MANUAL OVERRIDE

ITCLL Fail to Control Low Level MOR Manual Override... 

Electric actuator has hand-wind for authorized manual override... 

The problem of lamps being left on when not required could be solved by provision of automatic switching, of which there are a number of systems available. These can be time switch controlled with manual override at the point of use. 

COz sensors are suitable for living rooms, offices and bedrooms, whereas for bathrooms (main parameter humidity) and kitchens (main parameter smell ) other non-specific sensors may be used. Therefore combinations of different sensors like humidity sensors, smelF-sensors (unspecific VOC-sensors) and presence sensors could be the best solution. A simple movement detector with an additional manual override (ventilation on/off for a predetermined time) could be a low-cost alternative. 

In computer systems, program logic is an important component of the critical instrument loop. Security precautions must be taken to prevent inadvertent changes in programming. In addition, manual overrides are discouraged. For example, if it is critical to shut down a pump during an emergency situation, a manual on switch may not be desirable. 

Type-3 technologies require active control to mitigate a disturbance and consequently are protective systems associated with the process flowsheet. Notice that certain control actions cannot be modeled easily without overspecifying the system such as the manual override of the quench valve by the operator. For this reason, the constraint list, as described earlier, is associated with each piece of process equipment. This allows us to associate in an a posteriori manner additional control structures that are available to the process. 

Although no nuclear plants in the United States have exploded, there have been some scary incidents. The near melt-down at Three Mile Island, near Harrisburg, Pennsylvania, involved a faulty valve. At the Salem, New Jersey, nuclear plants there have been repetitive equipment problems and personnel errors, the latter including manually overriding safety alarms 95 The Nuclear Regulatory Commission shut down all three units at the site in 1995 for re-... 

The car processor refused to acknowledge his datavise. When he switched the car to manual override, it still wouldn t function. That was when he set off to find a police officer and demand to be told just what the hell was going on. It was a few minutes short of one o clock when the curfew was officially due to start. And in any case, he was an upstanding subject of the King, he had every right to be on the street. The curfew couldn t possibly apply to him. 

A schematic of the reactor setup that was used for the FTS reactions is shown in Figure 8. It is important to obtain a cyclic flow of CO and H2 by controlling the Brooks mass flow meters. This was obtained as follows. The Brooks mass flow meters are electronically controlled with a 0-15V signal and this signal can be overridden to close the mass flow meter. This override can then either open the mass flow meter fully if +15V is provided or fully close it if -15V is provided. Thus, the mass flow meter could be periodically closed and opened to the set point, as shown in figure 9. (Information about the response time of the mass flow meter when it is opened or closed is available on the internet at httD //www.uhv.co.kr/Ddfyds-5850e-97-4.Ddf.l The response time for the mass flow meter was within two seconds with an overshoot of approximately 15%. For slow periodic operation, this system woiked well. An electronic timer with a relay function was used to provide the -15V for the manual override of the mass flow meter. 

It is important to report at this point that since a batch of pharmaceutical product in an industrial freeze dryer can easily be worth significant amounts of money, it is of paramount importance that the units of the plant and the control systems of the process should always operate under conditions at which there is insignificant loss in the quality of the product that is freeze-dried. For this purpose, the freeze dryer usually has one additional refrigeration or vacuum unit in a standby condition and furthermore the control instrumentation is designed in such a way that the control policies can be implemented either automatically by computer or by manual override. 

The design of PCE safety systems must also account for maintenance and startup needs, ease of inspection and accessibility of aU components of the PCE. Manual overrides can be provided to allow inspection or repair of PCE safety instmmented systems during normal operation. 

The explosion occurred due to the convergence of several events a dangerous material (o-nitrobenzylnitrate) developed whilst the ONBALD was left in store (the drums of ONBALD had been stored for eight months) the use of different test tubes in the thermal stability test actually invalidated the test results when the runaway did occur, the temperature set point of the automatic quench system was too high and manual override did not work. 

