ch_client = “kb123″; ch_width = 300; ch_height = 250; ch_type = “mpu”; ch_sid = “Chitika Default”; ch_backfill = 1; ch_color_site_link = “#0000CC”; ch_color_title = “#0000CC”; ch_color_border = “#FFFFFF”; ch_color_text = “#000000″; ch_color_bg = “#FFFFFF”; Gauge Glass A very simple means by which liquid level is measured in a vessel is by the gauge glass method [...]
Ball Float The ball float method is a direct reading liquid level mechanism. The most practical design for the float is a hollow metal ball or sphere. However, there are no restrictions to the size, shape, or material used. The design consists of a ball float attached to a rod, which in turn is connected [...]
Chain Float This type of float gauge has a float ranging in size up to 12 inches in diameter and is used where small level limitations imposed by ball floats must be exceeded. The range of level measured will be limited only by the size of the vessel. The operation of the chain float is [...]
Magnetic Bond Method The magnetic bond method was developed to overcome the problems of cages and stuffing boxes. The magnetic bond mechanism consists of a magnetic float which rises and falls with changes in level. The float travels outside of a non-magnetic tube which houses an inner magnet connected to a level indicator. When the [...]
Conductivity Probe Method Figure 8 illustrates a conductivity probe level detection system. It consists of one or more level detectors, an operating relay, and a controller. When the liquid makes contact with any of the electrodes, an electric current will flow between the electrode and ground. The current energizes a relay which causes the relay [...]
Differential Pressure Level Detectors The differential pressure (DP) detector method of liquid level measurement uses a DP detector connected to the bottom of the tank being monitored. The higher pressure, caused by the fluid in the tank, is compared to a lower reference pressure (usually atmospheric). This comparison takes place in the DP detector. Figure [...]
Specific Volume Before examining an example which shows the effects of density, the unit “specific volume” must be defined. Specific volume is defined as volume per unit mass as shown in Equation 3-1. Specific Volume = Volume/Mass (3-1) Specific volume is the reciprocal of density as shown in Equation 3-2. Specific volume is the standard [...]
Figure 13 shows a typical pressurizer level system. Pressurizer temperature is held fairly constant during normal operation. The DP detector for level is calibrated with the pressurizer hot, and the effects of density changes do not occur. The pressurizer will not always be hot. It may be cooled down for non-operating maintenance conditions, in which [...]
Figure 14 illustrates a typical steam generator level detection arrangement. The DP detector measures actual differential pressure. A separate pressure detector measures the pressure of the saturated steam. Since saturation pressure is proportional to saturation temperature, a pressure signal can be used to correct the differential pressure for density. An electronic circuit uses the pressure [...]
Remote Indication Remote indication is necessary to provide transmittal of vital level information to a central location, such as the control room, where all level information can be coordinated and evaluated. There are three major reasons for utilizing remote level indication: Level measurements may be taken at locations far from the main facility The level [...]
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