ISO 23159:2020

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23159
ISO/TC 135/SC 5
Non-destructive testing — Gamma ray
Secretariat: DIN
scanning method on process columns
Voting begins on:
2020­03­30
Essais non destructifs — Méthode de balayage de rayon gamma sur
les colonnes de processus
Voting terminates on:
2020­05­25
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 23159:2020(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO 2020

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ISO/FDIS 23159:2020(E)

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© ISO 2020
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ISO/FDIS 23159:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Personnel qualification . 2
5 Protection against ionizing radiation . 2
6 Equipment requirements . 2
7 Execution of work at site . 3
7.1 Mechanical design of column and work permission . 3
7.2 Execution of scanning . 4
8 Data processing and reporting . 4
8.1 Data processing and documentation . 4
8.2 Report . 7
Annex A (informative) Recommendations for testing personnel . 8
Annex B (informative) Selection of sealed radiation source and its activity .10
Annex C (informative) Scanning equipment .12
Annex D (informative) Preparation of the scanning equipment .14
Annex E (informative) Selection of sources — Detector orientations for scanning .17
Annex F (informative) Interpretation of the scanning data .19
Bibliography .27
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ISO/FDIS 23159:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non­governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing,
Subcommittee SC 5, Radiographic testing.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/FDIS 23159:2020(E)

Introduction
Gamma ray scanning is a non-intrusive and non-destructive method, which is widely used in
petrochemical and chemical process plants for troubleshooting and diagnosing purposes. Gamma ray
scanning provides an indication of online conditions inside processing columns and vessels. Gamma ray
scanning has proven itself as a method for the identification of plant and process problems, resulting in
considerable economic savings. The gamma ray scanning method is an inspection which is carried out
while the process is in operation, without interruption.
The benefits, obtained from the application of the gamma ray scanning method for problem solving, are
many folds, such as safety improvement, environment pollution prevention and economic savings.
Gamma ray scanning is based on the gamma ray transmission techniques. When a gamma ray passes
through a column, the intensity of the transmitted beam is related to the path length and density of
the material through which the beam passes. An appropriate gamma source and a detector are aligned
at the same elevation opposite to each other on the exterior of the column. Measurements of radiation
intensity are taken at appropriate positions as the source and detector are moved together along the
column. The source-detector data obtained shown in plots of radiation intensity or material density
as a function of the position. Detailed analysis of these data enables making assessments about the
condition of internal structures and process materials within the column.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 23159:2020(E)
Non-destructive testing — Gamma ray scanning method on
process columns
IMPORTANT — The electronic file of this document contains colours which are considered to be
useful for the correct understanding of the document. Users should therefore consider printing
this document using a colour printer.
1 Scope
This document is used for non-destructive testing by the gamma ray scanning method for
troubleshooting and testing process columns in industries. This document is applicable to the testing
of all kinds of separation processes columns and pipes. This includes columns with different tray
configurations and with packed beds.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 5576, Non-destructive testing — Industrial X-ray and gamma-ray radiology — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5576 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
column
vertical cylindrical vessel used for facilitating the separation of a liquid mixture through distillation or
extraction
3.2
demister
device, often fitted with vapour-liquid separator vessels, to enhance the removal of liquid droplets or
mist entrained in a vapour stream
[SOURCE: ISO/TR 27912:2016, 3.25]
3.3
downcomer
device conveying liquid from one tray to the next one below it in a column (3.1)
3.4
entrainment
mist, fog droplets or particles transported by a fluid
[SOURCE: ISO 3857­4:2012, 2.37]
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ISO/FDIS 23159:2020(E)

3.5
flooding
phenomenon that upsets the normal operation of a distillation column (3.1) due to an excessive speed of
vapour travelling up the column, preventing liquid from flowing
[SOURCE: ISO 1998­4:1998, 4.10.052]
3.6
foaming
expansion of liquid that provides high interfacial liquid-vapor contact in a distillation column (3.1)
3.7
grid scanning
system of four or more individual scans in a grid pattern across equal quadrants of a packed column
(3.1) to investigate the packing and liquid/vapor distribution quality through packed or structured
trays beds
3.8
packed bed column
column (3.1) with one or more packed beds or structured trays beds that ensures the separation of two
or more components of a mixture
3.9
weeping
phenomenon that the pressure exerted by the vapor is insufficient to hold up the liquid on the tray and
the liquid leaks through perforations from one tray to the next one below
4 Personnel qualification
The personnel shall prove to have received additional training and qualification in gamma ray scanning.
NOTE Annex A provides recommendations for testing personnel.
5 Protection against ionizing radiation
WARNING — Exposure of any part of the human body to ionizing radiation can be highly
injurious to health. Wherever radioactive sources are in use, it is the responsibility of the user of
this document to identify the appropriate legal and safety requirements and regulations.
[9]
Further information can be found in the IAEA General Safety Requirements .
6 Equipment requirements
Equipment required for a column scan includes the following:
— a suitable sealed radiation source;
NOTE 1 The guidance for the selection of a sealed radiation source is provided in Annex B.
— a suitable source holder in which the source can be raised or lowered on the column; the source
holder should be capable of giving a collimated beam and the position at which the beam emerges
from the holder should be clearly indicated, see Annex C;
— a suitable radiation detection system (including data acquisition system) by which the radiation
intensity at a given measurement time can be measured and recorded at different elevations on
the column;
NOTE 2 E.g. the detector can be a sodium iodide crystal. A typical dimension is 5 cm × 5 cm (2'' × 2'').
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ISO/FDIS 23159:2020(E)

