Interlock, interlocking circuit

Vanadium raw materials are processed to produce vanadium chemicals, eg, the pentoxide and ammonium metavanadate (AMV) primary compounds, by salt roasting or acid leaching. Interlocking circuits, in which unfinished or scavenged material from one process is diverted to the other, are sometimes used. Such interlocking to enhance vanadium recovery and product grade became more feasible in the late 1950s with the advent of solvent extraction. 

The compressors are automatically started and stopped as the load varies. When the total flow can be handled by a single compressor or when any of the surge valves open, FSL-03 triggers the shutdown logic interlock circuit 1 after a time delay. Automatic starting of an additional compressor is also initiated by interlock 1 when PSH-04 signals that one of the compressors has reached full speed. The ratio flow controllers (FFIC-01 and... 

Safety and protective earth (PE) AC or DC power circuits AC control circuits DC control circuits Interlock circuits (external source)... 

Earlier models for the machine used interlock circuits to ensure the safety of the system. In this model, a computer and software controlled the process, including a check to prevent possible harm. The machine had two modes. An electron mode irradiated the patient directly. An X-ray mode involved much higher electron intensity to generate the desired rate of X-rays. The software was the only check to make sure the latter mode was correctly in place. ... 

FIGURE 10.177 A dual utility feeder system with interlocked circuit breakers. 

There has not been much guidance available on the eompetencies required for working in this area. This was a deficiency that needed to be remedied as the progressive introduction of programmable elements into systems that performed safety functions, such as PLCs used in machinery interlocking circuits, resulted in the systems becoming more complex, and increasingly difficult to assure for safety. 

Relay K3 may next be energized in the startup sequence, provided upper limit switches on all three safety rods are closed. A manually operated key switch completes the interlock circuit for Relay K3, allowing the dump valve to be closed by operation of the control switch. The "dump valve" key switch is bypassed by a contact of Relay K3 and may then be removed. 

After the dump valve is closed, with the toggle switch on the front console at the "Pump On" position, water may be pumped into the reactor vessel by operating the control switch, provided limit switches indicate full insertion of the control rods and the water level is below a "High Level Float Interlock" in the reactor vessel. A high-multiplication trip in the source interlock circuit, which de-energizes the safety rod clutches, insures that kgx in the reactor is below a preset value. 

Before and during the operation of the reactor, a safety interlock circuit must be satisfied to remove the reactor from a scram condition. The interlock circuit is a simple continuity circuit containing a number of switches and devices which assure that certain safety components of the system are in working order. The block diagram of Fig. 2.17 describes the interlock circuit. 

If the interlock circuit opens, relay K-5 opens and a negative voltage is placed on the grid of the scram tube, cutting the tube off and hence scramming the reactor. 

The low-temperature switch, which has been calibrated to open at 16 C, is a simple bimetal thermal switch. As the temperature of the switch reaches this low level, the bimetal strip which makes up one side of the switch bends, breaking the interlock circuit. The bending action takes place because the two metals used in the strip have different linear coefficients of expansion. 

To insure that no instrument can be made inoperative during the operation of the reactor by holding its reset button down, all reset buttons are included in the interlock circuit. Pushing one of these buttons physically breaks the continuity interlock circuit and causes a scram condition to exist. In addition, all cable connectors to the control and safety rods have two pins, which have been wired into the interlock circuit. Any connector which is not connected properly will therefore open the interlock circuit. If any of these circuits are interrupted, the "interlock open" light on the scram chassis panel will be lighted. 

Manual rheostats can be used in series with the motor armature for the current-limiting func tion. If the rheostat has ample thermal capacity, it can also Be usedto vaiy speed. If this system is used, interlocks should be included to prevent closing of the contactor unless maximum resistance is in the circuit. 

Test This is the position of the trolley when the power contacts are isolated but the control circuit is still connected, because it is tapped directly from Ihe auxiliary bus. This condition is essential to facilitate testing of control circuits with functional interlocks, without energizing the connected lotid. Isolation This is the position of the trolley when the power and the control circuits are both isolated. Depending upon the site requirements, sometimes the control circuit may be required to be still energized for some test requirements. 

To ensure correct cooling conditions, the water flow and/or the temperature difference between water outlet and water inlet shall be monitored continuously, acting on an electrical interlock with the motor s power supply, e.g. by intrinsically safe electric circuits. 

In Fig. 6.108(a) the door is mechanically interlocked with the isolating switch (the door cannot be opened in the ON position of the isolating switch, the switch cannot be set to the ON position when the door remains open). The contactor or power circuit breaker is mounted on a slip-in module. Two earthing... 

Primary selective circuit arrangements utilize two primary selectable feeders for each transformer. These feeders are either connected to the line side of two interlocked primary non-fused disconnect switches that have a common load side fuse or to the line side of two interlocked primary fused disconnect switches. The latter configuration is shown in Fig. 2. Only one primary disconnect switch can be closed at any time. 

Sometimes several control modes, e.g. gap control and screw feeder control by main motor amperage, are combined and/or integrated into the overall control circuit of an entire plant. In such cases, proper introduction of interlocks is also an important consideration. For quality control, modern plants often use PLC controllers with extensive data logging capabilities which include momentary information and trending. 

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