Automatically operated control valves and bypass valve in the recirculation line with provision for manual override. Vendor shall provide test certificates as per law for all units operating under pressure. 

The quantity to be fed to the process unit can be controlled by the recirculation of the liquid into the feeding tank. The throttle valve can be operated by automatic control with a manual override. 

Malfunctioning of ammonia and airflow control valves Chance of explosion in conveato NH3 % analyser at conveitCT inlet provision of manual override Consider additional stop valve in NH3 exit line from evaporator to converter... 

Automation of process (there shall be less reliance on human elements) Reliable instrumentation and automation shall be incorporated, with arrangement for manual override if required. 

The CLEM operator controls all machine operations from the control console in the cab mounted on the transporter trolley. The control of CLEM is semiautomatic that is, operations are performed automatically after the operator initiates a command. Interlocks to control the machine s operations have been incorporated into the design to meet safety requirements. Manual overrides are also provided to permit the operator to take control if necessary. The grapple speed and push-pull load requirements in handling fuel are controlled through all modes of operation. Indexing of the CLEM to a refueling station is accomplished by manually operated controls. 

The cask provides the shielding, inert environment, confinement, component grappling, andl.4-kW(t) cooling capability required to handle sodium-wetted, irradiated core components. Its inside diameter isabout 8 in. The dolly provides traverse drive, cask elevation, and seismic-restraint functions. The control system provides the control consoles, motor control equipment, and all interconnecting cables. Control of the transfer cask is semiautomatic that is, key operations are automatically performed after the operator initiates a command. Interlocks are incorporated to meet safety requirements. Status lights indicate the exact machine conditions during all operations and manual overrides permit the operator to complete key operations in case of a control system failure. 

All filters must occasionally be backwashed to remove accumulated solids. Most systems are set up to be backwashed at specified intervals. There must be at least a manual override that allows a filter to be backwashed when filtrate clarity is not up to standard or when the differential pressure is too high. Since this operation takes a filter out of service, the filter plant must be designed to operate at full process rate with at least one unit out of filtration service. 

The production process is usually automated such that all the feeders are synchronized with manual override. 

Provide for manual override and reset capability for automatic control fimctions utilized within the system ... 

Mechanical scenarios are mai r. They include metal presses, buzzers for dressing or planing timber, lathes and drill presses. Automatic or semi-automatic systems include contact or spot-welding machines on vehicle production lines, either controlled by an operator or fully robotic, automatic control of chemical process facihties such as oil refining (with a manual override), car cruise control and aircraft autopilots. Mechanical systems place large amounts of energy at the operator s disposal so a high-powered car and an inexperienced driver can be a fatal combination. 

At the time of writing, the authors are aware of only one commercially available device specifically designed for colonic insufflation (Fig. 5.5, Protocol colon insufflation system, E-Z-EM Inc, Westbury, NY, USA). This system electronically controls the flow rate of carbon dioxide increasing over time in a step wise fashion from 1 to 3 L/min to prevent spasm (1 L/min for the first 0.5 L, 2 L/min from 0.5 to 1.0 L, and then 3.0 L/min thereafter). The total volume of gas administered is displayed continuously and, if intracolonic pressure (measured at the rectal catheter tip) increases beyond the limit set by the user (up to a maximum of 25 mm Hg), the system automatically shuts down to prevent further insufflation and so reduces the risk of colonic perforation. In the latest version, insufflation automatically ceases when a total of 4 L of gas have been administered and then for every 2 L administered beyond this. To recommence insufflation, the operator needs to manually override this additional safety feature by pressing the start button. 

With any exhaust system, the fire department should have a manual override. This could be to actuate the system if there is a smoke buildup that hasn t tripped the system automatically or it could be to shut the system off if they deem it necessary to enhance the manual fire fighting. The smoke exhaust systems should be automatic. This allows the plant personnel to... 

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