ISO 23159:2020

INTERNATIONAL ISO
STANDARD 23159
First edition
2020-06
Non-destructive testing — Gamma ray
scanning method on process columns
Essais non destructifs — Méthode de balayage de rayon gamma sur
les colonnes de processus
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

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
Foreword
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This document was prepared by Technical Committee ISO/TC 135, Non-destructive testing,
Subcommittee SC 5, Radiographic testing.
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iv © ISO 2020 – All rights reserved

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 thus obtained are 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.
INTERNATIONAL STANDARD ISO 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 3857-4:2012, 2.37]
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 1998-4:1998, 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 bed column
(3.8) 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'').
2 © ISO 2020 – All rights reserved

— 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
...