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While
some vessels have automatic samplers permanently installed on deck most
automatic samplers used on board vessels are of the portable type that
are attached to the vessels manifold at the time of hose
connection. In either case, design and performance of all
automatic sampling equipment shall be in accordance with API MPMS
Chapter 8.2. See definition of automatic sampler.
Automatic Measurement Equipment
Automatic
measurement equipment, also known as remote or fixed measurement
equipment, is built into the vessel. Such measurement systems
on tank vessels normally have automatic level and/or temperature
measurement capability, with readouts located at the compartment or at
a remote point, such as the cargo control room. It includes
Automatic Tank Gauging (ATG) equipment which consists of, but is not
limited to, the following types of liquid level measurement
technologies:
-
Float-operated
Tank Gauge (FTG).
-
Hydrostatic
Tank Gauge (HTG).
-
Inductive
Level Tank Gauge (ITG).
-
Radar
Tank Gauge (RTG).
-
Resistive
or electro-ohmic tank gauge.
-
Servo-operated
Tank Gauge (STG).
Additionally,
many of these systems are designed so that liquid level and temperature
measurements are transmitted to an on board computer and automatically
converted to volumes.
In
all cases the tank capacity tables should be specifically developed or
issued for the automatic gauging system used. For more information, see
API MPMS Chapters 2.8B and 3.4.
The
operation and capabilities of these systems vary greatly by technology
and manufacturer. Some can only measure liquid levels in the
tank
while others have the capability to measure free water, temperature,
and ROB/OBQ. Fixed automatic measurement equipment does not
generally measure free water, and the level of ROB/OBQ, if the liquid
level falls beyond the measurement range or is not detectable by the
sensor. Therefore, automatic measurement equipment is usually
used for vessel operations purposes rather than marine custody transfer
measurement.
However,
if the overall accuracy of the ATG system and temperature taking
system, described in API MPMS Chapters 3.4 and 7.4 are met, they can be
used to determine cargo level and temperature for marine custody
transfers.
Detailed
description of the technologies used in each of these types of
equipment can be found in API MPMS Chapters 3 and 7 and in
manufacturer's instructions. These and other types not
described herein may be used if they can perform as well as or better
than the measurement parameters set out in Section 6.
Automatic Temperature Equipment
Temperatures
can be taken automatically if a shipboard automatic temperature
measuring system (ATS) is available. An ATS should contain
sufficient temperature sensors to enable the calculation of a
representative average cargo temperature in accordance with API MPMS
Chapter 7.4. Manufacturer's operating specifications and
installation literature must indicate location of sensors and if
automatic averaging of temperature is provided by immersed sensors.
Temperatures
taken using automatic measurement equipment should indicate the levels
at which temperature measurements are taken in each tank or if average
temperatures are used. The vessel should provide data indicating the
last date of verification of automatic temperature measurement
equipment against NIST (or equivalent) standards. A log of temperature
verification against a certified thermometer traceable to NIST must be
maintained by the vessel. In all cases, manufacturer's description of
each system and its capabilities must be fully reviewed and understood
before use.
Maintenance/Verification
In all cases the maintenance instructions and verification schedules as
described by the manufacturer and in accordance with the requirements
described in the respective referenced standards must be observed by
the owner of the equipment.
Sections of text taken from API - MPMS Chapter 17 Marine Measurement
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