Two types of measurement methods are used for tank gauge with LTD-level temperature and density: volume or mass based. In a volume based system, level is measured. In a mass based system, the measurement of the hydrostatic pressure of the liquid column is used. The users choice should, therefore, be based on how product inventory is calculated and accounted via volume or weight.
Both methods provide a direct measurement of one factor in the inventory equation, level or pressure. However, bulk storage tanks tend to have large diameters, store products with varying densities that can stratify, and require consideration for high tank levels and overfill protection. A small change in level can make a big difference in accountable volumes (level x diameter), while stratification can lead to level changes that are undetectable by mass based systems.
Float and Tape Tank Gauge with LTD-level Temperature and Density
These instruments have been the liquid level measurement technique of the petroleum tank gauge with LTD-level temperature and density market for over 90 years due to their simplicity, reliability and cost.
Float and tape tank gauge solution consists of a 2500 ATG selected for the appropriate tank type. The instrument provides a measurement to +/- 4 mm accuracy and tank side display that is suitable for inventory management to API specifications. If control room integration and volumetric calculations are required, a 2920 FTT tank gauge transmitter is recommended with a 8500 STS for spot temperature measurement. The selection of the transmitter often depends on the required or existing field communications and protocols. The 2500 ATG/2920 FTTcombination is ATEX approved and is also able to provide optional contact outputs for triggering alarms or relays. If only an analog (4…20 mA) level output is required (without temperature) the 8200 COT can be used.
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