1. Scope ……………………………………………………………………………………
2. References ……………………………………………………………………………………
3. Definitions ……………………………………………………………………………………
4. Design Considerations for ATG Systems …………………………..
4.1. General ……………………………………………………………………………………
4.2. Selection of Automatic Tank Gauging Systems …………………………..
5. Automatic Overfill Protection for Storage Tanks …………………………..
6. Automatic Tank Gauging Systems Requirements …………………………..
6.1 Radar Tank Gauging (RTG) System …………………………..
6.2 Hydrostatic Tank Gauging (HTG) System …………………………..
6.3 Servo-operated Tank Gauging (STG) System …………………………..
6.4 Automatic Temperature Measurement …………………………..
6.5 Display of ATG Systems ……………………………………………………….
6.6 Power Supply ……………………………………………………….
7. Tank Management System ……………………………………………………….
8. Calibration and Testing ……………………………………………………….
9. Documentation and Special Tools……………………………………………………….
9.1 Documentation ……………………………………………………….
9.2 Special Tools ……………………………………………………….
10. Attachment 1 ……………………………………………………………………………………
11. Revision History ……………………………………………………………………………………
1. Scope
This standard establishes minimum requirements for material, design, procedure, codes and
standards for engineering and design in liquid hydrocarbon facilities for,
the automatic tank gauging (ATG) systems, and
alarms and shutdown requirements for automatic overfill protection of storage tanks
2. References
Reference is made in this standard to the following documents. The latest issues, amendments
and supplements to these documents shall apply unless otherwise indicated.
SABIC Engineering Standards (SES)
R01-E01
Field Instrumentation Design Criteria
R11-C01
General Instrument Installation Criteria
X01-E01
Control System Design Criteria
X02-S01
Distributed Control System Specification
Basic Engineering Design Data (BEDD)
Applicable BEDD
American Petroleum Institute (API)
MPMS Chapter 3 Section 1B Standard Practice for Level Measurement of Liquid
Hydrocarbons in Stationary Tanks by Automatic Tank
Gauging
MPMS Chapter 3 Section 3
Standard Practice for Level Measurement of Liquid
Hydrocarbons in Stationary Pressurized Storage Tanks by
Automatic Tank Gauging
MPMS Chapter 3 Section 6
Measurement of Liquid Hydrocarbons by Hybrid Tank
Measurement Systems
MPMS Chapter 7 Section 4
Static Temperature Determination Using Fixed Automatic
Tank Thermometers
MPMS Chapter 11 Section 1
Temperature and Pressure Volume Correction Factors for
Generalized Crude Oils, Refined Products, and Lubricating
Oils
MPMS Chapter 16 Section 2 Mass Measurement of Liquid Hydrocarbons in Vertical
Cylindrical Storage Tanks by Hydrostatic Tank Gauging
RP 2350
Overfill Protection for Storage Tanks in Petroleum Facilities
National Electric Manufacturer Association (NEMA)
250
Enclosures for Electrical Equipment (1000 Volts Maximum)
National Fire Protection Association (NFPA)
30
Flammable and Combustible Liquids Code
International organization of Legal Metrology (OIML)
R 85 Part 1-2-3 Edition 2008 Automatic Level Gauges for Measuring the Level of Liquid in
Stationery Storage Tanks
Part 1: Metrological and Technical Requirements
Part 2: Metrological Control and Tests
Part 3: Report Format for Type Evaluation
3. Definitions
High-High Level Alarm. Level alarm, set above the high level alarm point that shall allow
sufficient time for an orderly shutoff or diversion of liquids before the overfill level is reached/
tank overflows
High Level alarm. Level alarm, set above the normal fill level of liquid in a tank
Hybrid Tank Measurement System (HTMS) (API MPMS 3.6). A Hybrid Tank Measurement
System (HTMS) is a system which uses the product level measured by an automatic tank gauge
(ATG), the product temperature measured by an automatic tank thermometer (ATT), and the
static head of the liquid measured by one or more pressure sensors. These measurements are
used, together with the tank capacity table and the product volume/density correction tables, to
provide level, temperature, mass, observed and standard volume, and observed and reference
density.
Hydrostatic Tank Gauging (API MPMS 16.2). A method of direct measurement of liquid mass
in a storage tank based on measuring static pressures caused by the liquid head above the
pressure sensor.
