Liquid Level Indicators

At the time of the solvent methanol experiments a metering pump was used. In some experiments the pulsating action of the pump can be disturbing, so a high-pressure syringe-type pump can be used. Since mass flow controllers are available now, the combination of a gas-pressurized feed tank on an electronic scale for liquid level indication and a mass flow controller seems to be a good choice. Both the feed tank and separator can be heated or cooled. In the case of the solvent methanol experiments. 

Figure 6.4 Split liquid-level indication caused by foam.

The receiver tank s liquid level indicator will not be in service during the transfer. A separate, high-liquid level switch is interlocked to stop the transfer when the tank is full. The quantity transferred can be monitored from the distribution system, but it will not be specified. 

As shown in the figure, float gaging is implemented using a float that rests on the surface of the liquid inside the float chamber. As water or wastewater enters the tank, the liquid level rises increasing the head. The increase in head causes the liquid to flow to the float chamber through the connecting pipe. The liquid level in the chamber then rises. This rise is sensed by the float which communicates with the liquid-level indicator. The indicator can be calibrated to read the liquid level in the tank directly. 

In the pressure-cell measuring arrangement, a sensitive diaphragm is installed at the bottom of the tank. As the liquid enters the tank, the increase in head pushes against the diaphragm. The pressure is then communicated to the liquid-level indicator, which can be calibrated to read directly in terms of the level in the tank. 

The liquid level in the 300,000-gal tanks that contain highly radioactive waste is continuously monitored. A level indicator in each tank is set to alarm when the volume reaches 285,000 gal. This alarm sounds in both the control house and the main process building. A second leak detection system is a liquid-level indicator in the sump of the vault surrounding the tanks. 

Different feedstocks and/or solvents require different solvent to feed ratios. Each packing has a specific flooding point These two effects can lead to a great difference in mass flow. Because of this, pressures and temperatures should be controlled automatically. The flow must be measured exactly, preferably with a mass flow meter, but automatic flow control is not suitable for a multi-purpose plant The valves which are used for pressure and temperature control should be installed so that they can be replaced easily or adapted to new conditions. A very important requirement for the continuous operation of the plant is liquid level indication and control in the extractor and regenerator. Therefore the plant is equipped with capacitive level sensors which are part of a control circuit. The suitability of these sensors for measuring the level of oily products, vitamins and some type of hydrocarbons in supercritical systems have been tested in the lab previously. 

Figure 3 shows the disassembled cryostat its cover, the fittings with which it is installed in the test machine, and the specially constructed dynamic load cell. Not shown is the liquid-level indicator probe, which is of the carbon-resistor type. 

Instruments used on steam boilers included pressure and flow indicators and controllers, carbon dioxide recorders, speed controls for mechanical stokers and liquid level indicators and controllers. As chemical manufacturers began to abandon batch processing in favour of continuous processing plants and also paid greater attention to fuel efficiency the possible uses of the type of instruments employed in steam raising plant must have become apparent. ... 

Plasticizer level indicators are essential to protect storage tanks from overflows. Differential pressure gauges and floating type indicators are used for the measurement of tank levels. It is possible to calibrate level gauges in volumetric units or to indicate depth of liquid. Level indicators can also have transmitters and these may be related to high level... 

Fig. 15.10 Whirlpool tanks of various designs, (a) With conical base (b) Combined copper and whirlpool tank (c) Whirlpool separator with inclined base. 1. Vent stack 2. Spray-water inlet 3. Spray ring with nozzles 4. Tangential wort inlet 5. Liquid level indicator 6. Manhole 7. Water shield ring for concrete base 8. Concrete base 9. Three-way valve for discharge of wort and sludge. (Courtesy of A. Ziemann, GmbH.)...

This paper presents a quantitative description of a floating insulation for the surfaces of cryogenic fluids stored in open-topped dewar flasks. The technique makes use of polystyrene beads, which provide good thermal insulation, conform to a complex surface geometry—such as partially immersed equipment—and act as a good electrical insulator as well. Since the beads float on the liquid surface, they need not be removed when refilling the container and provide an easily visible liquid level indication. 

Carbon Resistors and Variable Differential Transformers for Liquid Level Indication (1) 158... 

Refrigeration Below 100 C (5) 518 LIQUID LEVEL INDICATORS A Sensitive Electronic Liquid Level Indicator for Condensed Gases (1) 154 Carbon Resistors and Variable Differential Transformers for Liquid Level Indication... 

To find the true liquid level in the tower, one can determine the vapor-liquid interface by touch. The vapor inlet will be 20°F to 40°F cooler than the bottoms liquid. This temperature gradient level will correspond to the true liquid level in the tower. A properly designed external liquid level indicator is shown in Figure 4-4. 

In cargo tanks and portable tanks from 38 percent (tanks of 1200-gal or 4542-L capacity or less) for 0.473-0.480 specific gravity, to 60 percent (tanks of over 1200-gal or 4542-L capacity) for 0.627 and over specific gravity (except when using fixed-length dip tube or other fixed maximum liquid level indicators). 

Entry 3.6 again demonstrates how human error can lead to a catastrophic accident Of course, the best solution is to design the hazard out. In this case, you cannot take away the potential but have added numerous levels of redundant fail-safe mechanisms to prevent the mishap from occurring. Note that the ready tank already has a liquid-level indicator, but if it is only tied back to an alarm, it does not guarantee that the hazard will be prevented. It only means that the operator will be warned. The overfill hazard is too significant to be left to an alarm indication alone. 

At 0215, operators had started to introduce raffinate into the raffinate Splitter Tower, which is used to distil and separate gasoline components. (The word raffinate means a product in the refining process. In this case the raffinate was naphtha -raw gasoline - from the crude distillation column.) The tower was more than 30 m tall. A single instrument (shown as LT) was available for liquid level indication at the bottom of tower which had a maximum indicated level 9 feet (about 3 m). Above this level the instrument just indicated 9 feet . However, operators routinely filled above this level during start-ups to avoid the possibility of low level causing furnace damage. 

The bottom liquid level indicator on the panel indicated a less than full level, even when the bottoms level was above the top level tap. 

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