Volume control tank

Place equal volumes of solution, e.g. 50 cm of 0.10 mol dm ethanoic acid and methanol in flasks in a thermostatically controlled tank at 60 °C. 

Under normal operation, the chemical and volume control system is coimected to reactor coolant system cold leg No.l, and returns to the steam generator outlet chamber. The chemical and volume control system is made up of two sub-systems a chemical control subsystem, located inside containment, which consists of regenerative and letdown heat exchangers, mixed bed demineralisers and filters and a makeup subsystem, located largely outside containment and consisting of makeup pumps, mini flow heat exchangers and chemical dosing tanks. Containment isolation valves are provided on both sides of the containment penetrations. 

The chemical and volume control system is also isolable from the reactor coolant system in the event of a boron dilution accident. In this case, the redundant valves are closed, tripping the make-up pumps, and/or aligning the suction of the makeup pumps to the boric acid tank (see Section 9.3.6.4.5.1 of Reference 6.1). 

Isolation valves in the chemical and volume control system make-up pump suction line from the demineralised water tank. 

The remaining functions of the APIOOO chemical and volume control system consist of reactor coolant filling, make-up, let down and chemical control of the reactor coolant. The chemical and volume control system consists of regenerative and letdown heat exchangers, demineralisers and filters, make-up pumps, tanks, and associated valves, piping, and instrumentation. 

Adding another lag anywhere in the loop will change the previous level process to two-capacity, as shovm in Fig. 1.20. A chamber is attached to the tank although we wish to control tank level, chamber level is measured, which lags behind tank level. The time constant of the chamber is its volume divided by the maximum rate at which hquid can enter. This time constant will be designated n. Control of a two-capacity process is easiest to illustrate if one of the capacities is non-self-regulating. 

Trip Valves The trip valve is part of a system that is used where a specific valve action (i.e., fail up, Fail down, or lock in last position) is required when pneumatic supply pressure to the control valve falls befow a preset level. Trip systems are used primarily on springless piston ac tuators requiring fail-open or fail-closed acrion. An air storage or Volume tank and a check v ve are used with the trip valve to provide power to stroke the valve when supply pressure is lost. Trip valves are designed with hysteresis around the trip point to avoid instabihty when the trip pressure and the reset pressure settings are too close to the same value. 

An anaerobic digester is a no-recycle complete mix reactor. Thus, its performance is independent of organic loading but is controlled by hydraulic retention time (HRT). Based on kinetic theoiy and values of the pseudo constants for methane bac teria, a minimum HRT of 3 to 4 days is required. To provide a safety factor and compensate for load variation as indicated earlier, HRT is kept in the range 10 to 30 days. Thickening of feed sludge is used to reduce the tank volume required... 

Tanks that are enamelled or that have other high-resistance coatings with volumes below 4 m do not require automatic exhausts if they are equipped with galvanic anodes in which the surface area does not exceed 5 dm per square meter of surface to be protected, or with controlled impressed current anodes with a low current output of 150 mA. 

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