Normal Fill Level (API RP 2350). The level up to which the tank is allowed to receive product at
the maximum allowable receiving flow rate for a predetermined time prior to reaching the safe fill
level.
Overfill Level (API RP 2350). The maximum fill level of product within a tank as measured from
the gauging reference point (i.e. striker plate) above which level any additional product will
overfill and spill out of the tank; or at which level contact or damage will occur between the
floating roof and the tank structure or appurtenances.
Safe Fill Level (API RP 2350). The level up to which the tank is allowed to receive product
delivery after the normal fill level is attained. The safe fill level is always below the overfill level.
Tank Strapping Chart (API RP 2350). A chart or record developed for each individual tank
specifying the essential values related to tank capacity, normal fill level, safe fill level, overfill
level, and detector setting levels.
4. Design Considerations for ATG Systems
4.1. General
4.1.1 Refer to SES-R01-E01 for general design guidelines and specification.
4.1.2 Refer to SES-R11-C01 for general requirements of installation. Vendor’s recommendation
shall be followed for ATG system installation.
4.1.3 The ATG system shall be suitable for operation in the site conditions as per BEDD.
4.1.4 The ATG system shall comply with the requirements per OIML R 85 for custody transfer
applications.
4.1.5 Refer to API MPMS Chapter 3 Section 1B for the standard practice for level measurement of
liquid hydrocarbons in stationary tanks by Automatic Tank Gauging (ATG) system.
4.1.6 Refer to API MPMS Chapter 3 Section 3 for the standard practice for level measurement of
liquid hydrocarbons in stationary pressurized storage tanks by ATG system.
4.1.7 Refer to API MPMS Chapter 3 Section 6 for the tank gauging measurement of liquid
hydrocarbons by hybrid tank measurement systems (HTMS).
4.1.8 The ATG system shall have minimum 12 months field proven record of reliable performance
in similar industrial applications.
4.1.9 Process connections for level measurement shall not be made near or close to fill and drain
line areas.
4.1.10 If specified, the ATG system shall be capable to measure (or calculate) liquid level, spot and
average temperature, density, mass and gross volume, and transmit them via a common field
mounted remote terminal unit (RTU) to DCS or other control system.
4.1.11 A local liquid level indicator suitable for mounting at grade near the base of the relevant tank
shall be provided. Level indication shall be configurable in engineering units.
4.1.12 Where a stilling well is required, the size of the stilling well shall be as per manufacturer’s
recommendation. In general, the pipe size of the stilling well shall be dependent on the
following:
a. Stilling well height in meters
b. Type of gauge installed
c. Travel of the measuring wire over the measuring drum width in millimeters per meter
d. Required accuracy of final measurement
The following general rule can be used to size the stilling well:
D = d + 70 + L * n Where:
D = diameter of stilling well in millimeters
d = diameter of displacer in millimeters
L = height measured from top in meters
n = allowable deviation of the stilling well from the vertical in millimeters per meter
4.1.13 Any conflict(s) between this standard, SES and industry standards, engineering drawings, and
contract documents shall be resolved at the discretion of SABIC.
4.2. Selection of Automatic Tank Gauging Systems
4.2.1 If specified, product storage tanks shall be provided with ATG systems as defined in this
document.
4.2.2 The selection of ATG system shall be defined during project engineering based on the
accuracy requirements for inventory control, custody transfer or other application.
4.2.3 The installed overall accuracy for the ATG system used for custody transfer application shall
be per OIML R 85.
4.2.4 The installed overall accuracy for the ATG system used for inventory application should be
per API MPMS 3.1B. However based on the project requirements, the accuracy for ATG
system used for inventory applications shall be finalized.
5. Automatic Overfill Protection for Storage Tanks
5.1 Refer to API RP 2350 for the alarms and orderly shutdown requirements for automatic overfill
protection of storage tanks in liquid hydrocarbon facilities with following exceptions:
a. High-high level detector shall be independent from the automatic tank gauging system
for all class liquid hydrocarbons.
b. Automatic shutdown for overfill protection shall be implemented in SIS. Refer to SESX01-E01
for
the
details.
6. Automatic Tank Gauging Systems Requirements
The Automatic Tank Gauging (ATG) system shall be a field-proven, microprocessor based
system, suitable for custody transfer and /or inventory control purposes as defined in API MPMS
Chapter 3 Section 1B or API MPMS Chapter 3 Section 3 as applicable.
