API BUL 2509B-1961

$39.00

Shop Testing of Automatic Liquid-Level Gages

Published By	Publication Date	Number of Pages
API	1961	14

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Category: API

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Description

General

The procedure described herein sets forth a method for shop
testing automatic liquid level gages whereby performance and
accuracy may be certified to the user by the manufacturer. The
American Petroleum Institute does not certify any gaging equipment.
The certification covers only performance as determined under shop
test conditions. Field installations proposed for custody transfer
must conform with the procedure outlined in Sect. 1204, "Testing
and Calibration Procedure," of API Standard 2500: Measuring,
Sampling, and Testing Crude Oil.

Both direct-reading and remote-reading automatic liquid level
gages are described in Part III, "Automatic Gaging Devices," of API
Standard 2500. Remote-reading automatic liquid level gages require
a basic mechanism on which telemetering equipment is applied.
Telemetering equipment may affect the performance and accuracy of
the basic gage.

Appendix A explains installation and test procedures of basic
and total performance of gages, whether direct or remote readings
are taken. The performance of the basic gage and the total
performance should be indicated when the basic gage is equipped for
remote transmission, see Appendix A. If the basic gage is not
equipped for remote transmission, Appendix A does not apply because
transmission systems are not included in the shop tests.

The addition of any auxiliary equipment to an automatic tank
gage also may adversely affect the accuracy of the gage. Therefore,
in addition to the test for basic gage performance, separate tests
shall be conducted to evaluate accuracy whenever the gage is to be
used with any auxiliary equipment. Such auxiliary equipment may
include high or low level alarms or controls, level sensitive
switchgear, or any other mechanism which derives its operating or
positioning power from the same source that powers the basic
gage.

One or more direct-reading automatic liquid level gage units of
each model manufactured during each production schedule shall be
tested. The tests may be made by the manufacturer or may be
delegated to an appropriate outside agency.

Accuracy data shall be recorded in the form of tables in such a
way as to indicate the number of actual values read; the range over
which they were read; and the error, or absence of error, at each
test point. Readings shall be recorded by interpolating to the
nearest ¹/₁₆ in. or less.

Any gage used with auxiliary equipment, which derives its
positioning or driving power from the gage mechanism, must be
tested separately for basic gage performance and for accuracy after
application of the auxiliary equipment. If more than one item of
auxiliary equipment is added to the basic gage, a separate test
must be made after the application of each item of auxiliary
equipment.

When a test is run under the foregoing provisions, the recorded
data shall include at each point the following three items:

1. True liquid level (level of the liquid when float of
gage is at equilibrium on the liquid surface).

2. Indicated liquid level (automatic gage reading taken
according to the manufacturer's instructions on the particular type
gage being tested for direct and remote operation) .

3. Difference between the true liquid level and the
indicated liquid level.

Additional information