Alarm releaser

Terpenoid substances are of broad distribution and diverse function in insects. One set, elaborated by the mandibular glands of Acanthomyops claviger, acts both as a defensive secretion and as an alarm releaser. When fed Cu-labeled acetate or mevalonate, laboratory colonies of these ants produce radioactive citronellal and citral, providing unambiguous evidence for de novo synthesis of these terpenes by the ant. The incorporations of these precursors implicate the mevalonic acid pathway as the likely biosynthetic route. 

Recently, germacrene-A (III) has been identified as the alarm pheromone of the sweet clover aphid Therioaphis trifolii (38). This alarm releaser, which has often been proposed as the progenitor of cyclic sesquiterpenes, constitutes the second compound with a germacrane-type skeleton to be identified as an insect pheromone. 

Among bees, citral (130), 2-heptanone (131), and isopentyl acetate (132) have been shown to possess among other functions, that of alarm releasers. 

Riley et aK (157) identified S-(+)-4-methyl-3-heptanone as the alarm pheromone of Atta texana and reported that it was 100X more active as an alarm releaser than the unnatural (-)-enantiomer. Similarly, Benthuysen and Blum (158) demonstrated that workers of Pogonomyrmexbadius were more sensitive to the S(+) enantiomer than to the R-(-) enantiomer of this compound, which is the primary alarm pheromone of this species. 

Ghent, R.L. and Gary, N.E. (1962). A chemical alarm releaser in honey bee stings Apis mellifera L.). Psyche 69,1-6. 

The Pherobase database is an extensive compilation of behavior-modifying compounds listed in the various pheromone categories aggregation, alarm, releaser, primer, territorial, trail, sex pheromones, and others. The database contains over 30,000 entries. Jmol images of molecules are shown. The molecules can be projected as either space-filling or wire-frame models. They can be rotated in 3-dimensional space. In addition, the database includes mass spectral, NMR, and synthesis data for more than 2,500 compounds. This is a fun site ... 

Po> the event frequency A is to be inserted for the appearance of excess pressure. On the basis of experience with pressure toad variations found, only an excess of in 10 years was assumed. This corresponds to an event rate = 10 x 10 /h related to an hour. Probability q 2 for failure of the tank material W2 in the case that critical temperature is exceeded due to steam excess pressure can be derived from rupture strength. Accordingly, the result is a value of 3 x (4-26). Finally, the probability that the service personnel does not heed or does not react correctly to an alarm released via the temperature measurement or the connected alarm 31A is set at m4= 10 . This figure is based on [4-33] there the failure rate is stated as one operating error per average of lO service actions. 

Checks on the adequacy and location of fire-fighting, emergency rescue and alarm equipment Practice in emergency situations Emergency procedures for Eire/explosion Toxic release Serious accidents Spillage... 

Visual alarms may be required in loeations with a high level of baekground noise. Different alarms may be provided to warn of different emergeneies, e.g. a minor fire, a toxie release or an ineident requiring eomplete evaeuation. 

Eamiliarity with die different alarms, e.g. so as not to eonfuse a proeess plant alarm for a fire/ toxie gas release signal. 

Because of the potential hazard of release of unignited hydrocarbons at ground level, a flame scanner with alarm in the control house is included for each pilot. The flame scanner must be located so that interference of ultra violet rays from the main flame or other sources do not cause false readings. Ultraviolet detectors should be mounted such that they are looking straight down through the pilots toward the ground. The installation should also provide strainers in each gas or oil line to pilots. 

Pilots and Igniters - Two gas-fired pilots with igniters are installed adjacent to the inlet distributor. The igniter assembly and pilot gas valves must be located remote from the flare for protection of personnel and equipment. This restricts igniter selection to the forced air supply type. Location of these components should be such that the calculated radiant heat density at maximum load does not exceed permissible levels for personnel exposure. Because of the potential hazard of release of unignited hydrocarbons at ground level, a flame scanner (suitably shielded and aircooled and cotmected to an alarm in the control house), is provided for each pilot. 

Employers, at a minimum, must have an emergency action plan that will facilitate the prompt evacuation of employees when there is an unwanted release of a highly hazardous chemical. This means that the employer s plan will be activated by an alarm system to alert employees when to evacuate, and that employees who are physically impaired will have the necessary support and assistance to get them to a safe zone. The intent of these requirements is to alert and move employees quickly to a safe zone. The use of process control centers or buildings as safe areas is discouraged. Recent catastrophes indicate that lives are lost in these structures because of their location and because they are not necessarily designed to withstand over-pressures from shock waves resulting from explosions in the process area. 

Since process disturbances do take place, and accidental releases are possible, even from processes closed under normal conditions, the plants where highly toxic or sensitizing substances are in use or may be generated should be provided with continuous monitoring and alarm systems in the critical areas. 

A safety trip can be incorporated in a control loop as shown in Figure 5.24a. In this system the high-temperature alarm operates a solenoid valve, releasing the air on the pneumatic activator, closing the valve on high temperature. However, the safe operation of such a system will be dependent on the reliability of the control equipment, and for potentially hazardous situations it is better practice to specify a separate trip system such as that shown in Figure 5.24b. Provision must be made for the periodic checking of the trip system to ensure that the system operates when needed. 

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