Interlocking schemes

Figure 13.41 Three sources of supply and two bus couplers Figures 13.39-13.41 are mechanical interlocking schemes...

Electrical interlocking scheme (when the interrupters are manually operated)... 

The preferred way to achieve interlocking between more than one. source of supplies is through electrical schemes only, wherever possible. They are foolproof and can also be operated remotely. Mechanical schemes are generally for smaller installations where, as a result of smaller ratings or cost considerations, a breaker is not used and that imposes a limitation on adopting an electrical interlocking scheme. 

Figure 13.42 Electrical interlocking scheme for manually operated breakers for two sources of supplies...

Electrical interlocking scheme when the interrupters are also electrically operated... 

Figure 13.51 Control, protection and interlocking scheme for the air-conditioning plant of Figure 13,50...

The owner may have some restriction on how to start up and shut down equipment, e.g. limits on starting currents of motors, voltage dip limits at switchgear, duration of start up or shut down, purging with safe air or inert gas, interlocking schemes, manual or automatic sequences. 

Figure 1-30. Schematic illustrating Piper s interlocking scheme for linking cnticle...

Schematics Alarm trip list Interlock scheme System/component specification Operation manual Service manual Past records of failure Similar plant history...

This paper integrates interlock and design practices into the project safety management system so that design groups can implement cost effective, consistent, and safe interlocking schemes. The objective is to ensure that plants are safe and meet or exceed the safety requirements of the U.S.A-Occupational Safety and Health Administration. 

Guidance is provided in the classification of hazardous events and the implementation of interlocks relating to personnel safety, environmental protection, and significant financial loss. It gives instructions and examples and encourages the use of the most effective interlock schemes. 

The goal of the implementation phase is to provide detailed design and installation diagrams for a few extremely effective interlock schemes. The schemes are constructed with equipment selected by the methodology outlined in the integrity section. The interlock schemes are selected in the following priority order ... 

Interlocking and control scheme for a typical air-conditioning plant 13/387... 

The electrical interlocking should preferably be provided through shunt trip releases. It must have a separate a.c. or d.c. source of control supply, such that the operation of the scheme is independent of the main source of supply. For the same reason, interlocking through undervoltage (U/V) releases is not recommended as its... 

For the application of individutil schemes, as ilhistrated above and an etisy understanding of these schemes, we consider below a conventional type of air-conditioning plant for its various controls, interlocks and operating rer uirements. 

Figure 16.10 illustrates a typical scheme incorporating all these features and interlocks. 

In some applications (usually high pressure compressors using oil film seals) alternative pump schemes should be considered. It may be that the desired seal pressure is not achievable by one set of pumps or the quantity required by the seal is small relative to the main pump capacity. There are (imes when booster pumps are needed however, if the reason is energy, it would be worth reviewing the economics very carefully, because reliability tends to suffer with the booster. The booster pumps are paired into a main and standby and are configured to take suction fro lower pressure system. Sufficient interlocks have to be supplied drivers so that if the main pumps shutdown, the boosters come ... 

The above discussion has tacitly assumed that it is only molecular interactions which lead to adhesion, and these have been assumed to occur across relatively smooth interfaces between materials in intimate contact. As described in typical textbooks, however, there are a number of disparate mechanisms that may be responsible for adhesion [9-11,32]. The list includes (1) the adsorption mechanism (2) the diffusion mechanism (3) the mechanical interlocking mechanism and (4) the electrostatic mechanism. These are pictured schematically in Fig. 6 and described briefly below, because the various semi-empirical prediction schemes apply differently depending on which mechanisms are relevant in a given case. Any given real case often entails a combination of mechanisms. 

Solid tertiary amines and imines may be quantitatively alkylated by gas-solid and solid-solid techniques. Methylation of quinuclidine (176) to give the methoiodide 177 is achieved waste-free by exposure of 176 to a stoichiometric amount of methyl iodide vapor (Scheme 23). Difficulties with the disintegration of the crystals of 177 from those of 176 (reaction step 3) are overcome by ultrasound treatment from a cleaning bath at 20 °C [22]. Numerous applications of this technique to tertiary amines can be envisaged. However, solid Troeger s base (with interlocked layers, i.e., no possibility for molecular migrations) is not alkylated by methyl iodide vapor unless an excess of the vapor is applied to induce intermediate (partial) liquefying of the solid [22]. 

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