6.1 Radar Tank Gauging (RTG) System
The system shall be designed with the following minimum requirements:
6.1.1 The transmitter and radar receiving antenna shall be stand-alone combination with downward
facing.
6.1.2 The RTG shall be capable of being installed, as needed, in tanks with fixed roof or floating
roof, with agitators, in stilling wells and in bypasses.
6.1.3 The RTG system antenna protection shall be minimum NEMA 6P or equivalent, and suitable
for usage as per area classification.
6.1.4 The RTG shall be impervious to build-up and condensation at the antenna.
6.1.5 If specified, pressure transmitter shall be provided for measurement of hydrostatic head of
liquid in the tank.
6.2 Hydrostatic Tank Gauging (HTG) System
Refer to API MPMS Chapter 16 Section 2 for mass measurement of liquid hydrocarbons in
vertical storage tanks by hydrostatic tank gauging. The system shall be designed with the
following minimum requirements:
6.2.1 A typical HTG system and the required calculations are shown in attachment 1.
6.2.2 Two pressure transmitters shall be provided for measurement of hydrostatic head of liquid in
the tank. The first pressure transmitter P1 shall be located near the bottom of the tank above
the anticipated sediment level. The second pressure transmitter P2 shall be located above the
lower transmitter preferably in a vertical plane, approximately 2.5 meters or 25 percent of the
maximum safe fill height, whichever is less.
6.2.3 For the tank operating above atmospheric pressure, a third pressure transmitter P3 shall be
provided for measurement of static pressure in the tank. It shall be installed in the vapor
space of the tank.
6.2.4 Each tank shall be provided with a Hydrostatic Interface Unit (HIU). HIU shall be
microprocessor controlled and shall accommodate information up to three pressure
transmitters and a RTD temperature transmitter. All HIU’s shall be configured for continuous
‘Tank Level’ display.
6.3 Servo-operated Tank Gauging (STG) System
The system shall be designed with the following minimum requirements:
6.3.1 STG shall be microprocessor based, suitable for top mounting.
6.3.2 The material of construction for the STG shall be suitable for the application and process
fluid as specified in the instrument data sheet.
6.3.3 Stilling wells shall be supported directly by the bottom plate of the tank, where movement of
the bottom plate shall not occur, such as tanks on rigid foundations.
6.3.4 In case, where settlement of the bottom plate is anticipated, stilling wells shall be supported
by the tank shell.
6.3.5 For pressurized storage tank, servo-driven gauge transmitter shall be equipped with
calibration chamber and full bore ball valve.
6.3.6 The metallic measuring wire shall be of Invar material (an alloy of nickel and iron that
exhibits very low thermal expansion) or SABIC approved equivalent.
6.3.7 The measuring drum within the servo-driven gauge transmitter chamber shall be fully
temperature compensated.
6.3.8 The measuring drum of servo-mechanism shall be magnetically coupled to the positioner of
variable speed servo drive, such that the instrument compartment is physically isolated from
the drum compartment which is exposed to the tank contents.
6.3.9 The instrument compartment shall be gas tight, so that flammable vapor cannot enter the
instrument compartment and escape to the outside atmosphere.
6.3.10 Minimum of 10 density dips shall be provided for density profile.
6.3.11 The servo-driven displacer gauge shall have lower and upper reference points. The tank
level shall be zero at the lower reference point and maximum at the upper (stop) reference
point. The calibration shall be based on this reference points.
6.3.12 The lower reference point shall be a fixed horizontal plate. The plate may be welded directly
to the tank floor plate, or affixed to the tank shell, or attached to the fixed lower end of a
required stilling well. If the plate is attached to the stilling well, the plate height shall not be
less than 50 mm above the tank floor plate.
6.4 Automatic Temperature Measurement
6.4.1 The automatic temperature measurement requirement in storage tanks shall be applicable if
identified in instrument data sheet
6.4.2 The temperature measurement shall be provided in accordance with API MPMS Chapter 7
Section 4.
6.4.3 RTD and temperature transmitter shall be used for temperature measurement.
6.4.4 An average temperature measurement shall be provided for cryogenic tank, regardless of
tank size and application of level measurement.
6.5 Display of ATG Systems
6.5.1 The display of ATGs can be done in DCS or dedicated PC based workstation per project
requirements. However for custody transfer applications, dedicated setups shall be provided.
