Discharge devices, types

There are two more or less exploited types of corona devices—a pin corona discharge device and a wire corona discharge device. These devices are well described by Vaezi-Nejad and Juhasz [3]. 

Figure 15.3 —Ionisation devices, a) Continuous current arc (globular technique). The electrodes are inserted in a series circuit having a variable resistor, a cell and a continuous power source of a few tens of volts b) Glow discharge device using argon (hollow cathode lamp type). Samples can be introduced as powders or non-conductive pellets.

When considering the application of foam to hazardous material spills, key requirements include an adequate water supply, the foam concentrate, appropriate proportioning equipment, piping, foam makers, and discharge devices and protective equipment for the personnel involved. Activation may be automatic, but in most cases it is manual. There are four types of application systems. They include fixed, semifixed, mobile, and portable (NFPA 11, 1988). 

This paper attempts to provide a perspective showing the interrelationships existing among a few types of discharge devices of interest in... 

Depending on the chemical system of interest and the ultimate objective of the study or process, there will probably be one mode of discharge and one type of discharge device that will be best suited. Thus, advanced consideration of both the differences and similarities of various discharge modes and devices can prove extremely valuable. 

A combiuatiou of water discharge devices (sprinklers), distribution piping to supply water to the discharge devices or more sources of water under pressure, water flow controlling devices (valves), and actuating devices (temperature, rate of rise, smoke, or other type device). The system automatically delivers and discharges water in the fire area. 

Portable extinguishers should be manufactured to BS 5423 1987 which also specifies the tests necessary to determine the rating of the extinguisher for both A and B class of fires. The size and number of extinguishers provided for any application is determined by an assessment of the size of fire that may need to be tackled. A requirement of this standard is the inclusion of controllable discharge devices. However many of the older single discharge type are still in service and these will remain acceptable until the end of their effective life. 

On the other hand, the system illustrated in Fig.42 is much simpler, involving merely a weighing unit and a controlled feeder completely separate from it. Any of the familiar types of bin or hopper discharge devices can be used in conjunction with this equipment. 

In practice, there are five essentially different types of discharge devices [9]. These are by no means alternatives, for each application, there is but one optimum method of filter-cake discharge. 

An outstanding advantage of common differential pressure meters is the existence of extensive tables of discharge coefficients ia terms of beta ratio and Reynolds numbers (1,4). These tables, based on historic data, are generally regarded as accurate to within 1—5% depending on the meter type, the beta ratio, the Reynolds number, and the care taken ia manufacture. Improved accuracy can be obtained by miming an actual flow caUbration on the device. 

Other types of mechanical agitation consist of vibrating screens or expanded metal panels. However, if the device fails to perform for any reason, discharging material from the bin will be much more difficult than if the device were not present. 

Cylindrical alkaline cells are made in only a few standard si2es and have only one important chemistry. In contrast, miniature alkaline cells are made in a large number of different si2es, using many different chemical systems. Whereas the cylindrical alkaline batteries are multipurpose batteries, used for a wide variety of devices under a variety of discharge conditions, miniature alkaline batteries are highly speciali2ed, with the cathode material, separator type, and electrolyte all chosen to match the particular appHcation. 

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