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GB/T 21451.5-2019 (GB/T21451.5-2019)

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GB/T 21451.5-2019: PDF in English (GBT 21451.5-2019)
GB/T 21451.5-2019
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 75.180.30
E 30
Petroleum and Liquid Petroleum Products -
Measurement of Level and Temperature in Storage
Tanks by Automatic Methods - Part 5: Measurement of
Temperature in Marine Vessels
(ISO 4266-5:2002, MOD)
ISSUED ON: MARCH 25, 2019
IMPLEMENTED ON: OCTOBER 1, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 6 
2 Normative References ... 6 
3 Terms and Definitions ... 6 
4 Requirements ... 7 
5 Accuracy ... 8 
6 Selection of ATT ... 11 
7 ATT Equipment - Instruction of Electronic Temperature Sensing Element .. 12 
8 Installation of Marine ATT ... 12 
9 Calibration and On-site Inspection of Marine ATT ... 13 
10 Data Communication ... 17 
Appendix A (informative) Influencing Factors of Temperature Measurement
Accuracy of Marine Vessels ... 19 
Petroleum and Liquid Petroleum Products -
Measurement of Level and Temperature in Storage
Tanks by Automatic Methods - Part 5: Measurement of
Temperature in Marine Vessels
1 Scope
This Part of GB/T 21451 provides the selection, accuracy, installation, debugging,
calibration and inspection guidance for automatic tank thermometer (ATT), which is
adopted for the measurement of temperature of petroleum and liquid petroleum
products in marine vessels.
This Part is applicable to the custody transfer metering of petroleum and liquid
petroleum products with the Reid vapor pressure of not more than 100 kPa.
This Part is inapplicable to temperature measurement in refrigerated cargo hold or
pressure cargo hold in marine vessels.
2 Normative References
The following documents are indispensable to the application of this document. In
terms of references with a specified date, only versions with a specified date are
applicable to this document. In terms of references without a specified date, the latest
version (including all the modifications) is applicable to this document.
GB/T 8927 Petroleum and Liquid Petroleum Products - Temperature Measurement -
Manual Methods (GB/T 8927-2008, ISO 4268:2000, MOD);
ISO 1998 (all parts) Petroleum Industry - Terminology
3 Terms and Definitions
What is defined in ISO 1998, and the following terms and definitions are applicable to
this document.
3.1 Automatic Tank Thermometer; ATT
Automatic tank thermometer refers to an instrument which continuously measures
temperature in storage (or cargo) tanks.
NOTE: a type of marine ATT, also known as automatic tank temperature measurement
4.2.2 All the marine ATTs shall be designed, selected and installed in accordance with
corresponding national and/or international (IMO, IEC, CENELEC, ISGOTT, ISO, etc.)
vessel electronic safety standards. ATT shall have certified documents that are
consistent with the classification of dangerous zones that it is applied to.
4.2.3 In terms of ATT installed on vessels, all the exposed metal components shall be
firmly grounded, namely, connected to the vessel body.
4.2.4 All the ATT equipment shall be maintained under safe operating conditions.
Equipment maintenance shall be conducted in accordance with the manufacturer’s
requirements.
4.3 General Requirements
4.3.1 General requirements provided in 4.3.2 ~ 4.3.6 are applicable to various types of
ATT.
4.3.2 Temperature and liquid level in marine vessels shall be simultaneously measured.
4.3.3 When temperature measurement is conducted on bulk cargo transportation, the
data shall be immediately recorded, unless long-distance digital display equipment can
regularly and automatically record the temperature.
4.3.4 During the loading and/or unloading at multiple ports, before the transportation
of products (front reading) and after the transportation of products (rear reading), the
same standard procedure shall be adopted to measure the temperature in marine
vessels.
4.3.5 In order to prevent unauthorized adjustment or intervention, safety guarantee
shall be provided to ATT. When ATT is applied to custody transfer metering, certain
conditions shall be provided to the sealing of the calibration adjustment device.
NOTE 1: this kind of protection might need to install ATT sensor in a temperature casing.
NOTE 2: ATT sensor may be integrated in the combination (for example, float, belt or rod)
of automatic level gauge (ALG). When some designs (float and belt) are not in
service, the combination of liquid level/temperature sensor might be raised to the
location of “retention”. During the tank-washing period, ATT cannot be used.
4.3.6 When ATT is applied to special occasions, its design and installation might need
to obtain type approval from relevant national institutions. After conducting a series of
specific tests on ATT and complying with the authorized installation mode, type
approval will generally be released.
5 Accuracy
5.1 Overview
circumstances are exceptions here:
---Cargo tank capacity is less than 159 m3, or, liquid level is lower than 3 m;
---The maximum variation of vertical temperature is less than 1 °C;
---The manually measured average temperature is used for custody transfer
metering.
NOTE: when liquid temperature in the vessels is uniform, or, when temperature
stratification in the vessels is relatively small and acceptable (see GB/T 8927),
single-point temperature measurement may be adopted.
7 ATT Equipment - Instruction of Electronic
Temperature Sensing Element
7.1 Resistance Temperature Detector
In terms of generally used automatic temperature measurement equipment, its basic
operating principle is that the resistance of metal (for example, copper or platinum)
varies with the temperature.