6.5.2 SABIC prefers to use DCS to perform all of the functions of the ATG system, which would
normally be performed by the ATG system manufacturer’s PC. The ATG system manufacturer
shall furnish the software package suitable for configuration in DCS. The software package
shall be fully compatible with DCS capabilities to handle ATG system’s full functionalities.
6.5.3 The ATG system manufacturer shall provide detailed instructions for loading, initializing,
configuring, and operating the software in DCS.
6.5.4 The software shall include the standard system function, display, and report capabilities. The
list of optional capabilities shall also be clearly specified by manufacturer.
6.5.5 The software package shall be the current edition with a minimum of one year’s operation
time in service. The manufacturer shall provide historical performance data of software.
6.6 Power Supply
Power supply to the ATG system shall be 230 VAC, 60 Hz from UPS. Refer to SES-X01-E01
for the power supply requirements.
7. Tank Management System
If specified, Tank Management System shall be provided for plant’s ATG(s). The system shall
be designed with the following minimum requirements:
7.1 There shall be a dedicated workstation PC for tank management system.
7.2 All necessary hardware and software for interfacing between ATG units shall be considered
by the ATG systems vendor.
7.3 The workstation PC shall have configurable graphical screens such as bar graphs, tabular
details, tanks, etc.
7.4 The workstation PC software shall include the standard system function, customized display,
and report capabilities. The list of optional capabilities shall also be clearly specified by
manufacturer.
7.5 All calculations such as gross volume, on-line density, mass, etc., shall be performed in the
tank management system.
7.6 The software package shall be the current edition with a minimum of one year’s operation
time in service. The manufacturer shall provide historical performance data of software.
7.7 The workstation of tank management system shall provide an independent host
communication to DCS. Refer to SES-X02-S01 for requirements of interfacing with DCS.
8. Calibration and Testing
8.1 General
The calibration and testing of ATG(s) shall comply with the requirements of API MPMS
Chapter 3 Section 1B and API MPMS Chapter 3 Section 3 as applicable. The FAT and SAT
shall be performed for ATG systems and tank management system per project requirements.
8.2 Factory Acceptance Test (FAT)
a. Manufacturer shall perform factory calibration and testing on the ATG(s), including
software, before FAT. The test observations and results shall be recorded and made
available to SABIC.
b. After satisfactory completion of vendor internal functional test, the FAT can start.
c. Manufacturer shall provide FAT procedure to SABIC, 1 month in advance for review and
approval.
d. FAT schedule shall be communicated to SABIC at least 20 days before start date.
8.3 Site Acceptance Test (SAT)
a. Manufacturer shall submit SAT procedure for SABIC approval.
b. Manufacturer shall provide personnel to perform SAT and calibration of ATG at job site.
c. Manufacturer shall advise SABIC for any special tools, hardware or software required to
conduct SAT.
9. Documentation and Special Tools
9.1 Documentation
Manufacturer shall furnish following documents for SABIC review:
9.1.1 Calculations basis with all necessary formula
9.1.2 Wiring diagrams
9.1.3 Volume calculation table based on SABIC supplied ‘Tank strapping chart’.
9.2 Special Tools
Manufacturer shall provide list of all special tools for example hardware, software and other
devices for calibration, operation, and maintenance.
8.2 Factory Acceptance Test (FAT)
a. Manufacturer shall perform factory calibration and testing on the ATG(s), including
software, before FAT. The test observations and results shall be recorded and made
available to SABIC.
b. After satisfactory completion of vendor internal functional test, the FAT can start.
c. Manufacturer shall provide FAT procedure to SABIC, 1 month in advance for review and
approval.
d. FAT schedule shall be communicated to SABIC at least 20 days before start date.
8.3 Site Acceptance Test (SAT)
a. Manufacturer shall submit SAT procedure for SABIC approval.
b. Manufacturer shall provide personnel to perform SAT and calibration of ATG at job site.
c. Manufacturer shall advise SABIC for any special tools, hardware or software required to
conduct SAT.
9. Documentation and Special Tools
9.1 Documentation
Manufacturer shall furnish following documents for SABIC review:
9.1.1 Calculations basis with all necessary formula
9.1.2 Wiring diagrams
9.1.3 Volume calculation table based on SABIC supplied ‘Tank strapping chart’.
9.2 Special Tools
Manufacturer shall provide list of all special tools for example hardware, software and other
devices for calibration, operation, and maintenance.
