Principle of Float and Tape Tank Gauging
Using a proven float and tape level measurement technique, these instruments have been the main stay of the petroleum automatic tank gauging market for over 80 years due to their simplicity and cost.
Changes in the liquid level inside the tank raise or lower a large stainless steel float. The float is attached to a powerful negator spring via a perforated tape. The negator spring provides constant tension, which balances the float on the liquid level. The perforated tape engages pins on a sprocket wheel that, in turn, drives the counter assembly.
When a gauge board is used to display level in a float & tape system, the negator spring is replaced by a counter weight system. The liquid level in feet and inches or meters and decimeters is displayed on the gauge counter or indicated on a gauge board. This simple design and operation allows the gauge to perform with negligible maintenance throughout its working life.
A range of analog and digital tank gauge transmitters are available that mount directly to mechanical tank gauges. Level measurement data is encoded by the transmitter and output via industry standard communications to the control room.
Some transmitters also offer spot temperature measurement integration that can be used for inventory control applications. When a tank gauge transmitter is used, communications and power are required at the gauge head. Varec transmitters do not require an adaptor flange. When connecting third party equipment, a specific adaptor flange, depending on the transmitter, is often required.
Simplify the process of negator motor replacement and improve the performance of your mechanical tank gauge with a removable Negator Cassette with the negator motor enclosed.
Float and Tape Tank Gauging Solution
Varec's 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 2900 FTT or 4000 ATT 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/2900 FTT combination 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.
