Varec 2500, Installation And Operation Manual

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Introduction
Varec, Inc. 3
Tank Gauge Operation
The 2500 ATG uses a large, stainless steel float
attached to a stainless steel perforated tape to
detect the liquid level. The float follows the liquid
level as it rises and falls due to the tension
provided by a powerful negator spring or
cartridge motor. The precisely perforated tape
engages pins on a sprocket wheel that in turn
drive the counter assembly. This simple design
and operation allows the gauge to perform with
negligible maintenance throughout its working
life. (In some systems, the roof of the tank serves
as the float — Varec does not recommend this.)
Figure 2: 2500 ATG Powered by Negator Motor No
Electricity Required
Calibration and Volume Measurement
Tank gauging measurements provide appropriate inventory checks and a valuable method of
checking marine receipts and metered custody transfers. Accuracy of measurements requires
that a number of factors be considered:
•
Density and specific gravity of product as determined from representative samples
•
Sediment in the tank
•
Water content in the product
•
Gross volume
•
Temperature of the product
•
Tank-bottom deformation
It is the user's responsibility to appropriately consider these and other factors in this
application. For example, oil tank capacity tables are calculated for product at 60
o
F. A higher
temperature will cause the tank to expand, and the actual volume will be greater than the
volume at the standard temperature
Sprocket
Wheel
Mechanical
Counter
Motor
Drum
Perforated
Tape
Liquid-level Float
API Standard Description
2550 Method For Measurement And Calibration Of Upright Cylindrical Tanks
(ANSI/ASTM D1220)
2545 Method of Gauging Petroleum and Petroleum Products (ANSI/ASTM
D1085)