Alarm systems active protection systems

Provide safe separation distances Install fixed fire protection and alarms, water sprays (deluge), and/or foam systems activated by flammable gas, flame, and/or smoke detection devices... 

Switchgear and relay rooms are required to have smoke detection per NFPA 850, section 5.8.4 and IEEE 979, section 2.7. The activation of the fire alarm should shut down the air handling system. If the facility is especially critical to the continued hydrocarbon process consideration of a fixed fire protection system should be evaluated. 

Wet or dry chemical fixed suppression systems are typically provided over the kitchen cooking appliances and in exhaust plenums and ducts. Activation means is afforded by fusible links located in the exhaust ducts/plenums usually rated at 232°C (450°F). Manual activation means should not be provided near the cooking area, but in the exit routes from the facility. The facility fire alarm should sound upon activation of the fixed suppression system and power or gas to the cooking appliances should be automatically shut off. The ventilation system should also be shut down by the activation of the fire alarm system. Protective caps should be provided on the suppression nozzles to prevent plugging from grease or cooking particulates. 

An arming station, which is the main user interface with the security system, allows the user to arm (turn on), disarm (turn off), and communicate with the system. How a specific system is armed will depend on how it is used. For example, while IDSs can be armed for continuous operation (twenty-four hours/day), they are usually armed and disarmed according to the work schedule at a specific location so that personnel going about their daily activities do not set off the alarms. In contrast, fire protection systems are typically armed twenty-four hours/day. 

Flammable gas detection systems are typically used to initiate an alarm at a concentration level below the lower flammable limit (LFL). Two gas alarm levels (low and high) are often utilized to allow early warning prior to taking automatic actions. Detection systems may also be used to stop electrical power and initiate process shutdown. The low alarm setpoint should be —20% LFL and the high alarm level set point should be between 40%-60% LFL. Where these devices are used to initiate process shutdown or activate fire protection systems, it is common practice to use some form of voting, typically 2 out of 2, such that the frequency of spurious shutdowns or system activation is minimized. 

The project plan should encompass all aspects of a fire protection system, such as the underground fire water distribution system, fire pumps, aboveground water header, valving and standpipes, structural support, and detection and alarm systems. All work on the fire protection system must be coordinated with other work activities at the site or in the operating unit. The recommended installation practices for the different types of fire protection systems are covered in consensus standards, such as NFPA. The installation process is illustrated in Figure 9-1. 

Activation of layers of protection such as relief valves, interlocks, rupture disks, blowdown systems, halon systems, vapor release alarms, and fixed water spray systems... 

The sulfuric acid plant has boiler blowdown and cooling tower blowdown waste streams, which are uncontaminated. However, accidental spills of acid can and do occur, and when they do, the spills contaminate the blowdown streams. Therefore, neutralization facilities should be supplied for the blowdown waste streams (Table 15), which involves the installation of a reliable pH or conductivity continuous-monitoring unit on the plant effluent stream. The second part of the system is a retaining area through which non-contaminated effluent normally flows. The detection and alarm system, when activated, causes a plant shutdown that allows location of the failure and initiation of necessary repairs. Such a system, therefore, provides the continuous protection of natural drainage waters, as well as the means to correct a process disruption. 

Fire and explosion protection system drawings or arrangements (fire gas detection/alarm, protection - passive and active). ... 

A protection system can be designed to use passive or active approaches or both. Although active approaches, detection, and identification technologies are necessary to achieve LP-3 and LP-4, the components of passive protection (LP-1 and LP-2) are integral in these active systems. Sensor systems cannot perform to their best capacity without the high air quality provided by LP-1 and LP-2 systems. Similarly, LP-3 and LP-4 systems are not useful if operational plans are not available and in place to respond to alarms. 

The operational aspects of building protection are important considerations, even though they are less quantifiable than the protection metrics. The need for continuous operation has an important influence on protection system design. If part of the protective response is building evacuation or movement of personnel to an interior shelter, essential operations could be disrupted. Key activities that cannot be disrupted must be accounted for by the protective architecture. Similarly, the tolerance for false alarms could vary from building to building depending on the need for continuous operation. 

Proper designing of the alarm system, as the layer of protection in hazardous plant, will contribute to reducing the hmnan error probability (HEP), what will result in decreasing the risk of potential accidents. The human and organizational factors should be also care fully considered in designing and operating of protections to eliminate or reduce probability of latent and active failures (Kosmowski 2007). 

Figure 5 illustrates the relations between factors influencmg on possibility of latent error commitment which can induce active human errors. Relevant factors should be considered during analysis of protection layers, especially the alarm system and human machine interface (Scarborough et al. 2005). 

A control system for receiving fire alarm signals and initiating actions to highlight conditions (alarms and beacons) or institute actions to automatically activate fire protective systems (i.e., fire pump startup, HVAC shutdown, etc.). The fire alarm... 

A sprinkler system could have helped put out the fire at the initial stages, or at least cool down the warehouse stmctures. A heat- or smoke-activated chemical foam and fire alarm system could also have been installed in storage places. Materials for cleanup, self-contained breathing apparatus, protective clothing, and portable fire extinguishers should be available on-site. 

In this example a sensor (e.g. an automatic fire detector) is activated by combustion products such as smoke, heat or combustion gases. After activating the control unit (e.g. a fire alarm or detection system), it initiates programmed Controls of Fire Protection Systems (CFPS) or activates other actuators in the building. An actuator is for example a... 

For enclosed internal combustion engine facilities, the detection system should alarm and activate any emergency ventilation systems to keep air in the facility below 20% of the LFL. If the combustible levels continued to rise up to 60% of LFL, the detection system should activate further protections (e.g., shutting down the ventilation and shutting down the engine). Another consideration should be the location of ventilation exhausts with respect to outside ignition sources. 

Safety instrumented systems (SISs) should be completely separate from the normal control system. AU elements in the safety loop (measurement devices, logic systems, and actuators) must be highly reliable. This alarm system protects the facility against major catastrophes and will often take corrective actions to safely shutdown and isolate a piece of equipment or a facility, using emergency shutdown (ESD) systems that activate emergency block valves and emergency isolation valves. 

Associated with each of these demands that may cause the hazardous event were various protective systems. These were either hardware (e.g., ventilation system, flammable gas detectors) or procedural (e.g., instructions on allowable maintenance activities). For any particular demand to lead to the hazardous event, all the protective systems designed to protect against that demand must have failed to perform. Again, this failure may be a hardware failure (e.g., the gas detector has drifted out of calibration) or a human error issue (e.g., the flammable gas detector alarm warned of a flammable leak but Ihe operator failed to take appropriate action). 

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