Failure warning/indication

Failure rates of complex equipment can often be greatly reduced through redundant arrangements. Redundancy provides multiple means of warning and shut down systems to ensure personnel and equipment are safe from failures that could result in a hazardous situation. Redundancy is based upon how critical an event is to worker safety or process continuation. Two separate switches or two separate alarms provide redundancy. In addition, there is standby redundancy. In this case, a piece of equipment operates until a failure is indicated, at which time another duplicate piece of equipment is turned on either automatically or manually. An excellent example of redundancy is fire water pumps. There are always at least two or more. A unit does not want to experience a fire, the site has only one pump, and that is the day the pump fails. 

Failure warning or indication will provide detection of a condition before it can lead to a dangerous scenario. 

The quality of the architectural design ensures redundancy, warning indications, etc. However, it is a fallacy to assume that survivability is assured just because redundancy is provided. Although most essential and critical systems employ some sort of redundant technique, closer scrutiny soon makes it apparent that many of these systems have a single element (or common point ), the failure of which will cause multiple channel failures. 

Where an electric circuit is employed the valve should close on breaking, not making, the circuit and be reset manually. A warning device should be included to indicate that resetting is necessary, to cover the eventuality of temporary electrical failure. 

Formation of vapor bubbles in rapidly flowing or turbulent water causing risk of pumping failure and erosion and/or corrosion. Due to an increase in velocity at the pump head resulting in a localized pressure reduction and the subsequent collapse of the vapor into voids or cavities. Where FW temperatures are high (over perhaps 195-205 °F) the pump velocity can reduce FW vapor pressure below that corresponding to the temperature of the liquid and cavitation can occur accompanied by some noise. Warning of severe pump cavitation is often indicated by a heavy noise. 

Failure Detection Method. The means of failure detection should be identified, such as visual or warning devices, automatic sensing devices, sensing instrumentation, or other indicators. 

A filtered air supply should maintain a positive pressure relative to surrounding areas under all operational conditions and flush the area effectively. Final filtration should be at or as close as possible to the point of input to the area. A warning system should be included to indicate failure in the air supply and an indicator... 

Warning systems must be installed to indicate failure in the filtered air supply to the laboratory. Recording instruments should monitor the pressure difference between areas where this difference is of importance. 

The detection system must incorporate safeguards against system failure and provide an early warning system to indicate if the detector is becoming less sensitive, due... 

Felbamate. Felbamate is an adjuvant anticonvulsant, containing the warning that its use is associated with a marked increase in the incidence of aplastic anemia and that patients being started on the drug should have liver function tests performed before therapy is initiated. Animal studies have revealed a statistically significant increase in hepatic cell adenomas in high dose studies (18). It is postulated that this cancer was induced by toxic by-products urethane and methyl carbamate. Felbamate is not recommended as first-line therapy and is indicated for those patients who respond inadequately to alternative treatments and whose epilepsy is so severe that a substantial risk of aplastic anemia or liver failure is deemed acceptable in light of the benefits provided by its use. 

Early concern about resistance to the pyrethroids resulted in the initiation of monitoring programs. As early as 1975, studies by university researchers were initiated to determine H. virescens susceptibility to the pyrethroids (15-17. The results of these studies generally indicated localized shifts in tolerances in field collected strains of Ii. virescens. However, few of these studies related "resistance" levels detected in laboratory tests of field strains to insect control in the field. Martinez-Carrillo and Reynolds (16 pointed out that even though they detected high levels of resistance, no field control failures had yet been reported. They did warn, however, that failures were possible if application trends continued. Subsequently, FMC and ICI, two of the first manufacturers of pyrethroids, established monitoring programs in the early 1980 s Q ). ... 

A warning system should be induded to indicate failure in the air supply. An indicator of pressure difference should... 

Laminar flow workstations should comply with the requirements of AS1386.5 and 1386.7 Cleanrooms and clean workstations and those used for aseptic processing should be fitted with visual and/or audible warning devices to indicate failure of the air supply. 

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