Switches interlock

Figure 26.8 Direct manual switch interlock. (Detail design is crucial to ensure an effective arrangement.) (Courtesy Engineering)...

In addition to overcurrent devices, certain switching devices can reduce or eliminate electrical hazards. These include interlocks, lockouts, and thermal or overspeed switches. Interlocks are switches that prevent access to an energized or dangerous location. Often attached to access doors, panels, and gates, interlocks act to shut off power to the equipment whenever these devices are opened. Probably the most commonly used and most familiar interlock... 

Coker drum safety switch interlocks and controls are important. A few issues related these systems shall include but not be limited to the following ... 

Key switch positions. Mode switch interlocks for pulse, square wave, and manual and automatic operation. 

The entire x-ray exposure cabinet including it s extension into the lower electrical cabinet is shielded with a minimum of one-inch of steel clad, lead plate with fiilly welded (fused lead) joints. The safety interlock switch on the cam-lock inter-face ... 

Install high-high level switch in receiving vessel interlocked to feed and/or emergency dump... 

This lest is conducted to establish the satisfactory functioning of mechanical parts, such as switching devices and their interlocks, shutter assembly, draw-out mechanisms and interchangeability between identical draw-out modules, A brief procedure to test these features is as follows. 

The interlocks should be set in the intended position to prevent operation of the switching device and insertion or withdrawal of the removable parts. Fifty attempts must be made to operate the switching device and removable parts inserted and withdrawn 25 times each. 

An interlock is provided through a centrifugal type of pressure switch (PS) to trip the engine in the case of low lube (lubricating) oil pressure during a run. Since during a. start oil pre.s.sure has not built up, a timer, 7 j is introduced to bypass the trip interlock and avoid a false trip. A relay (contactor), d], is used to provide lube oil pressure interlock. 

Active—Using controls, safety interlocks, and emergency shutdown systems to detect and correct process deviations e.g., a pump that is shut off by a high level switch in the downstream tank when the tank is 90% full. These systems are commonly referred to as engineering controls. 

RECEPTACLE CONSTRUCTED WITH AN INTERLOCKED. SWITCH. ROTATING THE PLUG AFTER INSERTION ACTUATES THIS SWITCH. 

It is very important that the inert gas be available from a reliable source and that the proper pressure and flow rate are always provided. A low-pressure switch and alarm are sometimes installed in the inert gas supply line to the equipment and piping. The alarm will warn the operator that a problem may be occurring with the inert gas supply. The switch is also sometimes interlocked to open up a valve in piping from a backup inert gas cylinder bank. 

If the products of combustion can be diluted so that the carbon dioxide content is not greater than 1 per cent it is permissible to discharge them at ground level. This is the principle of the system shown in Figure 19.7, in which fresh air is drawn in to dilute the flue products which are discharged preferably on the same wall as the inlet to balance against wind effects. It is essential to interlock the airflow switch with the burner controls. 

All interlocks checked for correct setting and operation. These will include thermostats, pressurestats, limit switches, pressure switches, process interlocks, etc. ... 

Until all the switches in the interlock train are satisfied and closed, the compressor will not start or will not continue to mn. 

Currently the main interest in template reactions lies in their key role in the controlled synthesis or the self-assembly of a variety of supramole-cular entities (449). One needs a combination of intuition, conjecture, and serendipity (450) a recent example of successfully combining serendipity and rational design is provided by the silver(I)-promoted assembly of one-dimensional stranded chains (451). One also needs an understanding of mechanism in order to optimize the selection and design of building blocks and templates for the generation of yet more sophisticated supramolecular structures references cited in this present review contain at least some kinetic or mechanistic information or speculation. Template routes to interlocked molecular structures have been reviewed (452), while a discussion of switching by transition metal contains a little about the kinetics and mechanisms of this aspect of template... 

In addition to the basic control loops, all processes have instrumentation that (1) sounds alarms to alert the operator to any abnormal or unsafe condition, and (2) shuts down the process if unsafe conditions are detected or equipment fails. For example, if a compressor motor overloads and the electrical control system on the motor shuts down the motor, the rest of the process will usually have to be shut down immediately. This type of instrumentation is called an interlock. It either shuts a control valve completely or drives the control valve wide open. Other examples of conditions that can interlock a process down include failure of a feed or reflux pump, detection of high pressure or temperature in a vessel, and indication of high or low liquid level in a tank or column base. Interlocks are usually achieved by pressure, mechanical, or electrical switches. They can be included in the computer software in a computer control system, but they are usually hard-wired for reliability and redundancy. 

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