Pressure water level switches

The use of pressure sensors for water level switches, or in a more sophisticated form also for foam content surveillance in washing machines and dryers. 

The RO product water tank system shown in Figure 4.9 has a capacity of 76 m. The tank is3.7mD X 7.3m SSH FRP, flat-bottom, dome-top with 50 cm man-ways in the top dome and the side shell. It is provided with side-mounted level switches and a level transmitter, a pressure rehef valve/vacuum breaker, a nitrogen blanketing system, and a HEPA filter. 

The switching operations required for these safety functions are carried out by passive and diverse means without electric power, actuating fluids or I C signals as follows. The RPV is connected via a non-isolatable line to a heat exchanger which acts as a passive pressure pulse transmitter. When the water level in the RPV is normal, the tubes inside the heat exchanger are filled with water and do not transfer any heat. If the water level in the RPV starts to drop, the water drains from the heat exchanger tubes and is replaced by steam that is continuously condensed. The heat transferred during this process causes a buildup of pressure on the shell side... 

The fittings required for an air-loaded accumulator include a hand-operated shutoff valve arranged directly on the pressure-water connection, hand-operated stop valves for the air bottles, a safety device which stops the pump motor when a given pressure is exceeded, as well as a control panel with relays and appertaining pushbutton switches for the solenoids, a circuit breaker, a transformer, the indicator lamps for water level and electric current. 

The partially inserted rods were all (with one exception) on the east side of the core where reactor power level was indicated to be 2% or less. The west side of the core was subcritical. A second manual scram was initiated 6 minutes later and all partially inserted rods were observed to drive inward, but 59 remained partially withdrawn. A third manual scram was initiated 2 minutes later, and 47 rods remained partially withdrawn. Six minutes later, an automatic scram occurred and all the rods inserted fully when the scram discharge level bypass switch was returned from "bypass" to "normal" and there was a high water level in the scram discharge instrument volume. It appears that this was a coincidence in that a manual scram would probably have produced the same result. Core coolant flow, temperature, and pressure remained normal for the existing plant conditions. 

More formal inspections also verily the operation of safety and other controls such as low water and fuel cutoffs, level controls, fusible plugs, pressure gauges, water glasses, gage cocks, stop valves, safety/relief valves, and BD valves and lines. Also, FW pumps, flue and damper arrangements, combustion safeguards, name plate specifications, set pressures, boiler connections, floats, mercury switches, bellows, and other components may be inspected. 

In the last few years, a third type of microfiltration operating system called semi-dead-end filtration has emerged. In these systems, the membrane unit is operated as a dead-end filter until the pressure required to maintain a useful flow across the filter reaches its maximum level. At this point, the filter is operated in cross-flow mode, while concurrently backflushing with air or permeate solution. After a short period of backflushing in cross-flow mode to remove material deposited on the membrane, the system is switched back to dead-end operation. This procedure is particularly applicable in microfiltration units used as final bacterial and virus filters for municipal water treatment plants. The feed water has a very low loading of material to be removed, so in-line operation can be used for a prolonged time before backflushing and cross-flow to remove the deposited solids is needed. 

Should a fail-safe device be used, of the type that switches off the power when the cooling water ceases to flow, then the water pressure in that device can be varied by raising or lowering the level of the indicator. 

A small community in the Midwestern US wants to fluoridate their potable water system. The community has a population of approximately 1700 and serves a large rural school with an equivalent school population of 2667. The community has two wells that are located 2 miles apart and are automatically controlled with pressure switches. Each well has a well house that contains bleach, polyphosphate, and soda ash storage and feed systems. Average daily production from both weUs is 0.210 MGD. The water has natural fluoride level of 0.13 mg/L. The optimal fluoride level for this community system is 0.8 mg/L. Determine (a) the feed rate and annual amount of sodium fluoride and (b) the feed rate and annual amount of fluorosiUcic acid solution, (c) Provide the advantages and disadvantage of each chemical feed system. 

Basically the system is fed electrolyte or distilled water from a reservoir via a pump that can be manually and level sensor activated. The reservoir will supply water or electrolyte to the electrolyzer and a pressure tank with a sight glass. The sight glass on the pressure tank shows the fill level in the pressure tank and the electrolyzer, and when a predetermined level is reached, the pump is switched off, either manually or automatically with sensor switches. When the electrolyte reaches the fill level, the power to the electrolyzer is switched on manually or automatically, and the electrolyzer begins to disassociate hydrogen from oxygen in the electrolyte. 

In filter tanks, a pipe (at least DN15) with a test valve must be placed beneath the exhausters leading to the floor level through which water must be taken to the open air every day until the water is free from gas bubbles (see Fig. 20-4b). The partly filled cathodically protected pressure booster tank cannot be provided with automatic gas exhausters. Therefore, nozzles (at least DN15) with manually operated valves must be provided at the highest point of the tank. Before emptying, the protection system must be switched off and the tank filled with water through the manual valve. 

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