Close to trip

Final element components will fail also, and again the specific failure modes of the components can be classified into relevant failure modes depending on the application. It is important to know whether a valve will open or close on trip. Table 6-3 shows an example failure mode classification based on a close to trip configuration. 

The application of a valve will affect its failure rates and failure modes. One key variable is position of the valve in order for a safety instrumented function to achieve its safe state. The valve must be designed to be "close to trip" or "open to trip." There are generally no tight shut-off requirements when the valve opens to perform the trip. 

Clean service, close to trip. Class IV leakage allowed 0 400... 

Gate Valve, clean service Close to trip 87.9%... 

Gate Valve, severe service Close to trip 84.9%... 

Ball Valve, severe service, full stroke only Close to trip 45.2%... 

Does a valve have the same failure rates and failure modes if used in an open-to-trip configuration versus a close-to-trip configuration ... 

Trip Valves The trip valve is part of a system that is used where a specific valve action (i.e., fail up, Fail down, or lock in last position) is required when pneumatic supply pressure to the control valve falls befow a preset level. Trip systems are used primarily on springless piston ac tuators requiring fail-open or fail-closed acrion. An air storage or Volume tank and a check v ve are used with the trip valve to provide power to stroke the valve when supply pressure is lost. Trip valves are designed with hysteresis around the trip point to avoid instabihty when the trip pressure and the reset pressure settings are too close to the same value. 

For filter boxes, provide remote and automatic filter box lid closing on trip of appropriate fire detection device. Fire detection device may also be interlocked to stop solvent feed, trip deluge internal to filter box and/or trip inert gas blanket for filter box (caution, be aware inert gas is a potential asphyxiation hazard)... 

Motors are also recommended to have one bearing temperature detector in each bearing. This can be fitted within the threaded walls of the bearing that reach up to the bottom of the bearing shell, i.e. close to where the heat is produced. Each detector may have two sets of contacts, each having 2-NO contacts, rated for 5 A at 240 V a.c. and 0.5 A at 220 V d.c. One set can be set at a lower value to provide an audio-visual alarm and the other at a higher value to trip the motor. 

The NO (normally open) contact of I/C-1 (520 is wired in the trip circuit of I/C-2 (52 ii) and vice versa. As soon as an interrupter is closed, the tripping circuit of the other gets ready to trip. 

The function of a shunt trip coil is to trip an intetrupter. As. soon as its coil is energized, it releases the closing lever of the interrupter and trips it. The coil is rated for a short time, since it is in the circuit for a very, short period only when it is required to trip the interrupter. To ensure that it does not continue to remain energized after carrying out its function, the interrupter s NO contacts are also wired in scries with the coil as shown. The coil becomes de-energized as soon as the interrupter trips. Normally two NO contacts of the... 

To close or trip the interrupter locally or retnotely a breaker control switch is also wired with the closing and the shunt trip coils of the interrupter, as shown in Figure... 

This technique provides a method of initiating primacord—-and thus any explosive charge—if a regular blasting cap is not available. The device may be rigged as a booby trap with trip wire or it can be fired remotely by the operator. Since the technique does require the destruction of a usable rifle it likely would be used only when there is no other alternative. In addition, care should be taken in all phases of the preparation, because when the weapon is fired it will break into many fragments which would severely injure anyone holding the weapon or close to it. 

Now close the action of the rifle, release the safety, and retire to a safe position at least 50 yards away, being sure not to trip over the trip wire or pull cord. If the pull cord is used, take up any slack in the line and then pull firmly to fire the weapon and detonate the charge. 

The near IR spectra of the tetrakis(cumylphenoxy)phthalocyanines have not been reported before. The absorption in the Cu complex and one of the absorptions in the Co complex lie close to bands which have been tentatively assigned to trip-multiplet transitions in other phthalocyanines.(14) However, the other absorption bands shown in Table 1 have not been previously reported for phthalocyanines with no peripheral substitution. The small absorption cross sections of these bands in the cumylphenoxy phthalocyanines suggest that they are forbidden transitions. Possible assignments for these bands include a symmetry forbidden electronic transition (like the MLCT transitions in NiPc discussed above) becoming vibronically allowed, d-d transitions on the metal ion, or trip-multiplet transitions. Spectroscopic studies are in progress to provide a more definitive assignment of these absorptions. 

Are the contaminants of concern concentrations in the trip or equipment blank and in the samples close to the action level ... 

Always use reset-type circuit breakers instead of replaceable fuses. If possible, locate the breakers close to the area served by the circuit. It s a smart idea to put the lights on one circuit and everything else on a separate circuit. Then, if a momentary overload trips the circuit breaker, you won t be left in the dark. ... 

My family Jived in New York City, and there were no scientists in the family. My father was born in New York City, and was a Supreme Court judge in New York State. I was very close to him. My mother was born and raised in Belgium, where my grandfather was in the diamond business. The family is Jewish. On the day the Germans invaded Belgium, my grandfather was in London on a business trip. My mother and her family... 

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