Startup controls

Counter Measures acceptance and startup controls Maintainability Improvement... 

Accumulators can be used to help stabilize the lube system against pressure transients such as that from the turbine power operator during a large correction. For a sizing rule of thumb, the system pressure should not vary by more than 10%, while the turbine servo travels full stroke in a one second interval. The role of accumulators for pump switching was covered earlier in the section on Startup Control. 

Keywords divided wall distillation column, dynamic modeling, optimal startup control... 

In order to promote the generalisation of DWC in industrial application it is necessary to provide reliable design methodologies, but it is also very important to define strategies for a convenient startup of the column. The present paper proposes a new dynamic model for a DWC and applies it to formulate the startup control. 

Failures in the ex-vessel neutron detectors can result in erroneous signals. However, sufficient redundancy in neutron detectors exists so that loss of a detector does not result in unsafe operation or necessitate immediate plant shutdown. The startup control and power range fltix control both utilize several signals based on the input from several neutron detectors. Comparators between redundant channels automatically disconnect suspect inputs from the average signal and alert the operator. 

Reactivity Insertion (incl ATWS) PROTECTION LEVEL Strong negative temperature coefficient, avoiding a high heatup of fuel (L) Provision of two diverse neutron control systems, control rods and shutdown pellets (R) Provision of startup control rods m addition to operatmg control rods (L)... 

Reactivity control Operating control rods Diverse reserve shut down system Negative temperature coefFicient Startup control rods Active/Passive Active/Passive Passive Active(Passive Automatic activation, gravity drop Automatic activation, gravity drop Automatic activation, gravity drop... 

Startup control rods(12) Control rod penetration (above)... 

The Model 412 PWR uses several control mechanisms. The first is the control cluster, consisting of a set of 25 hafnium metal rods coimected by a spider and inserted in the vacant spaces of 53 of the fuel assembhes (see Fig. 6). The clusters can be moved up and down, or released to shut down the reactor quickly. The rods are also used to (/) provide positive reactivity for the startup of the reactor from cold conditions, (2) make adjustments in power that fit the load demand on the system, (J) help shape the core power distribution to assure favorable fuel consumption and avoid hot spots on fuel cladding, and (4) compensate for the production and consumption of the strongly neutron-absorbing fission product xenon-135. Other PWRs use an alloy of cadmium, indium, and silver, all strong neutron absorbers, as control material. 

Most sulfonation plants monitor and control operations by computer. Sulfur-buming catalytic SO -generating equipment may require a 1—2 h stabilization period on startup. The unit can be kept in a standby position by maintaining heat to the unit when it is off-line. Liquid SO -based sulfonation plants do not require such a stabilization period and hence are more flexible to operate than sulfur-buming sulfonation plants. 

Besides being slower, anaerobic treatment is more difficult to manage and can generate by-products that are more mobile or toxic than the original compound, for example, the daughter products of TCE, ie, dichloroethenes and vinyl chloride. It requires a longer acclimation period which means slower startup times in the field. The microbial processes are less well understood, and hence, ate less controlled than for aerobic systems. 

M. Ramanathan and W. E. Vedey, Evaluation, Design and Startup of an Innovative and Cost-effective Wastewater Treatment Plant at Concord, New Hampshire, paper presented at the 36th Annual Meeting, Virginia Water Pollution Control Association, Inc., Charlottesville, Va., 1982. 

The controller action can be disabled by triggering a binary deactivate input signal, during process startup, shutdown, or when some abnormal conditions exist. 

For control purposes it is advisable to estimate startup cost and time beforehand and then try to stay within the estimates. Tne general parameters which can be used to estimate startup cost Csu, which are usually between 2 and 20 percent of the batteiy-limit fixed-capital cost, are as follows ... 

Other advantages of gravity beds include flexibility in gas and sohds flow rates and capacities, variable retention times from minutes to several hours, space economy, ease of startup and shutdown, the potentially large number of contacting stages, and ease of control by using the inlet- and exit-gas temperatures. 

J-2 2-K Award control-device contract. Vendor prepares assembly drawings. 4-5 Startup, shakedown, source test. 

Some toll processes lend themselves to test runs in the pre-startup phase. Actual materials for the toll may be used in the test or substitute materials, typically with low hazard potential, are often used to simulate the charging, reaction, and physical changes to be accomplished in the toll. Flow control, temperature control, pressure control, mixing and transferring efficiency can be measured. Mechanical integrity can be verified in regard to pumps, seals, vessels, heat exchangers, and safety devices. 

Safety systems are typically divided into emergency trip/shutdown functions, controlled (slow) shutdown, alarm activation, or startup annunciation of auxiliary equipment such as oil pumps. 

Figure 4-70 shows a four-body TPG train (string). As before, the expander supplies power to the generator. The steam turbine supplies power to the generator, provides startup power, and provides control for synchronization. The generator provides electricity, and the gear is used to allow the expander and steam turbine to operate at near optimum efficiency with the generator at its desired speed. 

Setting control and monitoring parameters at the factory to streamline installation and startup. 

Synchronization Control. During startup, partial load is applied to the eddy current brake. The expander is then throttled to a speed below synchronous speed, and the brake voltage controller varied to lower the voltage of the coil, causing a small speed... 

A typical lubrication oil system is shown in Figure 15-1. Oil is stored in a reservoir to feed the pumps and is then cooled, filtered, distributed to the end users, and returned to the reservoir. The reservoir can be heated for startup purposes and is provided with local temperature indication, a high-tempera-ture alarm and high/low level alarm in the control room, a sight glass, and a controlled dry nitrogen purge blanket to minimize moisture intake. 

The gas turbine control systems are fully automated, and ensure the save and proper startup of the gas turbine. The gas turbine control system is complex and has a number of safety interlocks to ensure the safe startup of the turbine. 

Startup description. When the unit is prepared to start, the Ready to Start lamp will be lit. With local control, operating one of the following push buttons will initiate a start ... 

Column Bottom Temperature. The bottom temperature is often controlled on the reboiler outlet line with a control valve in the heating medium line. The control point can also be on a bottom section tray. Care must be exercised in location of the temperature control point. It is recommended, especially for large columns, that a cascade arrangement be used. The recommended scheme has a complete flow recorder/controller (FRC) in the heating medium line including orifice and control valve. The set point of this FRC is manipulated by the temperature recorder/controller (TRC). This eliminates the TRC from manipulating the control valve directly (recall that temperature is the most difficult parameter to control). This makes for smoother control for normal operations. Also, it is handy for startup to be able to uncouple the TRC and run the reboiler on FRC for a period. 

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