Relay devices

Therefore, the dispenser control panel should be equipped with a timer-relay device to insure that all admixture has been discharged from the conveying hoses or pipes. If the admixture dispenser system is operated manually, the plant operator should be furnished a valve with a detente discharge side to prolong the discharge cycle until it is ascertained that all admixture is in the concrete batch. 

IEC60364 Part 4, section 433, applies to cables and consumer equipment that are protected against overloading current by a fuse or relay device at the source of supply. This requirement should not be confused with protection against short-circuit currents that are disconnected in a short period of time. Overloading currents tend to cause the protective device to disconnect the circuit only after a long period of time has passed e.g. tens of minutes, one hour. The standard defines three particular currents, / , Ig and h as follows. 

Table 16.1. Relay devices and switchgear mechanism delay times...

The Relay device was one of the few devices that was designed specifically for the unique needs of the thoracic aorta. However, based on their... 

Rayleigh instability see axisymmetric varicose instability rayon, 4,6,18,20 recombinant silk fibres, 315-6 Recothrom, 581 relative density, 197 Relay devices, 661-2 resorbable biotextile, 94 resorbable polymers medical applications, 91-109 elastomeric properties of fibreforming copolymers, 97-101 elastomeric resorbable polymers, 101-8... 

Then the factory ladies would get down to business, individually assembling an intricate telephone relay device that consisted of some 40 separate parts. This was a thankless, monotonous task, time-tied to the usual strict production targets. 

Sihcone contamination has been impHcated as a cause of failure in telephone switching systems and other devices that contain relay switch contacts (507). Analysis of airborne particulates near telephone switching stations showed the presence of siUcones at these locations. Where the indoor use of sihcones is intentionally minimised, outdoor levels were found to be higher than inside concentrations (508). Samples of particulates taken at two New Jersey office buildings revealed sihcone levels that were considerably higher indoors than outdoors. In these cases, indoor sihcone aerosols are beheved to be generated primarily by photocopiers, which use sihcone fuser oils. 

Sonic Methods A fixed-point level detector based on sonic-propagation characteristics is available for detection of a liquid-vapor interface. This device uses a piezoelectric transmitter and receiver, separated by a short gap. When the gap is filled with liquid, ultrasonic energy is transmitted across the gap, and the receiver actuates a relay. With a vapor filling the gap, the transmission of ultrasonic energy is insufficient to actuate the receiver. 

The resulting motion of the beam is detected by the pneumatic nozzle amphfier, which, by proper sizing of the nozzle and fixed orifice diameters, causes the pressure internal to the nozzle to rise and fall with vertical beam motion. The internal nozzle pressure is routed to the pneumatic relay. The relay, which is constructed like the booster relay described in the Valve Control Devices subsection, has a direct hnear input-to-output pressure characteristic. The output of the relay is the controller s output and is piped away to the final control element. 

Limit Switches and Stem-Position Transmitters Travel-limit switches, position switches, and valve-position transmitters are devices that, when mounted on the valve, actuator, damper, louver, or other throtthng element, detect the component s relative position. The switches are used to operate alarms, signal hghts, relays, solenoid valves, or discrete inputs into the control system. The valve-position transmitter generates a 4-20-mA output that is proportional to the position of the valve. 

Programmable Logic Controller (PLC) A microcomputer-based solid-state control system which receives inputs from user-supplied control devices such as switches and sensors, implements them in a precise pattern determined by instructions stored in the PLC memory, and provides outputs for control or user-supplied devices such as relays and motor starters. 

Thiese can be drawn tor temperature versus time or current versus time as desired, depending upon the calibration of the device, such as a motor protection relay. Below we provide a brief procedure to draw these curves. 

Any of the above reasons tnay result in noise and an increase in temperature and must be corrected. Critical installations such as a refinery, a petrochemical plant, a chemical plant or a petroleum pipeline may require special precautions and control to avert any excessive heating of the bearings, which may become fire hazards. For these installations, bearing temperature detectors with a relay and alarm facility may also be installed in the control circuit of the switching device to give warning or trip the motor if the temperature of the bearing exceeds the preset safe value. 

In all these conditions protection against 2, 3, 4 and 5 is generally applicable to large LT motors, say 100 h.p. and above, and all HT motors. This protection is normally provided by a single-device motor protection relay, discussed in Section 12.5. 

Coordination of fuses with an overcurrent relay or any other overcurrcnt protective device The selection of the fuses should be such that ... 

They do not operate against overloads as these are taken eare of by the overcurrent relay or any other overcurrent protective device. 

The follow ing are the normal protections that may be available in both-a solid-state ora microprocessor-based relay, making them a single-device protection ... 

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