— a suitable device (e.g. computer and software) for displaying the data as a scan profile;
— a suitable calibrated radiation monitor by which the radiation level can be monitored for radiation
safety; the equivalent dose rate at the boundary of a controlled area is usually defined by national
legislation;
— barriers and warning notices to cordon off the “controlled area”;
— appropriate handling tools for the safe transfer of the radioactive source from the transport
container to the source holder to be used for scanning.
The equipment shall be tested before deployment to the site and securely packaged for transportation
to the work site to ensure good working condition.
The sealed radiation source shall be transported to the worksite in an approved Type A container,
labelled and documented, taking national and international regulations into account.
NOTE 3 This can include i.e.
— the vehicle equipment;
— a special driver qualification;
— a special personnel protective equipment;
— a transport permission.
A check list shall be prepared, and all items be checked before shipment. See an example in Annex D.
7 Execution of work at site
7.1 Mechanical design of column and work permission
Prior to carrying out any work, the Level 3 should agree with the client the objectives of the work and
scanning procedure. The Level 3
— will acquire details of the column diameter and wall thickness and details of the trays or packed beds;
— will acquire a suitable general arrangement drawing showing the location of features within the
column;
— will ensure that there is suitable and safe access to the parts of the column where the scanning team
needs to operate;
— will ensure that there are sufficient resources to carry out the work and that a suitable sealed
radiation source can be used at the site.
The documentation of the mechanical designs shall:
— select a proper reference (zero) point (manhole, external pipe, etc.);
— determine all positions of internal and external structures and refer it to the point zero;
— generate a list of the characteristics of the column, see an example in Table 1;

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ISO/FDIS 23159:2020(E)

Table 1 — Characteristics of the column
Type of the Type of the Identification Material of Internal Nominal wall Height of
process column of the column the wall diameters thicknesses the column
  D t h
i
  mm mm mm

… … … … … … …
— show the orientation of downcomers and liquid flooding;
— ensure that a suitable permit to work is issued by the local supervisor (upon arrival at the work site
by the Level 3 or the Level 2);
— inspect the work site;
— ensure that there is safe access;
— visually inspect the transport container;
— visually inspect the source holder;
— confirm by monitoring that the source is still present;
— immediately report any abnormalities to the Level 3, who shall decide on the required action.
7.2 Execution of scanning
The project team will carry out the scan in the agreed manner. Any deviation to the agreed scanning
procedure shall be approved by the Level 3 after consultation with the client.
Record the count rate (i.e. counts per time interval) each 5 cm (or other intervals according to the
distance between trays), either with a computer or a notebook. The count rates or dose measurements
can be registered in a table, see an example in Table 2.
NOTE 1 The determination of time interval for the count rate measurement is described in Annex B.
NOTE 2 The selection of sources (detector orientations for scanning) is described in Annex E.
Table 2 — Record of count rate along the column height
a b
Elevation Counts per time interval Remarks
mm

… … …
a
The counting time shall be documented.
b
Observations regarding obstacles or external structures shall be noted in the remarks. This will improve the
interpretation of the data.
8 Data processing and reporting
8.1 Data processing and documentation
The measurement of the count rate obtained by the radiation detector is recorded in a table. A
graphical representation (scan profile) shall be prepared. The gamma ray scanning profile provides
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ISO/FDIS 23159:2020(E)

information on the condition of the inside of the column, i.e. the internal structure, damages and liquid/
gas phases distributions. Figure 1 shows typical gamma scan profiles in tray columns and Figure 2 for
packed columns. The interpretation of the scan profile results in conclusions on the status of operating
conditions of the column. Some examples of the interpretations of different scan profiles are shown in
Annex F.
NOTE The client can decide on the provided report for further actions.
Key
1 demister pad 7 weeping tray
2 normal trays 8 missing tray
3 high liquid level 9 debris
4 flooding 10 base level
5 light foaming X counts per interval
6 heavy foaming ρ density (arbitrary unit)
Figure 1 — Typical gamma scan profiles in tray columns
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Key
1 demister 7  fouled packing
2 liquid distributer 8  mal liquid distribution
3 packed bed  scan 1
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4 liquid re-distributer  scan 2
5 base level  scan 3
6 missing packing  scan 4
Figure 2 — Example of gamma scan profiles in packed columns
8.2 Report
The result will be confirmed in a written report to the customer within the time frame agreed upon
between the contracting parties. The report contains a detailed description of the column as well as
the description of the scanning performances. The report shall include as minimum the following
information:
— name of the testing body;
— reference to the contract;
— names of the client;
— number of the contract;
— date of the contract;
— column reference and characteristic;
— Table 1 and Table 2;
— performed scanning tests;
— sealed radiation source and activity;
— detector type and brand;
— measurement time and detector settings (i.e. high voltage, thresholds);
— source-to-detector distance and geometry;
— data acquisition hardware and software;
— photograph or drawing of the column and the setup;
— any deviation from this document;
— drawing of the scan profile;
— interpretation of the scan profile;
— dates of scanning and report;
— name and signature of the responsible person(s);
— annexes.
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ISO/FDIS 23159:2020(E)

Annex A
(informative)

Recommendations for testing personnel
A.1 General
To enable column scans to be carried out efficiently, the qualification and responsibilities should be
defined prior to any work taking place as follows.
A.2 Level 3 (project manager)
The Level 3 is the person responsible for the planning and execution of
...