Alarm monitoring

In Chapter 5.4, optical ultraviolet radiation sensors are described, including UV-enhanced silicon-based pn diodes, detectors made from other wide band gap materials in crystalline or polycrystalline form, the latter being a new, less costly alternative. Other domestic applications are personal UV exposure dosimetry, surveillance of sun beds, flame scanning in gas and oil burners, fire alarm monitors and water sterilization equipment surveillance. 

The excellent detection ability for flames makes UV sensing a good method for remote fire alarm-monitoring. UV radiation after the outbreak of a fire reaches a sensor much faster than heat or smoke. Also, the distance between sensor and fire is less critical. Requirements for the sensor are high sensitivity and excellent selectivity. Radiation intensities at the sensor position may be even lower and the ambient light conditions less restricted than for combustion controlling. When used outside, solar-blindness is a must. These stringent requirements make UV fire alarm monitors expensive, and they are used in industrial environments such as production floors or warehouses rather than in private homes. 

The simple prototype unit discussed here is capable of continuously monitoring a process stream with rapid response to surface tension changes, and accuracy within 1-2%. Initial investigations indicate that a commercial unit based on this design would be capable of data acquisition, alarm monitoring, and/or closed-loop control of a process variable in a laboratory, pilot plant or production scale installation. A commercial instrument based on the work done in this laboratory is being developed and marketed. 

A new fire alarm monitor was installed in the central control room to verify the function of each fire detector. This monitor has a second alarm function that re-alarms if another detector goes off. 

Fire protection systems, including fire suppression fire detection alarms, monitoring, and communications and fire department operations... 

A continuous gas detection system must be provided to detect the presence of hazardous (toxic or highly toxic) gases at or below the permissible exposure limit (PEL) orthe ceiling limit (see UFC 8003.3.1.6). The detection system must initiate a local audible and visual alarm as well as transmit a signal to a constantly attended plant Emergency Control Station (ECS). Activation of the alarm/monitoring system must automatically close the shutoff valve on highly toxic or toxic gas supply lines. 

Requirements for pyrophoric materials storage are covered or referenced in UFC Section 8003.8. Included are requirements for signage, ignition control, spill control, drainage, secondary containment, ventilation, separation from incompatibles, fire protection, explosion control, electrical reliability requirements, and alarm/monitoring requirements. 

Figure 6. Integrated Life Safety Alarm/Monitoring Schematie.

Schematic diagrams of the control system are shown in Figures C-59 through C-67. There are many design features common to all control systems which promote system reliability. The high-low alarm monitors called summing point monitors are used extensively in all control systems.

Local/external alarm - once the alarm monitoring unit has detected a situation that triggers an alarm it may activate a local and external alarm. The local alarm which indicates that there is a flow in the system is commonly achieved by the use of a Pelton wheel where a small quantity of water that is flowing through the range pipes is diverted and turns a mechanical bell situated near the sprinkler control valve location. The alarm can be raised externally through an automatic link to a commercial, alarm receiving centre (ARC). 

For each failure mode, establish detectability (dependent upon several elements including alarm/monitoring devices in place)... 

The potential failure (P-F) interval indicates the time period before an actual failure during which potential failures are revealed. If the P-F interval is set to zero, failures will only be revealed if they have already occurred. Inspections of items with P-F intervals of zero are only effective for hidden failures. If potential failures can be identified before they occur (P-F interval > 0 ) then it may be worth inspecting items at regular intervals. The P-F factor is used to model the effects of non-zero P-F intervals for inspection tasks and alarm monitoring. For inspection tasks, the P-F factor is given by ... 

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