Emergency alarms

Example 11-2 assumes that all failures in either the alarm or the shutdown system are immediately obvious to the operator and are fixed in a negligible amount of time. Emergency alarms and shutdown systems are used only when a dangerous situation occurs. It is possible for the equipment to fail without the operator being aware of the situation. This is called an unrevealed failure. Without regular and reliable equipment testing, alarm and emergency systems can fail without notice. Failures that are immediately obvious are called revealed failures. 

Whenever ambient noise levels are above emergency alarm signals or tones, flashing lights or beacons should be considered that are visible in all portions of the affected area. The color of flashing lights should be consistent with the safety warning colors adopted at the facility. 

Each type of emergency alarm or signal must clearly inform those onsite of the actions to be taken. This requires training and testing of the alarm so personnel can recognize the alarm and take appropriate action. Some of these alarms may be automatic. For example, detection of a fire may be signaled directly by the protection or detection system rather than by an individual. This alarm signal may alert not only personnel in the immediate area, but all facility personnel and the community fire department. 

This section includes guidelines for the central control station equipment, emergency alarm stations, supervisory devices, and visual and audible alarm services. These systems can be used for all types of in-house emergencies, such as fires, explosions, vapor releases, liquid spills, and injuries. 

Process facilities may be divided into primary operational divisions called zones. These zones are divided into areas. A coded signaling system can be used to indicate the zones and area numbers. A third number may be used to indicate a station within the area boundaries. The plant emergency alarm system should ... 

Emergency alarm system design and installation should be in accordance with NFPA 72. Electrical aspects of the fire alarm systems should be designed and installed in accordance with NEPA 70. When devices are located in hazardous areas, they should meet the electrical requirements suitable for that hazardous area. 

Where releases of flammable or toxic chemicals are possible, a flammable or toxic gas alarm system is often established as part of the plant emergency alarm system. Best practices require different types of alarms to be annunciated differently, both audibly and visually. For example, the toxic alarm stations may be provided with a blue light to distinguish them from fire alarm stations that are red. A consistent color system for lights should be adopted. 

Emergency alarm systems should always have a manual means for initiating alarms. Manual alarm stations are normally located on the periphery of the processing or storage areas near an expected path of exit travel or at control rooms. The alarm boxes should not be located in areas that are electrically clas-... 

In plants having a central plant-wide fire and emergency alarm center (fire house or guard control station), consideration should be given to sending the... 

Activate Emergency Alarm Notification System and take defensive action until relieved by a more qualified employee. (Use Site notification system) First Responder... 

Activate appropriate plant emergency alarm Communication Center... 

Essential Plant Operations Plant operations such as the monitoring of plant power supplies, water supplies, and other essential services which cannot be shut down for every emergency alarm. They may also include chemical or manufacturing processes that must be shut down in stages or steps. Ester The hydrocarbon derivative with the general formula R-C-O-O-R . 

If the plant is small enough, the maximum possible accident may not pose a significant hazard to people, the environment, or property. This may result in an additional reduction in the equipment needed for the plant—it may not require as much (or any) safety equipment, emergency alarms and interlocks, or other layers of protection to manage risk. Even if the small plant still requires safety equipment, this equipment will be smaller and cheaper. Installation and ongoing operation of safety equipment is often a major expense if it can be eliminated or reduced in size and complexity, there will be cost savings. Safety need not cost money—safer can also be cheaper if a small, efficient, inherently safer process can be invented. 

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. 

In some facilities, the major emergency alarm is a steady blast on the facility steam whistle. Others use sirens or special bells. Whatever is chosen, the alarm must reach everyone on the site, triggering activation of the facility ERP and the initiation of a head-count procedure. 

It is essential that every employee on a chemical facility knows how, where, and when to turn in an appropriate and effective emergency alarm. The specifics will vary considerably, but the procedure for turning in an alarm is similar in all cases. 

Instrumentation philosophy (local/remote control, hardwired/data highway, failure mode(s), analog/digital, emergency alarms, etc.). 

What if an emergency alarm is confused with other instructional tones ... 

Critical safety systems are usually considered to be those that are necessary for safe plant operation during processing and also those required for the safe shutdown of the plant in the event of an unanticipated malfunction. Within an incineration plant, examples of critical safety systems inclnde agent monitoring systems, testing or inspection of pressure rehef valves, ventilation flow and control systems, fire protection systems, emergency alarm and shutdown systems, process interlocks, and furnace temperature control systems. 

The emergency alarm was sounded and operators in the plant withdrew to safe areas. The operators in the Central Control Room (CCR) in each reactor are the only operators to remain at their posts. Reactors 3 and 4 were probably controlled from a common CCR. Notification of the accident was made to the Ukrainian state authorities and assistance requested from local emergency services. 

The areas where hazardous chemicals are stored prior to shipment and where any ancillary operations are conducted should be carefiilly evaluated for hazards. Access and evacuation routes should be clearly marked and checked to ensure freedom fiom obstruction. Any very hazardous materials, especially any IDLH materials, should be in separate, well-marked areas. Means of annunciating an emergency alarm should be readily available. Assistance agencies, eg., fire departments, rescue squads, pohce, and haz-mat teams, should be identified and standard procedures for invoking their assistance prepared. 

As with all laboratory work, protection of the worker against the hazard consists of good facility design, operation, and monitoring, as well as good work practices on the part of the worker. The ALARA (as low as reasonably achievable) exposure principle is central to both levels of protection. The amount of radiation or radioactive material used should be minimized. Exposures should be minimized by shielding radiation sources and workers and visitors and by use of emergency alarm and evacuation procedures. Physical distance between personnel and radiation sources should be maximized, and whenever possible, robotic or other remote operations should be used to reduce exposure of personnel. 

The operations crew started shutting down within 15 s of receiving the radio message, but did not have time to sound the emergency alarm. The fuel gas valve was shut off five seconds before the explosion. Hundreds of alarms sounded on their computerized systems. Operators were assessing the situation and did not sound the emeigency warbler prior to the explosion [15]. 

The second group consists of people who perceive more or less correctly the risk and potential effects of a chemical emergency. Generally, they live in urban areas near relatively large industrial plants and have experience of emergency alarms. 

Employees must have emergency response training and be taught to recognize emergency alarms and obey them. 

Why is a manual shutdown needed at all The process requirements specification defines how manual shutdown should be executed from the process perspective. Operators are often provided with manual pushbuttons to initiate equipment shutdown. Operators are expected to initiate trained responses to a variety of shutdown indicators, such as process indications, process alarms, observed events, protective alarms, emergency alarms, or procedures. 

---