Generally speaking, copper or platinum RTD is used for temperature measurement in
custody transfer metering, because it has extremely high accuracy and stability. The
resistance of RTD may be measured through Wheatstone bridge circuit or other
suitable electronic components. RTD may be resistance wires intertwined on non-
conductor support core, or, thin-film type or other types. This component shall be
correctly installed in a stainless-steel shell. If necessary, circuit shall be intrinsically
safe. Temperature sensing element shall be installed in a suitable temperature casing.
The length of the sensing part of point-type temperature sensing element shall not
exceed 100 mm.
7.2 Other Temperature Sensing Element
Other temperature sensing elements (such as thermocouple, thermistor,
semiconductor and optical fiber, etc.) may also be adopted. However, they shall be
calibrated and comply with the inspection tolerance provided in this Part, otherwise, it
shall not be deemed that their accuracy is applicable to custody transfer metering.
8 Installation of Marine ATT
8.1 Overview
The installation of marine ATT shall comply with the requirements in the instructions
provided by ATT and ALG manufacturer.
applied for temperature measurement in custody transfer metering, the calibration
tolerance provided in this Part shall be satisfied. The reference standard of ATT
calibration shall be traceable to corresponding national standards.
NOTE 1: precise electronic temperature element and on-site transmitter used for fixed
automatic tank thermometer need to be calibrated before installation. Generally
speaking, on-site calibration adjustment device for transmitter will not be
provided.
NOTE 2: the objective of 9.2 ~ 9.4 is to inspect the calibration adequacy and accuracy of
ATT (including temperature element, transmitter and on-site/long-distance digital
display device) after its installation.
When manual temperature measurement is adopted to inspect or calibrate ATT,
manual temperature measurement shall be conducted in accordance with GB/T 8927.
The uncertainty of the reference standard for on-site calibration shall not exceed 0.1 °C
(necessary calibration correction value shall be adopted).
ATT may be calibrated/inspected in accordance with system or component.
9.2 Calibration and Inspection of Single-point ATT for Custody Transfer
Metering
9.2.1 Calibration before installation
The reference standard of ATT calibration shall be traceable to corresponding national
primary standards. Before installation, single-point ATT shall be calibrated under
controllable conditions (namely, factory or laboratory) in accordance with one of the
two methods below:
a) In three or more temperature points within ATT’s operating range, through
thermostatic bath and use standard thermometer to measure its temperature.
Conduct overall calibration of ATT (including temperature sensor, temperature
transmitter/converter and digital display device); the requirement of accuracy is
shown in 5.3.2.
b) Or, independently calibrate ATT components. Measure the resistance of
temperature element in thermostatic bath; use accurate resistor or thermal
calibrator (recently calibrated by a national metering institution). Respectively
simulate the input temperature of ATT temperature transmitter and digital
display device; the requirement of accuracy is shown in 5.3.3.
9.2.2 Initial inspection in shipyard or sea trial
9.2.2.1 Overview
In shipyard or sea trial, in accordance with ATT manufacturer’s instruction, conduct
a relatively low accuracy of temperature measurement of shipping cargos.
9.3 Calibration and Inspection of Multiple-point ATT for Custody Transfer
Metering
9.3.1 Calibration before installation
In accordance with the calibration procedure of single-point ATT provided in 9.2.1,
inspect every temperature sensing element of ATT. Please refer to 5.3.4 for the
requirement of accuracy.
9.3.2 Initial on-site inspection in shipyard or sea trial
9.3.2.1 Overview
In shipyard or sea trial, in accordance with ATT manufacturer’s instruction, conduct
initial inspection and debugging. When it is feasible, a method provided in 9.3.2.2 and
9.3.2.3 shall be adopted.
9.3.2.2 Component-based inspection
9.3.2.2.1 Temperature sensing element
Use a recently calibrated PET to inspect temperature sensing element’s measurement
data. When cargo hold approaches fully-loaded state, lower PET temperature
measuring probe to the depth of placement of the temperature sensing element; move
the temperature sensing probe up and down (within the range of around 300 mm), till
the temperature becomes stable. The difference between the temperature measured
by each temperature sensor of multiple-point ATT and the temperature measured by
PET shall be within 0.75 °C.
9.3.2.2.2 Temperature transmitter
Use temperature calibrator (for example, precise resistor or thermal calibrator) to
simulate the input of three or more temperatures within the expected operating range
of the vessels. Conduct inspection of ATT, excluding the temperature element. In each
temperature point, the difference between ATT digital display temperature and
resistor’s equivalent temperature shall be within 0.25 °C.
9.3.2.3 System-based inspection
As an alternative method for independent calibration and inspection of temperature
sensing element and transmitter, PET, which is calibrated before the inspection, may
be adopted to conduct overall inspection of ATT; it would be better if the storage tank
approaches fully-loaded state, and all the temperature sensing elements are
completely immersed. Measure the liquid temperature in the depth of the temperature
sensing element. In each measurement location, move PET temperature measuring
probe up and down (within the range of around 300 mm), till the temperature becomes
......
 
(Above excerpt was released on 2019-11-02, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT21451.5-2019