facilities may require many devices placed to reach all occupied areas of the site.) The system must function even when the facility has a general power failure. Alarm activation controls should be located so that an emergency condition is unlikely to prevent access to them. 

Microprocessor control generally results in less operator attention required, higher levels of reliability, and ease of changing groups of set points. Other advantages are automatically programmed startup sequences, over temperature alarm, thermocouple loss alarm, heater failure alarms, and closer temperature control accuracy (Chapter 3). 

A modem plant requires more information, events and alarms to be made available at the main control room than was generally the case in the past. This has been made much easier to achieve by the use of computer networking and fibre optical technology. Most of the information that is available at the switchboard can be transferred to the main control room so that, for example, a one-line diagram presentation can be made on a computer desk-top monitor (man-machine interface, MMI). 

In the development of the process automation and control system, the required testing of that control system and the factory-assembled components, and the process simulation program must be established with the general functional specifications. In an API facility, many of the control systems perform process functions that require strict validation. The functional description for the automation system should require a complete factory acceptance test (FAT). This test should simulate the entire process and process failures and alarms. The FAT should also check and verify that the control system cabinets and controllers operate as designed. The factory acceptance testing of the process automation system prior to shipment and installation in the field is a critical step in the validation and start-up of the facility. 

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